Manual to Veterinary Video-Oto-Endoscopy: Use and Utility in Canine and Feline Ear Diseases [1st ed. 2022] 9783030989101, 9783030989118, 3030989100

Citation preview

Giovanni Ghibaudo

Manual to Veterinary Video-OtoEndoscopy Use and Utility in Canine and Feline Ear Diseases

Manual to Veterinary Video-Oto-Endoscopy

Giovanni Ghibaudo

Manual to Veterinary Video-Oto-Endoscopy Use and Utility in Canine and Feline Ear Diseases

Giovanni Ghibaudo Fano, Italy

ISBN 978-3-030-98910-1 ISBN 978-3-030-98911-8 https://doi.org/10.1007/978-3-030-98911-8

(eBook)

0th edition: # Poletto Editore 2010 # The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

I dedicate this book to my family, To Francesca, my wife, for the time, the love and the patience she gave to me To Alessandro, my precious and beloved son.

Preface

After graduation, I spent the first few years as a veterinary surgeon learning about internal medicine and clinical pathology. But since discovering dermatology, I have had an enormous passion for this subject. While the tools for diagnosing skin diseases are known and used for each clinical case, I noticed that the information and guidelines were less defined for diagnosing and managing ear diseases. The sparks of knowledge and inspiration for otology as a subject began later. I started by reading articles, textbooks and attending conferences and courses by illustrious fathers of veterinary dermatology such as Craig Griffin, Lynette Cole, Rod Rosychuck, Ralf Muller, Tim Nuttall and Susan Patterson. Thanks to them, I realised that the management of ears was entirely the dermatologistʼs responsibility (considering that the external ear to the eardrum is covered with skin!). So, after about 20 years of clinical work and more than a thousand cases of ear diseases in which I used the otoendoscope, I thought it was time to share my experience and knowledge, not only theoretical but above all practical. How to start an otoendoscopy unit, which instruments to choose, how to use them and where to avoid missteps or clinical errors. An in-depth study on advanced imaging diagnostics has been included in the book due to the enormous importance these tools have in the definition and staging of otitis. In addition, the description of ear cleaning techniques and the use of therapeutic equipment such as surgical lasers are an integral part of the text. Therefore, this manual aims to guide and support the clinician and all students and new graduates who have an interest and passion for this discipline. Fano, Italy

Giovanni Ghibaudo

vii

Acknowledgements

As a veterinary surgeon, I have learned from every patient and owner I have seen, but mainly through mistakes rather than success. Meeting with colleagues to share experiences and knowledge has enriched me. I thank the experts in dermatology and otology who enlightened and inspired me to develop and apply the knowledge I have learned in this field. The iconographic part of the book is essential. For this reason, I would like to thank Massimiliano Crespi Medical Illustrator, whose anatomical drawings were faithful and very useful for the technical explanations. A special acknowledgement to my colleagues Dr. Daniele Spaziante, Dr. Marta Brusati and Dr. Anna Tomba for their kind permission to present their precious CT and MRI images. I would also like to thank my friend and colleague Francesco Albanese for contacting Lars Koerner, editor of Springer Nature. Thanks to Lars’ interest, it was possible to start working and developing this manual. Thank you to the Springer Nature staff for their assistance and professionalism; a special thank you to Silvia Herold, Bibhuti Sharma and Romana Feitsch. Finally, thank you to Dr. Vanessa Schmidt for essential support in reviewing and improving the English text.

ix

Contents

1

Technical Information of the Video-Otoendoscope . . . . . . . . . . . . . . . . . 1.1 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Cleaning and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . .

1 1 13 20

2

Patient Preparation and Otoendoscopy Operative Procedure . . . . . . . . . . Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 27

3

Ear Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 External Ear Canal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Tympanic Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Middle Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Outline of the Inner Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . .

29 29 37 41 51 54

4

Video Otoscopy Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Ear Cytology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Deep Cleaning of the External Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Biopsy and Mass Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Laser Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Myringotomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Deep Cleaning of the Middle Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . .

55 55 70 79 80 85 94 100

5

Indications of VOE in Canine and Feline Ear Diseases . . . . . . . . . . . . . . 5.1 Congenital Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Ear Canal Atresia and Malformations . . . . . . . . . . . . . . . . . . . 5.2 Acquired Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Acute Otitis Externa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Chronic Otitis Externa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 Otitis Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . .

103 103 103 115 115 126 157 183 xi

About the Author

Giovanni Ghibaudo graduated in Veterinary Medicine at the University of Milan in 1994. Since 1996 he has been involved in clinical dermatology, otology, oto-endoscopy, laser surgery (CO2 and diodes) and dermatological laser therapy for dogs and cats. He attended many congresses and courses in Italy and abroad. He is a member of both the European (ESVD) and the Italian (SIDEV) Society of Veterinary Dermatology. Speaker and instructor in dermatology courses at the University of Veterinary Medicine of Turin and at the University of Veterinary Medicine of Parma. Speaker and instructor of the Videotoendoscopy Courses and dermatological laser courses in Italy. Speaker at National and International Congresses. He has published in both national and international peer-reviewed journals, He has also written some books on feline and canine dermatology and videotoendoscopy such as the “Clinical and microscopic dermatology of dogs and cats” Poletto Ed. that has been translated into three languages and “Ear diseases in dogs and cats” Elanco Ed. Dr. Ghibaudo currently works on referred canine and feline dermatology e otoendoscopy in different private clinics in Italy.

xiii

1

Technical Information of the Video-Otoendoscope

Endoscopic examination as a diagnostic and therapeutic procedure has long been used in Veterinary Medicine. Rigid endoscopes investigate organs and systems such as the urinary tract, nose, throat, and joints. The term Video-otoendoscopy (VOE) describes the use of rigid endoscopes in the ear canal of dogs and cats. This chapter describes its characteristics and which tools and techniques are needed to visualise and treat physiological and pathological conditions of the external ear, tympanic membrane, and middle ear.

1.1

Instruments

The conventional otoscope consists of a battery light source (halogen or LED) that projects through a slit illumination or an operating head into a conical tube (Fig. 1.1). A large magnifying lens at the eyepiece focuses on the end of the otoscope cone and enlarges the image. This standard diagnostic tool can be used during routine clinical visits but has several limitations compared to endoscopes. Limitations include lower light intensity and magnification. It is necessary to have suitable equipment to perform VOE. Depending on your budget, a range of products are available on the market, but purchasing a VOE set that enables good quality images and prolonged instrument lifespan is recommended. Additionally, purchasing from retailers that guarantee excellent technical support is paramount. A complete VOE set consists of a light source and cable, a camera, a computer and software for image/video acquisition, an irrigation/suction machine and either a rigid endoscope (fibre-optic bundle) with a sheath or an otoendoscope and a monitor. Additional accessories include 2- and 3-way stopcocks, forceps, curettes, brushes, snares, myringotomy needles and 5 Fr (Box 1.1) feeding tubes or polypropylene urethral catheters for cleaning. An otoendoscopic set consists of devices for biopsy, grasping and cytological # The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 G. Ghibaudo, Manual to Veterinary Video-Oto-Endoscopy, https://doi.org/10.1007/978-3-030-98911-8_1

1

2

1

Technical Information of the Video-Otoendoscope

Fig. 1.1 Heine Otoscope 2.5 v halogen light and reusable specula

fine-needle aspirates and optional electro- and/or laser surgery. The light source should be sufficiently bright to acquire good quality images; it can be a halogen (cheaper, Fig. 1.2), xenon (more powerful but expensive, Fig. 1.3), or LED light source (a good compromise between cost and brightness of light). In addition, there is a battery light source LED (cheap and practical, Fig. 1.4) and light sources with a built-in video monitor and camera (Fig. 1.5). The light-transmitting cable must be compatible with the attachment of the endoscopic probes. Box 1.1 The French catheter scale (most correctly abbreviated as Fr) is commonly used to measure the outer circumference of cylindrical medical instruments, including catheters. 4 Fr is equivalent to 1.33 mm; 5 Fr is equivalent to 1.67 mm, and 6 Fr is equivalent to 2.00 mm. Camera options include portable, internal cameras, that are comfortable, small, inexpensive but with poor image quality and external cameras with 1 CCD (charge-coupled device) and 3 CCDs. The CCD is the true heart of a video camera. It is a small silicon plate covered in sensors that, together with the lens, captures images and transforms them into electrical signals. These, in turn, are interpreted by position, colour and intensity and transformed into bits, for digital video cameras, or pulses, for analogue ones. Multiple successive images are

1.1

Instruments

3

Fig. 1.2 Olympus CLK-4 Halogen Light Source

Fig. 1.3 Karl Storz Xenon Nova 300, Xenon Light Source (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

extracted from the sensor at close intervals to achieve motion. Cameras with 3 CCDs have improved colour rendering compared to 1 CCD. However, the range of colours in the ear canal is not so broad as to justify the additional cost. Therefore, as a first purchase, a 1 CCD camera is sufficient. The image quality and definition improvement are continuous thanks to Full HD (Fig. 1.6) and 4K cameras. In addition, there are efficient and portable solutions for the freelance veterinarian, such as devices with a tiny camera combined with a monitor

4

1

Technical Information of the Video-Otoendoscope

Fig. 1.4 Karl Storz Battery Light Source LED (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

Fig. 1.5 Karl Storz Telepack for Telecam one-chip camera heads, veterinary video camera heads and video endoscopes, incl. LED light source, integrated digital image processing module, 15” LCD TFT monitor with LED backlight, USB/SD memory module (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

1.1

Instruments

5

Fig. 1.6 Karl Storz Telecam C3, Full HD camera control unit (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

(Fig. 1.7) or smartphone adapters (Fig. 1.8). A magnification system (zoom) is helpful to view an image of adequate size. The zoom is in the coupler or camera head. It can be digital, so the picture is processed and often loses quality at maximum magnification, or optical, composed of a group of lenses (as in cameras) and maintains optimal definition at any magnification. The endoscopic probes must be rigid, of adequate length and suitable diameter. For cats and medium-small dogs, a lens with a 2.7 mm diameter is practical and helpful in entering and partially viewing the middle ear. In large dogs, endoscopes with a 4 mm diameter are optimal. The best lens configuration provides a 30
angle of view (especially in dogs where the angle between the horizontal ear canal and tympanic membrane is c.45
(Fig. 1.9) and a 0
angle of view (Fig. 1.10)). The quality of the endoscopes is essential. There is an otoendoscope where the optic is a single body with a sheath that takes the shape of the conventional otoscope (Fig. 1.11). This telescope has a 2 mm (6 Fr) diameter operative channel, separated from the lens system (in traditional rigid endoscopes with removable sheath) (Fig. 1.12) for inserting catheters (Fig. 1.13), curettes, and forceps (Fig. 1.14). This working channel exits the tip of the probe at the 12 o’clock position. It is possible to rotate the otoscope cone at its attachment to the coupler camera to change the orientation of the 12 o’clock exit point of the working channel. The otoscope makes its use limited to the ear canal, but it is much more functional, practical and resistant. The “classic” rigid endoscope

6

1

Technical Information of the Video-Otoendoscope

Fig. 1.7 Karl Storz C-Mac for one-chip CMOS camera head; screen size 700 with 1280  800-pixel resolution, two camera inputs, a USB and an HDMI port, optimised user interface, video and image capturing in real time on SD card. (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

Fig. 1.8 Karl Storz Smartscope, compatible with standard Storz eyepieces and various smartphones. (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

1.1

Instruments

7

Fig. 1.9 Hopkins Forward-oblique rigid endoscope 30
, diameter 2,7 mm, length 18 cm detail of the tip: without (above) and with (below) protection sheath

is also suitable for arthroscopies, cystoscopies or rhinoscopies. However, due to anatomic features, its use is more prone to mechanical damage in the ear. The main accessories useful during otoendoscopy are 2- and 3-way stopcocks that can be added to the port of the otoendoscope for simultaneous use of instruments and irrigation or suction (Fig. 1.15), biopsy forceps, grasping forceps (Fig. 1.16), myringotomy needle, ear curettes and oto-brush (Figs. 1.17 and 1.18). In addition, a suction and irrigation device to perform ear cleaning under endoscope vision. Some of these devices allow you to use digital pressure (via a handle attached to the tubing) to control irrigation or aspiration and modify their intensity (Fig. 1.19). Combined suction systems, composed of a traditional

8

1

Technical Information of the Video-Otoendoscope

Fig. 1.10 Karl Storz Otoscope, detail of the tip: endoscope 0
, 5 mm diameter and sheath in the same body with integrated operating channel 5 Fr. in diameter

Fig. 1.11 Karl Storz Otoscope, for dogs and cats, autoclavable, diameter 5 mm, length 8.5 cm, 0
(Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

surgical aspirator and irrigation system, e.g., a 2-litre bag of saline solution attached to a sterile giving (infusion) set, can be helpful for complete and deep ear cleaning. The end of the giving set line is attached to the second port of the stopcock (Fig. 1.20). The wheel cassette (and/or clip) on the giving set control the fluid flow for irrigation. Greater irrigation pressure can be achieved with a compression unit around the saline bag. For suction, one end of the plastic tube connects to the aspirator inlet and the other to a 4 Fr urinary catheter or feeding tube via a Christmas tree adapter (Fig. 1.21). First, the urinary catheter/or feeding tube tip should be cut to remove the lateral holes (Fig. 1.22).

1.1

Instruments

9

Fig. 1.12 Hopkins Forward-oblique rigid endoscope 30
, diameter 2.7 mm, length 18 cm (below) and protection sheath with a 3-way stopcock (above)

Fig. 1.13 Karl Storz Otoscope, detail of the tip: endoscope 0
, 5 mm diameter and sheath in the same body with 4 Fr. catheter inserting in the dorsal integrated operating channel 5 Fr. in diameter

Next, the catheter/tube is inserted into a stopcock inlet and passed through the otoendoscope operative channel until it is visualised within the ear canal. The diode laser (Fig. 1.23) is a device used successfully in the ear to remove masses. Lasers are expensive, and the decision to invest in the necessary equipment would depend

10

1

Technical Information of the Video-Otoendoscope

Fig. 1.14 Karl Storz Otoscope, detail of the tip: endoscope 0
, 5 mm diameter and sheath in the same body with 4 Fr. forceps inserting in the dorsal integrated operating channel 5 Fr. in diameter

Fig. 1.15 Karl Storz Otoscope with a 2-way stopcock connected to the port (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

1.1

Instruments

11

Fig. 1.16 Karl Storz grasping forceps, flexible, oval, double action jaws, 5 Fr., length 34 cm (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

Fig. 1.17 Karl Storz myringotomy needle, ear curettes and oto-brushes set (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

on the intended frequency of use. However, the availability of laser surgery may benefit several surgical departments within a clinic so that costs can be shared. Surgical lasers belong to class IV lasers, and knowledge of the warnings and correct use is necessary.

12

1

Technical Information of the Video-Otoendoscope

Fig. 1.18 Karl Storz oto-brushes, grasping forceps and myringotomy needle set (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

Before using the laser, the fibre must be activated by carbonisation. The laser fibre usually has a 300-to-600-micron diameter (Fig. 1.23) and is inserted into the otoendoscope 3-way stopcock (Fig. 1.24). Alternatively, if using a 2.7 mm “paediatric” rigid endoscope, the fibre connects to the stopcock of the sheath (Fig. 1.25). The surgeon must always see the tip of the laser fibre clearly on the monitor. Haemostasis is obtained with powers from 3 to 6 watts (continuous wave) in contact mode. Irrigation is crucial. If bubbles are seen forming near the tip of the fibre, the temperature is too high, and delivery must be suspended immediately. Each single application must not exceed 3 s. Following laser application with maximum power from 10 to 15 watts, the mass becomes blanched. Once the mass is no longer vascularised, it can be removed with endoscopic forceps. The laser may treat several pathological ear conditions, including hyperplastic proliferative otitis, feline apocrine cystomatosis, inflammatory and benign ear canal tumours. Furthermore, it may debulk and aid the palliative treatment of malignant neoplastic masses.

1.2

Cleaning and Maintenance

13

Fig. 1.19 Karl Storz Vetpump 2, adjustable suction and irrigation pump, power supply system (Source: Photo courtesy of Karl Storz: #Karl Storz SE & Co KG, Germany)

The correct use and maintenance of all endoscopic components is essential to ensure optimal instrument life and thus minimise costs. Creating a double set for each element allows the service to remain active and available. A monitor allows the client and veterinarian to view the patient’s ear canal during otoendoscopy. The most significant images and videos should be recorded by a software system and transferred to a computer. Documentation capability is beneficial in a referral practice. The referring veterinarian can receive a written report with photographs of the investigation (Fig. 1.26).

1.2

Cleaning and Maintenance

It is essential to establish an effective manual cleaning protocol before high-level disinfection. Manual cleaning permits the removal of organic debris and should start as soon as the otoendoscope is removed from the patient. The instruments should be soaked in an

14

1

Technical Information of the Video-Otoendoscope

Fig. 1.20 Irrigation/flushing system: sterile disposable infusion tube is connected to a 2-litre bag of physiological solution inserted in a squeezer for arthroscopy, and the other end to the second port of the stopcock

Fig. 1.21 Aspiration system: one end of a plastic tube connects to the aspirator at the inlet and the other (via a Christmas tree adapter) to a 4 Fr urinary catheter

1.2

Cleaning and Maintenance

15

Fig. 1.22 Cutting the tip of the urinary catheter beyond the lateral holes

enzymatic cleaning solution that has been mixed with lukewarm water according to the manufacturer’s instructions. The operative channel, internal stopcocks and instrument parts must be checked and cleaned appropriately. After enzymatic lavage, the endoscope and instruments must be thoroughly rinsed (Fig. 1.27) and dried. Always read the manufacturers manual first, particularly as some older endoscopes are not entirely waterresistant. In addition, the immersion time must not exceed the indications of the manufacturer. Only autoclavable scopes can be steam-sterilised following manufacturer instructions. The otoscope and all related instruments must always be used with care as they are fragile. A dry and quiet place in the clinic, sheltered from trauma, is an excellent site to leave and preserve the VOE set.

16

1

Technical Information of the Video-Otoendoscope

Fig. 1.23 K-laser Blue Vet, diode laser with a 10 W highest power—445, 660, 970 nm. (Source: Photo courtesy of K-laser: Eltech K-Laser s.r.l., Italy)

1.2

Cleaning and Maintenance

Fig. 1.24 A 300 μm diameter fibre emerges from the operating channel of the otoendoscope

17

18

1

Technical Information of the Video-Otoendoscope

Fig. 1.25 The white dot indicates the laser fibre and its insertion at the 3-way stopcocks

1.2

Cleaning and Maintenance

Fig. 1.26 An example of a document with otoendoscopy photographs and written comments

19

20

1

Technical Information of the Video-Otoendoscope

Fig. 1.27 After bathing in lukewarm water with an enzymatic cleaning solution (a–c), the endoscope and instruments must be thoroughly rinsed (d)

Further Reading Cole LK (2011) Otoscopy. In: Tams TR, Rawlings CA (eds) Small animal endoscopy, vol 20, 3rd edn. Elsevier – Mosby, St. Louis, MO, pp 587–605 Gotthelf LN (2005) Examination of the external ear canal. In: Small animal ear diseases an illustrated guide, vol 2, 2nd edn. Elsevier – Mosby, St. Louis, MO, pp 31–39 McCarthy TC (2021) Instrumentation for endoscopy. In: Veterinary endoscopy for the small animal practitioner, vol 2, 2nd edn. Wiley, Boca Raton, FL, pp 9–26 Sobel DS (2012) Endoscopy of the canine and feline ear: otoendoscopy. In: Ragni SA, Moore AH (eds) Clinical manual of small animal endosurgery, vol 9, 1st edn. Blackwell Publishing, London, pp 256–272

2

Patient Preparation and Otoendoscopy Operative Procedure

A complete patient’s history, including co-morbidities and concurrent medications, should be collected prior to the procedure; this is essential to establish an individualised and safe protocol. Informed consent is necessary to record that the animal’s owner is aware of the potential risks of general anaesthesia and the use of the Video-otoendoscope. An anaesthesia protocol that allows for complete pain management during and after the procedure is essential. The operating room should be prepared appropriately to allow the anaesthetist and the endoscopist (and, if available, a technician) unrestricted access to the patient as needed. The approach to a patient suffering from chronic and recurrent otitis is the same as for all dermatological cases. A detailed history is followed by a thorough general physical and dermatological examination. Additionally, a careful neurological assessment should be performed, paying particular attention to the cranial nerves and central cortical status. Before VOE, imaging studies with magnetic resonance imaging (MRI), computed tomography (CT), or conventional radiography may be performed to inform the prognosis and guide therapeutic decisions. Treatment with glucocorticoids (prednisolone 0.5–1.0 mg/kg or methyl-prednisolone 0.4–0.8 mg/kg, q24hrs per os) for 10–14 days before otoendoscopy helps to reduce inflammation, ulceration, and stenosis. This protocol enables easier passage of the endoscope, reduces potential trauma, improves visualisation and cleaning, and minimises neurological complications post endoscopy. Patients should be starved of food for 12 h before the procedure in preparation for general anaesthesia. Prior to anaesthesia, some patients may require further investigations such as echocardiography in the case of a detected heart murmur or blood work to assess general health further. Given the hyperaesthetic nature of the ears, especially in the diseased state, VOE should always be performed under general anaesthetic with a cuffed endotracheal tube; this also provides an increased measure of safety to prevent aspiration pneumonia when using irrigation.

