Idiopathic Intracranial Hypertension Explained: A Guide for Patients and Families 3030800415, 9783030800413

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Idiopathic Intracranial Hypertension Explained A Guide for Patients and Families Kyle M. Fargen

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Idiopathic Intracranial Hypertension Explained

Kyle M. Fargen

Idiopathic Intracranial Hypertension Explained A Guide for Patients and Families

Kyle M. Fargen Wake Forest Baptist Medical Center Winston Salem, NC USA

ISBN 978-3-030-80041-3    ISBN 978-3-030-80042-0 (eBook) https://doi.org/10.1007/978-3-030-80042-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 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 translation, 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

For my wife, Christine, and for Chelsea, Eric, and Cooper. I love you all more than you know.

Preface

This book was written with the purpose of providing patients and families with a guide to help understand a very complex, painful, and scary disease. Our understanding of idiopathic intracranial hypertension (IIH) is surprisingly limited, especially given that we have known about it for decades. I have attempted to explain this disease, to the best of my current understanding, in a manner that can be appreciated by individuals with no medical knowledge. I am hopeful that this will help patients understand why they are suffering and explain the treatments so that they don’t seem so scary when they are discussed. Before going forward, it is important for the reader to understand my perspective on IIH because it colors the book and the way I present information. My personal interest in this disease stems from my training as an endovascular neurosurgeon and my interest in cutting-edge interventional therapies, most notably venous sinus stenting. As a surgeon, my experience is mostly with medically refractory IIH, meaning that most of the patients I see have severe symptoms that have persisted even when treated with medications. Also, as a surgeon, my skill set resides in doing procedures, not in managing headaches with medications. Those patients with mild-­ moderate IIH that are successfully treated with medications alone are not usually sent to me in referral. The patient population that I regularly treat tend to be people that are suffering with significantly impaired quality of life and therefore are willing to undergo aggressive surgical treatments to get better. As such, I tend to see the patients that are more severely affected by IIH, and my perspective on medical treatments (which tend not to help all that much in this population of patients) tends to be more cynical than other physicians that routinely see success managing patients with mild symptoms with medications alone. Further, I tend to be more aggressive than the average physician in trying to improve quality of life. This means that, in my practice, I may be more likely to offer stenting or shunting to people than other neurosurgeons around the country. There are practice variations among different physicians in determining candidacy for different surgical procedures, in the work-up and diagnostic tests ordered, in medications used, and differences in surgical technique or devices used. I have developed my personal protocols for patient management based on what I think is vii

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Preface

best; however, I am young in my career, am to some degree a product of the places I trained as a physician, and my practice is shaped by the environment and devices available at the hospital where I practice. It is likely that every neurosurgeon around the country has their own patient management strategies. In instances where I think what I do or use really matters, I’ll point this out. But otherwise it’s probably merely a matter of physician preference. Finally, I do a fair amount of research studying the brain and the pressures within the skull and publish frequently in medical journals. My default writing style is “doctor speak,” which I have done my best to try to hold at bay for this book. Also, I have academic interests in this disease that I discuss because I think they are fascinating, but in reality may not be that helpful to a given patient. In summary, I think it is important to understand my personal biases in patient management and experience because everything you will read in this book derives from that perspective. Hopefully this book will help you or your loved one understand this perplexing disease and make it seem less frightening. Winston Salem, NC, USA

Kyle M. Fargen

Acknowledgments

Thanks to Jennifer Aldridge for taking such great care of my patients and helping me with this book. Without you this book would not be possible!

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Contents

1 Introduction��������������������������������������������������������������������������������������������     1 2 Basic Brain Anatomy and Physiology��������������������������������������������������     3 The Brain and its Fluid����������������������������������������������������������������������������     3 The Flow of Brain Fluid��������������������������������������������������������������������������     5 The Reabsorption of Brain Fluid Is into Veins����������������������������������������     6 Brain Veins ����������������������������������������������������������������������������������������������     7 Blood Pressure: Arteries Vs. Veins����������������������������������������������������������     9 Cerebrospinal Fluid Reabsorption Is Dependent on Venous Sinus Pressures��������������������������������������������������������������������������������������������������    10 What Are Normal Venous Sinus Pressures?��������������������������������������������    13 Venous Sinus Pressures Are Not Uniform throughout the Brain������������    13 IIH Is Due to High Venous Sinus Pressures��������������������������������������������    15 Hydrocephalus Is Not the Same as IIH����������������������������������������������������    16 Intracranial Pressure and CSF Pressure ��������������������������������������������������    18 Normal Intracranial Pressures (ICP)��������������������������������������������������������    19 References������������������������������������������������������������������������������������������������    20 3 Idiopathic Intracranial Hypertension (IIH)����������������������������������������    21 Diagnosis��������������������������������������������������������������������������������������������������    21 Presentation����������������������������������������������������������������������������������������������    22 Common Symptoms��������������������������������������������������������������������������������    23 Headache����������������������������������������������������������������������������������������������    23 Visual Symptoms ��������������������������������������������������������������������������������    25 Papilledema and Visual Loss ��������������������������������������������������������������    26 Light Sensitivity����������������������������������������������������������������������������������    28 Pulsatile Tinnitus����������������������������������������������������������������������������������    28 “Brain Fog”������������������������������������������������������������������������������������������    29 Cerebrospinal Fluid Leak (Rhinorrhea or Otorrhea) ��������������������������    30 Other Symptoms��������������������������������������������������������������������������������������    31 Symptoms Are Worsened by Weather Changes ��������������������������������������    32 Symptoms Are Often Related to Intracranial Pressure����������������������������    33 xi

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Distinguishing ICP That Is Too High (Hyper) vs. Too Low (Hypo)�������    34 Ehlers-Danlos Syndrome ������������������������������������������������������������������������    35 4 The Fundamental Reasons Patients Get IIH��������������������������������������    39 IIH Is Actually Not Idiopathic ����������������������������������������������������������������    39 Venous Pressures in the Body and the Brain ������������������������������������������    40 Normal Venous Pressures in the Body and Brain������������������������������������    41 Venous Pressures in the Body and Brain When CVP Is High ����������������    42 Venous Narrowing (“Stenosis”) ��������������������������������������������������������������    44 Why Does Venous Sinus Stenosis Occur? ����������������������������������������������    46 What Triggers the Positive Feedback Loop to Start?������������������������������    49 Vein Narrowing May Occur at More Than One Site ������������������������������    49 The Pressure Gradient������������������������������������������������������������������������������    51 Venous Congestion and Collaterals ��������������������������������������������������������    53 Venous Sinus Thrombosis������������������������������������������������������������������������    54 Confusion Between Thrombosis and Aplasia������������������������������������������    56 Other Causes of High Venous Pressures��������������������������������������������������    57 Not All IIH Patients Are the Same����������������������������������������������������������    58 IIH Links to Medications or Surgeries����������������������������������������������������    59 General Treatment Strategies������������������������������������������������������������������    61 IIH Is a Chronic Condition����������������������������������������������������������������������    62 References������������������������������������������������������������������������������������������������    63 5 Understanding Your Brain Imaging����������������������������������������������������    65 Imaging in IIH������������������������������������������������������������������������������������������    65 CT Scan����������������������������������������������������������������������������������������������������    66 MRI Scan ������������������������������������������������������������������������������������������������    68 MRV and CTV ����������������������������������������������������������������������������������������    70 Brain Imaging Findings You May See in Your Report����������������������������    70 Empty Sella������������������������������������������������������������������������������������������    70 Optic Hydrops or Distention of Optic Nerve Sheath ��������������������������    71 Venous Sinus Stenosis�������������������������������������������������������������������������    71 Venous Sinus Thrombosis��������������������������������������������������������������������    72 Chiari Malformation����������������������������������������������������������������������������    73 Collapsed Ventricle������������������������������������������������������������������������������    74 Pneumocephalus����������������������������������������������������������������������������������    75 Cerebral Edema������������������������������������������������������������������������������������    75 Bone Dehiscence����������������������������������������������������������������������������������    76 Metal Artifact ��������������������������������������������������������������������������������������    77 6 Measuring Intracranial Pressure ��������������������������������������������������������    79 Obtaining Intracranial Pressure Measurements ��������������������������������������    79 Lumbar Puncture (Spinal Tap) ����������������������������������������������������������������    81 The Basic Principles����������������������������������������������������������������������������    81 Who Performs this Procedure?������������������������������������������������������������    82

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Procedural Location ����������������������������������������������������������������������������    82 What to Expect: Pre-procedure������������������������������������������������������������    82 What to Expect: During the Procedure������������������������������������������������    82 What to Expect: Post-procedure����������������������������������������������������������    85 Complications��������������������������������������������������������������������������������������    86 Lumbar Drain Placement ������������������������������������������������������������������������    87 The Basic Principles����������������������������������������������������������������������������    87 Who Performs this Procedure?������������������������������������������������������������    87 Procedural Location ����������������������������������������������������������������������������    88 What to Expect: Before the Procedure������������������������������������������������    88 What to Expect: During the Procedure������������������������������������������������    88 What to Expect: After the Procedure ��������������������������������������������������    89 Complications��������������������������������������������������������������������������������������    89 Intracranial Pressure Monitor (Bolt) Placement��������������������������������������    90 The Basic Principles����������������������������������������������������������������������������    90 Who Performs this Procedure?������������������������������������������������������������    91 Procedural Location ����������������������������������������������������������������������������    91 What to Expect: Before the Procedure������������������������������������������������    92 What to Expect: During the Procedure������������������������������������������������    92 What to Expect: After the Procedure ��������������������������������������������������    92 Complications��������������������������������������������������������������������������������������    93 7 Lifestyle Modification and Weight Loss����������������������������������������������    95 The Link Between IIH and Being Overweight����������������������������������������    95 How We Measure Normal Weight Versus Overweight����������������������������    95 Is Being Overweight Dangerous?������������������������������������������������������������    97 The Relationship Between Body Mass Index and Central Venous Pressure����������������������������������������������������������������������������������������������������    98 Weight Loss Is an Effective Treatment for IIH in Most Patients ������������    99 Lifestyle Modification������������������������������������������������������������������������������   100 Tips for Being Successful with Lifestyle Modification ��������������������������   101 Weight Loss Surgeries ����������������������������������������������������������������������������   102 The Importance of Weight Loss After Surgical Treatment of IIH ����������   104 References������������������������������������������������������������������������������������������������   104 8 Medical Therapies for IIH��������������������������������������������������������������������   105 An Overview of Medications for IIH������������������������������������������������������   105 Acetazolamide (Trade Name: Diamox) ��������������������������������������������������   106 Methazolamide (Trade Name: Neptazane)����������������������������������������������   107 Topiramate (Trade Name: Topamax, Trokendi)��������������������������������������   108 Furosemide (Trade Name: Lasix)������������������������������������������������������������   110 Opiate (Opioid) Medications ������������������������������������������������������������������   111 Over-the-Counter Medications����������������������������������������������������������������   113 Reference ������������������������������������������������������������������������������������������������   114

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9 Cerebral Angiography ��������������������������������������������������������������������������   115 Overview��������������������������������������������������������������������������������������������������   115 Timing of the Procedure Is Important������������������������������������������������������   118 Anesthesia Affects Pressure Measurements��������������������������������������������   119 Angiograms in Patients Who Have Shunts����������������������������������������������   120 Contrast Dye, Allergies, and Kidney Problems ��������������������������������������   122 Cerebral Angiogram Procedure����������������������������������������������������������������   123 The Basic Principles����������������������������������������������������������������������������   123 Who Performs this Procedure?������������������������������������������������������������   123 Procedural Location ����������������������������������������������������������������������������   124 What to Expect: Pre-procedure������������������������������������������������������������   124 What to Expect: During the Procedure������������������������������������������������   124 What to Expect: Post-procedure����������������������������������������������������������   127 Complications��������������������������������������������������������������������������������������   127 References������������������������������������������������������������������������������������������������   129 10 Venous Sinus Stenting����������������������������������������������������������������������������   131 Reasons to Have a Surgical Procedure Performed for IIH����������������������   131 Venous Sinus Stenting Overview������������������������������������������������������������   132 Stents Reduce Intracranial Venous and CSF Pressures and Relieve the Pressure Gradient ����������������������������������������������������������   135 Candidacy for Stenting����������������������������������������������������������������������������   136 Usually the Larger Transverse Sinus Is Treated��������������������������������������   138 Timing of the Procedure Is Less Important Than the Angiogram ����������   139 Venous Sinus Stenting Symptom Improvement Rates����������������������������   140 Defining Success with Stenting ��������������������������������������������������������������   142 Sudden Visual Loss����������������������������������������������������������������������������������   143 Venous Sinus Stenting in Children or Mentally Handicapped Individuals������������������������������������������������������������������������������������������������   144 Blood Thinners����������������������������������������������������������������������������������������   145 Venous Stenting Procedure����������������������������������������������������������������������   147 The Basic Principles����������������������������������������������������������������������������   147 Who Performs This Procedure? ����������������������������������������������������������   147 Procedural Location ����������������������������������������������������������������������������   147 What to Expect: Pre-Procedure������������������������������������������������������������   148 What to Expect: During the Procedure������������������������������������������������   149 What to Expect: Post-Procedure����������������������������������������������������������   151 Complications��������������������������������������������������������������������������������������   152 Stent Pain ������������������������������������������������������������������������������������������������   153 Stopping IIH Medications After Stenting������������������������������������������������   154 Evaluation of Patients with Persistent Symptoms After Stenting������������   155 Reasons for Stent Failures ����������������������������������������������������������������������   157 New Vein Narrowing Can Develop After Stenting����������������������������������   161 Using Spinal Tap Opening Pressure After Stenting ��������������������������������   163 Repeat Cerebral Angiography After Stenting������������������������������������������   165