# The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 G. Ghibaudo, Manual to Veterinary Video-Oto-Endoscopy, https://doi.org/10.1007/978-3-030-98911-8_2

21

22

2

Patient Preparation and Otoendoscopy Operative Procedure

The sedation and general anaesthesia protocols for such patients must consider the potential of severe otic pain and hyperaesthesia and be formulated individually. Postoperative pain relief is also paramount, and patients usually continue on systemic glucocorticoids to reduce inflammation. Treatment options, doses, frequency, and duration should be decided upon on an individual basis. Post-anaesthesia deafness in dogs and cats following dental and ear cleaning procedures have been reported. This deafness seems more common in older dogs, so obtaining informed consent of the risks of otoendoscopy procedures and general anaesthesia is essential. The patient is positioned based on the preferences of the endoscopist. The choice of recumbency can be dictated by the design of the operating room, the operator’s location, and the location of the endoscopic equipment tower. The procedure should be performed on a wet table or surgical sink table as large amounts of irrigant are often used; this is essential to keep the patient warm and dry and prevent flooding the operating room floor. In unilateral otitis, the patient could be positioned in lateral recumbency with the affected side uppermost (Fig. 2.1). In the author’s preference, the endoscopy tower is next to the dorsal aspect of the patient, near the level of the head; however, the endoscopy tower should be positioned to allow the endoscopist a full view of the screen. In this case, the hand that holds the endoscope also grasps the pinna and pulls it up and out to straighten the auditory canal (Fig. 2.2). If the endoscopist is working from the back of the head, the image on the video monitor screen is upside down. Therefore, it may be helpful to stand with the patient’s limbs towards you so that the image is the correct way up on the screen; this may necessitate moving from one side to the other during the procedure if both ears are examined. In addition, it may be beneficial to place a rolled towel under the head to allow the muzzle to point downward (Fig. 2.3). This care allows for drainage of the irrigant out the nose rather than back into the posterior pharynx. The position of the patient preferred by the author is sternal (Fig. 2.4). The patient’s head is positioned at 10 o’clock to view the left ear and at 2 o’clock to view the right one. This positioning has the advantage of not moving the patient in between ears; the disadvantage is the need to move on both sides of the operating table, as mentioned above. When the patient is placed in sternal recumbency, one hand holds the endoscope, and the other grasps the pinna and pulls it up and out to straighten the auditory canal (Fig. 2.5). Once the patient, the endoscopist and the VOE machine are set up, before performing the procedure, it is helpful to calibrate the white camera balance (Fig. 2.6). Also, check the focus using one hand (shaped as a loose fist) to simulate the shape of the otic canal (Fig. 2.7). Finally, wiping the lens with a cotton ball soaked in 70% isopropyl alcohol avoids lens fogging or obstruction of the visual field with debris (Fig. 2.8). This process must usually be repeated during any otoendoscopy; in this way, clear and good quality images are obtained before, during and after any procedure.

2

Patient Preparation and Otoendoscopy Operative Procedure

23

Fig. 2.1 Patient in lateral recumbency

Fig. 2.2 Patient in lateral recumbency: the otoendoscopist using the same hand to hold the endoscope and grasps the pinna, pulling it up and out to straighten the auditory canal; the other hand is free to use instruments

24

2

Patient Preparation and Otoendoscopy Operative Procedure

Fig. 2.3 A rolled towel under the head (white arrow) allows the muzzle to point downward

Fig. 2.4 Patient in sternal recumbency. This positioning has the advantage of being able to examine both ears without moving the patient

2

Patient Preparation and Otoendoscopy Operative Procedure

25

Fig. 2.5 Patient in sternal recumbency: the otoendoscopist handles the endoscope like a pistol; one hand holds the endoscope, and the other grasps the pinna and pulls it up and out to straighten the auditory canal

Fig. 2.6 White camera balance check. Point the endoscope/otoendoscope at a white surface and push the white balance button, so the degree of whiteness is corrected

26

2

Patient Preparation and Otoendoscopy Operative Procedure

Fig. 2.7 Focus adjustment using the hand (shaped as a loose fist) to simulate the ear canal

Fig. 2.8 Wiping the lens with a cotton ball soaked in 70% isopropyl alcohol is essential to maintain a clear and good quality of the visual field

2

Further Reading

27

Further Reading Cole LK (2011) Otoscopy. In: Tams TR, Rawlings CA (eds) Small animal endoscopy, vol 20, 3rd edn. Elsevier – Mosby, St. Louis, MO, pp 587–605 Rosychuk R (2021) Video otoscopy. In: McCarthy T (ed) Veterinary endoscopy for the small animal practitioner, vol 10, 2nd edn. Wiley, Boca Raton, FL, pp 637–659 Sobel DS (2012) Endoscopy of the canine and feline ear: otoendoscopy. In: Ragni SA, Moore AH (eds) Clinical manual of small animal endosurgery, vol 9, 1st edn. Blackwell, London, pp 256–272 Stevens-Sparks CK, Strain GM (2010) Post-anesthesia deafness in dogs and cats following dental and ear cleaning procedures. Vet Anaesth Analg 37(4):347–351

3

Ear Anatomy

Knowledge of the anatomy of the external ear, tympanic membrane and middle ear are essential for using the VOE effectively and safely. Endoscopic images of normal dogs and cats are the basis for learning how to use the otoscope. Differences in breeds, especially dogs, must be known to interpret the images during VOE correctly. The anatomical differences between dogs and cats have diagnostic and therapeutic implications.

3.1

External Ear Canal

When performing a deep ear flush, it is mandatory to be aware of the delicate structures of the ear to avoid damaging them and causing neurological complications. The opening of the external ear canal is bounded by the helix rostrally, by the tragus laterally and by the antitragus caudally. The antitragus is a thin, elongated piece of cartilage caudal to the tragus and separated from it by the intertragic incisure (intertragic notch). This anatomical site is where the otoendoscope is inserted to begin the procedure (Fig. 3.1). The dogs’ external ear canal or auditory canal is 5–10 cm long and 0.5–1 cm in diameter. It consists of two portions: the first with a vertical course (Figs. 3.2 and 3.3), in direct communication with the pinna, the second with a horizontal course (Figs. 3.4 and 3.5), which connects the vertical portion to the tympanic membrane (Figs. 3.6 and 3.7). Different shapes of the duct are recognised according to the breeds: dolichocephalic (Fig. 3.8), mesocephalic (Fig. 3.9) or brachycephalic (Fig. 3.10). Some breeds, such as Cocker Spaniels, have a twisted and long duct conformation (Fig. 3.11); others are coneshaped as in French Bulldogs (Fig. 3.12). In the cat, the external ear canal is 1.8–2.5 cm long and 0.2–0.4 cm wide (Fig. 3.13). The auricular cartilage of the pinna rolls on itself, starting the cone (the vertical ear canal). The vertical ear canal extends ventrally and slightly rostrally before turning medially, forming # The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 G. Ghibaudo, Manual to Veterinary Video-Oto-Endoscopy, https://doi.org/10.1007/978-3-030-98911-8_3

29

30

3

Ear Anatomy

Fig. 3.1 Intertragic incisure (notch) in the dog (a) and the cat (b). This area (grey circle) is the starting point landmark for video otoscopic examination

the horizontal ear canal. A prominent cartilaginous ridge, the luminal fold, separates the vertical-horizontal ear canals (Figs. 3.14 and 3.15). To access the horizontal canal with an otoscope, the luminal fold can be elevated by grasping the ear pinna and lifting the ear (Fig. 3.16). The luminal fold is less prominent in the cat but still warrants minimisation utilising the techniques outlined above for the dog. The horizontal ear canal turns ventrally and extends to the tympanic membrane (Figs. 3.17 and 3.18). The horizontal ear canal is composed of

3.1

External Ear Canal

31

Fig. 3.2 Video otoscopic image. Dog. Left vertical ear canal

Fig. 3.3 Video otoscopic image of the vertical ear canal, left ear, cat

auricular and annular cartilage (Fig. 3.19). The annular cartilaginous band sits within the distal auricular cartilaginous tube and attaches to a projection of the temporal petrous bone, the osseous external acoustic meatus.

32

3

Ear Anatomy

Fig. 3.4 Video otoscopic image of the horizontal ear canal, right ear, dog

Fig. 3.5 Video otoscopic image of the horizontal ear canal, left ear, cat

Fibrous connective tissue ensures the annular-auricular cartilaginous and osseouscartilaginous junctions and gives pliability. The tympanic membrane forms the bottom of the external auditory canal and separates the external ear from the middle ear (Figs. 3.20

3.1

External Ear Canal

33

Fig. 3.6 Schematic diagram of the external, middle, and internal ear, dog. Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

and 3.21). In dogs, it is common to see a small amount of cerumen accumulated within the hairs growing on the floor of the horizontal canal, just in front of the tympanic membrane; this is considered a normal finding. When working in the depths of the horizontal canal with the video-otoendoscope, these hairs provide orientation and the approximate location of the tympanic membrane. Skin covers the external ear canal in direct continuation with the pinna and extends over the tympanic membrane, forming the external layer. The aural epidermis is thinner compared to normal skin. In the epidermis of the skin surface, the

34

3

Ear Anatomy

Fig. 3.7 Schematic diagram of the external, middle, and internal ear, cat. Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

corneocytes exfoliate directly into the external environment, while in the ear canal, exfoliation occurs within the lumen of the canal. Since there are no ciliated cells capable of removing exfoliated cells, a self-cleaning mechanism has been hypothesised that avoids obstruction of the terminal part of the external ear canal. This physiological mechanism, known as epithelial migration, is described and documented in humans, laboratory animals and recently in dogs. It consists of radial and centrifugal migration of the keratinocytes of the tympanic membrane up to the point where the epidermis lines the auricular cartilage.

3.1

External Ear Canal

35

Fig. 3.8 Schematic diagram of the external, middle, and internal ear, dolichocephalic breed (German shepherd, dog). Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

During this process, cerumen is transported away from the tympanic membrane and towards the opening of the auditory canal. Therefore, the mechanism of epithelial migration represents a natural cleaning of the tympanic membrane and plays an essential role in repairing ear drum lesions. The underlying dermis is rich in elastic fibres and collagen, also giving the external ear canal flexibility, which can be appreciated during otic palpation and otoscopic examination. The hair follicles are present along the entire ear canal with variable density (Figs. 3.22 and 3.23), linked to the breed and, unlike those that compose the haircoat, are of the simple type, except for the Cocker Spaniel in which, in addition to a higher concentration, there is a predominance of compound follicles (Fig. 3.24). Hair is usually sparse or absent in the cat’s ear canal (Fig. 3.25).

36

3

Ear Anatomy

Fig. 3.9 Schematic diagram of the external, middle, and internal ear, mesocephalic breed (Cavalier King Charles, dog). Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

There are sebaceous glands within the dermis, and modified apocrine glands called ceruminous glands. The sebaceous glands are in the superficial dermis, and their density is generally greater in the vertical compared to the horizontal canal. The ceruminous glands are in the deep dermis and, unlike the sebaceous glands, generally tend to be more numerous in the horizontal portion of the duct, near the tympanum. In normal dogs and cats, blood vessels are often seen within the walls of the canals with VOE (Fig. 3.26). One of the earliest signs of canal wall thickening due to inflammation is an inability to visualise these vessels. Branches of the auricular and superficial temporal arteries are located medial to the vertical ear canal; the caudal auricular artery provides the main blood supply to the external ear. The parotid salivary gland overlaps the lateral and proximal portions of the vertical ear tract, and underneath it is the facial nerve, the internal maxillary vein, and the external carotid artery branches. The facial nerve emerges from the skull (through the stylomastoid foramen) and passes under the rostroventral part of the horizontal canal (Fig. 3.27). Branches of the facial nerve and the auriculo-temporal branch of the mandibular part of the trigeminal nerve run rostrally to the vertical ear canal.

3.2

Tympanic Membrane

37

Fig. 3.10 Schematic diagram of the external, middle, and internal ear, brachycephalic breed (French Bulldog, dog). Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

3.2

Tympanic Membrane

In relation to the central axis of the horizontal ear canal, the tympanic membrane (TM) forms an angle of 45 degrees in the dog (Fig. 3.28) and 90 degrees in the cat (Fig. 3.29). It is a semi-transparent three-layer membrane that separates the external ear canal from the middle ear: it appears thin in its central portion and thicker at the periphery. The internal epithelium originates from the pharyngeal bag; the central layer consists of fibrous connective tissue of the pharyngeal wall, while the external stratified squamous epithelium derives from the formation of the ectoderm of the first pharyngeal groove and is, technically, part of the external ear canal. The TM is divided into two parts: the smaller, pink, and vascularised pars flaccida, located dorsally, and the larger pars tensa, located inferiorly (Fig. 3.30). In most dogs, the pars flaccida is noticeable and flat. This structure has the potential to dilate or “bulge” into the horizontal canal with relatively minor

38

3

Ear Anatomy

Fig. 3.11 Video otoscopic image of the right vertical ear canal, Cocker Spaniel, dog. Notice twisted and long duct conformation

Fig. 3.12 Video otoscopic image of the left vertical ear canal, French Bulldog, dog. Notice the “physiologic” stenosis (cone-shaped) of the duct typical of these breeds

3.2

Tympanic Membrane

39

Fig. 3.13 Schematic diagram of the external, middle, and internal ear, European cat. Cross-section through the skull (Source: Photo courtesy of Massimiliano Crespi)

increases in air pressure within the middle ear (Fig. 3.31). Thus, it is likely a part of the pressure-equalising system across the TM of the dog. Finding a dilated pars flaccida during ear examination is considered a normal variant in the dog and can be seen in healthy dogs and dogs with otitis externa (Fig. 3.32). A dilated pars flaccida in the Cavalier King Charles Spaniel, however, indicates primary secretory otitis media (PSOM). The pars flaccida is separated from the larger pars tensa by the malleolar fold (Fig. 3.33). The pars tensa occupies the rest of the TM. It is thin, taut and grey with radial striations. The striations extend from the handle of the malleus to the periphery of the tympanum. The manubrium (or handle) of the malleus adheres to the medial surface of the pars tensa, and its outer part, the stria mallearis, can be visualised when the TM is viewed with an otoendoscope. In the dog, the stria mallearis takes on a “C” shape, while in the cat, it is more straight, reminiscent of a “J”. Observed during otoendoscopy, the pars tensa assumes a concave appearance following the traction exerted by the manubrium of the malleus on its internal surface; the point of greatest depression is called the umbo (Fig. 3.34). Under normal conditions, the TM, following experimental rupture, regenerates between 21 and 35 days.

40

3

Ear Anatomy

Fig. 3.14 Video otoscopic image of the left vertical ear canal, German shepherd, dog. A prominent cartilaginous ridge, the luminal fold, separates the vertical from the horizontal ear canal

Fig. 3.15 Video otoscopic image of the left vertical ear canal, European cat. A sketched cartilaginous ridge, the luminal fold, separates the vertical from the horizontal ear canal

3.3

Middle Ear

41

Fig. 3.16 When the ear is in its usual position (a), the luminal fold makes otic examination of the horizontal ear canal difficult. However, when the otoendoscopist elevates this ridge by grasping the ear pinna and lifting the ear (b, c), it is possible to view the rest of the ear canal (d)

3.3

Middle Ear

The tympanic cavity is divided into three portions: dorsal, intermediate and ventral. The dorsal portion, the epitympanic recess, is the smallest and is occupied almost entirely by the head of the malleus, incus, and stapes (auditory ossicles). The baseplate of the stapes connects medially to the oval (vestibular) window. The intermediate portion (the tympanic cavity proper) is rostral and lateral to the tympanum and harbours the round window dorsomedial and auditory tube, ventromedial. The ventral, largest portion of the tympanic cavity is within the bony tympanic bulla. The ventral tympanic cavity is air-filled and is lined by respiratory epithelium with simple or cuboidal squamous epithelial cells, some ciliated, upon a thin layer of connective tissue. Small numbers of yeasts and bacteria usually inhabit the canine middle ear. The septum bulla is a bony shelf that separates the tympanic cavity from the ventral cavity or ventral bulla. In the dog, it is a narrow, incomplete ridge contacting the rostral portion of the petrous temporal bone (Fig. 3.35). It is, therefore, possible to access, sample

42

3

Ear Anatomy

Fig. 3.17 Video otoscopic image of the right horizontal ear canal, Jack Russell Terrier, dog

Fig. 3.18 Video otoscopic image of the right horizontal ear canal, European cat

3.3

Middle Ear

43

Fig. 3.19 Video otoscopic image of the right horizontal ear canal, Irish Setter, dog. If the ear is not lifted, it is possible to see the invagination of the annular cartilage in the auricular one

Fig. 3.20 Video otoscopic image of the tympanic membrane, left ear, dog. A prominent tuft of hair and cerumen is immediately distal to the tympanic membrane. In the dog, the stria mallearis is distinctly “C”-shaped

44

3

Ear Anatomy

Fig. 3.21 Video otoscopic image of the tympanic membrane, left ear, cat. The stria mallearis in cats is much more straightened and perpendicular, lacking the “C” shape observed in dogs (it looks more like a “J” shape)

Fig. 3.22 Video otoscopic image of the left ear canal, Maltese, dog. Notice the abundance of hairs

3.3

Middle Ear

45

Fig. 3.23 Video otoscopic image of the left ear canal, Poodle, dog. Notice the abundance of hairs

Fig. 3.24 Video otoscopic image of the right ear canal, Cocker Spaniel, dog. Notice the abundance of hairs and the predominance of compound follicles

and/or treat the ventral cavity. While in the cat, the septum bulla is almost complete, separating the tympanic cavity into two compartments. These are the dorsolateral and

46

3

Ear Anatomy

Fig. 3.25 Video otoscopic image of the left ear canal, cat. Notice the absence of hairs

Fig. 3.26 Video otoscopic image of the left vertical ear canal, Beagle, dog. Notice a normal vasculature

3.3

Middle Ear

47

Fig. 3.27 The caudolateral aspect of canine skull skeleton. The external ear meatus (white arrow) and the stylomastoid foramen (black arrow) are adjacent

Fig. 3.28 Video otoscopic image of the left ear canal, dog. The tympanic membrane is located at a 45
angle with the central axis of the horizontal part of the external ear canal

48

3

Ear Anatomy

Fig. 3.29 Video otoscopic image of the left ear canal, cat. The tympanic membrane is located at a 90
angle with the central axis of the horizontal part of the external ear canal

Fig. 3.30 Video otoscopic images of the tympanic membrane of the dog (left) and cat (right). Note the size difference of pars flaccida (a) and pars tensa (b). The handle of the malleus (c) is more curved in the dog and straighter in the cat. The ventral wall of the external ear canal (d) helps to direct the endoscope correctly

ventromedial tympanic cavities, which communicate through a thin cleft adjacent to the petrous temporal bone, caudolateral to the cochlear window (Fig. 3.36). The access route to the tympanic bulla is wide and ventral in the dog, while it is minute and lateroventral in the cat (Fig. 3.37). Nevertheless, care must be taken as sympathetic nerve plexus courses between the compartments, along the medial wall, through the septal communication. The tympanic tensor muscle, innervated by a branch of the trigeminal nerve, moves the malleus by contracting. The chorda tympani is a branch of the facial nerve that passes

3.3

Middle Ear

49

Fig. 3.31 Video otoscopic image of the left ear canal, dog. The pars flaccida of the tympanic membrane is normal but dilated (bulge), air-filled

Fig. 3.32 Video otoscopic image of the left ear canal, dog. The pars flaccida of the tympanic membrane is normal but dilated (bulge) in a ceruminous otitis externa

50

3

Ear Anatomy

Fig. 3.33 Video otoscopic image of the right ear canal, dog. The pars flaccida is separated from the pars tensa by the malleolar fold (black arrows)

Fig. 3.34 Schematic video otoscopic image of the right canine tympanic membrane

under the insertion of the tympanic tensor muscle and close to the pars flaccida. The tympanic tensor muscle and the stapedius muscle (innervated by the branch of the facial

3.4

Outline of the Inner Ear

51

Fig. 3.35 Schematic diagram of the inner ear, middle ear, and external acoustic meatus of a dog (Source: Photo courtesy of Massimiliano Crespi)

nerve that inserts into the stapes) have the function of protecting the middle and inner ears from loud or recurring sounds. In fact, in response to very loud or sudden sounds, they themselves contract, reducing the intensification of the sound waves. The auditory (Eustachian) tube connects the middle ear to the nasopharynx and functions to equalise pressure inside and outside the tympanic membrane and ventilate the middle ear. The short oval tube runs in the bony auditory cavity. It is lined by pseudostratified ciliated columnar epithelium, and in the dog, its maximum diameter is 1.5 mm. The tube is formed from bone in the anterior, middle ear and cartilage in the nasopharynx. The cartilaginous part opens (thanks to the elevator and tensor palatini muscle function) during swallowing.

3.4

Outline of the Inner Ear

The inner ear structures (cochlear and vestibular apparatus) are contained within promontory, a bony prominence of the petrous temporal bone on the medial side of the tympanic cavity. The oval (dorsolateral) and round (caudolateral) windows are covered with thin membranes that separate the middle ear cavity from the inner ear. The windows and the

52

3

Ear Anatomy

Fig. 3.36 Schematic diagram of the inner ear, middle ear, and external acoustic meatus of a cat (Source: Photo courtesy of Massimiliano Crespi)

tympanic membrane are intimately involved in sound transmission. The auditory ossicles form a chain within the epitympanic recess connecting the tympanic membrane to the oval window: the malleus connects to the tympanum and the incus; the incus attaches to the stapes, which in turn, is attached to the oval window. Sound waves, captured by the external ear canal, hit and oscillate the tympanum. These vibrations are increased and focused onto the oval window via the auditory ossicle chain. The vibration of the oval window creates waves within the cochlear fluid that in turn stimulate hair cells and transduction of electrical impulses to the brain and hearing. The round window acts as a rebound point for the cochlear fluid waves and is important in dispersal. Adjoined to the cochlear, the vestibular apparatus consists of the Vestibule and Semi-circular Canals and is responsible for detecting head movement and maintaining balance.

3.4

Outline of the Inner Ear

53

Fig. 3.37 Video otoscopic images of the left middle ear (skeleton) of dogs and cats. (a) top view, (b) bottom view in the dog; (c) top view, (d) bottom view in the cat. 1 ¼ round window (cochlear); 2 ¼ oval window (vestibular); 3 ¼ septum bulla; 4 ¼ auditory tube; 5 ¼ promontory; 6 ¼ tympanic bulla; 7 ¼ handle of the malleus; * ¼ window of communication between the tympanic cavity proper and the tympanic bulla in the cat

54

3

Ear Anatomy

Further Reading Bischoff MG, Kneller SK (2004) Diagnostic imaging of the canine and feline ear. Vet Clin North Am Small Anim Pract 34:437 Bloom PB (2010) Anatomy of the ear in health and disease. In: August JR (ed) Consultations in feline internal medicine, vol 6. Saunders Elsevier, St. Louis, MO, p 319 Cole LK (2009) Anatomy and physiology of the canine ear. Vet Dermatol 20(5–6):412 Cole LK (2010) Anatomy and physiology of the canine ear. Vet Dermatol 21(2):221 Cole LK (2011) Otoscopy. In: Tams TR, Rawlings CA (eds) Small animal endoscopy, vol 20, 3rd edn. Elsevier – Mosby, St. Louis, MO, pp 587–605 Cole LK, Weisbrode SE, Smeak DD (2007) Variation in gross and histological appearance of the canine pars flaccida. Vet Dermatol 18:464 Evans HE, De Lahunt AA (2013) The ear. In: Evans HE, De Lahunt AA (eds) Miller’s anatomy of the dog, 4th edn. Elsevier, St. Louis, p 731 Ghibaudo G (2010) Principi di video-otoendoscopia nel cane e nel gatto. Poletto, Milan Griffin C (2009) Otitis: anatomy every practitioner should know. Compend Contin Educ Vet 31(11): 504 Harvey RG, Harari J, Delauchea J (2001) The normal ear. In: Harvey RG, Harari J, Delauchea J (eds) Ear diseases of the dog and cat, vol 9. Iowa State University Press, Ames, IA Heine PA (2004) Anatomy of the ear. Vet Clin North Am Small Anim Pract 34(2):379 Johnson A, Hawke M (1986) An ink impregnation study of the migratory skin in the external auditory canal of the guinea-pig. Acta Otolaryngol 101(3–4):269 Kumar A (2005) Anatomy of the canine and feline ear. In: Gotthelf NL (ed) Small animal ear disease, vol 1, 2nd edn. Elsevier Saunders, St. Louis, MO Lee J et al (2006) Ultrasonographic evaluation of the external ear canal and tympanic membrane in dogs. Vet Radiol Ultrasound 47:94 Najaa BL, Cole LK, Tabacca N (2012) Practical otic anatomy and physiology of the dog and cat. Vet Clin North Am Small Anim Pract 42(6):1.109 Paterson S, Tobias K (2013) Atlas of ear diseases of the dog and cat. Wiley-Blackwell, Oxford Rosychuk R (2021) Video otoscopy. In: McCarthy T (ed) Veterinary endoscopy for the small animal practitioner, vol 10, 2nd edn. Wiley, Boca Raton, FL, pp 637–659 Stout-Graham M et al (1990) Morphologic measurements of the external horizontal ear canal of dogs. Am J Vet Res 51:990 Tabacca NE, Cole LK, Hillier A et al (2011) Epithelial migration on the canine tympanic membrane. Vet Dermatol 22(6):502

4

Video Otoscopy Procedures

In this chapter, the author describes the VOE procedures. The cytological examination has a fundamental diagnostic role in daily clinical practice. For this reason, a detailed box has been included on the methods of obtaining, preparing, examining and interpreting the cytological specimen. Deep cleaning of the external ear is the most frequent and important otological procedure for diagnosing and initiating therapy for patients with otitis. During this phase, it is possible to see masses that can be removed and examined. The use of the surgical laser in VOE is described for its features and advantages. The correct procedure to perform iatrogenic tympanic rupture (myringotomy) is discussed, and deep cleaning of the middle ear concludes this chapter.

4.1

Ear Cytology

Microscopic examination of the material present in the ear canal provides essential information for the aetiological diagnosis of otitis that is not obtainable with macroscopic evaluation alone (Box 4.1). The technique is simple, fast and cost-effective. An indirect impression smear using a cotton swab is performed. The cotton swab is gently inserted into the ear canal up to the end of the vertical canal. The cotton swab samples the correct location if the pinna is not held and pulled upwards to straighten the vertical and horizontal canals. This procedure may be performed in the conscious patient if accepted and does not cause pain or distress. Under sedation or anaesthesia, if needed, a long swab may be inserted into the otoscope cone to sample the distal vertical canal, avoiding possible surface contamination (Fig. 4.17).

# The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 G. Ghibaudo, Manual to Veterinary Video-Oto-Endoscopy, https://doi.org/10.1007/978-3-030-98911-8_4

55

56

4

Video Otoscopy Procedures

Box 4.1 The macroscopic appearance of the secretions present in the ear canal (colour, odour and consistency) can sometimes suggest the responsible etiological agent. For example: • Dark brown-black dry secretion (with a “coffee ground” appearance) may be indicative of otoacariasis (Fig. 4.1). • Moist, yellow-brown, rancid malodourous secretion may be indicative of Malassezia overgrowth (Fig. 4.2). • Abundant foul malodorous cream-yellow secretion may be indicative of bacterial infection (Fig. 4.3). Other clinical indications are the presence of purulent mucoid material (may be indicative of biofilm) or the presence of greenish-yellow purulent material associated with blood and the smell of ripe fruit (may be indicative of Pseudomonas infection). a. Microscopic examination for mites (Otodectes cynotis or Demodex canis) Otoscopic examination of the external ear canal may reveal macroscopic Otodectes cynotis (Fig. 4.4). Cytological specimens should be obtained before performing ear cleaning. A small cotton-tipped swab is inserted into the distal vertical ear canal. The collected material is mixed in a drop of mineral oil on a glass slide before placing a coverslip and examining under the microscope (Fig. 4.5). In the presence of abundant secretion, a keratolytic solution (e.g., 10% potassium hydroxide) can be used instead of oil to dissolve the debris on the slide and allow better visualisation of parasites; the sample should be left for 10–15 min before it is examined. The observation of parasites under the microscope can be optimised by partially closing the diaphragm and reducing the intensity of the microscope’s light. Like all diagnostic procedures available in skin parasitology, the method is specific (finding adult or larval forms or eggs confirms the diagnosis), but not sensitive (a negative finding does not exclude). b. Cytological evaluation of ear secretion Cytological examination of otic material provides critical diagnostic and therapeutic information. Otic cytology is required to understand the role of infectious agents (bacteria and yeasts) and allow the differentiation between overgrowth and infection. As the organisms most involved in otitis are commensals, bacterial culture is less valuable. Furthermore, serial cytological specimens during therapy will monitor the evolution of disease. The sampling procedure is described in more detail elsewhere in this chapter. In short, obtain cytological specimens from both ear canals, even in the presence of (continued)

4.1

Ear Cytology

57

Box 4.1 (continued) unilateral otitis. Slides should be pre-labelled using a pencil (Fig. 4.6). After collection, the material is transferred by gently rolling the ear swab onto the glass slide. This method is important as it prevents cellular damage that could compromise interpretation (Fig. 4.7). The slides should be air-fixed until dry. The main stains used for cutaneous and otic cytology are rapid Romanowsky-type (Emacolor®, DiffQuick®) which are also commonly used in haematology. The colouring is panchromatic and provides excellent cytoplasmic detail and microorganism shape. In contrast, the nuclear details are less appreciable than with other stains like Papanicolaou. Gram stain is not crucial in ear cytology. The bacteria involved in ear infections are usually Gram-positive coccoid bacteria (e.g. staphylococci, streptococci) and Gram-negative rods (e.g. Proteus spp., Corynebacterium spp., Pseudomonas spp., Escherichia coli). The microscopic examination of the prepared slide always starts from the lowest magnification (4) as this allows evaluation of the sample adequacy and identifies the fields of most interest. Moving then to a higher magnification (10) will refine the search and evaluate the cellularity of the preparation. The 40 magnification allows the morphological evaluation of cells and the observation of yeasts and bacteria; finally, the 100 magnification (with immersion oil) is reserved for the morphological study of the bacterial population. Cytology of a normal ear Ear cytology is rarely performed in a healthy ear of an asymptomatic patient. Good knowledge of normal ear cytology, however, is needed to understand and analyse the changes in a pathological ear canal. The typical ear canal contains a thin layer of cerumen, which lines the epidermis. Cerumen represents the secretion of the sebaceous and ceruminous glands and regular epidermal exfoliation. Under normal conditions, cerumen has a high lipid content, with poor dyeing affinity with the stain. Normal ear canal cytology is characterised by a weak colouring and the presence of few epidermal cells that have completed their differentiation. The cells of the outer layer of the epidermis, the stratum corneum, are called corneocytes or keratinised squames as they are completely keratinised and anucleated. Corneocytes are the largest cell on cutaneous cytology, but their morphology and staining are variable. They may appear white, pink, purple or blue coloured under the microscope. They can either be large, flattened, polygonal and lighter staining or folded (rolled-up), fusiform and deeper staining (Fig. 4.8). There may also be a low number of bacteria (coccoid and/or rod-shaped) and Malassezia, in the absence of inflammatory cells. Cytology of uncomplicated ceruminous otitis (continued)

58

4

Video Otoscopy Procedures

Box 4.1 (continued) In the presence of an inflammatory stimulus, there is an acceleration of the normal process of epidermal keratinisation such that the cytology of ceruminous otitis is characterised by a high number of both anucleated and nucleated corneocytes (Fig. 4.9). Cytology of bacterial otitis The bacteria found in ear cytology are of two types: coccoid-shaped and rod-shaped. In the standard stains, they appear basophilic (stained blue) and have a distinct shape: the coccoid bacteria are spherical, and the rods are elongated. A small number of bacteria, exclusively coccoid-shaped, may be present in a healthy ear. In the absence of inflammatory cells response, many bacteria are called “bacterial overgrowth” (BOG). It is not always simple to define the limit between normal and abnormal bacterial populations present in the external ear canal. Bacterial overgrowth must be differentiated from a bacterial infection in which bacteria evoke an inflammatory response, almost always neutrophilic. Neutrophil granulocytes under normal conditions are not found in the ear canal. In combination with bacterial phagocytosis, their presence is evidence of bacterial infection (Fig. 4.10). Degenerative neutrophils, characterised by nuclear (DNA) streaming, rarely remain well preserved. During ear infections, the karyolitic nuclear changes may be so severe that it is difficult to recognise them as degenerated neutrophils. Several bacterial strains produce biofilm to protect themselves from the environment and antimicrobic agents. The presence of “slimy” purulent material (Fig. 4.11) that cytologically shows amorphous proteinaceous material, incorporating bacteria and neutrophils, is highly suggestive of the presence of biofilm (Fig. 4.12). Cytology of yeast otitis Malassezia pachydermatis is a lipophilic yeast that belongs to the normal ear microbiota. In certain conditions, it becomes a pathogen, aggravating and complicating ear diseases (secondary infection). It is a unicellular yeast with a round or oval shape which, in budding, takes on the characteristic American peanut shape (Fig. 4.13). Less frequently, another yeast Candida albicans, may be identified (Fig. 4.14). Cytology of middle ear Samples are obtained from the bony tympanic bullae for cases with otitis media, otitis interna, otogenic meningitis and para-aural or brain abscessation. The aspirated material is used for cytological examination and bacterial and fungal culture and susceptibility testing. The external ear canal is first cleaned. If the tympanic membrane is intact, a myringotomy is performed using a sterile catheter or feeding tube. To facilitate this the tip of the tube can be cut at a diagonal to form a point. A sterile syringe is attached to the end of the tube. Aspirate using the syringe immediately (continued)

4.1

Ear Cytology

59

Box 4.1 (continued) after penetrating the tympanic membrane. Remove the syringe to draw in air. The material in the tube can then be expressed onto a sterile swab for culture and a labelled slide to make an impression smear. The material may be sterile or infectious. Sterile material, for example in Primary Secretory Otitis Media (PSOM) or middle ear effusion in brachycephalic breeds will reveal blue-staining mucus (Fig. 4.15)  small numbers of neutrophils, macrophages and less so, lymphocytes, eosinophils and corneocytes (Fig. 4.16); the inflammatory cells may be deteriorated and difficult to identify. In cases of cholesteatoma (tympanokeratoma), corneocytes will predominate. Infectious material will contain degenerative neutrophils and macrophages and occasionally other inflammatory cells. Microorganisms may be scarce as in deep infections of the skin so a meticulous search (e.g. in a battlement pattern) is required. Infectious otitis media is usually associated with bacteria, but other organisms, e.g. fungi may be involved. Red blood cells are expected to be present in both sterile and infectious cytological preparations. Cytology of otic masses (inflammatory or neoplastic) are discussed, with examples, in Chap. 5.

Furthermore, during VOE, it is possible to direct the swab to the most appropriate area to obtain more reliable organic material and information (Fig. 4.18). Several studies have confirmed different pathogenic bacteria in different parts of the ear canal and the middle ear

Fig. 4.1 Otoacariasis in a dog: dry discharge blackish with a “coffee ground” appearance

60

4

Video Otoscopy Procedures

Fig. 4.2 Chronic otitis externa in a dog. A moist yellowish-brown secretion is evident and suggestive of Malassezia otitis

Fig. 4.3 Purulent and ulcerative otitis externa in a dog. A Creamy yellowish secretion is present and suggestive of a bacterial infection

4.1

Ear Cytology

61

Fig. 4.4 Fresh microscopic examination. Cat’s ear secretion due to otoacariasis. An adult Otodectes cynotis is evident

Fig. 4.5 Ear cytology preparation technique with vaseline oil and coverslip

62

4

Video Otoscopy Procedures

Fig. 4.6 It is essential to mark information on the slide with a pencil. The slide is labelled with the patient and client’s name and the two ear sides of the sample

of the same ear. In cases with concurrent otitis externa and media with spontaneous tympanic membrane rupture, however, obtaining a representative sample from the middle ear for cytology  culture may not be possible. Deep ear cleaning of the external ear canal is first required to reach and view the eardrum and middle ear. This procedure could potentially mix the organic material present in the external with that in the middle ear. Nevertheless, samples can be obtained and interpreted depending on the clinical picture. In cases with otitis media  externa, samples were taken from the middle ear cavity after myringotomy is likely representative of the disease process (Fig. 4.19). Myringotomy is performed under otoendoscopic view using a needle or 5 Fr catheter as mentioned above. A sterile 5 ml syringe filled with sterile saline solution is attached to the end of the tube. The technique is like bronchoalveolar lavage (BAL). Once the tube is positioned in the tympanic bulla, the middle ear is irrigated with the saline solution, and immediately afterwards, the material is aspirated (Fig. 4.20). This organic liquid can be instilled into liquid culture media (BHI Brain Heart Infusion) and/or applied to a sterile cotton swab

4.1

Ear Cytology

63

Fig. 4.7 The swab is rolled onto a clean frosted-end microscope slide; the secretion from the left ear is rolled onto the left side of the slide, and the material from le right ear onto the right side of the slide

directly for bacterial culture and dropped onto specimen slides for routine cytological preparation. A fine-needle aspiration procedure is indicated to collect cells from masses present in the ear canal. If the tumour is easily accessible, a syringe (5–10 ml) with a needle (21–22G) is used. Cells can be sampled at different locations in the lesion, increasing the possibility of collecting representative material. Connect the needle and syringe, direct the needle into the mass, drawback the plunger and release several times. With pressure released, withdraw the needle from mass, disconnect the needle and fill the syringe with air, reconnect and gently expel the needle contents onto the glass slide. The slide is then air-dried and stained according to standard cytological techniques (rapid Romanowsky stain). The needle alone technique consists of directing the needle into the mass, withdrawing (yet staying within the lesion) and pushing back into the mass several times rapidly, rotating and moving the needle in different directions, allowing the cells to ascend by capillarity. If the lump is not

64

4

Video Otoscopy Procedures

Fig. 4.8 Cytology. Diff Quick stain. 10 magnification. A healthy canine ear canal. A small amount of ear wax and rare lanceolate corneocytes are observed

Fig. 4.9 Cytology. Diff Quick stain. 10 magnification. Ceruminous otitis in a dog. Clusters of earwax and keratinocytes are observed

easily accessible, the material can be collected during VOE using a spinal needle of a suitable length, inserted in the working channel of the otoendoscope (Figs. 4.21 and 4.22).