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Repeat Stenting����������������������������������������������������������������������������������������   167 Re-Equilibration Phenomenon����������������������������������������������������������������   169 Some Final Comments About Stents ������������������������������������������������������   170 References������������������������������������������������������������������������������������������������   171 11 Cerebrospinal Fluid Shunting��������������������������������������������������������������   173 Overview��������������������������������������������������������������������������������������������������   173 Shunting for Impaired Quality of Life ����������������������������������������������������   176 Life Expectancy of Shunts ����������������������������������������������������������������������   177 Any of the Three Parts Can Stop Working and Cause the Shunt to Fail ������������������������������������������������������������������������������������������������������   179 Ventriculo-peritoneal (VP) Shunts����������������������������������������������������������   181 Ventriculo-atrial (VA) Shunts������������������������������������������������������������������   184 Lumbo-peritoneal (LP) Shunts����������������������������������������������������������������   186 Other Shunts��������������������������������������������������������������������������������������������   188 Shunt Valves��������������������������������������������������������������������������������������������   189 Blood Thinners����������������������������������������������������������������������������������������   192 Shunt Surgical Procedure������������������������������������������������������������������������   193 The Basic Principles����������������������������������������������������������������������������   193 Who Performs This Procedure? ����������������������������������������������������������   193 Procedural Location ����������������������������������������������������������������������������   193 What to Expect: Pre-Procedure������������������������������������������������������������   193 What to Expect: During the Procedure������������������������������������������������   194 What to Expect: Post-Procedure����������������������������������������������������������   195 Complications��������������������������������������������������������������������������������������   196 Pain, Swelling, and Numbness at Shunt Site ������������������������������������������   198 Cerebrospinal Fluid Leak from Incision��������������������������������������������������   200 Evaluating Patients with IIH Symptoms After Shunting ������������������������   201 Shunt Series ��������������������������������������������������������������������������������������������   203 CT Brain��������������������������������������������������������������������������������������������������   204 Nuclear Medicine Shuntogram����������������������������������������������������������������   205 Ventricular Collapse��������������������������������������������������������������������������������   207 Shunt Tap ������������������������������������������������������������������������������������������������   211 Shunt Re-programming����������������������������������������������������������������������������   212 VP Shunt Peritoneal Catheter, Catheter Migration, and Pelvic Pain ������   215 Shunt Infection����������������������������������������������������������������������������������������   217 Re-Equilibration Phenomenon after Shunting ����������������������������������������   219 Shunt Revision Surgery ��������������������������������������������������������������������������   220 Some Final Comments About Shunts������������������������������������������������������   223 Reference ������������������������������������������������������������������������������������������������   224 12 Other Surgical Treatment ��������������������������������������������������������������������   225 Overview��������������������������������������������������������������������������������������������������   225 Internal Jugular Vein Treatments ������������������������������������������������������������   225 Optic Nerve Sheath Fenestration ������������������������������������������������������������   228

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Cranio-Cervical (Occipito-Cervical) Fusion��������������������������������������������   229 Cerebrospinal Fluid Leak Repairs ����������������������������������������������������������   231 Chiari Decompression������������������������������������������������������������������������������   233 Reference ������������������������������������������������������������������������������������������������   235 Glossary����������������������������������������������������������������������������������������������������������   237 Index����������������������������������������������������������������������������������������������������������������   245

Chapter 1

Introduction

Idiopathic intracranial hypertension (IIH, or “pseudotumor cerebri,” or “benign intracranial hypertension”) is an uncommon condition that causes symptoms of severe headache and visual changes. It is most commonly seen in overweight women in their child-bearing years (usually 20–40 years) but occasionally is seen in other patient groups. The symptoms are a result of high pressure (“hypertension”) in the cerebrospinal fluid (CSF) inside and around the brain. Patients with this condition usually present with progressive, chronic headaches. Often times patients will say they have had headaches for months or years that were tolerable but then seek medical attention finally because of progressive worsening to where they significantly affect quality of life. Rarely, patients may present with symptoms other than headache. Some patients have visual blurring or vision loss that occurs in the absence of headache. Some patients only have a loud whooshing sound in their ears that sounds like they are hearing their heartbeat at all times. Others present with dripping of CSF from their nose or ears due to the high pressure squeezing fluid out through small holes in the base of the skull. Others have no symptoms at all but are found to have swelling of the optic disc in the back of the eye when a doctor checks using an eye scope during a routine physical exam. IIH therefore may manifest as a spectrum of symptoms, ranging from mild headache or no headache with no visual complaints to severe, unrelenting headaches with severe visual loss. The classic symptom of IIH is a pressure-type headache. Most people with IIH say that they feel a gnawing or throbbing ache behind their eyes. This feeling of “pressure” behind the eyes is in fact due to a literal buildup of pressure in the cerebrospinal fluid (CSF) behind the eyes. That fact alone is easy for patients and their families to understand and easy for doctors to communicate: “too high of pressure” causing your headaches. But the rest of IIH—the anatomy, the reasons for the pressure buildup, and the treatments—are not so simple. In fact, as someone who has spent countless hours trying to explain the condition and its treatments to patients and their families in my clinic, I will be the first to tell you that IIH is not easy. The anatomy, the normal physiology, and the reasons for the disorder are, let’s just say © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0_1

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1 Introduction

complex. Not to mention the fact that we discuss separate and totally distinct “pressures” while discussing treatment options: arterial blood pressure, venous blood pressures, and intracranial pressures. And these have different units of measure that have to be converted mathematically! Talk about confusing. Over the last few years, I have developed and repeatedly performed a 60-minute run-through of the main principles when seeing patients in my clinic. This summary, which I now have memorized like a speech, starts with the symptoms, then an explanation of pressure within the head, then to why we thought the pressure was high, followed by older treatment strategies based upon this hypothesis, then to our new understanding of the disease, and then finally to our treatment options knowing what we know now. This seems to work as a rough outline, but so much information is left out during this 60-minute discussion that would be of use to patients. Since I now have the ability to talk as much as I want, I am going to walk through an explanation of IIH from the beginning to the end, hitting on all the things that I think are important for patients and their families to understand. This book basically contains almost everything I know about this condition. Some of the information presented will be unnecessary. Much of it will be a little confusing. But hopefully by following this logical stepwise format, we will make a very confusing and scary disease something that is not so complex and not so scary.

Chapter 2

Basic Brain Anatomy and Physiology

The Brain and its Fluid An explanation of IIH requires understanding a thing or two about how the brain looks and functions. I completely understand that most readers will have little or no medical background and that’s OK—the point here is to establish some important anatomical or physiologic concepts because they will help us understand why we do what we do from a treatment standpoint. So let’s begin by discussing some normal anatomy about the brain. The brain sits within the skull and is surrounded by a membrane. This membrane is called the “dura mater,” or just “dura.” It is a tough membrane that houses the brain and its fluid. The same membrane extends down into the spine around the spinal canal where the spinal cord sits. The brain and spinal cord are surrounded by a clear fluid called cerebrospinal fluid (CSF, also known as “spinal fluid”). CSF is made by the brain continuously, travels through fluid chambers inside the brain, and then bathes the brain and spinal cord, serving as a protective fluid surrounding the nervous system. The dura keeps brain fluid from leaking out. The fluid chambers in the brain are called “ventricles” (note: there are chambers in the heart called ventricles too, but these are totally unrelated). There are two large ventricles called the “lateral ventricles,” one on each side of the brain, and they communicate with a smaller midline “third ventricle” (Fig. 2.1). Under normal conditions, the structures of the brain are symmetric, so the two lateral ventricles appear like mirror images of each other. CSF that leaves the brain’s chambers (ventricles) then bathes the brain. Fluid extends forward and surrounds the optic nerve that goes to the eye. Fluid also extends down out of the skull and into the spine where it surrounds the spinal cord. In the lower spine, the spinal cord separates into a bunch of nerve roots that float in this fluid. Therefore fluid in the ventricles (within the chambers of the brain) is continuous with the fluid surrounding the brain, in the spine, and around the optic © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0_2

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2  Basic Brain Anatomy and Physiology

Fig. 2.1  Brain scan with cerebrospinal fluid (CSF) appearing bright. The brain tissue is grey. Everything inside and around the brain that appears bright is CSF. CSF is inside the lateral ventricles and the third ventricle, as well outside and around the brain

nerves. Fluid can move freely within these spaces. Another way to put it: if you mixed a few drops of blue food coloring into the fluid, in a short while the fluid inside and around the brain, outside the optic nerve, and in the spine would all be colored blue, as it would mix throughout all of this fluid freely. Key Points 1. The brain and spinal cord are surrounded by clear fluid called cerebrospinal fluid, or CSF. 2. CSF is contained within a membrane called the dura, which surrounds the fluid spaces. 3. The large fluid chambers in the brain are called ventricles. 4. CSF in the ventricles mixes freely with CSF outside the brain, around the optic nerves to the eye, and down into the spinal canal around the spinal cord.

The Flow of Brain Fluid

5

The Flow of Brain Fluid Cerebrospinal fluid (CSF) is made inside the brain, circulates through the ventricles of the brain, then leaves the brain, and eventually surrounds the brain. Most of the CSF gets reabsorbed into the blood stream outside the brain. At any given time, there is about 150 ml of fluid inside and surrounding our brain and spinal cord. To put this into perspective, 150 ml is about 2/3 of a cup or about ten tablespoons. Our brains make about 450 ml per day, which means that we produce (and reabsorb) the entire volume of CSF within and around our brains three times per day. For this reason, fluid drained off (by a spinal tap, for instance) tends to be replaced in a very short period of time (a few hours). The best way to think of the CSF around the brain and spinal cord is to use the “sink” analogy. I think this analogy simplifies the CSF space into an easily understandable example for most people and helps to explain how our brains make, and then reabsorb, fluid. In the sink analogy, there is a (1) faucet that produces fluid, (2) a drain at the bottom that drains fluid from the sink, and (3) some amount of standing water in the sink (Fig. 2.2). The faucet of the sink is similar to the small organs that make CSF within our brains. In people, the faucet is always “on,” because these small little organs are constantly producing CSF. Therefore, in our analogy, consider that the faucet is always producing the same amount of water. This water flow into the sink never stops. Sink Analogy for Cerebrospinal Fluid Faucet = Organs in Brain that Make Fluid (Constantly Producing Fluid)

Water Level In Sink = Fluid Inside and Around Brain (Stays the Same)

Drain = Arachnoid Granulations that Reabsorb Fluid into Veins (Works at Same Speed as Faucet)

Fig. 2.2  The sink analogy of cerebrospinal fluid (CSF) production and reabsorption. In a normal situation, the water level does not change because the faucet and the drain are working at the same speed

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2  Basic Brain Anatomy and Physiology

The second key element of the sink analogy is the drain at the bottom of the sink. We have small organs that reabsorb CSF back into the large veins outside the brain. The little organs represent the drain in the analogy. The drain functions only as well as the pipes that lead out of the sink, and the drain holes can be blocked by debris within the sink. Lastly, the standing water in the sink is similar to the CSF sitting within the ventricles of our brains and in the space around our brain and spinal cords. This amounts to about 150 ml of fluid at any given time (25 mL in the ventricles, the rest around the brain and in the spinal column). In a normal situation, the water level is constant in the sink. A steady water level in the sink means that the faucet and the drain are working at the same speed (fluid is being produced at the same speed at which it is being reabsorbed). Therefore, in a normal situation, our brains produce CSF constantly, reabsorb CSF constantly, and have a constant volume of CSF inside and around our brains. In abnormal situations, where either the drain holes are blocked or if the pipes leading out of the sink are partially clogged, water won’t move through the drain as quickly. However the faucet is unaware of this and will continue to pour out water at the same speed. This will cause the water level in the sink to rise. For example, a patient with bleeding in the brain may have blood “block the drain holes” which causes a buildup of CSF within the brain, causing increased pressure within the brain and enlargement of the ventricles (fluid chambers) in the brain. Key Points 1. The brain constantly makes CSF.  This fluid constantly gets reabsorbed. CSF drained off (by a spinal tap, for instance) is replaced by the brain over a few hours. 2. The easiest way to think about the flow of CSF is to think about your brain like a “sink.” The faucet is always on and therefore always producing fluid, and the drain is always draining water out at the same speed as the faucet is making it, so in normal situations the water level is at a constant level in the sink. 3. Abnormal situations occur when the drain doesn’t work as well as it should. A drain that stops draining fluid out of the sink will cause the water level to rise in the sink. This leads to a buildup of fluid (and pressure) inside the brain.

The Reabsorption of Brain Fluid Is into Veins In our sink analogy, the water that leaves the sink through the drain has to go somewhere. In our brains, the CSF that is reabsorbed from the fluid space around the brain travels through small organelles called arachnoid villi and then into the big veins outside the brain. These veins are large and surrounded by the membrane

Brain Veins

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outside the brain (the “dura”) and therefore are called the “venous sinuses” or “dural venous sinuses.” The venous sinuses are not the same as the air-filled spaces of the skull that are also called “sinuses” (sinus infections are of the air-filled spaces in the skull, not the veins). CSF leaving the brain travels through the arachnoid granulations into the venous sinuses and then mixes with the blood in these veins. As fluid gets reabsorbed, it dissolves into the blood and becomes one with it. This blood is then carried back to the heart through the large veins in the neck and chest. The fact that CSF gets reabsorbed into the veins outside the brain is critical for understanding why IIH occurs. So in our analogy of the sink, imagine that the drain at the bottom of the sink leads to the veins outside the brain. In the next few sections, I’ll describe the anatomy of the brain veins and those leading back to the heart. Afterward, I’ll do my best to explain how this fluid gets reabsorbed and why there is a reabsorption problem in patients with IIH. Key Points 1. Cerebrospinal fluid (CSF) gets reabsorbed into the bloodstream by traveling from the space around the brain, through tiny organelles called arachnoid villi, and then into the large veins outside the brain. 2. The big veins outside the brain are covered in membrane called the dura and therefore are called “dural venous sinuses.”

Brain Veins Like most organs in the body, arteries carry blood from the heart to the brain. Blood that leaves the brain travels in veins back to the heart. Because the brain needs a lot of blood to function normally, 15–20% of the total amount of blood that your heart pumps goes to the brain. This means that a lot of blood is being pumped to the brain through arteries and a lot of blood is traveling through the veins from the brain back to the heart. The brain is covered in small veins that collect the blood and drain into the large veins outside the brain, called the venous sinuses. Remember that these veins are within the membrane outside the brain, called the dura, and therefore are often called “dural venous sinuses.” As mentioned previously, these sinuses are different than the air-filled sinuses (holes) in the skull. The dural venous sinuses are inside the skull, outside the brain. In some people, part of the sinuses may appear to be missing, which may be entirely normal. The word “aplasia” (or “aplastic”) usually refers to a normal variant where part of the sinus is missing. You may also see the word “hypoplastic,” which is medical jargon for “small.” The main venous sinus in the center of the head is the superior sagittal sinus. This big vein collects blood from both sides of the brain (Fig.  2.3). As it travels down toward the base of the skull, the superior sagittal sinus splits into two separate veins at a site called the “torcula”, with one traveling on each side of the head by the ear. These

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2  Basic Brain Anatomy and Physiology Side View of Veins

Front View of Veins

Superior Sagittal sinus

Torcula Superior Sagittal Sinus Right Transverse Sinus Right Sigmoid Sinus Right Internal Jugular Vein

RIGHT

Transverse Sinus

Left Transverse Sinus

Torcula

Left Sigmoid Sinus Left Internal Jugular Vein

LEFT

Sigmoid Sinus Internal Jugular Vein

FRONT

BACK

Fig. 2.3  Major veins of the brain and neck, as viewed from the front and the side. A single superior sagittal sinus splits at the torcula into the right and left transverse sinuses, which then travel downward to become the internal jugular veins. In this image, the transverse sinuses are co-­dominant (both large and about the same size). On the side view, the right and left transverse sinuses, sigmoid sinuses, and internal jugular veins overlap as they are at the same location on both sides

are called the transverse sinuses. The size of the two transverse sinuses can vary. In some people, the two transverse sinuses are the same size (or “co-dominant,” meaning both are large). In most people, the right transverse sinus is larger (“dominant”), and the left transverse sinus is small (“non-dominant”). Sometimes, the left transverse sinus is larger, and the right transverse sinus is smaller (Fig. 2.4). The transverse sinus is very important for the treatment of IIH as it is a common site of narrowing. The transverse sinus on each side takes a turn and becomes the sigmoid sinus. The two sigmoid sinuses then leave the skull by the ear on each side, where the vein becomes the internal jugular vein. The internal jugular vein (or just “jugular vein,” or “IJ” for short) travels from the skull down to the chest where it joins the bigger veins by the heart. Key Points 1. The brain requires a lot of blood. This blood travels to the brain from the heart in arteries and leaves the brain in veins to get back to the heart. 2. The large veins outside the brain are within the membrane outside the brain called the dura and are called the “dural venous sinuses” or just “venous sinuses.” 3. The large vein in the middle of the head is the superior sagittal sinus. This vein splits into the two transverse sinuses at a site called the “torcula.” 4. In most people, the right transverse sinus is large and the left transverse sinus is small. However everyone is different. In some people, the two are equal in size; in others, the left side is bigger. 5. Blood traveling through the transverse sinus next travels through the sigmoid sinus and then leaves the skull and drains back to the heart in the internal jugular vein.

Blood Pressure: Arteries Vs. Veins

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Co-dominant Transverse Sinuses Dominant Right Transverse Sinus, (Equal in Size) Small Left Transverse Sinus

RIGHT

LEFT

RIGHT

LEFT

Dominant Left Transverse Sinus, Small Right Transverse Sinus

RIGHT

LEFT

Fig. 2.4  Examples of different sizes of the transverse sinuses. On the left, the right and left transverse sinuses are both large and roughly equal in size. An angiogram of an example patient with co-dominant sinuses is shown below. In the middle is a right transverse sinus dominant illustration with angiogram below. On the right is a left-side dominant example

Blood Pressure: Arteries Vs. Veins When you go to the doctor and have your blood pressure checked, the doctor is checking the blood pressure in your arteries. A normal arterial blood pressure is somewhere around 130 over 80 and is measured in a unit of measure called millimeters of mercury (mmHg, as “Hg” is the abbreviation for mercury). By convention, blood pressures, in either the arteries or veins, are measured in this unit of measure, mmHg. So in a normal individual, arterial blood systolic pressure is somewhere around 130 mmHg. Veins, on the other hand, have dramatically lower pressures. Even in the biggest veins by the heart, the pressures in the veins are usually 8 mmHg or less. So while arteries have high pressures (130 mmHg) because of the blood being pumped from the heart, when blood is traveling back to the heart, its pressure is dramatically lower (8 mmHg). Because arteries and veins deal with blood of wildly different pressures, they are designed differently. Arteries bound with each heartbeat because of the high pressure, which generates a “pulse” that you can feel. The walls of arteries tend to be more rigid, meaning that they are harder to compress. For example, feel the radial pulse at your wrist by the base of your thumb. Feel how the artery bounds with each heartbeat. Now push on the artery to make the pulses stop. You have to push pretty hard to make the pulse go away.

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2  Basic Brain Anatomy and Physiology

Veins, in contrast, are soft and easily compressible. Vein walls are thin because they don’t deal with high pressures. Veins, consequently, are easy to squish. Note how easy it is to compress the veins that stick out of your hand. The large veins outside the brain (venous sinuses), just like the veins in your hand, are also easy to squish. This will be important when we talk about IIH, because the transverse sinuses may get compressed which can lead to IIH symptoms. In addition, veins in the abdomen may be compressed by excess body fat which can also lead to IIH symptoms.

Key Points 1. Blood pressure is measured in millimeters of mercury, or “mmHg.” Both artery and vein blood pressures are measured in this way. 2. Arterial blood is high pressure and pulsatile. The pressure in veins is dramatically lower in pressure and, even in the biggest veins by the heart, is very low (10 mmHg). 3. Arteries are rigid and hard to compress, while veins are soft and easy to compress. 4. The venous sinuses outside the brain and veins in the abdomen are therefore susceptible to being compressed.

 erebrospinal Fluid Reabsorption Is Dependent on Venous C Sinus Pressures Thus far, we’ve hit on some important basic brain anatomy and physiology principles. We’ve established that cerebrospinal fluid (CSF) is made by the brain constantly, travels through the chambers of the brain (ventricles), and then gets reabsorbed into the venous sinuses outside the brain. Our brains constantly make CSF, and therefore we constantly reabsorb CSF. CSF that gets reabsorbed does so through tiny organs (arachnoid granulations) into the venous sinuses, where the fluid mixes with venous blood. This blood then travels through the superior sagittal sinus, through transverse and sigmoid sinuses, and then through the internal jugular veins back to the heart. So how exactly does CSF get reabsorbed? CSF reabsorption back into the blood stream occurs via a pressure-dependent mechanism, such that the pressure of the CSF has to be slightly higher than the pressure in the venous sinuses outside the brain for fluid to be reabsorbed. Understanding this point is critical in understanding why IIH occurs. Old studies performed in animals suggest that CSF pressure has to be roughly 3 mmHg higher than the pressure in the venous sinuses to allow fluid to move through the arachnoid granulations into the veins. This means that higher pressures in the dural sinuses will cause the CSF pressure inside the brain to be higher. This is confusing, so let’s think of a hypothetical patient with our sink

Cerebrospinal Fluid Reabsorption Is Dependent on Venous Sinus Pressures Venous Pressures Normal, Fluid Level Normal

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Venous Pressures HIGH, Fluid Level HIGH

Drain Working Normally (Normal venous pressure) Clogged Drain (HIGH venous pressure)

Fig. 2.5  High venous pressures are like a clogged drain. Water doesn’t travel as well through the drain, causing the water level to rise, and the pressure in the water to be higher

analogy, where the venous pressure is analogous to a bunch of hair blocking the drain in the sink (Fig. 2.5). The higher the pressure in the veins, the more hair is clogging the drain pipes. Remember that the faucet is always on. If an average person has a pressure of 10 mmHg in the venous sinuses, CSF will build up in and around the brain until the pressure reaches a value slightly higher than 10, to approximately 13 mmHg. Once this pressure is reached, CSF can get reabsorbed, so now the pressure will stabilize. In our analogy, the water level will rise to a point where enough pressure is in the sink to force water through the hair clogging the drain pipes. Once the water level rises far enough, the water level will stabilize, because the water being produced by the faucet equals the rate at which water is going through the drain. If we take that person and then increase their venous pressure to 15 mmHg suddenly, no CSF will be reabsorbed until the CSF builds up under pressure to an even higher pressure. The faucet keeps producing CSF, and the drain now allows no water to escape (pressure not high enough yet), so the water level rises. Once the CSF slowly builds up under pressure until the pressure is 18 mmHg, the fluid can now be reabsorbed again, and the CSF pressure stabilizes at 18 mmHg. Similarly, if we now suddenly decrease the venous pressure in the sinuses to 5 mmHg, CSF is rapidly reabsorbed into the veins until the CSF pressures reaches 8  mmHg, at which point reabsorption slows considerably, and eventually a new steady state is reached.

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2  Basic Brain Anatomy and Physiology

Therefore, the pressure in the CSF is dependent on the pressure in the venous sinuses outside the brain (Fig. 2.6). If the pressure in the veins goes up, CSF pressure will go up. If the venous pressure goes down, CSF pressure goes down. In a normal situation, the drain in the sink has no hair clogging its pipes and is functioning at full speed. In patients with IIH, the drain pipes are clogged, and the reabsorption of CSF only occurs at high pressures, leading to a steady state where CSF pressures are constantly high.

Key Points 1. Cerebrospinal fluid (CSF) reabsorption occurs via a pressure-dependent mechanism into the dural venous sinuses. 2. CSF pressure has to be roughly 3 mmHg higher than the pressure in the venous sinuses to allow fluid to move through the arachnoid granulations into the veins. 3. The pressure in the CSF is dependent on the pressure in the venous sinuses outside the brain. If venous pressures increase, CSF pressures must also increase. If venous pressures decrease, CSF pressures will decrease.