4.1

Ear Cytology

65

Fig. 4.10 Cytology. Diff Quick stain. 100 magnification (immersion oil). Purulent otitis in a dog. Neutrophils granulocytes in normal conditions are not found in the ear canal and during bacterial overgrowth; their presence, combined with images of bacterial phagocytosis, is direct evidence of bacterial infection (rod-shape bacteria)

Fig. 4.11 Purulent otitis from a dog. Cotton-tipped swab with slimy pus with the formation of purulent bridges suggestive of bacterial biofilm production

66

4

Video Otoscopy Procedures

Fig. 4.12 Cytology. Diff Quick stain. 40 magnification. Purulent otitis in a dog. Amorphous proteinaceous material is evident that incorporates and harnesses bacteria and neutrophils; this is highly suggestive of the presence of biofilm

Fig. 4.13 Cytology. Diff Quick stain. 100 magnification. Ceruminous otitis in a dog. Numerous corneocytes and Malasseziae characterise the cytological picture. Yeasts are free or attached to epithelial cells

4.1

Ear Cytology

67

Fig. 4.14 Cytology. Diff Quick stain. 40 magnification. Ceruminous otitis in a dog. The cytological picture is characterised by corneocytes and yeasts round-shape, suggestive of Candidiasis

Fig. 4.15 Cytology. Diff Quick stain. 40 magnification. Dog with otitis media. A large amount and thickness of homogeneous, pale to deep blue-staining mucus is evident

68

4

Video Otoscopy Procedures

Fig. 4.16 Cytology. Diff Quick stain. 40 magnification. Dog with otitis media. Inflammatory cells (a vacuolated macrophage—black arrow; a neutrophil—black asterisk) were embedded in the mucus, spread more diffusely in the background. Few bacteria are present, too (white arrows)

Fig. 4.17 Cytological sampling procedure using an ear swab in the canine external ear canal (a) introduction of the cone in the ear canal, (b) insertion of the swab into the cone, (c) insertion of the cone, (d) exit of the swab from the cone after cytological sampling in the terminal part of the vertical ear canal

4.1

Ear Cytology

69

Fig. 4.18 Video otoscopic image. Cytological sampling procedure using an ear swab in the canine external ear canal, notice a large amount of purulent material with biofilm bridges

Fig. 4.19 Video otoscopic image of the left eardrum ear. Dog. Bulging pars tensa with otitis media

70

4

Video Otoscopy Procedures

Fig. 4.20 The sampling procedure executes a myringotomy performed under otoendoscopic view (a). First, a 5 ml syringe with a sterile saline solution is attached to the needle. The technique is like bronchoalveolar lavage (BAL). Once the needle (or catheter) is positioned in the tympanic bulla, the middle ear is irrigated with the saline solution (b), and immediately afterwards, the material is aspirated (c). Then, the organic liquid can be placed in liquid culture media (BHI Brain Heart Infusion) and on a blood agar petri dish. CT in this dog confirmed a monolateral otitis media (d). At the bottom on the right of the figure, it is possible to see the different results in blood agar bacterial culture by cotton swab with several different bacterial colonies (1) and by BAL-like procedure with a unique type of bacterial colonies—Pseudomonas aeruginosa (2)

Alternatively, if a biopsy is taken from the mass, a direct impression smear can be made by gently pressing the piece of harvested tissue onto the slide several times (Fig. 4.23).

4.2

Deep Cleaning of the External Ear

Deep ear canal cleaning is a fundamental step in the diagnostic/therapeutic protocol for otitis externa. Cleaning the ear canal helps restore a normal ear environment, but it can be an obstacle to the resolution of otitis if not done correctly. Cleaning a healthy ear canal is unnecessary as it can increase humidity and promote maceration of the duct, predisposing to secondary infections.

4.2

Deep Cleaning of the External Ear

71

Fig. 4.21 Video otoscopic image of the external ear canal. Dog. A needle is reaching the lesion under endoscopic view

Fig. 4.22 Anatomic drawing. Dog. A needle is inserted into the lump in the ear canal under otoendoscopic vision (Source: Photo courtesy of Massimiliano Crespi)

72

4

Video Otoscopy Procedures

Fig. 4.23 A nodule, surgically removed from a canine ear canal, is applied several times onto the slide to obtain a cytological specimen

The purpose of ear cleaning is both diagnostic and therapeutic: • Remove abundant secretions to inspect the ear canal and eardrum. • Remove foreign bodies that may be minuscule and hidden within the secretion. • Remove organic material which can inactivate antimicrobials, e.g. aminoglycosides, polymyxin B and bacitracin, and act as an inflammatory stimulus. • Remove purulent material with bacteria and their toxins to avoid the perpetuating development of ulceration in the ear canal. Deep ear cleaning can only be performed under general anaesthesia. The use of endotracheal intubation is essential to prevent the risk of aspiration of ear fluids via the auditory tube in the presence of a tympanic membrane perforation. The operator must wear protective gloves to minimise the risk of contamination related to ear secretions. In addition, the patient must have adequate eye protection to prevent contact with cleaning liquids during the procedure.

4.2

Deep Cleaning of the External Ear

73

Fig. 4.24 Image of two dogs before (a) and after (b) the clipping of the concave pinna. Note that the intretragic notch is only visible after shearing

The collection of samples for complementary examinations (ear cytology and culture) and any diagnostic imaging investigation must be carried out before VOE and lavage. The removal of hair from the ear canal, if not necessary, is not recommended as it can cause an additional inflammatory stimulus. Moreover, depilatory creams should be avoided as they are potentially irritating and sensitising. It is, however, helpful to trim the concave pinnae and clip the tuft of hair that comes out of the external auditory meatus; only after trimming, the intertragic notch is visible (Fig. 4.24). An aqueous ceruminolytic agent (e.g. dioctyl sodium sulfosuccinate and carbamide peroxide) could be used to speed up the removal of organic material. The ceruminolytic agent is applied 5 min before ear cleaning, gently massaging the base of the ear to increase its effect. However, with a tympanic membrane rupture, the use of cerumenolytics agents (except squalene) into the canals is contraindicated. They should only be used on the pinnae and ear folds (Fig. 4.25). After their use, it is essential to remove them entirely from all skin surfaces by deep cleaning with a lukewarm saline solution. Saline solution is a safe, non-irritating irrigation liquid for otitis externa and media. The fluid should, however, be warmed to body temperature to reduce ear stimulation and avoid vertigo phenomena. Irrigation is ideally done with a simple gravity-fed bag of lukewarm

74

4

Video Otoscopy Procedures

Fig. 4.25 The application of an aqueous ceruminolytic agent speeds up the cleaning of the pinna and ear folds. Foaming agents (e.g. carbamide peroxide) allow the detachment of the organic material. The use of soft sponges and wet with lukewarm water allows the total removal of the product. A rash is typical to see for a few minutes

saline via a standard administration set. The author, however, prefers to use a pressure bag (Fig. 4.26). Again, an irrigation/suction pump can be used (Fig. 4.27) via an irrigation cannula delivered through the endoscope’s working channel. This keeps the field of view clear intra-operatively and removes collected blood and debris. With the otoendoscope assembly held pistol-style in one hand, the tip of the pinna is held in the other hand and retracted dorsally (Fig. 4.28). This action opens the vertical canal to ease access to the endoscope. Next, the otoendoscope is placed in the intertragic notch and angled ventrally into the vertical canal (Fig. 4.29). As soon as entering the canal with an otoendoscope, start the irrigation (Fig. 4.30) and wait a few moments until the view of the canal is sufficiently clear (Fig. 4.31). Finally, at the base of the vertical canal, the endoscope is deflected medially towards the patient’s head into the horizontal canal (Fig. 4.32). With continued traction on the pinna and ongoing saline irrigation, this motion should allow visualisation of the eardrum (Fig. 4.33). Any debris and plugs of earwax (ceruminolyth) that, after cleaning, remain adhered to the wall of the duct or near the tympanic membrane can be removed mechanically using a curette, forceps or a catheter introduced inside the working channel. The instrument of

4.2

Deep Cleaning of the External Ear

75

Fig. 4.26 Ear cleaning can be performed using a squeezer bag with a 2-litre saline solution (at a body temperature)

Fig. 4.27 Karl Storz Vetpump2 is a suction/irrigation pump to perform ear cleaning

76

4

Video Otoscopy Procedures

Fig. 4.28 Anatomic drawing. Dog. Position to view the vertical ear canal, the otoendoscope assembly held pistol-style in one hand, the tip of the pinna is held in the other hand and retracted dorsally (Source: Photo courtesy of Massimiliano Crespi)

choice is placed close to the plug and rotated above the residue before gently extracting (Fig. 4.34). Alternatively, the aspirator can be used via the catheter to remove the material by suction (Fig. 4.35). Using a 5 Fr diameter catheter, debris commonly blocks the catheter, so it is necessary to exit the ear to flush it out (Fig. 4.36) or cut the blocked tube tip (Fig. 4.37) with scissors before continuing the procedure. The use of an otobrush allows hair and debris to be collected and removed from the ear canal. The insertion into the working channel must continue until the otobrush is seen

4.2

Deep Cleaning of the External Ear

77

Fig. 4.29 The otoendoscope is placed in the intertragic notch and angled ventrally into the vertical canal in a canine left ear canal

Fig. 4.30 Karl Storz Otoscope details of the 2-ways stopcock: to allow irrigation to start, the tap indicated by the arrow must be in this position

78

4

Video Otoscopy Procedures

Fig. 4.31 As soon as entering the vertical ear canal, wait for the irrigation to detach and remove the organic material (1, 2, 3). Then, when the view becomes clear (4), continue with the insertion of the otoscope deeper into the ear

dorsally. Then, rotational movement on its axis is repeated by positioning the instrument at the desired level of the duct (Fig. 4.38). Finally, removing the otobrush and the endoscope from the canal must be synchronous. During ear cleaning, foreign bodies, such as vegetal ones like awns, can be detected and removed by grasping them with endoscopic forceps (Fig. 4.39). Once the tympanic integrity has been assessed, ear cleaning is ended by completely aspirating the liquid. If not contraindicated, instilling a few drops of cleansing solution with astringents such as salicylic or lactic acid can reduce residual moisture and prevent maceration. Local therapies are chosen based on the diagnostic information (cytology, tympanic integrity, degree of inflammation and otitis staging through diagnostic imaging tests). Pain relief should be prescribed during and after deep ear cleaning. Complications from deep ear cleaning are rare and often transitory in the dog while more frequent in the cat. Informed owner consent, however, is required before undertaking such procedures. In addition, frequent head shaking and/or other signs of otic irritation can indicate inadequate analgesia and/or anti-inflammatory medication. After inflammatory polyp removal, cats may develop vestibular disease with incoordination, falling or circling to one side, horizontal nystagmus, and head tilt (Fig. 4.40), and often nausea or vomiting and/or Horner’s syndrome. Symptoms are often transient and last a few weeks.

4.3

Biopsy and Mass Removal

79

Fig. 4.32 Anatomic drawing. Dog. Position to view the horizontal ear canal, at the base of the vertical canal, the endoscope is deflected medially towards the head into the horizontal canal (Source: Photo courtesy of Massimiliano Crespi)

4.3

Biopsy and Mass Removal

During ear cleaning, it is possible to detect the presence of ductal masses (Fig. 4.41). In this case, it is necessary to perform cytology and biopsies for histopathological examination. Manual mass removal can be done by grasping the lesion with endoscopic forceps (Figs. 4.42 and 4.43) or tiny curved haemostatic forceps and gentle traction. While this

80

4

Video Otoscopy Procedures

Fig. 4.33 Anatomic drawing. Dog. Position to view the eardrum, the hand holding the pinna must go down, and the hand holding the endoscope must push medially, keeping the instrument as horizontal as possible (Source: Photo courtesy of Massimiliano Crespi)

can be an effective technique, the subsequent haemorrhage (Fig. 4.44) can make the rest of the otoendoscopic examination difficult (Fig. 4.45).

4.4

Laser Surgery

Diode lasers used for surgery generate laser energy via a semiconductor chip that emits light (photons) energy. Diode laser energy is absorbed by haemoglobin, oxyhaemoglobin, and melanin (so-called chromophores). As a result, lasers have anti-oedema, anti-inflammatory, and pain-relieving properties, so the patient has less postoperative swelling and pain. In addition, most of the ears operated on are infected, and laser energy effectively sterilises the surgical site, so there is minimal ear preparation required for these procedures.

4.4

Laser Surgery

81

Fig. 4.34 Video otoscopic image. Dog. A ceruminous plug is adjacent to the eardrum (1). A 5 Fr catheter was introduced inside the working channel. It is placed close to the plug (2) and rotated above the residue (3) before gently extracting (4)

The diode lasers help perform myringotomies, ablation of proliferative inflammatory lesions and control haemorrhage. Ideally, a diode laser has 810 or 980 nm wavelengths. These wavelengths are in the near-infrared region of the electromagnetic spectrum; diode laser energy in the 980 nm range is also absorbed by water. This feature makes the 980 nm a more effective excisional and dissection tool than the 810. Diode surgical lasers penetrate more deeply than CO2 lasers; therefore, the underlying structures at the surgical site must be considered during treatment planning. Iatrogenic carbonisation, necrosis or underlying tissue damage are potential contraindications, especially for beginners. For this reason, with the diode laser is true the sentence: “What you don’t see can hurt you”. Diode laser energy is delivered via a flexible silica fibre with plastic or silicone cladding. These fibres are available in various diameters from 300 to 1000 μm used in free-beam contact mode (Fig. 4.46). Powers of 3–4 W (Watts) are usually needed, although thicker nodules or less vascular tissues require more laser bream power. The contact mode may be used in pigmented tissues to deliver the laser energy to the tissue directly. In less or non-pigmented tissues, a thin layer of char (Fig. 4.47) should be created on the tip of the fibre to enhance the delivery of thermal energy to the target. This layer of char absorbs the diode laser energy and converts it to thermal energy. The thermal energy is then directly transferred to the tissue, causing vaporisation. With the

82

4

Video Otoscopy Procedures

Fig. 4.35 Video otoscopic image. Dog. A ceruminous plug is adjacent to the eardrum (1). A 5 Fr catheter was introduced inside the working channel. An aspirator connected with a tube to the catheter is activated, and the plug (2, 3) is removed from the ear canal. After this procedure, it is possible to view the tympanic membrane (4)

Fig. 4.36 A 5 Fr diameter catheter, the debris frequently blocks the tip, so it is necessary to exit from the ear and clean the tube

4.4

Laser Surgery

83

Fig. 4.37 Sometimes it is impossible to clean the blocked catheter. In this case, it is necessary to cut the distal blocked part of the tip with scissors before continuing the procedure

Fig. 4.38 The use of otobrush allows hair and debris to be collected and removed from the ear canal

84

4

Video Otoscopy Procedures

Fig. 4.39 Video otoscopic image. Dog. An awn is grasped and removed with endoscopic forceps from an ear canal

non-immersion fibre mode, a cloud of smoke is produced and, during the resting phase, is dissipated by air through the laser tip (Fig. 4.48). If a continuous wave exposure is chosen, the surgeon must periodically stop to allow smoke dissipation. A modality that avoids the vision of smoke and material that can obliterate the otoscope is to operate in immersion (irrigation). This method also allows the control of the saline solution temperature; bubble formation indicates that 100  C is exceeded (Fig. 4.49), and there is the risk of carbonisation. The procedure should be stopped immediately for a while to taper the temperature. The fibre is inserted into the endoscope’s working channel, and the laser is fired on a continuous cutting mode. The mass is vapourised by progressive cranial-to-caudal, backand-forth cutting motion in a continuous (not more than 3–4 seconds) or short-pulse mode (Fig. 4.50). This procedure usually allows for serial resection of the lesion, allowing the operator to identify its point of origin, paying particular attention to surgical margins (Fig. 4.51). With the laser resection complete, there may be pieces of charred tissue that require removal (Fig. 4.52) with biopsy or rat-tooth-type forceps. Another technique that detaches the mass is debulking with the laser fibre, which vaporises the attachment base of the lump. Subsequent laser treatment of the canal area where the mass was attached is necessary for haemostasis and removal of neoplastic cells (Fig. 4.53).

4.5

Myringotomy

85

Fig. 4.40 Head tilt in a cat with an inflammatory polyp

4.5

Myringotomy

Myringotomy is the surgical incision of the intact eardrum. It is performed under general anaesthetic. It is indicated when access to the middle ear is required for sample collection, drainage, cleaning, and administration of drugs. It may also be helpful for inserting a trans tympanic drain. The ear canal is cleaned and subsequently dried by aspiration before myringotomy. A sterile 5 Fr polypropylene catheter with the tip cut at a 45-degree angle or a rigid spinal

86

4

Video Otoscopy Procedures

Fig. 4.41 Video otoscopic image. Dog. A nodule is evident in a left vertical ear canal

Fig. 4.42 Video otoscopic image. Dog. A lump is grasped and removed with endoscopic forceps from an ear canal

4.5

Myringotomy

87

Fig. 4.43 Video otoscopic image. Dog. A nodule is grasped and removed with endoscopic forceps from an ear canal—notice haemorrhage after the procedure

Fig. 4.44 Video otoscopic image. Dog. Haemorrhage after a mass was grasped and removed with endoscopic forceps from an ear canal. (Source: Photo courtesy of Massimiliano Crespi)

88

4

Video Otoscopy Procedures

Fig. 4.45 Video otoscopic image. Dog. Abundant haemorrhage after a mass was grasped and removed with endoscopic forceps from an ear canal

Fig. 4.46 Laser fibres of various diameters 300 and 800 μm

4.5

Myringotomy

89

Fig. 4.47 Notice a layer of char on the tip. The activated laser fibre can be used in non-pigmented tissues

Fig. 4.48 Video otoscopic image. Ear canal of a dog. A cloud of smoke is produced by laser fibre (a), during the resting phase, the fog disappears (b)

needle can be used to make the incision. The tip of the catheter/needle continually advances under a good otoendoscopic visualisation. The pars tensa is perforated in the 5–7 o’clock area (Figs. 4.54, 4.55, and 4.56) to avoid vessels present in the pars flaccida and the malleus of the manubrium. The landmark is evident when the eardrum is visible (Fig. 4.57). With good postoperative medical management, the canine and feline tympanum usually heal quickly within 3–4 weeks. Alternatively, following the same procedure, a myringotomy can be performed with the laser fibre (Fig. 4.58) so that surgical healing of

90

4

Video Otoscopy Procedures

Fig. 4.49 Video otoscopic image. Ear canal of a dog. Bubble formation is produced by laser fibre during the removal of a mass in immersion mode

Fig. 4.50 Video otoscopic image. Dog. Multilobulated tumour in the external ear canal. The mass is vapourised by laser fibre

4.5

Myringotomy

91

Fig. 4.51 Video otoscopic image. Dog. Ceruminous gland adenoma in the external ear canal. The tumour is vapourised by laser fibre, and it is possible to identify its point of origin

Fig. 4.52 Video otoscopic image. Dog. A tumour in the external ear canal. The mass is vapourised by laser fibre and is visible as charred tissue

92

4

Video Otoscopy Procedures

Fig. 4.53 Video otoscopic image. Dog. Ceruminous gland adenoma in the external ear canal. The tumour is debulked by laser fibre, and it is possible to identify its point of origin for treatment

Fig. 4.54 Video otoscopic image. Dog. Tympanic membrane with the clock face, where to identify the area suitable for performing the myringotomy (the pars tensa is perforated in the 5–7 o’clock area)

4.5

Myringotomy

93

Fig. 4.55 Video otoscopic image. Cat. Tympanic membrane with the clock face, where to identify the area suitable for performing the myringotomy (the pars tensa is perforated in the 4–6 o’clock area)

Fig. 4.56 Video otoscopic image. Cat. Myringotomy technique. The black arrow indicates the hole after the procedure

94

4

Video Otoscopy Procedures

Fig. 4.57 Video otoscopic image. Dog. Myringotomy technique. When the eardrum is visible, the landmark is evident

the tympanum is delayed. This can be advantageous in cases that require longer periods of drainage, for example, PSOM. In cases where the tympanic membrane is not visible (chronic stenotic otitis or due to breed anatomy), it is recommended to move away from the eardrum and slide the catheter following the anatomy ear (Fig. 4.59). The catheter, in this way, rests on the floor of the ear canal and, following the duct, penetrates the eardrum in the safe area of the pars tensa to enter the middle ear cavity ventrally. This procedure prevents the catheter from being positioned dorsally, the anatomical area to avoid (promontory with oval and round windows and the branches of the sympathetic and parasympathetic nerves).

4.6

Deep Cleaning of the Middle Ear

This procedure is paramount for the successful medical management of otitis media. It allows the removal of the middle ear secretions that represent a perpetual inflammatory stimulus for the mucoperiosteum. The procedure must be performed with the utmost

4.6

Deep Cleaning of the Middle Ear

95

Fig. 4.58 Video otoscopic image. Dog. Myringotomy technique. The pars tensa is perforated by a laser fibre

Fig. 4.59 Video otoscopic image. Dog. Myringotomy technique. When the eardrum is not visible, move away from the eardrum and slide the catheter following the anatomy ear

96

4

Video Otoscopy Procedures

Fig. 4.60 Anatomic drawing. Dog. Position to make a myringotomy incision and perform deep ear cleaning of the middle ear. (Source: Photo courtesy of Massimiliano Crespi)

delicacy, and the patient must always be under deep general anaesthesia. The otoendoscope is introduced inside the external ear canal until the tympanic membrane, if present, is visualised. The tympanic membrane may already be perforated (Fig. 4.60); otherwise, a myringotomy is required. Next, a feeding probe or 5 Fr catheter is introduced into the endoscope’s working channel. The catheter is pushed into the middle ear by directing the tip of the probe ventrally (tympanic bulla) to avoid damaging the delicate structures located dorsally (tympanic cavity proper) (Figs. 4.61 and 4.62). Once the material has been collected for any diagnostic examination (Fig. 4.63), it is possible to start cleaning using

4.6

Deep Cleaning of the Middle Ear

97

Fig. 4.61 Schematic model of the external, middle and internal ear. Dog. Cross-section through the skull. Position to make myringotomy incision and deep ear cleaning of the middle ear

Fig. 4.62 Video otoscopic image. Deep cleaning of the middle ear in a dog with the eardrum entirely ruptured. The catheter is positioned in the tympanic bulla (white arrow). Note where the tympanic cavity proper is (asterisk), and the remaining pars tensa remains in place (black arrows)

98

4

Video Otoscopy Procedures

Fig. 4.63 VOE in a French Bulldog. Note the syringe with a sterile saline solution connected through a catheter into the middle ear. In PIP (picture in picture), you can see the brownish mucoid material taken after the BAL-like technique

a continuous irrigation-aspiration technique until debris is not evident in the catheter (Fig. 4.64). The cleaning solution must not be ototoxic or irritating; physiological saline solution at body temperature is recommended. Although infrequent, the patient can develop transitory vestibular clinical signs and/or deafness following the procedure due to the mechanical stimulation of liquids on the oval and round windows (Fig. 4.65). Deep

4.6

Deep Cleaning of the Middle Ear

99

Fig. 4.64 Video otoscopic image. Dog. Deep middle ear cleaning. It is crucial to view the catheter’s colours (yellow-brown combined to red) using a continuous irrigation-aspiration technique until no more debris is evident in the catheter (transparent like in 1 e 4)

cleaning of the middle ear is painful, so it is advisable to administer an opioid analgesic such as butorphanol or methadone during and at the end of the anaesthesia.

100

4

Video Otoscopy Procedures

Fig. 4.65 Head tilt in a Bulldog with labyrinthitis after an aggressive deep ear middle ear cleaning

Further Reading Albanese F (2016) Canine and Feline Skin cytology: a comprehensive and illustrated guide to the interpretation of skin lesions via cytological examination, 1st edn. Springer, New York Angus JC (2004) Otic cytology in health and disease. Vet Clin North Am Small Anim Pract 34:411 Angus JC, Campbell KL (2001) Uses and indications for video-otoscopy in small animal practice. Vet Clin North Am Small Anim Pract 31(4):809–828 Apostolopoulos N, Glaeser SP, Bagwe R et al (2021) Description and comparison of the skin and ear canal microbiota of non-allergic and allergic German shepherd dogs using next generation sequencing. PLoS One 16(5):e0250695 Berger N, Eeg PH (2006) Veterinary laser surgery. A practical guide. Blackwell, London Boord M (2006) Laser in dermatology. Clin Tech Small Anim Pract 21(3):145–149

4

Further Reading

101

Cole LK (2009) Anatomy and physiology of the canine ear. Vet Dermatol 20(5–6):412–421 Cole LK (2011) Otoscopy. In: Tams TR, Rawlings CA (eds) Small animal endoscopy, vol 20, 3rd edn. Elsevier – Mosby, St. Louis, MO, pp 587–605 Ghibaudo G (2010) Principi di video-otoendoscopia nel cane e nel gatto. Poletto Editore, Milan, p 109 Ghibaudo G (2011) Otoendoscopia, Chapter 9. In: Bottero E, Ruggiero P (eds) Endoscopia negli animali d’affezione. Testo Atlante. Poletto Editore, Milan, pp 157–172 Ginel PJ, Lucena R, Rodriquez JC et al (2002) A semiquantitative cytological evaluation of normal and pathological samples from external ear canal of dogs and cats. Vet Dermatol 13:151 Gotthelf LN (2019) Laser surgery procedures of the ear. In: Winkler CJ (ed) Laser surgery in veterinary medicine, vol 10, 1st edn. Wiley, Boca Raton, FL, pp 106–115 Milne E, Nuttall T, Marioni-Henry K et al (2020) Cytological and microbiological characteristics of middle ear effusions in brachycephalic dogs. J Vet Intern Med 34(4):1454–1463 Njaa BL, Cole LK, Tabacca N (2012) Practical otic anatomy and physiology of the dog and cat. Vet Clin North Am Small Anim Pract 42(6):1109–1126 Reinbacher E et al (2020) Myringotomy in dogs: contamination rate from the external ear canal: a pilot study. Vet Anim Sci 10(100125):18 Rosychuk R (2021a) Video otoscopy. In: Veterinary endoscopy for the small animal practitioner, vol 10, 2nd edn. Wiley, Boca Raton, FL, pp 637–659 Rosychuk R (2021b) Video otoscopy. In: McCarthy T (ed) Veterinary endoscopy for the small animal practitioner, vol 10, 2nd edn. Wiley, Boca Raton, FL, pp 637–659 Sobel DS (2012) Endoscopy of the canine and feline ear: otoendoscopy. In: Ragni SA, Moore AH (eds) Clinical manual of small animal endosurgery, vol 9, 1st edn. Blackwell, London, pp 256–272 Stevens-Sparks CK, Strain GM (2010) Post-anesthesia deafness in dogs and cats following dental and ear cleaning procedures. Vet Anaesth Analg. 37(4):347–351 Tater KC, Scott DW, Miller WH et al (2003) The cytology of the external ear canal in the normal dog and cat. J Vet Med A Physiol Pathol Clin Med 50:370

5

Indications of VOE in Canine and Feline Ear Diseases

This last chapter includes all the external and middle ear pathologies where VOE is indicated as a diagnostic procedure. Congenital diseases are briefly mentioned before discussing acquired diseases in detail. According to how much time passes from the onset of the ear problem, otitis is divided into acute and chronic forms. This section discusses the diagnostic imaging tests used to set up a diagnostic algorithm (staging of otitis) that have implications on the most appropriate choice of therapy and prognosis. Finally, a mention is made on the diagnosis of deafness and which tests are indicated.

5.1

Congenital Diseases

5.1.1

Ear Canal Atresia and Malformations

Congenital atresia of the external auditory meatus and ear canal is extremely rare in dogs and humans. Atresia can occur with and without abnormal development of the pinna; the most common auricular pathology is microtia (hypoplasia of pinna). If the onset atresia is very early, it is likely to be congenital within the first few months of life. However, it is important to consider that trauma of the ear canal resulting in cicatricial canal stenosis may mimic atresia of the meatus or duct (Fig. 5.1). Canal atresia results in otic inflammation and cerumen accumulation within the external canal  and the middle ear if the tympanic membrane is not intact. Therefore, clinical signs include otic pain, headshaking, and paraaural abscesses of the affected ear. Usually, bacteria cultures from the contents of the external and middle ear canals are sterile. A surgical approach to correct congenital deformities is required, e.g. total ablation of the ear canal and lateral bulla osteotomy (TECALBO), drainage of the vertical canal and others. Cat eye syndrome (a rare disorder

# The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 G. Ghibaudo, Manual to Veterinary Video-Oto-Endoscopy, https://doi.org/10.1007/978-3-030-98911-8_5

103

104

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.1 Video otoscopic image. Unilateral ear canal atresia in a two-year-old dog. Note the complete absence of the right ear duct in comparison to the normal left one

5.1

Congenital Diseases

105

of chromosome 22) may also feature auricular malformations along with coloboma and heart and renal anomalies. Box 5.1 Diagnostic Imaging Diagnostic imaging plays a fundamental role in establishing the severity and extent of the ear disease. All procedures are performed under general anaesthesia. The diagnostic process is often completed during the same session by combining techniques, for example, endoscopy with either radiographic/CT or MRI examination. This diagnostic approach allows the patient to be staged and treated for otitis under one anaesthesia. About 20% of canine chronic otitis externa cases are associated with occult otitis media, and this percentage could be significantly reduced by using diagnostic imaging. a. Radiology Radiology is the most used diagnostic imaging procedure, although, in recent years, it has been progressively supplanted by more advanced procedures such as CT scan (computed tomography) and MRI (magnetic resonance imaging). The radiographic examination can provide information on the cartilages of the external ear canal if, for example, auricular and annular cartilages are mineralised (due to chronic inflammatory metaplasia) (Fig. 5.2). In addition, radiography detects severe bony alterations of the tympanic bulla, e.g. thickening, irregularities, erosion, reactive phenomena, and on the contents of the tympanic bulla (air or dense material, vascularised or not) (Fig. 5.3). The alterations, however, are generally non-specific. Therefore, especially in advanced disease states, radiography must be correlated with the clinical and video otoscopic findings and laboratory results (cytological, histological, and microbiological examinations) to confirm the diagnosis. The most useful are the dorsoventral (or ventrodorsal) and rostrocaudal (open mouth) views. These views enable comparisons between the left- and right-hand sides to aid abnormality recognition. However, in each view, the tympanic bullae are superimposed on other parts of the skull, complicating interpretation (Fig. 5.4). An additional projection that minimises superimposition is the left (or right) 20 ventral-right (or -left) dorsal oblique view. In cats, the rostro-10 ventralcaudodorsal (closed-mouth) projection is an alternative to the rostrocaudal (open-mouth) view (Fig. 5.5). Both projections enable good visualisation of the tympanic bullae. b. Computed Tomography Computed tomography (CT) is based on the same physical principles as radiography and produces images resembling radiographs of body sections. A significant advantage of cross-sectional images is the ability to examine structures without the confusing effect of superimposition. CT images of the ears are usually (continued)

106

5

Indications of VOE in Canine and Feline Ear Diseases

Box 5.1 (continued) acquired in the transverse plane using thin contiguous slices (1
5 mm) and a highresolution reconstruction algorithm. Patients are usually placed in sternal recumbency, with the head supported in a padded trough to facilitate stable and symmetrical positioning (Fig. 5.6). The scanning time is usually about 1 min. CT enables a relatively detailed examination of the ears and adjacent structures. As in conventional radiographs, air and bone can be readily distinguished, making CT an excellent choice for imaging the middle ear (Fig. 5.7). If abnormalities are suspected in other structures, such as the brain, a second CT scan with settings more appropriate for the brain can be acquired. A repeat CT scan following intravenous administration of organic iodide contrast medium may aid the detection of lesions affecting soft tissues because the contrast medium tends to accumulate in vascular structures (Fig. 5.8). A CT study is indicated when a disease confined to the middle ear is suspected without neurological symptoms. Poor bone definition on MRI prevents satisfactory examination of the tympanic bulla wall and visualisation of the ossicular chain and tympanic membrane. In addition, the air signal usually present in the tympanic bulla is like that of the bone wall, preventing visualisation of the air/bone boundary. CT scan is better to detect auricular and annular cartilage mineralisation and ear canal alterations (Fig. 5.9). In addition, a CT scan is helpful to identify bone damage often associated with malignant external (Fig. 5.10) and middle ear neoformations (Figs. 5.11 and 5.12). c. Magnetic resonance imaging Since its first applications in the veterinary field, magnetic resonance imaging (MRI) has been widely used in middle and inner ear investigations. This examination’s information is complementary, rather than a substitute, to that obtainable with a CT scan. It would therefore be ideal, in cases where the diagnostic protocol requires an investigation of the region of the tympanic bulla, to perform both tests. Unfortunately, this is infrequently achievable, both for the rarity of the simultaneous availability of the two devices and for the associated costs. The choice to do an MRI or CT scan should be based on diagnostic suspicions and indications of other tests already performed. A middle ear diagnostic study based on conventional radiography is inferior to advanced imaging that should be used as a standard diagnostic method. MRI is not indicated to investigate the osteolytic and osteoproductive tympanic bulla processes. MRI is the first-choice exam in many other cases. • Non-infectious secretory forms, often asymptomatic and without changes in the bone wall (PSOM—Primary Secretory Otitis Media; OME—Otitis Media (continued)

5.1

Congenital Diseases

107

Box 5.1 (continued) with Effusion); typical of Cavalier King Charles Spaniels, they are often an occasional finding in studies carried out for the investigation of other pathologies (Fig. 5.13). • Presence of peripheral vestibular symptoms, which involve the involvement of the structures of the inner ear or the vestibulocochlear nerve, which cannot be otherwise explored. Furthermore, in the acute phase of a significant number of vestibular cases, it may be difficult to distinguish clinically whether the symptoms are central or peripheral. Therefore, in addition to the tympanic bullae, it is essential to explore the brain stem, the cerebellum and the cerebellopontine angle during the same study. This investigation can be satisfactorily performed using MRI, which, unlike CT, allows a good analysis of these structures contained in the posterior fossa. • Presence of trigeminal nerve neoplasms (Fig. 5.14); sometimes associated with effusion within the ipsilateral tympanic bulla. • Symptoms referable to dysfunctions of the facial nerve may occur with pathologies of the tympanic bulla due to their close anatomical relationships. Consequently, a pathology of the tympanic bulla must be suspected whenever there is a deficit of the facial nerve, regardless of the detection of signs referable to otitis. In these cases, MRI is useful in evaluating the presence of otitis media and evaluating the same nerve in its intratemporal portion, highlighting alterations of its signal even in the absence of pathologies in the tympanic bulla (so-called idiopathic forms). • Clinical suspicions of meningitis-meningoencephalitis secondary to the intracranial extension of infections originating from the middle-inner ear via the vessels and nerves present in the internal acoustic meatus. MRI can provide information on the state (acute, sub-acute or chronic) of the process. This occurrence is more common in cats than dogs (Fig. 5.15). The study of the middle-inner ear must be carried out with T1 and T2 weighted sequences, before and after the administration of paramagnetic contrast medium, on the transverse and dorsal planes, which allow the comparison between the right and left sides. T2 or T2-like sections with a thickness of less than 1 mm can highlight the structures of the inner ear very well. d. Ultrasonography Ultrasonography has some advantages for clinical use in otic imaging in that it is relatively quick, non-invasive and may be used in conscious patients. In a normal animal, the air within the external and middle ear effectively blocks ultrasound transmission. However, if the external ear is filled with saline or the middle ear contains fluid or solid material due to disease, the ultrasound beam may be transmitted through the ear, and its internal structure may be examined.

108

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.2 Ventrodorsal radiograph projection of a dog with bilateral dystrophic calcification or mineralisation of the external ear cartilages (white arrows). This appearance is observed in animals with advanced otitis externa

Fig. 5.3 Ventrodorsal radiograph projection of a dog with mild bilateral dystrophic mineralisation of the external ear cartilages (white arrows). The walls of the right bulla are markedly thickened, and the tympanic bulla appears opaque (dense material). (White asterisk): right otitis media

5.1

Congenital Diseases

109

Fig. 5.4 Ventrodorsal radiograph of a healthy dog. An open-mouth projection allows to visualise both tympanic bullae and make comparisons

Fig. 5.5 Ventrodorsal radiograph of a healthy cat. The rostro-10 ventral-caudodorsal (closedmouth) projection allows to visualise both tympanic bullae and make comparisons

110

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.6 CT Scan room. Patients are usually placed in sternal recumbency, with the head supported in a padded trough to facilitate stable and symmetrical positioning

5.1

Congenital Diseases

111

Fig. 5.7 Transverse CT soft tissues window, at the level of the ears in a healthy Sharpei; dog. The anatomy of the ear canals and the middle and inner ears are visible (Source: Photo courtesy of CentroTacVet)

Fig. 5.8 Transverse CT soft tissues window, of the same dog of the previous figure; following intravenous administration of organic iodide contrast medium: soft tissues and vascular structures are evident (Source: Photo courtesy of CentroTacVet)

112

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.9 Transverse CT bone window of a dog with chronic otitis. Slight thickening of the wall of the external ear canals and a small amount of tissue material in the deep portion of the ear canals. Mild cartilage mineralisation. A small amount of fluid attenuation material ventrally in the left tympanic bulla (Source: Photo courtesy of CentroTacVet)

Fig. 5.10 Transverse CT soft tissues window of a dog with a right ear canal sebaceous glands adenocarcinoma. Mass infiltrating the surrounding soft tissues with strong contrast medium enhancement. Furthermore, the mass involves the ipsilateral tympanic bulla (Source: Photo courtesy of Centro Veterinario Futuravet)

5.1

Congenital Diseases

113

Fig. 5.11 Transverse CT soft tissues window of a dog with middle ear cholesteatoma. Non-aerated right tympanic bulla due to accumulation of tissue density material with heterogeneous contrast enhancement and hypodense cavity areas in their context (Source: Photo courtesy of Centro Veterinario Futuravet)

Fig. 5.12 Transverse CT soft tissues window of a one-year-old cat with left monolateral otitis externa and media. A lesion occupies the horizontal ear canal and the middle ear, compatible with an inflammatory polyp (Source: Photo courtesy of Centro Veterinario Futuravet)

114

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.13 Transverse MR post-contrast T1-weighted image (a) T2-weighted image (b), of a Cavalier King Charles Spaniel with PSOM. Note the presence of opaque material in both tympanic bullae

Fig. 5.14 Transverse MR post-contrast T1-weighted image of a dog with a trigeminal tumour. Hyperintense neoformation in the T2-weighted sequences, isointense in the T1-weighted sequences of the trigeminal nerve presents with defined margins and ovoid shape. This mass determines the compression of the adjacent parenchymatous structures (Source: Photo courtesy of Centro Veterinario Futuravet)

5.2

Acquired Diseases

115

Fig. 5.15 Transverse MR post-contrast T1-weighted image (a) T2-weighted image (b), of a French bulldog with otogenic meningoencephalitis. Accumulation of hyperintense material in the long TR sequences within the right tympanic bulla. Same hyperintensity of the signal on the soft tissues ventrally to the bulla with a collection of material with defined margins and rounded shape, diameter about 1.5 cm; diffuse and homogeneous acquisition of contrast medium. Signal hyperintensity in T2-weighted and FLAIR sequences of the emergence of the right vestibulocochlear and facial nerves and the ipsilateral cerebellar peduncle (Source: Photo courtesy of Centro Veterinario Futuravet)

5.2

Acquired Diseases

Otitis externa has a multifactorial aetiology. According to the etiological classification, two categories can trigger otitis externa (primary and secondary), and two factors contribute to the maintenance and worsening of otitis (predisposing and perpetuating). The primary causes are those factors that alone are sufficient to cause otitis even in a healthy ear, while the secondary causes can induce otitis but only in an already altered ear. The predisposing factors significantly increase the risk of the onset of otitis in an individual patient. The perpetuating factors are those capable of propagating and maintaining inflammation by aggravating clinical disease and preventing its resolution (Table 5.1).