30

25

PRESSURE

20

15

10

5

V E I N

C S F

0 Normal Vein Pressure Normal CSF Pressure

If Vein Pressure Increases, CSF Pressure Increases

If Vein Pressure Decreases, CSF Pressure Decreases

Fig. 2.6  CSF pressure (blue) is dependent on vein pressure (red). If vein pressures increases, CSF pressure will increase accordingly. If vein pressure decreases, CSF pressure will decrease accordingly

Venous Sinus Pressures Are Not Uniform throughout the Brain

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What Are Normal Venous Sinus Pressures? If we’re going to talk about abnormally high venous sinus pressures, we should probably define what “normal” pressures are. Unfortunately, we have yet to define what normal venous sinus pressures are in humans. There are essentially no studies out there where people without IIH have undergone venous sinus pressure measurements. This is for multiple reasons, including the following: (1) no one has thought to do it yet, (2) it is not something we ever do in patients without IIH, so we would have to convince people without IIH to undergo an additional procedure strictly for research purposes, and (3) the extra cost. So to date there are no studies that have reported on what normal venous sinus pressures would be in individuals without IIH. With that being said, we can use logic to predict what these pressures should be. We know what a normal CSF pressure is (see Chap. 3), so we can infer that venous sinus pressures will be similar based on what we know about the relationship between venous and CSF pressures. This means that most normal people probably have a venous sinus pressure that is 16–18 mmHg or less. Further, we can use “accidental” data that we obtained on certain patients where their clinical picture was not clear. I have done a few pressure measuring procedures on patients who turned out not to have IIH. In these patients, the venous sinus pressures in the superior sagittal sinus (large central venous sinus) average about 13–18 mmHg. It is probably therefore safe to assume that normal venous sinus pressures should be less than 16–18 mmHg or so. Once again, this has not been confirmed with scientific study but more of an educated guess. At this time a study is underway in which I am measuring venous sinus pressures in people without IIH. We are only part of the way through the study, but so far, venous sinus pressures in these individuals have all been 16 mmHg or less. Key Points 1. We have yet to do scientific studies to define what constitutes “normal” venous sinus pressures. 2. Based on anecdotal evidence, normal venous sinus pressures should probably be less than about 16–18 mmHg.

 enous Sinus Pressures Are Not Uniform throughout V the Brain When we measure venous pressures at different points in the venous sinuses, the pressures usually vary. Almost uniformly, the superior sagittal sinus has the highest venous pressures. In people who have normal venous sinus anatomy, there is a slight decrease in pressures as we move from the superior sagittal sinus to the transverse sinus. There is additionally a lower pressure in the sigmoid sinus and usually a

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lower pressure in the internal jugular vein. So in people with normal venous sinus anatomy, the pressures usually decrease as we measure from the top of the head to the heart. As I mentioned in the last section, there has yet to be scientific studies looking at what normal pressures are. Consequently, we don’t have good data on how the venous sinus pressures should decrease from point to point along the venous system. In the “accidental” data I mentioned in the last section where we performed venous pressure measurements on patients who turned out not to have IIH, we saw a decrease in about 1–2  mmHg from the superior sagittal sinus to the transverse sinus and an additional 1–2 mmHg decrease from the transverse sinus to the sigmoid sinus (Fig. 2.7). These values continue to decrease in the internal jugular vein and then eventually near the heart. Therefore, it is likely that the highest venous pressures are in the superior sagittal sinus and the pressures decrease slightly as the blood moves closer to the heart. In people with normal anatomy, we think the pressure in the superior sagittal sinus is usually about 4–5 mmHg more than the pressure in the large veins by the heart. If the numbers are different in different locations, is there one single place that best summarizes the venous pressures in the head? We don’t know for sure, but based on data from our studies suggest, it is at the point where the superior sagittal sinus splits into the transverse sinuses, which we call the “torcula” or “confluens.” It gives us a single value that probably best summarizes any given patient’s venous pressures and allows us to correlate venous pressures to CSF pressures. In an article we recently published (Lee et  al. 2021), torcula pressures were the most closely linked venous sinus pressure to CSF pressure based on immediate spinal tap in almost 50 patients with IIH. By analyzing the relationship statistically, we were able to generate a calculation that allows us to predict venous sinus pressures based on knowing what the CSF pressure was on the most recent spinal tap (Table 2.1). There Fig. 2.7  Side view angiogram with pressure measurements (yellow numbers in blue boxes) in a patient with normal venous pressures. Notice that the pressures are highest in the superior sagittal sinus and they steadily decrease toward the internal jugular vein. Blue arrows show the direction of venous blood flow from the top of the head toward the heart

IIH Is Due to High Venous Sinus Pressures

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Table 2.1  Expected torcula pressures based on cerebrospinal fluid (CSF) pressure on spinal tap in IIH patients. Remember that the torcula is the bottom of the superior sagittal sinus where it splits into the two transverse sinuses. As venous sinus pressures increase, CSF pressures increase accordingly Cerebrospinal fluid (CSF) pressure (cm of water) 15 20 25 30 35 40 45 50

Torcular pressure (mmHg) 14.9 20 25 30.1 35.1 40.2 45.2 50.3

is almost a one-to-one relationship between venous sinus pressure and CSF pressure. Notice that as CSF pressure on the spinal tap increases, superior sagittal sinus pressures increase by a similar amount.

Key Points 1. The highest venous sinus pressures are measured in the superior sagittal sinus. 2. In patients with normal anatomy, the venous pressures appear to progressively decrease as we measure from the superior sagittal sinus to the transverse sinus, sigmoid sinus, internal jugular vein, and eventually the heart. Usually the superior sagittal sinus is about 4 or 5 mmHg higher than the pressure by the heart. 3. The venous pressure obtained at the torcula, where the superior sagittal sinus splits into the transverse sinuses, is probably the best single measure to summarize an individual patient’s venous sinus pressures.

IIH Is Due to High Venous Sinus Pressures In patients with IIH, the high pressures in the cerebrospinal fluid (CSF) are because of higher than normal pressures in the venous sinuses. We know this fact to be true because we often measure the pressures in these veins in patients with IIH and can correlate the high venous pressures with CSF pressures. There is ample evidence from scientific research that (1) the high venous pressures are the cause of the high CSF pressures and (2) that lowering the venous pressures causes an immediate reduction in CSF pressures. Specifically, there are two studies where patients with IIH and high venous pressures underwent placement of an intracranial pressure

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monitoring device to monitor CSF pressures during a stenting procedure that significantly reduced the venous sinus pressures (Liu et al. 2017; Matloob et al. 2017). I will explain later how we go about measuring these pressures and how stents lower pressures, so don’t worry about that for now. However, in both studies, CSF pressures dropped immediately upon reducing venous pressures. Because we know that venous sinus pressures are the cause of the high CSF pressure in IIH, many of the treatments are designed around reducing venous pressures, with some being more effective than others. In patients with medically refractory IIH (meaning they continue to have severe symptoms even while on medications), I routinely record venous sinus pressure measurements in a procedure called an angiogram. The specifics on this procedure will be discussed later in Chap. 9. Among patients with medically refractory IIH, essentially all patients have high venous sinus pressures. Superior sagittal sinus pressures range from anywhere as low as the high teens to as high as 60 or 70 mmHg in severe cases. In the majority of patients, the pressures range from the 20–40 mmHg. Keep in mind that in normal individuals, the pressure is probably somewhere around 18 mmHg or less. Often times we can actually predict the CSF pressure by the venous sinus pressure, because they are interrelated. Remember from previous sections that CSF is reabsorbed into veins via a pressure-dependent mechanism, where CSF pressures have to be slightly higher than pressure in the veins to move into the veins. As a reminder from the last section, this usually means that the venous sinus pressure obtained in the superior sagittal sinus or torcula will roughly approximate CSF pressures. Key Points 1. Patients with IIH have high venous sinus pressures. High venous sinus pressures directly cause CSF pressures to be too high. 2. Most patients with IIH have venous sinus pressures (recorded from superior sagittal sinus) that are in the 20–40  mmHg range. Rarely pressures may be severely elevated to upward of 60 or 70 mmHg. 3. Venous sinus pressures tend to correlate with CSF pressures, which may allow us to roughly predict CSF pressure if we know venous sinus pressures, and vice versa.

Hydrocephalus Is Not the Same as IIH Hydrocephalus, or “water on the brain,” is a dangerous condition where excess CSF builds up in and around the brain. Sometimes this condition has similar symptoms to IIH and can cause headache, visual loss, and vomiting. While the causes are varied, hydrocephalus is a condition where CSF inappropriately builds up and causes pressure on the brain.

Hydrocephalus Is Not the Same as IIH

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Using our sink analogy, consider if we suddenly clog some of the holes in the drain at the bottom of the sink. The faucet doesn’t know to stop making fluid and keeps producing it at the same steady rate. With less fluid now going through the drain, the water level in the sink will rise. In a person, the fluid spaces of the brain expand and exert pressure on the brain, which causes symptoms of hydrocephalus. The treatment for this condition is usually to either temporarily or permanently lower CSF pressures in the brain by removing fluid, often with spinal taps or “shunt” procedures. Importantly, IIH is fundamentally different than hydrocephalus and therefore should not be treated the same way. These are different disease processes. Many healthcare providers continue to think about IIH as a type of hydrocephalus, which should be discouraged. Most importantly, in hydrocephalus, the impairment in CSF reabsorption is independent of the venous sinus pressures. This means that the CSF pressures rise regardless of the venous sinus pressures. In many instances, we think the venous sinus pressures are totally normal in patients with hydrocephalus, while the CSF pressure can be very high. The lack of correlation between venous sinus pressures and CSF pressures is somehow related to the manner in which fluid reabsorption is impaired. In IIH, fluid reabsorption functions normally, it’s just that the venous sinus pressures are too high. Therefore in IIH normal fluid reabsorption occurs; it’s merely occurring at higher pressures than normal. In hydrocephalus, CSF does not get reabsorbed appropriately, regardless of how high or how low the venous pressures are. Lowering the venous pressure in a person with hydrocephalus will do little to change the CSF pressure. Hydrocephalus also differs from IIH in important ways that help doctors differentiate the two. In most patients with IIH, the fluid chambers (ventricles) of the brain are actually small, while in hydrocephalus the ventricles are usually larger than normal. Patient history may be helpful, as often times patients with hydrocephalus have previously had a brain surgery, bleeding in the brain, or an infection of the brain. While both may present with headache and nausea, patients with hydrocephalus more commonly become sleepy and/or comatose; some patients with hydrocephalus may die if they do not have the pressure lowered emergently. So while hydrocephalus and IIH have some common features, they are very different diseases with different causes and are treated differently. Key Points 1. Hydrocephalus, or “water on the brain,” is a condition where CSF builds up under pressure causing symptoms that may be similar to IIH (headache, visual loss). 2. Hydrocephalus is fundamentally different than IIH. In hydrocephalus, the impairment in CSF reabsorption is unrelated to the venous sinus pressures; CSF does not get reabsorbed appropriately in hydrocephalus, regardless of how high or how low the venous pressures are. 3. While hydrocephalus and IIH have some common features, they are very different diseases with different causes and are treated differently.

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Intracranial Pressure and CSF Pressure Most doctors refer to the pressure inside and around the brain as “intracranial pressure,” or “ICP” for short. I specifically avoided that term thus far in the book because, up until now, the relationship between cerebrospinal fluid (CSF) production and reabsorption and its relationship to venous sinus pressures required that we focus specifically on the CSF. In the previous sections, I described both blood pressure measurements and CSF pressure measurements in millimeters of mercury (mmHg). However, we need to start shifting toward describing the pressure in and around the brain as the slightly different “intracranial pressure” (ICP). Luckily, in most instances ICP and CSF pressures are synonymous. We most frequently measure ICP by measuring CSF pressures, so usually they are one and the same. In fact, for the purposes of this book, it is reasonable to basically assume that these two pressures are essentially equal. So anytime you see a mention of “CSF pressure” or “ICP,” they basically mean the same thing. But unfortunately, by convention we describe ICP in a unit of measure that is very different than that in which we describe blood pressures. When measuring arterial or venous blood pressures, we use millimeters of mercury (mmHg) as the unit of measure. Intracranial pressure, on the other hand, is almost uniformly reported in centimeters of water (cm of water) or less frequently millimeters of water (mm of water). A single cm of water is equal to 10 mm of water (there are 10 mm in 1 cm), so mm and cm of water values can be converted by multiplying or dividing by a factor of 10. For instance, if you had a spinal tap and the doctor says the pressure measurement is 230 mm of water, this is equivalent to 23 cm of water (230 divided by 10 is 23). So as not to cause more confusion, for the remainder of this book, we will refer to ICP in the units of cm of water, as this is the most common way in which ICP is discussed among doctors. However, mmHg and cm of water are not so easily converted. As you would expect, 1 mmHg does not equal 1 cm of water. There is a mathematical equation that allows us to easily convert cm of water to mmHg, should we need to:

1 mmHg = 1.36 cm of water

I have included a table (Table 2.2) just to showcase how these two units compare, in case you don’t want to have to do math. I understand that this is confusing, but don’t worry if this doesn’t make sense. I will make it a point to comment on this difference when it is necessary so I don’t lose you.