5.2.1

Acute Otitis Externa

All inflammatory, infectious, and neoplastic diseases involving the external ear canal and eardrum are considered. The timing of the initial onset distinguishes acute from chronic otitis. Usually, if up to 3–4 weeks of history, otitis is considered acute. Sometimes, however, the owner does not notice acute otitis, especially if the ears are only erythematous (e.g. allergic dermatitis). This is likely because the clinical signs of infectious otitis,

116

5

Indications of VOE in Canine and Feline Ear Diseases

Table 5.1 Otitis: multifactorial aetiology. PSPP System# for Otitis Externa by Craig Griffin Primary causes Hypersensitivity Foreign bodies Parasites Keratinisation defects Metabolic diseases Autoimmune diseases Viral diseases

Secondary causes Bacteria Yeasts Excess cleaning Drug reaction Swimming

Predisposing factors Anatomic conformation Excessive humidity Consequence of treatments Obstructive diseases of the duct Systemic diseases

Perpetuating factors Excessive wax production Impaired or absent migration of ear wax Progressive pathological changes Otitis media

Glaze M.B. Diseases of Eyelids, Claws, Anal Sacs, and Ears. In Miller, Griffin, Cambell: Muller & Kirk’s Small Animal Dermatology, 7th Ed. Elsevier Mosby. (19):743–745

including pruritus, irritation, pain, malodour and the production of otic material, is more evident and concerning for the owner. The ear canal is not a sterile environment, and, under normal conditions, the resident microflora is made up of a small number of bacteria, mainly Gram-positive bacteria and yeasts. An inflammatory process induces a sequence of events that alters the microenvironment and microanatomy. At the beginning of the inflammatory phase, vasodilation (erythema) (Fig. 5.16) and increased vascular permeability (oedema) are visible during VOE. With persistent inflammatory stimulus, qualitative-quantitative alterations of the glandular tissue occur. Progressive hyperplasia of the sebaceous glands, followed by ceruminous apocrine glands, increases secretory activity. In more sub-acute otitis, the ducts undergo cystic dilation with small white spots appearing in video otoscopic images (Fig. 5.17). The activity of the ceruminous glands modifies the earwax composition. The lipid content significantly decreases to the advantage of the aqueous component; therefore, earwax’s hydrophobic and antibacterial properties are reduced, with a consequent increase in relative humidity and multiplication of bacteria (BOG or Bacterial Overgrowth) and yeasts.

5.2.1.1 Causes 5.2.1.1.1 Allergic Skin Diseases Allergic dermatitis (food and/or environmental) is the most common underlying cause (i.e. primary cause) of otitis externa in dogs. Contact hypersensitivity is relatively rare but should be considered if there is a worsening of clinical signs following treatment. Otitis externa may affect up to 85% of atopic individuals, and in many cases (25%), otitis is the

5.2

Acquired Diseases

117

Fig. 5.16 Video otoscopic image. Acute otitis externa in a left ear canal of an allergic dog. Note the presence of an erythematous duct

Fig. 5.17 Video otoscopic image. Sub-acute otitis externa in a left ear canal of an allergic dog. Note the presence of erythema and numerous white spots indicating glandular hyperplasia

118

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.18 Clinical image. Acute otitis externa in a left ear canal of an allergic dog. Note the presence of erythema, especially in the proximal portion of the medial pinna and entrance to the vertical canal

first sign. An atopic patient may have several bouts of otitis before developing other cutaneous lesions. On the other hand, erythematous otitis may be the only clinical sign. The proximal portion of the concave pinna and the auditory meatus (Fig. 5.18) tend to be the primary and initial focus of the clinical signs in allergic individuals. With progression, the canals become involved with the subsequent development of secondary infections. Some individuals have only concave pinnae involvement, and acute atopic flares may result in pinnal oedema and stenosis of the auditory meatus. Most patients have bilateral involvement, but it is possible to see atopic otitis affecting predominantly one ear. Interestingly, a higher incidence of dilatation of the pars flaccida is reported in affected ears. The pathogenesis is unknown, but the hypothesis includes head shaking or Eustachian tube dysfunction.

5.2

Acquired Diseases

119

5.2.1.1.2 Ectoparasitic Diseases Parasitic infestation of the external ear canal caused by Otodectes cynotis is responsible for more than 50% of otitis externa diagnosed in cats and c. 5–10% in dogs. Otic parasites feed on epidermal debris. The constant mechanical irritation of the duct results in increased production of cerumen, sometimes combined with blood. Mites may also feed on epidermal fluids, sensitising the patient to parasitic antigenic material. The degree of pruritus, often severe, may be out of proportion to the number of mites present in the auditory duct. In addition, in one study, cross-reactions have been demonstrated with 50% of cats with Otodectes infestation testing positive on intradermal testing for Dermatophagoides spp. These cats were negative after acaricide therapy. Otoacariasis with O. cynotis is usually responsible for pruritic erythroceruminous otitis externa, generally bilateral, with abundant dry, blackish-brown ear wax, reminiscent in its appearance to “coffee grounds” (Figs. 5.19 and 5.20). On the other hand, otitis externa due to Demodex canis infestation is uncommon. Rarely, otitis externa may result from an extension of pinnal disease associated with Sarcoptes scabiei var. canis, Notoedres cati (cats), Neotrombicula autumnalis larvae, and from infestations of ticks or fly larvae. 5.2.1.1.3 Foreign Bodies Several foreign bodies (for example, awns, sand, small pieces of cotton or gauze) can accidentally locate within the external ear canal (Fig. 5.21). It is essential to recognise a foreign body from a hard ceruminolyth (a cerumen plug with hairs) (Fig. 5.22). They are

Fig. 5.19 Video otoscopic image. Otoacariasis. Sub-acute otitis externa in an ear canal of a dog. Note the presence of a large amount of cerumen with mites (black arrows)

120

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.20 Video otoscopic image. Otoacariasis. Sub-acute otitis externa in an ear canal of a dog. Note the presence of a large amount of blackish-brown cerumen

Fig. 5.21 Video otoscopic image. Foreign body. Acute otitis externa in an ear canal of a dog. Note the presence of an awn in the deepest part of the horizontal canal

5.2

Acquired Diseases

121

Fig. 5.22 Video otoscopic image. Acute otitis externa in an ear canal of a dog. Note the presence of hairs and cerumen in the deepest part of the horizontal canal. Important not to confuse it with a foreign body

mostly seen in hunting type dogs. Generally, the clinical signs are characterised by the sudden onset of acute unilateral very painful otitis, which rapidly undergoes secondary bacterial infection. Some foreign bodies are entirely asymptomatic and may be responsible for the failure of otitis to resolve. Sometimes, the material can migrate into the deepest portions of the ear canal, rupturing the tympanic membrane and causing otitis media (see related chapter). Therefore, the search for otic foreign bodies must be systematic. 5.2.1.1.4 Neoformations The growth of any space-occupying lesion in the ear canal can trigger the onset of acute otitis externa. Granulomas may present in dogs. In young cats, inflammatory polyps. Feline ceruminous cystomatosis in the ear canal, particularly in some breeds such as the Persian, can occur at a young age (Fig. 5.23). Additionally, these blueish brown nodules can also develop on the face (perilabial and periocular areas), medial pinna and ear folds. Canine and Feline Inflammatory Polyps In dogs and cats, nodules, histologically referable to inflammatory polyps (IP) with a ductal attachment, may rarely develop (Fig. 5.24). However, it is quite common in young cats to see the development of acute otitis externa, usually unilateral. The cause is often the presence of IP, potentially originating from the respiratory epithelium of the tympanic cavity or auditory canal. The polyp may rupture the tympanic membrane and extend into the external ear canal (Fig. 5.25). Secondary infection due to the space occupied in the duct

122

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.23 Video otoscopic image. Feline ceruminous cystomatosis in an ear canal of a cat. Note the presence of several blueish brown nodules in the ear folds and canal

Fig. 5.24 Video otoscopic image. Ductal inflammatory polyp in a dog. Note the presence of a nodule in the ear canal

5.2

Acquired Diseases

123

Fig. 5.25 Video otoscopic image. Inflammatory polyp in a cat. Note the presence of the polyp that occupies the entire ear canal

by the polyp or the sudden onset of neurological symptoms is often the reason for the visit (see the chapter on otitis media). IP may also extend into the nasopharynx with resultant clinical signs. Canine and Feline Ear Canal Benign Neoplasia Tumours of the ear canal are uncommon in dogs, and c. 50% are benign compared to c. 15% in cats. The most common tumours arise from ceruminous glands (adenomas and adenocarcinomas). Other benign otic tumours in dogs include papillomas, epitheliomas and histiocytomas.

5.2.1.1.5 Secondary Infections (Bacteria and Yeasts) The development of secondary infections is considered a frequent complication secondary to an underlying primary cause. For example, acute otitis externa is usually caused by allergic dermatitis, foreign bodies, ectoparasites and inflammatory polyps. The transition from BOG (bacterial overgrowth) to infection is rapid. Bacterial infections, in acute forms, are usually caused by Gram-positive bacteria such as Streptococci and Staphylococci. At the same time, yeast infections are caused by Malassezia. If the primary cause is identified and managed, topical therapy can cure these infections within weeks. However, sometimes predisposing factors such as anatomical conformations

124

5

Indications of VOE in Canine and Feline Ear Diseases

in some canine breeds (e.g. English Bulldog or Bassett hound) or the production of thick and hard cerumen (e.g. hunting breeds) are the reason for relapses of these infections. Ceruminous Otitis Ceruminous or erythroceruminous otitis is the most frequent acute form. There is an excess cerumen production in the dog due to glandular hyperplasia and an arrest of natural cleaning mechanism (cerumen migration) due to the inflammatory pattern (Fig. 5.26). In cats, ceruminous otitis (Fig. 5.27) is less frequent but still linked to the factors mentioned above for the dog. Exudative Otitis Exudative or purulent otitis is frequently complicated with infection, especially in dogs. Purulent material is often whitish to yellow (Gram-positive bacteria) (Fig. 5.28). Generally, young cats present as unilateral otitis due to foreign bodies or inflammatory polyps (Fig. 5.29), while unilateral otitis in older cats may be due to neoplasia. Bilateral ceruminous otitis is expected during otoacariasis. Ulcerated Otitis In some cases, the development of bacterial infections caused by Gram-negative rods, such as Pseudomonas spp. or Escherichia coli, is possible in acute otitis externa. Usually, the pathogenesis is due to intense self-trauma and subsequent secondary infection with opportunistic pathogenic bacteria (with a predilection for growth in moist environments such as

Fig. 5.26 Video otoscopic image. Ceruminous otitis in a dog; cerumen fills the ear canal

5.2

Acquired Diseases

125

Fig. 5.27 Video otoscopic image. Ceruminous otitis in a cat; a large amount of cerumen fills the ear canal

Fig. 5.28 Video otoscopic image. Purulent otitis in a dog; a large amount of white purulent material effaces the ear canal

126

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.29 Video otoscopic image. Purulent otitis in a cat; yellow purulent material effaces the ear canal and covers the polyp (black arrows)

soil, vegetation, and faeces). Vegetative foreign bodies can also carry these soil bacteria. Many strains of these bacteria produce inflammatory toxins that cause ulcers and pain.

5.2.2

Chronic Otitis Externa

In chronic otitis, since the ear canal is contained within a scarcely extensible cartilage structure, inflammation and oedema lead to an initial reduction in the lumen diameter (Fig. 5.30). The cells of the basal layer of the epidermis respond to inflammation by increasing the rate of turnover. Moreover, the sebaceous and ceruminous glands increase their secretory activity. The increase in epidermal exfoliation and ceruminous secretion results in excessive production of earwax (Fig. 5.31). This, in turn, acts to further narrow the ear canal and provides an ideal environment for the overgrowth of microorganisms, whose antigens and exotoxins greatly amplify local inflammation. Glandular hyperplasia and dilation of the ducts of the ceruminous glands can sometimes be so substantial as to completely obliterate the lumen of the ear canal (Figs. 5.32 and 5.33). In addition, one study showed a peculiar chronic otic inflammatory response in the Cocker Spaniel compared to other canine breeds. In this breed, the hyperplasia and ectasia of the ducts predominate (Fig. 5.34), while in the other breeds, dermal fibrosis is more relevant (Fig. 5.35). This abnormal inflammatory response, together with predisposing factors, such

5.2

Acquired Diseases

127

Fig. 5.30 Video otoscopic image. Oedematous otitis in a dog; narrowing of the ear canal is evident

Fig. 5.31 Video otoscopic image. Ceruminous otitis in a dog; a large amount of cerumen fills the ear canal

128

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.32 Video otoscopic image. Hyperplasic otitis in a dog; narrowing of the ear canal is evident in the horizontal part. In addition, the hyperplasia (white spots) and dilation of the ceruminous gland ducts (marked by black arrows) are visible

Fig. 5.33 Video otoscopic image. Hyperplasic and stenotic otitis in a dog; narrowing of the ear canal is evident. In addition, the severity of hyperplasia and dilation of the ducts of the ceruminous glands resemble masses and nodules

5.2

Acquired Diseases

129

Fig. 5.34 Video otoscopic image. Hyperplasic and stenotic otitis in a Cocker Spaniel dog; narrowing of the ear canal is evident. In addition, the severity of hyperplasia and dilation of the ducts of the ceruminous glands resemble masses and nodules

Fig. 5.35 Video otoscopic image. Chronic otitis in a dog; narrowing of the ear canal is determined by dermal fibrosis

130

5

Indications of VOE in Canine and Feline Ear Diseases

as pendulous pinna and canal length, may account for the greater severity of clinical signs observed in this breed. In chronic otitis, it is often impossible to view the tympanic membrane; important landmarks for VOE are the tuft of hairs adjacent ventrally to the eardrum (Fig. 5.36). Alternatively, a curette can be used to feel the ventral wall of the ear canal; the consistency remains soft (skin, dermis and annular cartilage) until c. 1 cm from the eardrum, where the floor of the horizontal ear canal is supported by the petrous bone process (Fig. 5.37). At the same time, the ear cartilages can undergo bone metaplasia, further reducing the expansion capacity of the canal (Fig. 5.38). Furthermore, the increase in soft tissues, canal lumen stenosis, and variation of the ear wax composition lead to an increase in relative humidity and temperature. There is consequential progressive maceration and development of secondary infections, which induce more inflammation. As a result, qualitativequantitative variations of the microflora coincide, with a notable increase in the number of Gram-positive bacteria and yeasts. After that, there is the appearance and increase of Gram-negative bacteria, particularly Pseudomonas spp. The dermis is infiltrated by inflammatory cells that release inflammatory mediators: chronic inflammatory stimulation causes progressive dermal fibrosis, with further stenosis of the canal lumen (Figs. 5.39 and 5.40). For chronic otitis externa, it is necessary to stage the otitis (see Box 5.2).

Fig. 5.36 Video otoscopic image. Chronic and stenotic otitis in a dog; narrowing of the ear canal is evident. In addition, it is not possible to view the eardrum, but the tuft of hairs suggests this is the end of the horizontal canal and near the tympanic membrane

5.2

Acquired Diseases

131

Fig. 5.37 Schematic diagram of the external, middle, and internal ear, dog. Cross-section through the skull. In this example, a curette is positioned to touch the floor of the horizontal ear canal at the annular cartilage level (a); palpation with the catheter should give a “soft sensation”. As the catheter continues deeper (the last centimetre above the tympanum), the sensation becomes “hard to the touch” (b) where the canal is supported by the bony acoustic meatus (the process of the petrous bone). So, in cases where the narrowing of the canal obscures the visibility of the eardrums, this method allows you to know when the catheter is close to the tympanic membrane (Source: Photo courtesy of Massimiliano Crespi)

132

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.38 Schematic diagram of the external, middle, and internal ear, dog. Cross-section through the skull. In this example, chronic otitis with the narrowing of the ear canal and the formation of folds and swellings due to glandular hyperplasia, ectasia of the ducts and finally, profuse cerumen production. A cross-section of the ear canal and its anatomical changes are visible alongside (Source: Photo courtesy of Massimiliano Crespi)

5.2

Acquired Diseases

133

Fig. 5.39 Schematic diagram of the external, middle, and internal ear, dog. Cross-section through the skull. In this example, the evolution of chronic otitis with the narrowing of the ear canal and the formation of folds and swellings due to glandular hyperplasia, ectasia of the ducts tends to obliterate the lumen; finally, profuse organic material. It is possible to have pathological rupture of the eardrum and the passage of organic material into the middle ear with the development of otitis media. A crosssection of the ear canal and its anatomical changes are visible alongside (Source: Photo courtesy of Massimiliano Crespi)

134

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.40 Video otoscopic image. Chronic and stenotic otitis in a dog; narrowing of the ear canal is evident. Note the ectasia severity and the presence of stalagmite-like formations

Box 5.2 Algorithm Chronic Staging Otitis

Algorithm Staging Chronic OƟƟs Signalment

O

History Clinical examina on General physical examina on Dermatological examina on Ear examina on

s Externa and/or media

Blood examina ons and heart check. If ok systemic treatment with glucocor coids for 2 weeks

VOE Inner o

s

Xrays or CTs IF OK: Medical management

IF diagnosƟc imaging: OK

g/c non-responsive ear canal stenosis

Neurologic visit and MR

Ear car lagines mineraliza ons with complete ear canal stenosis and bullae osteomyeli s

Medical management Medical management

Different Protocols with ear cleanings, topical and systemic molecules

Surgical management

Surgical management

TECA or TECALBO (Total ear canal abla on and lateral bulla osteotomy)

VOE: Video OtoEndoscopy; MR: Magne c Resonance; CTs: Computed Tomography

(continued)

5.2

Acquired Diseases

135

Box 5.2 (continued) An algorithm for the management of otitis is essential. First, the chronological path must pursue collecting all the data necessary to issue a precise diagnosis and prognosis. Based on the diagnostic picture and in agreement with the owners, the decision on the therapeutic approach (medical or surgical) can then have a good outcome and compliance. This algorithm has the enormous advantage of defining the problem quickly, avoiding the common and frequent recurrence risks. The first step is the collection of the signalment and the entire history of the patient. Next, a general clinical visit is essential to ascertain the animal’s condition and evaluate the presence of other concomitant pathologies. If the symptoms are referred to an otitis externa, performing an otoscopic examination is functional where cases allow it. But looking at the pinna and the auricular folds (with their organic material) helps identify the severity and chronicity of the otitis. In addition, the palpation of the ducts, with the operator placed in front of the patient’s head, is crucial to evaluate the elasticity or, on the contrary, the rigidity of the ear canals. In the presence of stenotic ear canals, giving the patient 10–14 days of oral glucocorticoids is helpful. But it is essential to check the state of health with recent blood tests and cardiological checks previously. At this point, the algorithm indicates to perform under general anaesthesia, VOE and CTs or MRI. If the endoscope reaches the final part of the ear canal and the eardrum and the diagnostic imaging excludes significant anatomical alterations, management is medical. While there are pictures in which the only effective management is surgical. For example, if the stenosis of the ducts does not respond to glucocorticoids therapy. Or the presence of severe auricular cartilages calcifications and the presence of otitis media with signs of osteomyelitis of the tympanic bulla. The algorithm suggests a neurological examination and imaging examination (usually MRI) if the animal has neurological symptoms (inner otitis). In otogenic meningitis or labyrinthitis cases, a VOE with a deep tympanic bulla cleaning is indicated.

5.2.2.1 Causes Acute otitis externa tends to recur and become chronic if the underlying primary causes are not diagnosed and managed. In this way, the anatomical alterations become important perpetuating factors. 5.2.2.1.1 Allergic Skin Diseases In allergic pets where pruritus has not been well managed, skin and ear infection recurrences are frequent. These relapses often require repeated anti-inflammatory (steroid), antibiotic and antifungal treatments. The use of antimicrobial therapies, over time, lose effectiveness with the development of drug-resistant strains of bacteria and yeasts. Many of

136

5

Indications of VOE in Canine and Feline Ear Diseases

these microorganisms also produce a biofilm with defensive properties against antimicrobials. VOE patterns in chronic allergic dogs are often characterised by ear canal stenosis and other perpetuating factors. 5.2.2.1.2 Ectoparasitic Diseases Cases of chronic ectoparasitic otitis are rare. These patients usually suffer from intense pruritus prompting the owner to seek veterinary attention early. Furthermore, the new families of parasiticides (e.g. isoxazoline), with their high efficacy and a broad spectrum of action (fleas, ticks, and mange), have considerably reduced clinical cases. Only in colonies of stray cats, there can be continuous reinfestation by Notoedres cati or Otodectes cynotis. Some dogs not treated with parasiticides that live with outdoor cats can become infested (Fig. 5.41). Particular attention must be paid to allergic dogs whose pruritus is as severe as the ear mange! 5.2.2.1.3 Foreign Bodies Foreign bodies usually cause evident and sudden symptoms. However, if they are not removed quickly, some may position in the deep part of the ear canal and become asymptomatic. Many foreign bodies carry environmental microorganisms that can cause recurrent ear infections (Fig. 5.42). Sometimes, the search can be difficult even with VOE, as small pieces can macerate and no longer be recognisable (Fig. 5.43). In addition, they are usually embedded in earwax and hair plugs, making identification challenging. In chronic

Fig. 5.41 Video otoscopic image. Otoacariasis in a dog; note erythema, cerumen, and several whitish adult mites in the ear canal

5.2

Acquired Diseases

137

Fig. 5.42 Video otoscopic image. Chronic ceruminous otitis in a dog; cerumen and debris (Malassezia ear infection) are evident. Note at the end of the ear canal a macerated foreign body (white arrow)

Fig. 5.43 Video otoscopic image. Chronic relapsing otitis in a dog; a brownish, macerated awn is present in the ear canal

138

5

Indications of VOE in Canine and Feline Ear Diseases

forms of otitis caused by foreign bodies, their location near or on the eardrum can suddenly cause pain or irritation for the animal. Therefore, their removal must be complete and followed by deep ear cleaning. Once foreign bodies are removed, a ruptured eardrum is often visible (Fig. 5.44). If supported by appropriate therapy, it usually heals within 4–5 weeks. 5.2.2.1.4 Neoformations Neoformations in chronic otitis are frequent. In dogs, they are often lesions caused by chronic hyperplasia of the glands and ectasia of the ducts. In cats, ceruminous gland cystomatosis is linked to genetic predispositions and chronic inflammatory stimuli. Moreover, it is possible to detect inflammatory nodules such as pyogranulomas or granulomas. Finally, canine and feline inflammatory polyps that protrude into the ear canal. Canine Otic Polypoid Glandular Hyperplasia In dogs with chronic or relapsing otitis, it is possible to observe the formation of polypoid hyperplasia of the ear folds and ear canal (Fig. 5.45). Particularly in brachycephalic breeds such as Pug, English and French Bulldog, it is more common to find these lesions that mimic tumour masses. Previously, such hyperplastic otitis cases were always considered end-stage with surgical indications (TECALBO). Nowadays, if irreversible anatomical alterations are not noted on the CT scan, it is possible to have a less invasive approach with laser surgery (Fig. 5.46). In addition, maintenance management, often with low-dose oral

Fig. 5.44 Video otoscopic image. A ruptured eardrum in a cat; shortly before, a large foreign body that was engaged in the eardrum, was removed

5.2

Acquired Diseases

139

Fig. 5.45 Clinical image. Polypoid hyperplasia of a dog’s ear folds and ear canal (VOE imagine); Note the cotton swab inserted into the external ostium as a landmark

and/or topical glucocorticoids, reduces relapses. The primary underlying cause is often allergic. Feline Ceruminous Gland Cystomatosis This condition (i.e. ceruminous adenoma, apocrine cystadenomatosis) is cats’ uncommon, non-neoplastic disorder. Lesions most commonly affect the medial pinna and external auditory meatus (Fig. 5.47), and occasionally, the ear canal. The lesions may represent a congenital or degenerative and senile change. Cats of all ages may be affected but are more common in middle-aged animals. A breed predisposition for Abyssinian and Persian cats has been reported, along with a slight predominance in males. Surgical laser treatment is indicated and effective (Fig. 5.48). Granulomas Chronic inflammation of the ear canal can create granulomas (Fig. 5.49) that can be confused with tumours; cytological examination is indicated. Canine and Feline Inflammatory Polyps As already described for acute otitis, inflammatory polyps (IP), if not diagnosed quickly, can cause chronic and relapsing ear infections. In these cases, however, the narrowing of

140

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.46 Clinical image. Polypoid hyperplasia of the ear folds in a French Bulldog; At D0 (day 0) before the laser diode surgery and after 2 months (D60; day 60)

the canal and the purulent material of secondary infections make them difficult to visualise. For this, it is essential to perform the VOE and ear cleaning. Clinical signs are usually unilateral, although bilateral IP occur more frequently than previously reported. These findings suggest the usefulness of advanced imaging techniques (e.g. MRI/CT with contrast) in diagnosing IP.

5.2

Acquired Diseases

141

Fig. 5.47 Video otoscopic image. Feline ceruminous cystomatosis in an ear canal of a cat. Note the presence of several blueish brown nodules in the ear folds and canal

Fig. 5.48 Video otoscopic image. Feline ceruminous cystomatosis in an ear canal of a cat. Diode laser cysts ablation

142

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.49 Video otoscopic image. Granuloma in an ear canal of a dog. A lump is present in the vertical ear canal

5.2.2.1.5 Neoplasia For primary ear canal tumours (Table 5.2), the stimulus induced by chronic ear infections may have a carcinogenic role. On the other hand, obstruction/occlusion of the canal leads to inflammation and secondary infection. Therefore, most external ear canal tumours are characterised by clinical signs of unilateral otitis externa that are not responsive to rational treatment. Patients may also demonstrate conductive deafness due to the mass  the secondary infection. Therefore, neoplasia should be suspected when the patient presents with unilateral otitis with otorrhagia.

Table 5.2 Neoplastic conditions of the canine ear canal

Benign neoplasms Ceruminous gland Adenoma Basal cell tumour Sebaceous gland adenoma Papilloma Histiocytoma Plasmacytoma

Malignant neoplasms Ceruminous gland Adenocarcinoma Squamous cell carcinoma Soft tissue sarcoma Malignant melanoma

5.2

Acquired Diseases

143

5.2.2.1.6 Benign Neoplasia Benign tumours of the ceruminous glands (adenomas) are most frequent in adult and elderly dogs (Fig. 5.50). In elderly cats, the formation of ceruminous gland adenoma (Figs. 5.51, 5.52 and 5.53) is often associated with a chronic otitis history. More rarely, it is possible to detect sebaceous glands adenomas and papillomas (Figs. 5.54 and 5.55). Removing benign tumours with the diode laser is very effective and minimally invasive (Fig. 5.56).

5.2.2.1.7 Malignant Neoplasia Malignant neoplasia in the ear canal is derived from ceruminous glands and epidermis. Adenocarcinomas are more likely to be invasive and ulcerative than occlusive. These tumours occur in older animals; in cats, the average age of onset is 12 and 9 years in dogs (Figs. 5.57 and 5.58). Tumour removal/biopsy, potentially with laser, for cytology (Fig. 5.59) and histopathology (Fig. 5.60) confirms the diagnosis. Squamous cell carcinomas are malignant neoplasms derived from epidermal cells (Fig. 5.61) and occur more often in cats (Fig. 5.62) than dogs. They tend to progress rapidly with proliferation and ulceration, and infiltration into local tissues. If there is lymphadenomegaly, pain on opening the mouth and/or swelling of nearby tissues, it is always recommended to perform staging with diagnostic imaging, e.g. CT scan (Fig. 5.63).

Fig. 5.50 Video otoscopic image. Ceruminous gland adenoma in an ear canal of a dog

144

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.51 Video otoscopic image. Ceruminous gland adenoma in an ear canal of a cat. Note the polylobate aspect of the tumour

Fig. 5.52 Microscopic examination. Cytology (Fig. 5.51). An aggregate of uniform clustered epithelial cells with basophilic cytoplasm and acinar cytoarchitecture are observed (Stain Diff Quick stain, 40 high power field)

5.2

Acquired Diseases

145

Fig. 5.53 Microscopy examination. Histopathology. Ceruminous gland adenoma (Fig. 5.51). The dermis is characterised by glandular epithelial cells of apocrine origin organised in tubular formations, delimited by cuboidal/cylindrical cells with basal/polar nuclei that tend to be monometric or mildly anisocariotic. The tubular structures show cystic lumens of various sizes filled with eosinophilic secretion and luminal inflammatory infiltration (hidradenitis). (haematoxylin and eosin stain, 40 high power field) (Source: Photo courtesy of Francesco Albanese)

Fig. 5.54 Video otoscopic image. Papilloma in an ear canal of a dog

146

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.55 Video otoscopic image. Papilloma in an ear canal of a cat

Fig. 5.56 Video otoscopic image. Adenoma in an ear canal of a dog. Note the tumour debulking by a diode laser fibre

5.2

Acquired Diseases

Fig. 5.57 Video otoscopic image. Adenocarcinoma in an ear canal of a dog

Fig. 5.58 Video otoscopic image. Adenocarcinoma in an ear canal of a cat

147

148

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.59 Microscopic examination. Cytology. (Fig. 5.57). An aggregate of clustered epithelial cells with basophilic cytoplasm and acinar cytoarchitecture are observed. These cells show anisocytosis, anisocariosis, with prominent nucleoli. Note numerous neutrophils and erythrocytes (Stain Diff Quick stain, 40 high power field)

5.2.2.1.8 Rare Neoplasia Trichoblastoma The author reports a case of this rare ear canal tumour. A 7-year-old female spayed crossbreed dog was referred to our clinic to evaluate a right vertical ear canal mass. An endoscopic biopsy of the unilateral ear canal mass revealed a trichoblastoma tumour (Fig. 5.64). The localisation and staging of the neoformation were made by performing otoendoscopy (Fig. 5.65) and CT scan (Fig. 5.66). The neoplasia was successfully removed by diode laser surgery. Trichoblastoma is a benign epithelial neoplasm that arises from the hair germ. The incidence ranges from 0.4% to 4.0% of canine cutaneous tumours. Glomus Tympanicum Tumour The author reports a case of this sporadic tympanic tumour. An 11-year-old male English Setter was presented for sudden bleeding from the left ear canal and unilateral deafness. An endoscopic biopsy of the unilateral, red-coloured ear drum mass revealed a glomus tympanicum tumour (Fig. 5.67). The localisation and staging of the neoformation were made by performing otoendoscopy (Fig. 5.68) and CT scan (Fig. 5.69). The neoplasia was successfully removed by diode laser surgery. Glomus tumours (paraganglioma) are rare neuroendocrine tumours arising from paraganglionic cells. In people, glomus tumours are

5.2

Acquired Diseases

149

Fig. 5.60 Microscopic examination: Ceruminous gland adenocarcinoma in a dog. The infiltrating malignant epithelial neoplastic proliferation is composed of multiple solid formations of variable size, composed of cuboidal to round epithelial cells, with notable aspects of cytological malignancy. These neoplastic cells show anisocytosis, anisocariosis, often bulky nucleoli and numerous and atypical mitoses. (haematoxylin and eosin stain, 60 high power field) (Source: Photo courtesy of Francesco Albanese)

Fig. 5.61 Video otoscopic image. Squamous cell carcinoma in an ear canal of a dog

150

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.62 Video otoscopic image. Squamous cell carcinoma in an ear canal of a cat

Fig. 5.63 Transverse CT soft tissue window, Invasive Squamous cell carcinoma in a cat. Postcontrast medium administration. Aggressive tissue mass in the ear canal near the left temporomandibular joint, with the invasion of the ipsilateral tympanic bulla and extra-axial invasion of the skull near the left temporal lobe. Mild adenopathy of the left retropharyngeal lymph node is compatible with reactive or metastatic adenopathy (Source: Photo courtesy of CentroTacVet)

5.2

Acquired Diseases

151

Fig. 5.64 Microscopic examination: the tumour was characterised by multiple densely packed epithelial nests and rows of basaloid keratinocytes, sustained by a moderate amount of fibrovascular stroma. (haematoxylin and eosin stain, 40 high power field) (Source: Photo courtesy of Francesco Albanese)

Fig. 5.65 Video otoscopic image. Trichoblastoma tumour in a dog; the mass arises ventrally in the right vertical ear canal

152

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.66 Transverse CT soft tissue window, trichoblastoma tumour in a dog. Post-contrast medium administration. Soft tissue lesion of the vertical right ear canal, hyperattenuating in the interstitial phase (Source: Photo courtesy of CentroTacVet)

Fig. 5.67 Microscopic examination: the tumour was characterised by round and oval cells with uniform nuclei, dispersed chromatin pattern, granular eosinophilic vacuolated cytoplasm, arranged in solid nests, separated by fibrovascular tissue (haematoxylin and eosin stain, 40 high power field) (Source: Photo courtesy of Antonella Vercelli)

5.2

Acquired Diseases

153

Fig. 5.68 Video otoscopic image. Glomus tympanicum tumour in an English Setter, dog; the mass occupies the eardrum and protrudes towards the ear canal. Note the abundant vascularisation of the tumour

Fig. 5.69 Transverse CT soft tissue window, Glomus tympanicum tumour in an English Setter, dog. Post-contrast medium administration. Soft tissue lesion of the horizontal left ear canal, hyperattenuating in the interstitial phase (Source: Photo courtesy of CentroTacVet)

154

5

Indications of VOE in Canine and Feline Ear Diseases

benign, highly vascular neoplasms, which arise in a small and limited space behind the eardrum.

5.2.2.1.9 Secondary Infections (Bacteria and Yeasts) In recurrent and chronic ear infections, secondary infections are more challenging to manage. The development of perpetuating factors often prevents clinical recovery with only local ear therapies. In addition, the bacteria involved are often Gram-negative organisms that produce biofilm and develop resistance to antimicrobials; these bacteria can also produce exotoxins that degrade epithelium, producing painful erosions and ulcers. Ceruminous Otitis During chronic otitis, earwax production is excessive, its quality changes, and the cerumen becomes drier and harder (Fig. 5.70). In addition, the self-cleaning function of the external ear, primarily achieved by epithelial migration, is absent. These conditions lead to the development of cerumen plugs (ceruminoliths) (Fig. 5.71), which form near or on the tympanic membrane (Fig. 5.72). This position leads to painful sensations or rupture of the eardrum (Fig. 5.73). Ceruminoliths are frequent in some hunting dog breeds, even without ear infections. Earwax plugs are also found in cats (Fig. 5.74). Ceruminous otitis is often quickly complicated by secondary Malassezia infection.

Fig. 5.70 Video otoscopic image. Ceruminous otitis in a dog; dry and hard cerumen is present in the ear canal

5.2

Acquired Diseases

155

Fig. 5.71 Video otoscopic image. Ceruminous otitis in a dog; ceruminolyth is evident in the ear canal

Fig. 5.72 Video otoscopic image. Ceruminous otitis in a dog; ceruminolyth is near the eardrum

156

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.73 Video otoscopic image. After removing the ceruminolyth (Fig. 5.71), the ruptured eardrum is visible

Fig. 5.74 Video otoscopic image. Ceruminous otitis in a cat; ceruminolyth is near the eardrum

5.2

Acquired Diseases

157

Exudative Otitis Exudative otitis is very common in chronic ear infections. The presence of rod-shaped bacteria such as Corynebacterium spp. or Pseudomonas aeruginosa creates characteristic greenish-yellow discharge (Fig. 5.75)  haemorrhage. Instead of the yellowish-white discharge present during Staphylococcus spp. or Streptococcus spp. exudative otitis. Many strains of these bacteria are biofilm-producers. Thus, the biofilm is already suspected with clinical presentations like Fig. 5.76 or purulent “glue” bridges on VOE (Fig. 5.77). Ulcerated Otitis After ear cleaning, it is possible to appreciate ulcers and erosions caused by these infections (Fig. 5.78). Together with ulcers, it is common to observe varying degrees of epithelial exfoliation, which appears as a whitish material in the shape of a flag (Fig. 5.79) or epithelial islands (Fig. 5.80). In the presence of ulcers in the ear canal, it is recommended to prescribe anti-inflammatory and pain relief drugs.

5.2.3

Otitis Media

Otitis media (OM) can result from descending disease from the external ear canal, ascending disease from the nasopharynx through the auditory tube, or a primary disease of the tympanic bulla. Rarely OM is a result of a haematogenous spread.

Fig. 5.75 Clinical image. Chronic purulent otitis externa in a right ear canal of an allergic dog. Note the presence of greenish-yellow mucoid discharge typical of Pseudomonas spp. infection

158

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.76 Clinical image. Chronic purulent otitis externa in a right ear canal of dog. Note the presence of greenish-yellow mucoid discharge typical of Pseudomonas spp. infection. The cotton swab is leaning against the slide in the box, forming a mucoid and stringy bridge of slimy purulent material (biofilm)

Fig. 5.77 Video otoscopic image. Purulent infection in a dog; greenish exudative discharge creates mucoid bridges in the ear canal

5.2

Acquired Diseases

159

Fig. 5.78 Video otoscopic image. Purulent infection in a dog; purulent discharge is present in the ear canal (pre), and ulcerations and exfoliations are evident only after ear cleaning (post)

Fig. 5.79 Video otoscopic image. Purulent infection in a dog after ear cleaning; extensive ulcers are present, and the whitish material is due to skin exfoliation

160

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.80 Video otoscopic image. Purulent infection in a dog after ear cleaning; severe ulcers are present, and the whitish islets are skin exfoliation

The most common cause of OM in the dog is secondary to otitis externa and ruptured tympanic membrane, e.g. infection and/or foreign bodies. Ascending infection, possibly from respiratory virus or inflammatory polyps, is more common in cats. After the initial perforation, the tympanic membrane can heal, closing the infectious material within the tympanic bulla. Therefore, a careful assessment of the eardrum is crucial when assessing a patient for OM. It is necessary to distinguish a chronically inflamed eardrum, myringitis (Fig. 5.81), from a pathological eardrum (Fig. 5.82). Different techniques help to assess the patency of the tympanic membrane. For example, to see if air bubbles are coming out from the pars tensa during ear cleaning (Fig. 5.83), or to open and close the suction valve several times to make the pars tensa move like a boat sail and induce the pars flaccida to bulge (Fig. 5.84). The reposition of the eardrum without loss of material or air is a sign of tympanic integrity. Tympanic ruptures can be only a minute tear (Fig. 5.85) or hole (Fig. 5.86) and maybe partial (Fig. 5.87), or total (Fig. 5.88). Complete ruptures only partially heal; a scar ring leaves a central hole (window). Other types of ruptures usually heal completely within 4–6 weeks. The ear that has suffered from a total eardrum rupture must continuously be monitored because it is more prone to relapsing diseases.

5.2

Acquired Diseases

161

Fig. 5.81 Video otoscopic image. Myringitis in a dog; the eardrum is thickened and whitish due to chronic inflammation

Fig. 5.82 Video otoscopic image. The otitis media in a dog; the tympanic membrane is thickened and whitish, and the pars tensa is bulging

162

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.83 Video otoscopic image. Check eardrum integrity: opening and closing the suction valve several times makes the pars tensa move like a boat sail (asterisk). The air bubbles (black arrow) confirm a partial eardrum rupture

Fig. 5.84 Video otoscopic image. Check eardrum integrity: opening (b) and closing (a) the suction valve several times makes the pars flaccida bulge, and the air bubbles absence confirms an intact eardrum

5.2

Acquired Diseases

163

Fig. 5.85 Video otoscopic image. The eardrum in a dog; a tear is evident in the pars tensa of this ruptured tympanic membrane

Fig. 5.86 Video otoscopic image. The eardrum in a dog; a hole is evident in the pars tensa of this ruptured tympanic membrane

164

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.87 Video otoscopic image. The eardrum in a dog; a partial rupture is evident in the pars tensa of this tympanic membrane

Fig. 5.88 Video otoscopic image. The eardrum in a dog; a complete rupture is evident in the pars tensa of this tympanic membrane (only the manubrium of the malleus is present)

5.2

Acquired Diseases

165

5.2.3.1 Causes 5.2.3.1.1 Evolution from Exudative/Ceruminous Otitis Externa (OE) When an acute case of OE becomes chronic, there is a risk that the patient develops otitis media (OM); it is reported that 32–89% of dogs with chronic otitis externa have concurrent otitis media. As said above, most cases of OM in dogs are an extension of OE. Consequently, OM is a perpetuating factor (Fig. 5.89), playing an important role in chronic or recurrent OE. Patients with OM may not develop neurological signs, and the tympanic membranes may be intact. If left untreated, however, OM may progress to the internal ear structures and/or the surrounding tissues with the development of neurological deficits and chronic irreparable pathological changes. Such “end-stage” otitis cases are no longer amenable to medical management and benefit from surgical removal of diseased tissues.