Normal Intracranial Pressures (ICP) Table 2.2  Conversion of mmHg and cm of water

19 Millimeters of mercury (mmHg) 1 2 5 10 15 20 25 30 40 50

Centimeters (cm) of water 1.5 3 7 14 20 27 34 41 54 68

Key Points 1. Intracranial pressure, or “ICP,” is the usual way in which doctors refer to the pressure in and around the brain. 2. In most situations, CSF pressure and ICP are equivalent, so we can use the two terms interchangeably. 3. ICP, by convention, is measured in centimeters of water. If you see an ICP measurement in millimeters of water, you can just divide the number by 10 to convert to cm of water. 4. Converting mmHg to cm of water is not so easy and requires a calculation. Refer to the table if you don’t want to do the math.

Normal Intracranial Pressures (ICP) Before we move on to Chap. 3 where we discuss specifics about IIH and why it occurs in individual patients, I will finish with our discussion of brain anatomy and physiology by commenting on what we consider “normal” intracranial pressures (ICP). ICP measurements are a critical part of diagnosing and treating patients with IIH. This section is very important so pay attention! Under normal conditions, most people have intracranial pressures (ICP) that are 15 cm of water (or 150 mm of water) or less. However, doctors generally identify 20 or 25 cm of water as the threshold for intracranial pressure being too high, but there is not a lot of true scientific data supporting 20 as a firm cutoff. It is important that you, as a patient or family member, understand this strong (but relatively unsubstantiated) threshold that neurosurgeons or neurologists will use to suggest that a pressure is too high (20 or higher) or normal (19 or less). Further, the diagnosis of IIH technically requires a pressure of 25 cm of water or higher. The truth is that a pressure of 18 or 19 may still be too high in certain people and cause significant symptoms (although this is rare) and should not be considered “normal.” Just keep in mind that the 20 or 25 cutoff is deeply engrained in doctors and colors the way they

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interpret ICP measurements. My personal bias is to argue that a normal ICP should be 15 or less. I refer to ICP from 16 to 20 as “marginally elevated” and ICP greater than 20 as too high. Importantly, throughout any given day, ICP changes. This is related to your head position as well as our activities. When we lay flat, our pressure increases in the head. When we stand up, ICP decreases. When we cough, sneeze, or strain, our pressures go up temporarily. When we lean down to tie our shoes, our pressures go up. When we sleep, we don’t breathe as well and retain carbon dioxide, which causes ICP to be higher during sleep and for a period of time after awakening in the morning. In addition, there are other changes in pressure that occur regardless of what we are doing or what position we are in. Think of this as a normal minute-to-minute, day-to-day variability. If we were to have our pressures measured five times in a single day, each pressure measurement is likely to be slightly different. Taking an average of these readings would provide a more accurate single number to describe the pressure. What about low pressures? Most “normal” people have CSF pressures that exist somewhere between 8 and 15 cm of water. If pressures get too low, symptoms of intracranial hypotension (“hypo” meaning “too low”) may occur. Sometimes these symptoms may be hard to differentiate from high pressure symptoms. We’ll discuss this more later in Chap. 3. Key Points 1. Normal intracranial pressures (ICP) should usually be between 8 and 15 cm of water. 2. Most doctors use the relatively arbitrary threshold of 20 cm of water as the cutoff for deciding normal (19 or less) versus abnormal (20 or higher). This threshold is deeply engrained in doctors. 3. Our ICP changes from minute to minute based on our head position and activities. 4. Intracranial pressures that are too low (intracranial hypotension) can also cause symptoms.

References Lee K, Kittel C, Aldridge JB, et al. Correlation between intracranial pressure and venous sinus pressures in patients undergoing cerebral venography and manometry. J NeuroIntervent Surg. Published Online First: 04 March 2021. https://doi.org/10.1136/neurintsurg-­2020-­017161. Liu KC, Starke RM, Durst CR, et al. Venous sinus stenting for reduction of intracranial pressure in IIH: a prospective pilot study. J Neurosurg. 2017;127(5):1126–33. Matloob SA, Toma AK, Thompson SD, et al. Effect of venous sinus stenting on intracranial pressure in idiopathic intracranial hypertension. Acta Neurochir. 2017;159(8):1429–37.

Chapter 3

Idiopathic Intracranial Hypertension (IIH)

Diagnosis The diagnosis of IIH, as is currently accepted by most medical societies, requires an intracranial pressure (ICP) measurement that is greater than 25 cm of water (250 mm of water) and imaging studies of the brain showing no other explanation for the high pressure. Most patients with symptoms will first have the back of their eyes checked by a doctor, which may reveal a swollen optic disc, suggestive of high ICP. Most patients will then undergo a CT of MRI of the brain to evaluate for an abnormality, such as a brain tumor. If this does not show a reason for the high pressure, doctors will next order a spinal tap to measure ICP and often times to send fluid to make sure that there is no evidence of an infection or other concern. Later in the book we’ll describe these imaging studies in more detail, as well as the spinal tap procedure. If the ICP is greater than 25 cm of water and there is no other reason for the fluid pressure to be high, the diagnosis of IIH will be made. Sometimes doctors use other terminology to describe the condition. You may see the term “pseudotumor cerebri,” which is the old name for IIH. Alternatively, you may see the term “benign intracranial hypertension,” or “secondary intracranial hypertension.” All of these names more or less refer to the same condition and basically mean the same thing. There are very few doctors that are truly experts in this disease, and to the majority of doctors, these names are essentially interchangeable. Importantly, the 25 cm of water threshold is not really set in stone. Often patients will be diagnosed with IIH after a spinal tap with a lower pressure (20–24 cm of water). So classically the condition is defined by an intracranial pressure of 25 cm of water or high, but in practice, patients with abnormally high pressures that are below 25 cm of water will usually end up with this diagnosis as well.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0_3

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Key Points 1. Technically, the diagnosis of IIH requires brain imaging showing no reason for elevated intracranial pressure (ICP) followed by an ICP measurement, usually from spinal tap, of 25 cm of water or higher. 2. To most physicians, the names “idiopathic intracranial hypertension,” “pseudotumor cerebri,” “benign intracranial hypertension,” and “secondary intracranial hypertension” are interchangeable and all refer to the same diagnosis. 3. Patients with symptoms of IIH and an ICP measurement between 20 and 24  cm of water usually get diagnosed with IIH even though they don’t meet the strict 25 cm of water ICP cutoff.

Presentation The majority of patients who are diagnosed with IIH are women during their childbearing years (20–40 years of age). The majority of these patients are overweight, with most being obese. In my practice, about 50% of the patients I treat for elevated ICP fit this group. One study performed in 1989 aimed at documenting the percent of the population with this condition and found that IIH was present in 15–19 people per 100,000 (or about 0.02% of the population). As the US population has slowly grown heavier over time and the knowledge of the disease increases, it is with certainty that I can say that 0.02% of the population would represent a serious underestimation of the current disease incidence. I would like to make an educated guess and suggest that IIH is probably significantly higher than in 1989 and likely present in up to 0.20% of the population currently, or 1  in every 500 people. This disease is not so rare anymore. Most patients present with long-standing headaches. Other symptoms may include visual symptoms (blurring, spots, etc.) or progressive visual loss, a whooshing sound in the ear, light sensitivity, eye pain, nausea, or dizziness. Usually these symptoms are “chronic,” meaning that they are present for a long time. Most patients have these symptoms for a while before they seek medical treatment. Often times the symptoms (or their effect on quality of life) progressively worsen, and eventually patients hit a breaking point where they finally go to see a doctor to get help. However, not all patients present in this “classic” way. A minority of patients have no symptoms other than visual loss or a swollen optic disc detected by their eye doctor. Some patients only have a loud whooshing sound in their ears that makes it hard to sleep at night or talk on the phone. Other patients will present with painless cerebrospinal fluid (CSF) leaking from their nose or ears. Lastly, some patients may be nothing like the classic patient. I have treated a 10-year-old skinny boy, teenage thin girls, middle-aged thin or obese men, elderly thin men, and elderly thin women. Many patients with connective tissue diseases,

Common Symptoms

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such as Ehlers-Danlos syndrome, do not fit the “classic” presentation. So while most patients are larger women in their child-bearing years, people of all ages, genders, and sizes can develop IIH. Key Points 1. The majority of patients with IIH are women, aged 20–40 years and are overweight. 2. 30 years ago, IIH was found in 0.02% of the population. I would argue the incidence today is dramatically higher. 3. Most patients present with long-standing (chronic) headaches. Headaches are often accompanied by visual symptoms, visual loss, whooshing in the ears, light sensitivity, eye pain, and dizziness. 4. Some patients have no headaches and instead have vision loss, CSF leaking out their nose or ear, or a loud whooshing sound in the ear. 5. While most patients are young overweight women, IIH occurs in individuals of all ages, genders, and sizes.

Common Symptoms Headache The most common symptom of IIH is headache. Headache is present in nearly all patients with IIH and most people report that the headache is the most troublesome of the symptoms. While visual symptoms or vision loss can cause actual physical disability, most people with IIH report the most disabling symptom to be the headache. This is because the headache tends to be severe and relentless and interferes with all aspects of life. Usually, people with IIH describe the headache as a “pressure” headache. Many people will say that they feel as though their eyes are being pushed forward out of their head. Often the headache is in the front of the head, near the eyes, on the forehead, or like a band across the forehead. Less commonly, headaches are on the sides or the back of the head and neck. Rarely, headaches are predominantly near the ear. Classically, these headaches are worse with body positions or activities that increase intracranial pressure (ICP). Coughing, sneezing, straining, and lowering the head while bending over (tying shoes, for instance) all cause a temporary increase in ICP.  Many people report temporary worsening of the headache with these actions. The headache tends to be worse once awakening from sleep. This is because we usually lie flat when we sleep, which makes ICP higher, and we don’t breathe off carbon dioxide as well while we’re sleeping, which also causes ICP to be higher. Usually once people with IIH wake up, sit up, and resume normal awake breathing, the headache tends to lessen.

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From a doctor’s point of view, headaches are problematic to understand and treat. They are very common (nearly everyone suffers from at least one headache every now and again), vary from day to day, are very subjective (meaning there’s not a good way for us to quantify how bad they are), are caused by a number of different diseases, and often overlap. For instance, there are tension (stress) headaches, caffeine-­withdrawal headaches, migraine headaches, cluster headaches, high blood pressure headaches, etc. In fact, if you look at 100 patients who go to their doctor complaining of headaches, very few are actually due to something serious (like a brain bleed or tumor). Most headaches are not worrisome and are benign. Migraine headaches are a specific kind of headache that usually affects women and has classic symptoms. Often times people will refer to severe headaches as “migraines,” but this is not actually correct. Migraines are a specific type of headache that usually are severe, may be preceded by a visual aura of flashing lights, and are worsened by bright lights or loud sounds. Many people have to lie down in a dark room with no sound and eventually fall asleep for the headache to go away. Migraines also tend to recur at regular intervals. Most people with migraine headaches take medication to prevent them and to make them stop once they start. IIH is often defined by the headache, but the reality is that many patients with IIH suffer from other types of headaches as well. As both migraine headaches and IIH are more common in young women, we see many patients that have both conditions simultaneously. Sometimes it can be challenging to understand which headaches are occurring at which times. Also, these two types of headaches are due to completely different reasons. If we treat the IIH, patients may continue to have migraine headaches. Similarly, if migraine medications are started, patients may be disappointed that they still have IIH headaches. The severity of headaches is also very subjective. Often we’ll ask patients to describe their average headaches on a scale of 1–10, but this is very nonspecific. How do you explain, on a simple 1–10 scale, the variability in daily headaches and its effect on your life? Other scoring systems that are more valid look at the effect of the headache on quality of life. These are probably more accurate but still depend on the individuals’ interpretation of their own headache. As a doctor, there is no way for me to tell the difference between a patient with daily, severe headaches who rates it as “severe and disabling” and a person without headaches who is lying about their symptoms. There’s no confirmatory test or blood work we can send to confirm that headaches are severe. In fact, many doctors may misinterpret IIH patients as being “drug seekers” or, in other words, are seeking narcotic prescription pain medications. So while IIH is best defined by the pressure-type headache that comes with it, headaches are, in general, a difficult symptom to understand and treat.

Common Symptoms

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Key Points 1. The most common complaint of people with IIH is headache. Usually it is a “pressure” headache that occurs on the front of the head or face. 2. The headache is usually bad when waking up in the morning and is worsened by coughing, straining, and lowering the head. 3. Many patients with headaches have multiple types of headaches all acting at once. Most commonly this incudes tension (stress) headaches or migraine headaches. Treating one type of headache may make those headaches better but will do little to improve the other types of headaches. 4. Headaches are probably best understood by looking at not only their frequency and severity but their effect on overall quality of life. This lets us understand how seriously headaches affect your work, family life, and ability to function on a day-to-day basis. 5. Headaches are problematic for doctors to understand and treat.