Fig. 5.89 Video otoscopic image. Purulent otitis externa (a) in chronic pattern leads to anatomical changes such as canal stenosis (b), and imaging diagnostics like X-rays (c) confirm the presence of otitis media (right OM) and the need for tympanic bulla cleaning (d)

166

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.90 Video otoscopic image. A dog has a persistent purulent infection due to foreign bodies; greenish exudate is present in the right ear canal

Fig. 5.91 Video otoscopic image. Several awns (Fig. 5.90) excised from the middle ear after ear washing

5.2

Acquired Diseases

167

Fig. 5.92 Transverse CT soft tissue window. Post-contrast medium administration (Fig. 5.90). Signs of right otitis externa and media (Source: Photo courtesy of Centro Veterinario Futuravet)

Fig. 5.93 Video otoscopic image. A Cavalier King Charles Spaniel (CKCS), dog with PSOM. It possible to see the bulging eardrum and whitish mucoid material in the figure

168

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.95 Video otoscopic image. A CKCS dog with PSOM. The images (from a–d) describe the technique for removing mucous material with otobrush

5.2.3.1.2 Foreign Bodies Foreign bodies, often awns, may not be seen and removed in the initial phase; after a period with no symptoms, the development of unilateral purulent otitis can be caused by the persistence of this material (Fig. 5.90). The foreign body can rupture the eardrum and reach the middle ear causing deep infection and inflammation (Fig. 5.91). In addition, the anatomical damage and chronicity of the infection can cause severe alterations (Fig. 5.92). 5.2.3.1.3 Primary Secretory Otitis Media (PSOM) Primary secretory otitis media (PSOM) is a syndrome that has been reported frequently and almost exclusively in Cavalier King Charles Spaniels (CKCS). The age of detection ranges from 11 months to 12 years old. The tympanic cavities of affected individuals are filled with sterile mucus material; it may be unilateral or bilateral. The condition may trigger pain and other sensations in the head and neck region that mimic the clinical signs of syringomyelia (SM); PSOM and SM are often concurrent in this breed, and differentiation should be made for appropriate therapy. Dogs often exhibit deafness, and neurological signs, such as Horner’s and vestibular syndromes, may occur. PSOM can be further suspected by visualising a bulging pars flaccida (Fig. 5.93). Imaging (CT/MRI), performed as part of the

5.2

Acquired Diseases

169

Fig. 5.94 Video otoscopic image. A CKCS dog with PSOM. The images (from a–d) describe the technique for removing mucous material with irrigation and suction with a catheter

investigation for SM and/or due to the development of deafness and/or neurological signs, identify soft tissue opacity within the tympanic cavity. In asymptomatic cases, it may be an incidental finding. Diagnosis is usually confirmed with the detection of sterile mucus following myringotomy. The techniques for removing the mucous material are irrigation and suction with a catheter (Fig. 5.94) and the use of otobrush to collect and remove the mucoid material (Fig. 5.95). The irrigation of N-Acetyl Cysteine (NAC) solution, after ear cleaning, into the tympanic bulla reduces the density of the mucus. 5.2.3.1.4 Neoformations Canine and Feline Inflammatory Polyps Inflammatory polyps (IP) are benign pedunculated ‘pink’ nodules within the ear and/or nasopharynx. They are suspected to be derived from the respiratory epithelium of the tympanic cavity or auditory canal. The pathogenesis of IP is unknown; however, it is thought that they arise due to a prolonged inflammatory process and Eustachian tube dysfunction. Traditional diagnostics involve imaging of the tympanic bulla either with skull radiographs or CT scan. IP formation is less frequent in dogs (Fig. 5.96) than cats but can occur unilateral or bilateral. Due to the greater use of diagnostic imaging, detection of bilateral IP in cats is not uncommon. Young cats with unilateral purulent otitis usually have

170

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.96 Video otoscopic image. Inflammatory polyp in a dog. An inflammatory polyp (IP) is visible in the ear canal (a) and after traction and avulsion of the polyp (b)

an IP that has ruptured through the eardrum and occupied part of the external ear canal (Fig. 5.97). Alternatively, the IP can grow into the epitympanic recess and cause early neurological symptoms (head tilt, Horner’s syndrome, deafness) while the tympanic membrane remains intact (Fig. 5.98). Treatment consists of traction and avulsion of the polyp (Fig. 5.99) or ventral bulla osteotomy (VBO). The percentage of recurrence depends on several factors: the operator’s skill (making the right movements with the pliers rotating

5.2

Acquired Diseases

171

Fig. 5.97 Video otoscopic image. Inflammatory polyp in a cat. A reddish and smooth IP is visible in the ear canal

Fig. 5.98 Video otoscopic image. Inflammatory polyp in a cat. An intact pathological eardrum is visible. A small Inflammatory polyp is present just behind the inner face of the tympanic membrane

172

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.99 Video otoscopic image. Inflammatory polyp in a cat. In the images in sequence, the operation of traction and avulsion with the operative forceps under otoendoscopic view

Fig. 5.100 Microscopy. Cytology from a feline aural inflammatory polyp. Epithelial cells have cilia (arrow) with background neutrophils and erythrocytes. This cytological picture is suggestive of an IP. (Diff Quick stain, 40 high power field)

5.2

Acquired Diseases

173

Fig. 5.101 Microscopy. Histopathology. Feline aural inflammatory polyp. Dermal tissue is devoid of annexes and entirely composed of a mixed pyogranulomatous inflammation with lymph-plasma cells. (haematoxylin and eosin stain, 40 high power field) (Source: Photo courtesy of Francesco Albanese)

in both directions and waiting before traction that the polyp comes off slowly). Cytological (Fig. 5.100) and histological (Fig. 5.101) examinations confirm the diagnosis. After avulsion, it is recommended to identify and ensure that the IP tract that assumes the anatomical imprint of the auditory tube has been removed (Fig. 5.102). Another factor is the polyp consistency: some are compact and easy to remove, while others are friable. With traction, c. 57% of cases can relapse compared to 13.5% with the per-endoscopic trans-tympanic traction (PTT) technique and 0–33% of cases treated with VBO surgery. However, it must be considered that the surgical approach is more likely to lead to neurological signs such as Horner’s syndrome and head tilt, and they may be permanent (57–81%). Furthermore, repeat VOE traction and avulsion procedure for a polyp relapse only involve further anaesthesia, while a second surgery is impossible. Cholesteatoma (Tympanokeratoma) Cholesteatomas are formed by invagination of the tympanic membrane into the dorsal tympanic cavity due to negative pressure in the tympanic bulla. They are usually acquired in the dog associated with chronic otitis externa/media and/or abnormal auditory canal function. Initially, these lesions may be small, asymptomatic, and found incidentally on imaging, VOE and/or during surgery (TECA BO). Clinical signs attributable to an expansile mass within the tympanic cavity occur with time. Furthermore, recurrent external otitis can be

174

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.102 Clinical image. Size and shape of a feline inflammatory polyp just after avulsion. Note the presence of the tail (black arrows)

caused by a tympanokeratoma that engages and ruptures the eardrum (Figs. 5.103 and 5.104). The diagnosis is suspected following imaging, e.g. MRI or CT (Fig. 5.105) and VOE and confirmed with a histological examination (Fig. 5.106). Cases with a late diagnosis of cholesteatoma have a guarded prognosis as the damage caused by the expansion of the mass can cause rupture of the bulla and inflammation of the surrounding tissues. These end-stage cholesteatomas behave biologically like a neoplasm. Neoplasia Cases of papillary adenoma (dog, cat), auditory tube adenoma (dog) and fibromyxoma (dog) are reported among benign neoplastic lesions.

5.2

Acquired Diseases

175

Fig. 5.103 Video otoscopic image. Tympanokeratoma in a dog. The mass has ruptured the eardrum and is protruding into the canal

Fig. 5.104 Video otoscopic image. Cholesteatoma in a dog. A pale and whitish mass has ruptured the eardrum and is visible during the ear cleaning

176

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.105 Transverse MR post-contrast T1-weighted image of a French bulldog with a bilateral otitis media. A small tympanokeratoma (large white arrow) is visibly attached to the inner face of the tympanic membrane (small white arrows) (Source: Photo courtesy of Norad Diagnostica)

Fig. 5.106 Microscopy. Histopathology. Tympanokeratoma in a dog (see Fig. 5.103). The lesion consists of a stratified squamous keratinised epithelium supported by a fibrous stroma in which moderate lymphoplasmacellular infiltrate and pyogranulomatous inflammation is evident. (haematoxylin and eosin stain, 40 high power field) (Source: Photo courtesy of Giancarlo Avallone)

5.2

Acquired Diseases

177

Fig. 5.107 Video otoscopic image. Otitis media, lymphoma in a cat. A mass is protruding into the lumen and occupying the right tympanic bulla

Middle ear malignant neoplasia includes gland adenocarcinoma and squamous cell carcinoma (most frequent in cat), fibrosarcoma (reported in cat), lymphoma (reported in cat) (Fig. 5.107), paraganglioma (reported in dog) and primary sarcomas of the bone (osteosarcoma, chondrosarcoma).

5.2.3.1.5 Diagnosis of Deafness The owner’s information about the suspicion of deafness can help, but it is necessary to perform objective tests to confirm the diagnosis. For example, the owner can suspect unilateral deafness if the animal responds by moving in a different direction (there must be no eye contact with the person). On the other hand, if the owner produces load sounds and there is no response, then bilateral deafness is suspected. BAER (Brainstem Auditory Evoked Response) test may be performed under general anaesthetic, at the same time as VOE and diagnostic imaging (CTs or MRI), or under sedation, along with wideband tympanometry (WBT). The BAER is an objective test to measure the animal’s hearing response to sound stimulation. It is performed by attaching three small needle electrodes under the skin and placing soft foam ear inserts into the ear canal. The equipment produces a sound, usually a click, in decibels (dB) at a specific intensity (60–100 dB). The equipment records an electrical response elicited by the cochlea and brainstem to the sound (Fig. 5.108). Each ear is tested separately, and the response waveform consists of a series of peaks numbered with Roman numerals from I to V (Fig. 5.109). The first peak refers to the global potential

178

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.108 Clinical image. A 2-month-old Dalmatian puppy during the BAER test

5.2

Acquired Diseases

179

Fig. 5.109 Typical BAER test - Evocorti# waveforms in a dog (Source: Photo courtesy of Audiocorti#: Italy.)

of the distal portion of the acoustic nerve, so a lack of it suggests vestibulocochlear nerve deficit. It is indicated during stenotic otitis externa and in otitis media in which the onset of conductive deafness is frequent. Once the cause has been managed, another BAER test should be assessed to understand if the deafness was transient or permanent. In puppies of predisposed breeds (e.g. Dalmatian, Dogo Argentino, Bull Terrier), the BAER exam is the test of choice to diagnose the onset of congenital hereditary sensorineural deafness. It is essential to combine the VOE exam to exclude some form of conductive deafness (e.g. ceruminous otitis externa) and assess the tympanic integrity. The WBT assesses the middle ear function and the mobility of the eardrum, with a transient wideband stimulus to capture the middle ear behaviour at a wide range of frequencies. For example, Vetwave# is analysing acoustic admittance for each frequency between 100 and 1500 Hz with the admittance peak for each ear (Fig. 5.110). It is a non-invasive test because it is made without applying mechanical pressure variations to the ear canal. To conclude, Table 5.3 summarises the neurological signs that may be seen during otitis media and interna and their associated neurologic deficit (Figs. 5.111, 5.112, and 5.113).

180

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.110 Different WBT Vetwave# waveforms referred to different conditions (Source: Photo courtesy of Neuranix#: Italy.)

Table 5.3 Clinical neurological signs in Dogs & Cats with otitis media and interna Deficit Vestibular dysfunction Cranial nerves involved: – VIII. Vestibulocochlear nerve Facial nerve paralysis Cranial nerves involved: – VII. Facial nerve Lesions affecting the sympathetic pathway

Neurological signs Nystagmus, strabismus, head tilt (Fig. 5.111) and abnormalities in balance and locomotion such as ataxia, circling, falling, or rolling. Deafness. Other clinical signs may include postural deficits, vomiting, behavioural changes, Horner’s syndrome. Drooping of the ear on the affected side (more noticeable in dogs with erect ears). If parasympathetic function is affected a dry eye and dry nose (xeromycteria Fig. 5.112) may be noticed on the affected side. Horner’s syndrome (Fig. 5.113)

5.2

Acquired Diseases

Fig. 5.111 Clinical image. Head tilt in a dog with unilateral otitis media and interna.

181

182

5

Indications of VOE in Canine and Feline Ear Diseases

Fig. 5.112 Clinical image. Dry nose (xeromycteria; sympathetic nose) in a dog with unilateral left otitis media

Further Reading

183

Fig. 5.113 Clinical image. Horner’s syndrome in a dog with unilateral right otitis media and interna (Source: Photo courtesy of Vincenzo Montinaro)

Further Reading Allgoewer I, Lucas S, Schmitz SA (2000) Magnetic resonance imaging of the normal and diseased feline middle ear. Vet Radiol Ultrasound 41(5):413–418 Anders BB et al (2008) Analysis of auditory and neurologic effects associated with ventral bulla osteotomy for removal of inflammatory polyps or nasopharyngeal masses in cats. J Am Vet Med Assoc 233(4):580–585 Angus JC, Campbell KL (2001) Uses and indications for video-otoscopy in small animal practice. Vet Clin North Am Small Anim Pract 31(4):809–828 Banco B, Grieco V et al (2014) Canine aural cholesteatoma: a histological and immunohistochemical study. Vet J 200(3):440–445 Benigni L, Lamb C (2006) Diagnostic imaging of ear disease in the dog and cat. Practice 28:122–130

184

5

Indications of VOE in Canine and Feline Ear Diseases

Beula AP et al (2014) Importance of ear and face abnormalities in cat eye syndrome – a prenatal and postnatal report. Eur J Biotechnol Biosci 1(4):12–15 Bichsel P, Schärer V (1985) Un néoplasme de l’oreille moyenne à l'origine d'un syndrôme vestibulaire chez le chien [A neoplasm of the middle ear causing a vestibular syndrome in a dog]. Schweiz Arch Tierheilkd 127(11):717–722 Bischoff MG, Kneller SK (2004) Diagnostic imaging of the canine and feline ear. Vet Clin North Am Small Anim Pract 34(2):437–458 Classen J et al (2016) Comparison of ultrasound imaging and video otoscopy with cross-sectional imaging for the diagnosis of canine otitis media. Vet J 217:68–71 Cole LK (2009) Anatomy and physiology of the canine ear. Vet Dermatol 20(5–6):412–421 Cole LK (2011) Otoscopy. In: Tams TR, Rawlings CA (eds) Small animal endoscopy, vol 20, 3rd edn. Elsevier – Mosby, St. Louis, MO, pp 587–605 Cole LK, Kwochka KW et al (1998) Microbial flora and antimicrobial susceptibility patterns of isolated pathogens from the horizontal ear canal and middle ear in dogs with otitis media. J Am Vet Med Assoc 212(4):534–538 Cole LK, Samii VF et al (2015) Diagnosis of primary secretory otitis media in the cavalier King Charles spaniel. Vet Dermatol 26(6):459–466 Dickie AM et al (2003a) Ultrasound imaging of the canine tympanic bulla. Res Vet Sci 75:121–126 Dickie AM et al (2003b) Comparison of ultrasonography, radiography and a single computed tomography slice for the identification of fluid within the canine tympanic bulla. Res Vet Sci 75:209–216 Fernandez M et al (2020) Invasive histiocytoma in the ear canal of a dog. Vet Dermatol 31:317–e80 Garosi LS, Dennis R, Schwarz T (2003) Review of diagnostic imaging of ear diseases in the dog and cat. Vet Radiol Ultrasound 44(2):137–146 Ghibaudo G (2010) Principi di video-otoendoscopia nel cane e nel gatto. Poletto Editore, Milan, p 109 Ghibaudo G (2011) Otoendoscopia, Chapter 9. In: Bottero E, Ruggiero P (eds) Endoscopia negli animali d’affezione. Testo Atlante. Poletto Editore, Milan, pp 157–172 Greci V, Mortellaro CM (2016) Management of otic and nasopharyngeal, and nasal polyps in cats and dogs. Vet Clin North Am Small Anim Pract 46(4):643–661 Greci V, Vernia E, Mortellaro CM (2014) Per-endoscopic trans-tympanic traction for the management of feline aural inflammatory polyps: a case review of 37 cats. J Feline Med Surg 16(8): 645–650 Hargis AM, Thomassen RW (1980) Adenoma of the epithelium lining the eustachian tube in a beagle dog. Vet Pathol 17(2):238–240 Hoppers SE, May ER, Frank LA (2020) Feline bilateral inflammatory aural polyps: a descriptive retrospective study. Vet Dermatol 31(5):385 Imai A, Kondo H et al (2019) Clinical analysis and nonsurgical management of 11 dogs with aural cholesteatoma. Vet Dermatol 30(1):42 Janssens SDS, Haagsman AN, Haar GT (2017) Middle ear polyps: results of traction avulsion after a lateral approach to the ear canal in 62 cats (2004–2014). J Feline Med Surg 19(8):803–808 Little CJ, Pearson GR, Lane JG (1989) Neoplasia involving the middle ear cavity of dogs. Vet Rec 124(3):54–57 Little CJ, Lane JG et al (1991) Inflammatory middle ear disease of the dog: the clinical and pathological features of cholesteatoma, a complication of otitis media. Vet Rec 128:319–322 London CA, Dubilzeig RR et al (1996) Evaluation of dogs and cats with tumors of the ear canal: 145 cases (1978–1992). J Am Vet Med Assoc 208:1413–1418

Further Reading

185

Lorek A, Dennis R et al (2020a) Occult otitis media in dogs with chronic otitis externa - magnetic resonance imaging and association with otoscopic and cytological findings. Vet Dermatol 31(2): 146–153 Lorek A et al (2020b) Occult otitis media in dogs with chronic otitis externa - magnetic resonance imaging and association with otoscopic and cytological findings. Vet Dermatol 31(2):146–153 Moisan PG, Watson GL (1996) Ceruminous gland tumors in dogs and cats: a review of 124 cases. J Am Anim Hosp Assoc. 32(5):448–452 Pratschke KM (2003) Inflammatory polyps of the middle ear in 5 dogs. Vet Surg 32(3):292–296 Reinbacher E et al (2020) Myringotomy in dogs: contamination rate from the external ear canal - a pilot study. Vet Anim Sci 10(100125):18 Rezaei M, Mahmoudi T, Ebrahimi M et al (2015) First report of microtia in dog. Comp Clin Pathol 24:699–702 Rohlerder JJ et al (2006) Comparative performance of radiography and computed tomography in the diagnosis of middle ear disease in 31 dogs. Vet Radiol Ultrasound 47(1):45–52 Rosychuk RA (1994) Management of otitis externa. Vet Clin North Am Small Anim Pract. 24(5): 921–952 Rosychuk R (2021) Video otoscopy. In: Mccarthy T (ed) Veterinary endoscopy for the small animal practitioner, vol 10, 2nd edn. Wiley, Boca Raton, FL, pp 637–659 Russo M et al (2002) Computed tomographic anatomy of the canine inner and middle ear. Vet Radiol Ultrasound 43(1):22–26 Schmidt K, Piaia T, Bertolini G et al (2007) External auditory canal atresia of probable congenital origin in a dog. J Small Anim Pract. 48(4):233–236 Shahnaz N, Feeney MP, Schairer KS (2013) Wideband acoustic immittance normative data: ethnicity, gender, aging, and instrumentation. Ear Hear. 34(Suppl 1):27S–35S Simpson D (1997) Atresia of the external acoustic meatus in a dog. Aust Vet J 75:18–20 Sobel DS (2012) Endoscopy of the canine and feline ear: otoendoscopy. In: Ragni SA, Moore AH (eds) Clinical manual of small animal endosurgery, vol 9, 1st edn. Blackwell Publishing, London, pp 256–272 Strain GM, Tedford L, Jackson RM (1994) Postnatal development of the brainstem auditory-evoked potential in dogs. Am J Vet Res 52:410