Visual Symptoms While headaches are often viewed as the most disabling symptom of IIH, visual symptoms and visual loss can actually cause disability. From a doctor’s point of view, vision loss is the scariest aspect of IIH and is the thing we worry about the most with our patients. Classically, patients with IIH report blind spots, worsening peripheral vision (vision on the side), double vision, or short episodes where vision goes out. In severe cases, permanent vision loss may occur. Usually, vision loss occurs slowly and may be progressive, meaning that it worsens slowly over time. Rarely sudden vision loss can occur. Patients with sudden visual loss are treated emergently to prevent irreversible blindness. Most of the visual symptoms are due to the fact that cerebrospinal fluid (CSF) travels forward around the optic nerve to the eye. High intracranial pressures (ICP) are transmitted through the CSF directly to the back of the eyeball, where the retina is located. The effect of this pressure on the retina causes injury to the nerve fibers that are responsible for vision. The severity of the visual symptoms appears to be related to the severity of ICP elevation and the length of time in which ICP is elevated. Progressive visual loss is uncommon in people with ICP less than 25, while it is common in people with ICP greater than 40. In general, the higher the ICP, the more likely vision is at risk. Similarly, IIH treatments that lower ICP reduce the risk of vision loss.

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Key Points 1. The most common visual symptoms are blind spots, poor peripheral vision, double vision, and temporary visual loss. 2. Severe, progressive, irreversible vision loss may occur, resulting in blindness. 3. Visual symptoms are mostly a result of high intracranial pressure being exerted onto the back of the eye. 4. The severity of visual symptoms depends on how high ICP is elevated and how long it has been elevated. The higher the ICP, the more likely visual loss is to occur.

Papilledema and Visual Loss Papilledema, or swelling of the optic disc, is a common finding in patients with IIH.  Papilledema is not technically a symptom but is a finding your doctor can detect on eye examination. This finding requires a fundoscopic exam where an optometrist, eye doctor, or other physician looks into the back of eye with a special scope. The optic disc is basically the point where the nerve enters the back of the eyeball. As the optic nerve is surrounded by cerebrospinal fluid (CSF) all the way up to its entrance into the back of the eye, the appearance of the optic disc can be used as a marker for elevated intracranial pressures (ICP). In a normal situation, the optic disc is pink with a clear, sharp border. Blood vessels appear smooth and normal. As ICP increases, the increased pressure of the CSF on the back of the disc results in blurring of the disc edges with engorged veins. The disc may appear elevated. Most eye doctors use a grading scale of 0–5 to describe the severity of the papilledema. In this grading scale, a grade of 0 refers to a normal optic disc, 3 is moderate disc swelling, and 5 is severe swelling (Fig. 3.1). The higher the papilledema grade, the higher the visual impairment present. The development of papilledema can occur after only a few days of having high ICP. Papilledema is worrisome because the pressure on the back of the eye can cause injury to the optic nerve fibers. This nerve carries visual information from the eye to the brain to allow you to see. Papilledema can cause the nerves to stop working correctly, which can cause temporary visual loss, spots, or blurring. Long-standing pressure on the nerve can cause irreversible vision loss. This is thought to be due to slow injury to the nerve fibers which, when lost, are lost forever as they do not regenerate. Most commonly, the nerve fibers serving peripheral vision are lost first. This means that people usually lose vision on the sides before losing vision in the center. Thankfully, lowering of ICP can result in improvement in papilledema. This usually leads to slow improvement in visual symptoms and in visual fields. Eye doctors will perform a number of other tests to assess your visual function. These include visual acuity tests, visual field testing, optical coherence tomography,

Common Symptoms

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Fig. 3.1  A normal optic disc on the left. The optic disc has a sharp border (green dashed line), and blood vessels are easy to see. An optic disc with high-grade papilledema is shown on the right side. The optic disc is swollen and the margin is blurred. Blood vessels on the disc appear disconnected (obscured)

etc. These tests are designed to understand the effect of the elevated pressure on your eye and its function. These tests are important because, while papilledema is an important marker for elevated ICP, the papilledema grade does not necessarily correlate to ICP or degree of visual symptoms. Every patient is different: some people with high ICP will have no papilledema or visual symptoms, while some people with mild papilledema will have significant visual symptoms or visual field deficits. Importantly, papilledema can help us understand ICP elevation noninvasively, meaning without placing needles or devices into the body. Changes in papilledema can therefore be used as a means of monitoring ICP over time. Key Points 1. Papilledema, or swelling of the optic disc, is a common finding in patients with IIH. 2. Optic disc swelling is a direct result of high intracranial pressures exerted on the back of the eye. 3. Most eye doctors use a grading scale of 0–5 to describe the severity of the papilledema. In this grading scale, a grade of 0 refers to a normal optic disc, 3 is moderate disc swelling, and 5 is severe swelling. 4. Papilledema can cause the nerves to stop working correctly, which can cause temporary visual loss, spots, or blurring. Long-standing pressure on the nerve can cause irreversible vision loss, most commonly in peripheral (side) vision. 5. Monitoring of papilledema over time provides a noninvasive means of understanding changes in ICP.

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Light Sensitivity Many patients with IIH complain of being sensitive to bright lights. Bright lights often make the headache worse. Sunlight is especially irritating to patients. Even the lights in hospital or clinic rooms may be too bright for patients. Light sensitivity is not unique to IIH; in fact, it is very common in other headache disorders too, especially migraine headaches. I can usually readily identify my new IIH patients when they arrive at clinic because many of them are wearing sunglasses. When I walk into the clinic room, my IIH patients often have their sunglasses on, or the lights are turned off in the room. This light sensitivity, just like other symptoms of IIH, improves when intracranial pressure (ICP) is lowered. Key Points 1. Sensitivity to sunlight or bright indoor lights is common in IIH.

Pulsatile Tinnitus “Tinnitus” is a term used to describe abnormal sounds in the ears, such as ringing or “whooshing.” In IIH, patients commonly say they hear their heartbeat in their ears. This is referred to as “pulsatile” tinnitus because a sound is heard with each heartbeat synchronized with their pulse. Often times this sound is louder on one side than the other, and usually the sound is louder when intracranial pressure is higher. In some patients, the sound may be so loud that it interferes with daily life. Some patients have difficulty sleeping because the sound is so loud. Others report difficulty using a phone with that ear because the sound makes it difficult to hear the voice on the phone. The tinnitus is thought to be due to venous sinus narrowing on the side the sound is heard, as the transverse sinus and sigmoid sinus are next to the ear. We think the “whooshing” sound is a result of blood being forced through the narrowed vein with each heartbeat. In my experience, the pulsatile tinnitus is a good marker for narrowing of the veins, and we tend to find significant vein narrowing when patients report this symptom. However, in my patients there does not seem to be a clear relationship between higher ICP and the severity of the whooshing sound, although often times the sound is present and louder when headaches are worse. Other patients do not have a whooshing sound but instead have a high-pitched constant ring. The high-pitched ring appears to be related to high ICP, and not to narrowing of the veins. Other patients, particularly those with CSF leaks into the ear, complain of muffled hearing or loss of hearing.

Common Symptoms

29

Key Points 1. Whooshing or ringing in the ears is common in IIH. 2. Often times the sound is louder in one ear than the other and tends to be louder when ICP is higher. 3. Pulsatile tinnitus, or hearing the heartbeat in the ear, is a good marker for underlying venous sinus narrowing. A high-pitched ringing sound in the ears is often present but probably is not related to vein narrowing.

“Brain Fog” Many patients with IIH will complain about difficulty concentrating. Others will report poor short-term memory, forgetfulness, being easily confused, or difficulty with doing simple math problems or staying attentive during conversations. These symptoms may be mild or severe. Severe brain fog may affect a person’s ability to function at work or in day-to-day chores or routines. It is likely that these symptoms arise from high intracranial pressures (ICP) that interfere with the brain’s ability to process complex information. Severe headaches, fatigue, and depression from poor quality of life may also contribute to the feeling of “brain fog” and make it worse. A major contributor to brain fog in patients with IIH is the medications prescribed to treat the condition. Two of the most common medications used for IIH, acetazolamide and topiramate (discussed later), are notorious for worsening brain fog. Some patients may not be able to take these medications due to the worsened brain fog and difficulty concentrating. Successful treatment of IIH with lowering of ICP to normal tends to improve brain fog in two ways: firstly, lowering pressure restores normal ICP and allows the brain to function normally and, secondly, lowering the ICP to normal means that the medications are no longer required, so these can be stopped. Stopping these medications then removes the brain fog that may result as a side effect of the medication.

Key Points 1. Difficulty concentrating is a common symptom of IIH and is often referred to as “brain fog” 2. Brain fog is likely due to elevated intracranial pressure (ICP), but headaches, fatigue, and depression probably also contribute. 3. Brain fog is a common side effect of the main medications used to treat IIH. 4. Brain fog usually improves with lowering ICP and stopping these medications.

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3  Idiopathic Intracranial Hypertension (IIH)

Cerebrospinal Fluid Leak (Rhinorrhea or Otorrhea) Some patients are born with or develop small openings in the skull, known as encephaloceles or dehiscences. Often times these openings are asymptomatic and do not cause problems. Patients with these openings who develop IIH with high intracranial pressures may develop leaking of cerebrospinal fluid (CSF) through the opening. Leaking of CSF into the back of the nose is called “rhinorrhea”; leaking of CSF out the ear is called “otorrhea.” This is usually recognizable by dripping of clear fluid from the nose or ear and usually is first misdiagnosed as nasal allergies. Most patients who have CSF rhinorrhea report dripping into the back of the throat which may taste metallic or salty. Usually, when these people lean forward and put the head down, there is a steady drip of clear fluid from one of the nostrils. People with otorrhea commonly report waking up in the morning to a soaked pillow. CSF is clear like water, so usually the pillow looks like water was dumped onto it. In patients with allergies or mild leaks, it may be difficult to tell the difference between a true CSF leak and a persistent runny nose. Your doctor may order a test that will definitively determine the fluid to be CSF, called beta-2 transferrin. This is a protein that is not found in blood, tears, or nasal mucous and is almost exclusively found in CSF. This test requires that the patient collect fluid in a cup and then bring it to a lab for testing. Sometimes patients with CSF leaks do not have classic symptoms of IIH like headaches or visual symptoms, just leakage of clear fluid. Other patients have mild headache symptoms but develop leaking as well. Leaking of CSF from the nose or ear is dangerous because bacteria can potentially enter the central nervous system, causing meningitis. Due to the risk of meningitis, most patients with IIH and CSF leaks are managed aggressively to stop the leak. Often this requires a surgery to repair the hole at the base of the skull. Patients with IIH and CSF leak may also potentially benefit from stenting or shunting to reduce the amount of CSF leakage and also reduce the chance of CSF leak following skull repair. Some patients never need to have the hole repaired because the leak may stop with a shunt or a stent alone. Depending on the doctor you see, they may quote varying percent risks of meningitis with a CSF leak. From my personal experience, the risk of a patient getting bacterial meningitis from an ongoing CSF leak from IIH is very low, probably less than 3% per year. Finally, we should briefly talk about spinal CSF leaks that can occur in the setting of IIH. While spinal CSF leaks are common after spinal tap procedures (see Chap. 6), some patients develop spontaneous CSF leaks in and around their spines in the absence of trauma, surgery, or other procedures. CSF can leak from inside the dura of the spine into the space around the dura or sometimes directly into spinal veins. We think that IIH and high fluid pressure lead to development of these leaking sites. However, a leak such as this usually causes low intracranial pressure (ICP) and low-pressure symptoms because the fluid drips continuously out of the spine. This can cause a confusing picture where the reason the leak developed was IIH

Other Symptoms

31

(high-pressure), but the symptoms the patient has are low pressure in nature, and spinal tap shows low ICP.  When these leaks are treated, patients will often then swing back into high pressure. We don’t have a good understanding of why these spinal leaks can occur or how best to manage them, but they appear to be similar to CSF leaks from the nose or ear in that they are often associated with IIH. Key Points 1. In patients with holes at the base of the skull, high intracranial pressure (ICP) may lead to cerebrospinal fluid (CSF) leaks through the nose or ear. 2. CSF leaks are usually recognizable by a steady dripping of fluid when the head is placed down. 3. A lab test called beta-2 transferrin can be ordered to definitively tell whether the fluid is CSF. This requires that you collect the fluid in a cup. 4. If CSF can get out of the brain, bacteria can potentially get in, causing a severe infection of the brain called meningitis. 5. Patients with CSF leaks are usually managed either with ICP-reducing surgeries, surgeries to repair the defect at the base of the skull, or both. 6. Some patients with IIH develop spontaneous CSF leaks in the spine into the space around the dura or into spinal veins. These patients usually develop low ICP symptoms, and spinal tap usually shows low ICP, making the diagnosis confusing. Often times when these leaks are treated, the patient will swing back into high pressure.

Other Symptoms Many patients with IIH have other symptoms that are not clearly related to the underlying disease but may be a manifestation of associated conditions. For instance, symptoms of depression are common given that many people with IIH are disabled from headaches and have poor quality of life. These include feelings of sadness, difficulty sleeping, and poor energy. Others have chronic body aches, just as back or neck pain, from excess weight and lack of exercise due to the disabling, chronic headaches. In some people, neck pain may be related to high pressures in neck veins, and in others, neck pain is present likely as referred pain from the head. Dizziness, nausea, and vomiting may also occur. In patients with IIH related to connective tissue disorders, such as Ehlers-Danlos Syndrome, other symptoms may be present. These include neck or head pain from cranio-cervical instability from loose ligaments between the skull and the neck resulting in excess motion occurring at the joint, orthostatic hypotension (low arterial blood pressure with changes in posture that may cause fainting), tremors or shaking, and difficulty walking with veering to the side. For the most part, these symptoms are rare and only occur in a small fraction of patients with IIH.

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3  Idiopathic Intracranial Hypertension (IIH)

Key Points 1. Depression is common in patients with IIH. 2. Back pain and neck pain are common symptoms in people with IIH and may be due to excess weight and lack of exercise. 3. In people with connective tissue disorders, most notably Ehlers-Danlos syndrome, a number of other strange symptoms may be present. These are rare in people without such disorders.

Symptoms Are Worsened by Weather Changes A fascinating observation in patients with IIH is the worsening of symptoms with weather changes. Most patients with IIH report that they feel worse, with more pronounced symptoms, on days where it rains or there are thunderstorms. Frequently patients will say that on rainy days they feel terrible and have bad headaches with loud tinnitus. Many people can actually tell when the weather is going to change because their symptoms are worse. This phenomenon is so commonly reported in patients with IIH that I think it is one of the most useful ways of telling whether headache symptoms are from IIH. Almost without fail, patients with IIH note worse headaches with bad weather or when weather fronts move in. Some patients also report changes in symptoms with changes in altitude, such as when they drive up or down mountains, or move to a new city that is located at a different height from sea level. We don’t really understand why this phenomenon occurs, but it likely has to do with barometric pressure. Barometric pressure is the pressure exerted by the atmosphere on the earth and changes slightly from day to day based on the weather. There are headaches known as barometric pressure headaches, which are thought to be due to the atmospheric pressure changes. In IIH, it is likely that barometric pressure affects venous pressures in the body, which can affect venous pressures in the brain, or that the changes in barometric pressure somehow affect the way the headache is experienced, making it seem more severe. Usually the headaches, tinnitus, and other symptoms are worse when intracranial pressure (ICP) is higher, which suggests that certain barometric pressure changes may actually cause ICP to be higher. There is very little scientific evidence supporting this theory, though. While we don’t understand why this relationship occurs, we do know that it is very common for weather to have a pronounced effect on the severity of symptoms. Key Points 1. IIH symptoms are usually worse with weather changes. Most patients with IIH report worse headaches on days with bad weather. 2. Barometric pressure, the pressure in the atmosphere, is probably the cause of this phenomenon, although we don’t really understand how or why. It is likely that changes in barometric pressure can affect intracranial pressure (ICP) and make symptoms more severe.

Symptoms Are Often Related to Intracranial Pressure

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Symptoms Are Often Related to Intracranial Pressure As would be expected, the severity of symptoms of IIH is related to the severity of the pressure elevation in the head. Most patients with intracranial pressures (ICP) that barely meet the 25 cutoff for a diagnosis of IIH tend to have milder headaches and visual symptoms, while those with high pressures (35 or higher) tend to have more prominent headaches and visual loss. However, it is important to understand that pressures between 15 and 20 are marginally elevated and pressures between 20 and 25 are still high even if they don’t technically meet the threshold of 25 that is used to diagnose IIH. Many patients have ICP of 22 or 23 and complain of significant headaches. These patients should still be considered for treatments, even though they don’t hit the 25 landmark because there is potential for significant symptomatic relief. At the same time, some individuals with pressures of 22 or 23 may be entirely asymptomatic. Rarely, we see patients with pressures in the 30s with minimal, if any, symptoms. Therefore, it is best to think of IIH as a spectrum with individual patients having varied responses to pressures (Fig. 3.2). Pressure measurements are also very helpful in determining response to treatment. If a patient has high pressure (30, for instance) and we perform a treatment, we can check the patient’s pressure measurement afterward to see if the treatment was effective. If the pressure is still 30 after treatment, we know the treatment had minimal effect. If the pressure is 20 after the treatment, we know the treatment has successfully reduced the pressure by 10 points. This is useful when patients have persistent symptoms even after treatment, and we are trying to figure out whether the treatment helped. Low ICP most commonly causes headache and dizziness with nausea and vomiting (we’ll discuss the difference between these two headaches later). Similarly, Normal sensitivity

Low sensitivity

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40

Intracranial pressure (in centimeters of water)

Fig. 3.2  Examples of different intracranial pressures (ICP) causing varied symptoms in different people. In most people, ICP less than 5 causes symptoms of low pressure, while symptoms of high pressure only develop after ICP rise above 20. Some people are more or less sensitive than others to high or low ICP, and therefore symptom severity may differ at different ICP based on the person

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3  Idiopathic Intracranial Hypertension (IIH)

response to low pressure is different and variable among different people. As such, the measured ICP value is important, but more important is the symptoms that are present. Therefore every patient’s symptoms need to be correlated to their pressure. As (hopefully) should now be very clear, ICP is one of the most important measures for treating patients with IIH. Establishing a baseline ICP measurement before treatment and then obtaining pressure measurements after treatment can be integral in successfully managing a patient’s IIH. Key Points 1. Intracranial pressure (ICP) is not just how we diagnose IIH but is critical in understanding and treating a patient’s symptoms. 2. Intracranial pressure (ICP) varies throughout the day and changes based on head position and activity. 3. Different people have different symptoms at different pressures, so an elevated ICP may cause severe symptoms in one person and next to no symptoms in another. 4. Pressures that are too low can also cause similar symptoms of headache, dizziness, and vomiting. 5. Pressures can be obtained after a treatment and be compared to pressures before the treatment to see if it was effective.

 istinguishing ICP That Is Too High (Hyper) vs. Too D Low (Hypo) Sometimes symptoms that develop from intracranial pressure (ICP) being too high can be confused for pressures that are too low. There are a number of conditions that result in the pressure in the head being too low. Usually this occurs because of leaking of cerebrospinal fluid (CSF) out of the chambers around the brain or spine, resulting in lower ICP than normal. Sometimes, patients with IIH who have shunts placed where the shunt drains too much fluid from the brain may similarly experience low-pressure symptoms. There are some helpful features about the symptoms that can help us decide whether the pressure is too high or too low (Table 3.1). Most Table 3.1  Comparison of high vs. low-pressure symptoms High-pressure symptoms Headache that worsens with lying flat Headache worsens with coughing, straining Whooshing sound in ear may be present Visual symptoms may be present Nausea and vomiting not prominent Dizziness not prominent

Low-pressure symptoms Headache that improves with lying flat Does not worsen with coughing, straining Whooshing sound in ear usually not present Visual symptoms usually not present Nausea and vomiting prominent Dizziness often present when sitting up or standing

Ehlers-Danlos Syndrome

35

importantly, low-pressure headaches improve when lying flat and worsen when standing upright or sitting upright. This is because the fluid in the brain pools in the spine due to gravity, which causes the intracranial pressure (ICP) to lower when standing up and to increase when lying down. Conversely, high-pressure headaches get worse when lying flat and tend to be better when sitting or standing up. Sometimes it is impossible to tell from symptoms whether the pressure is too high or too low. Sometimes imaging studies, like a brain MRI scan, can be helpful. In very challenging situations where the symptoms are not clearly one or the other, obtaining an ICP measurement by spinal tap may definitively answer the question. Key Points 1. Symptoms of intracranial hypertension (pressure too high) and intracranial hypotension (pressure too low) may be similar. 2. When we stand up, CSF leaves the brain and pools in our spines, which makes our ICP lower. When we lie down, the reverse occurs, causing our ICP to go up. 3. The feature that is most helpful in distinguishing the two is the headache severity based on head position: in IIH, the headache tends to worsen with lying flat, while in intracranial hypotension, the headache worsens with standing or sitting up.

Ehlers-Danlos Syndrome Ehlers-Danlos syndrome, or “EDS” for short, is a condition that affects connective tissues in the body. There are actually a number of different types that are defined based on the exact connective tissue problem that the body has. Classically, EDS is characterized by hypermobility of the joints (joints that can bend further than normal), skin that can be stretched further than normal, and weak tissues. Many patients with EDS develop IIH, as well as a host of other problems. This section will briefly discuss EDS and IIH and hit on some of the important points when treating patients with this problem. Patients that have IIH associated with EDS tend to look very similar and have similar medical problems. Most of these patients are Caucasian, young, tall, of normal weight or only slightly overweight, blonde women. The IIH symptoms tend to be different than “classic” patients with IIH in a few ways. First, EDS patients tend to be “highly sensitive” to pressure, meaning that the IIH symptoms tend to be more severe at lower pressures (Fig. 3.2). Additionally, low-pressure symptoms tend to be more severe. As such, the intracranial pressure (ICP) window where people feel well without symptoms tends to be narrower in EDS than in classic IIH patients. Second, there is a propensity for the symptoms to be “weird.” While headaches and tinnitus are common, EDS patients are more likely to have neck pain, problems being upright even when high pressure (usually this is a low ICP finding), brain fog

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3  Idiopathic Intracranial Hypertension (IIH)

and confusion, or other strange symptoms like tremor or falling to one side while walking. Third, EDS patients tend to leak cerebrospinal fluid (CSF) from their nose (rhinorrhea) or ears (otorrhea) more often than classic IIH patients. Fourth, patients tend to commonly have venous narrowing in the neck in the jugular veins, as well as of the transverse sinuses. This is probably because the vein walls are weaker and are prone to narrowing. Lastly, other conditions associated with EDS can influence these symptoms which can make the diagnostic process challenging. Patients that have IIH associated with EDS tend to have a similar list of other conditions. These include (1) “cranio-cervical instability,” which means that the head moves on the spine more than normal because of loose ligaments; (2) postural orthostatic tachycardia syndrome or “POTS,” which causes the heart to race or dizziness with changes in body position, such as from sitting to standing; and (3) mast cell activation syndrome, which causes a heightened allergic response to drugs, foods, or other substances. Other brain or spine conditions are also common. Cranio-cervical instability (CCI), or excessive movement of the head on the spine, can sometimes cause symptoms that are very similar to IIH. Sometimes X-rays of the head and neck with the head in different positions can show an abnormal amount of movement. Treatments that stabilize the head on the neck usually make symptoms better with CCI.  Sometimes placing the patient in a cervical collar (to limit head movement) and see if the symptoms improve can be one way to see whether we think CCI is contributing to the head or neck pain. Alternatively, performing a spinal tap, draining cerebrospinal fluid (CSF) off, and lowering the ICP and then checking to see if symptoms improve can help point to IIH as the cause instead of CCI. Postural orthostatic tachycardia syndrome (POTS) is a condition that causes the heart to race and dizziness with changes in body position. POTS is common in patients with EDS and IIH. POTS makes treating IIH difficult because the two conditions are treated in opposite ways. The usual treatment for POTS is to give fluids and medications to increase blood pressure, which make the central venous pressure (CVP) higher, and helps prevent dizzy episodes. Treatments that increase CVP in IIH patients will increase brain venous pressures, making the IIH worse. Similarly, medications that are used to treat IIH by lowering the venous pressures in the body will often times make POTS symptoms worse. Due to the hypersensitivity to pressure and pain, surgical procedures on patients with EDS often times hurt for longer. Stents tend to be more painful for longer time periods, and shunts are often more tender to the touch. Wound healing is also a problem, meaning that surgical incisions have a tendency to break down more frequently in patients with EDS. Many of these patients have allergies to certain suture types which makes wound breakdown even higher risk. Importantly, patients with EDS are also higher risk for developing leaking after spinal tap procedures. In my experience, about ½ of EDS patients will get low-pressure symptoms after spinal taps, many of which may require a blood patch (this is discussed in more detail in Chap. 6). Overall, IIH patients with EDS tend to be more sensitive to pressure and pain, have more severe symptoms at lower pressures, have other conditions making management of IIH more complex, and are higher risk for complications related to spinal tap or surgery.

Ehlers-Danlos Syndrome

Key Points 1. Ehlers-Danlos syndrome (EDS) is a condition characterized by loose ligaments, skin, and joints. 2. Patients with IIH and EDS tend to be Caucasian, tall, normal weight, blonde women. They tend to have other related conditions, such as postural orthostatic tachycardia syndrome (POTS) and cranio-cervical instability (CCI, abnormal movement of head on spine). 3. IIH patients with EDS tend to have “high sensitivity” to pressure, meaning that symptoms tend to be more severe at lower pressures compared to classic patients with IIH.  These patients are also more sensitive to “low” pressures. 4. Patients with IIH and EDS tend to more commonly have cerebrospinal fluid (CSF) leaks, have “weird” symptoms, and have narrowing of the jugular veins in the neck. 5. It is very common for patients with EDS to develop low-pressure symptoms after spinal tap, requiring a blood patch. 6. Cranio-cervical instability (CCI) symptoms sometimes blend with those of IIH. 7. Treatment of postural orthostatic tachycardia syndrome (POTS) to prevent dizziness often times makes IIH symptoms worse and vice versa. 8. Surgical complications, such as wound healing or persistent pain from implanted materials, are more common in patients with EDS.

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Chapter 4

The Fundamental Reasons Patients Get IIH

IIH Is Actually Not Idiopathic We have spent the last two chapters of this book talking about brain anatomy, the importance of venous pressures on intracranial pressures (ICP), and the symptoms that develop from high ICP. Let’s now put everything together and explain why we think this condition occurs. As a disclaimer, I must begin by saying that most of this part of the book is based on my personal understanding and opinions based on my observations from patients with the condition, not on proven fact. So going forward, it is important that you understand that the things I am going to discuss in this section are not universally supported by physicians or researchers. However, most would agree that this information is at least “on the right track.” To begin with, I want to make a relatively bold statement by arguing that the name “idiopathic intracranial hypertension” is not accurate. The term “idiopathic,” by definition, refers to a condition of “unclear or unknown cause.” We now know, from a preponderance of evidence, that IIH is actually not idiopathic but is actually a result of elevated intracranial venous pressures. The elevated intracranial venous pressures in turn cause elevated cerebrospinal fluid (CSF) pressures, as previously described in the second chapter of this book, which then cause the symptoms we discussed in the third chapter of the book. The term “idiopathic” is therefore outdated and should actually be discarded. In my opinion, I think a much more accurate name to describe the condition is “chronic intracranial venous hypertension syndrome,” which puts the emphasis on the underlying cause of the condition (the elevated venous pressures). I wrote a commentary in a medical journal that further describes why I believe this name is more accurate (Fargen 2020). The rest of this section will focus on how and why patients develop high venous pressures, because ultimately the different treatments will affect patients differently based upon the causes of their high venous pressures.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0_4

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4  The Fundamental Reasons Patients Get IIH

Key Points 1. There is little hard evidence explaining why patients get IIH. My personal understanding of this condition is based on scientifically analyzing my extensive experience with patients with this condition. 2. It is important that you understand that the concepts discussed in this part of the book are not universally supported by physicians or researchers. 3. IIH is actually not idiopathic but is a condition that results from elevated intracranial venous pressures. In the vast majority of cases, we now understand why these pressures are elevated.

Venous Pressures in the Body and the Brain Blood that goes to the brain in the arteries supplies the brain with oxygen and energy and then returns to the heart. Blood leaving the brain travels through the venous sinuses, then the internal jugular veins, and then the superior vena cava before entering the heart. The largest veins in the body, the vena cava, are located right next to the heart. Blood going into the heart is then pumped into the lungs, where the blood gets recharged with oxygen. The blood in the largest veins in the body, right next to the heart, has a dramatically lower pressure than blood in arteries. Remember that your blood pressure, for example, 120 over 80, is referring to the pressure in the arteries at different points in time based on your heartbeat. Regardless of the time, the pressures are high (usually 70 mmHg or higher). Veins, on the other hand, contain blood under significantly lower pressure. In a normal condition, the blood pressure in the largest veins by the heart is less than 10 mmHg, usually around 3–8 mmHg. The pressure in the veins near the heart is called “central venous pressure” or CVP for short. CVP is very important because it forms the foundation for pressures in the veins in the head and neck. As central venous pressure (CVP) increases, venous pressures in the jugular veins or venous sinuses outside the brain will also increase. This is because, as CVP increases, this pressure “wells up” into the neck and brain. The pressure in the veins outside the brain will never be lower than the CVP. So if CVP goes up, the venous sinus pressures will go up. In a normal situation, superior sagittal sinus pressures are about 4–5 mmHg higher than CVP. The most important factor causing elevated CVP in IIH patients is excess body weight. Obesity is a known cause of elevated CVP. The reason that excess body fat causes higher CVP is thought to be due to the excess body mass “squeezing” the veins inside the chest and abdomen. The extra weight in and around the belly causes higher venous pressures in the abdomen and chest. In turn, this causes the CVP to be high. In some cases, CVP may be as high as 15–20 mmHg. People with CVP that high will also have high venous pressures outside the brain, as this pressure will back up into the head. This relationship is further evidenced by the fact that bariatric surgery (“stomach stapling” or weight loss surgery), which can cause a dramatic weight loss in a short time period, may cure some people of IIH.

Normal Venous Pressures in the Body and Brain

41

There are a number of other conditions that can change CVP. People with poor heart pumping ability (heart failure) can develop high CVP because not enough of the blood going to heart is being pumped to the lungs, leading to it building up under pressure in the large veins by the heart. Similarly those with too much fluid in their bodies can have elevated CVP because the fluid builds up in the veins. People with certain types of lung conditions can also have elevated CVP. For the most part, these conditions do not present in relation to IIH but due to other symptoms (leg swelling, breathing difficulties, shortness of breath, etc). Most patients with IIH do not have these conditions, and in most instances patients with IIH do not require testing for these conditions. Therefore, when thinking about venous pressures in the body and brain, there are two major venous pressures of interest: the central venous pressure (CVP) and the intracranial venous sinus pressures. Remember from Chap. 2 of the book that we most commonly use the torcula pressure as the best marker of venous pressure in the brain, as the venous sinus pressures usually drop slightly as we move from the top of the head to the base of the skull. The relationship between CVP and the venous sinus pressures is critical in understanding this condition. In the next two sections, we’ll show examples to better explain this relationship. Key Points 1. Normally, the blood pressure in the largest veins by the heart, called the “central venous pressure (CVP),” is around 3–8 mmHg. These pressures are significantly lower than arterial pressures. 2. As CVP increases, venous pressures in the jugular veins and venous sinuses outside the brain will also increase because the pressure “wells up” into the neck and brain. The pressure in the veins outside the brain will never be lower than the CVP, so if CVP is high, venous sinus pressures will also be high. 3. In a normal situation, superior sagittal sinus pressures are usually about 4–5 mmHg higher than CVP. 4. Excess body fat can cause CVP to be higher than normal. This is the most common reason for high CVP in patients with IIH. 5. There are other heart or lung conditions that can cause elevations in CVP, but these are rare in patients with IIH.

Normal Venous Pressures in the Body and Brain Let’s look at the venous pressures in a person without IIH as an example to help explain the relationship between the venous pressures in the body and brain. In the following example, let’s think about an adult of normal weight, without lung or heart conditions, and with no narrowing of the veins leaving the head or neck (Fig. 4.1).

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4  The Fundamental Reasons Patients Get IIH

Normal transverse sinus pressure 9 mmHg Normal sigmoid sinus pressure 8 mmHg

Normal superior sagittal sinus pressure 10 mmHg

Normal spinal tap opening pressure 50% loss of head movement. Additionally, patients are likely to need further surgeries in the years that follow due to the advanced degeneration that occurs at the spine joints below the fusion. 6. These surgeries can be very beneficial in improving symptoms related to CCI. In addition, because the head is not able to move like before, narrowing of the internal jugular veins with head turning will also improve after this operation.

Cerebrospinal Fluid Leak Repairs

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Cerebrospinal Fluid Leak Repairs Some patients are born with or develop small openings in the skull, known as encephaloceles or dehiscences. Often times these openings are asymptomatic and do not cause problems. Patients with these openings who develop IIH with high intracranial pressures (ICP) may develop leaking of cerebrospinal fluid (CSF) through the openings. This leaking is a direct result of high ICP “pushing” fluid out under pressure. Leaking of CSF into the back of the nose is called “rhinorrhea;” leaking of CSF out the ear is called “otorrhea.” See Chap. 3 for more details on CSF leaks. There is an ongoing risk of brain infection (meningitis or brain abscess) with CSF leaks, because if fluid can get out, bacteria can potentially get in. In my experience this risk is quite low, though. CSF leaks, especially those that cause heavy dripping, represent a good reason to perform a surgical procedure for patients with IIH. Patients with CSF leaks from high ICP from IIH are often treated surgically to stop the leaking. Ear, nose, and throat (ENT or otolaryngology) surgeons perform procedures to help repair CSF leaks, either by operating within the nose using cameras or by operating on the ear. Neurosurgeons will often help with these surgeries if they involve working around the brain. Currently, there is no standard, universal treatment strategy for helping patients with IIH-related CSF leaks. In general, the options can be divided into three main strategies: (1) treat IIH first and perform repair of the leak site later if leaking persists after lowering ICP, (2) perform repair of the leak site first and deal with IIH later, and (3) treat both at the same time. Different surgeons will have different opinions on how best to deal with individual patients. In my view, if the opening pressure on spinal tap is high, I lean toward treating IIH first. If we lower ICP through stenting or shunting, the leak may stop altogether just by bringing ICP down. This may mean that a repair surgery is not even necessary. Additionally, a repair surgery that seals the leak will result in higher ICP afterward because CSF can no longer get out. This is likely to make IIH symptoms worse and potentially cause failure of the repair or lead to more leaking from a different site. If opening pressure is low on a spinal tap, we often will recommend leak repair first, and if IIH symptoms or leaking recurs, consider surgical management of IIH at that time. Treating both the CSF leak and the high pressure at the same time is usually problematic and rarely done. CSF leak repairs depend on where the openings are in the skull that are causing the leaking. Most leaking in the nose (rhinorrhea) can be treated by an endoscopic trans-nasal surgery (cameras in the nose) performed by an ENT surgeon. In this surgery, instruments are placed through the nose, and the hole in the base of the skull is identified. A repair is performed, and a flap of tissue from inside the nose is placed over the hole to reinforce the repair. In some cases, a spinal tap or lumbar drain (see Chap. 6) are placed before the procedure. Often times a bright yellow-­ green dye called fluorescein is injected into the CSF, which helps the ENT surgeon see the site of leaking. Most patients spend a few days in the hospital to make sure

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the leaking has stopped afterward. Overall the risk of these operations is relatively low and the procedures are safe. CSF leaks out the ear (otorrhea) or into the structures within the ear are often repaired by doing a surgery on the side of the head where the skull is opened, the membrane outside the brain is lifted, and materials are placed under the brain and over the bone by the ear to repair the leak. This surgery often involves both ENT surgeons and neurosurgeons. Most patients spend a day or 2 in the hospital. The risk of serious complication from this surgery is low. Patients that undergo a CSF leak repair may develop IIH symptoms afterward that were worse than before the procedure. This occurs because the leak was previously acting as a “pop-off” valve; when ICP got high, CSF would squeeze out to lower the pressure. Once this hole is closed after a surgical repair, CSF has nowhere to go and can build up under even high pressure. This can make the IIH symptoms worse and lead to failure of the leak repair or eventually a leak from elsewhere. In my view, CSF leaks are best thought of as a result of IIH. Performing a leak repair by itself may stop the leaking but does not address the underlying cause of the leak, which is the high ICP from IIH. That is why a strategy that addresses the IIH first, or shortly after the leak repair, is probably best in preventing recurrent leaking in the future.

Key Points 1. Cerebrospinal fluid (CSF) leaks may occur out the nose (rhinorrhea) or the ear (otorrhea) in patients with IIH, due to small openings in the skull at these locations. There is a risk of brain infection (meningitis or brain abscess) with an ongoing CSF leak. 2. Three main surgical strategies exist for dealing with CSF leaks: (1) treat high pressure (IIH) first and then leak repairs after if needed, (2) perform leak repair first and then deal with IIH second, and (3) treat both at the same time. 3. In my opinion it makes the most sense to treat the high intracranial pressure (ICP) first, because often the leaking stops and no leak repair is needed. Treating an IIH patient by leak repair first will cause higher ICP once the hole is plugged and CSF can no longer get out. This will cause worse IIH symptoms and potentially cause the repair to fail or new leaking to occur elsewhere. 4. Leaking into the back of the nose is usually treated by ear, nose, and throat (ENT) surgeons using a camera placed into the nose. Leaking through the ear is usually treated by a procedure on the side of the head above the ear performed by both ENT surgeons and neurosurgeons. 5. These surgeries are safe with a low risk of complications.

Chiari Decompression

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Chiari Decompression Chiari malformations are often reported on imaging in patients with IIH.  Chiari malformations are present when the bottom of the cerebellum (part of the back of the brain) hangs down lower than normal into the hole at the base of the skull (foramen magnum). The way this is measured and what this means is discussed in more detail in Chap. 5. Radiologist reports on brain MRI or CT scans will often make note of this finding if the cerebellum hangs lower than normal, regardless of how low it may be. Some will make note of the amount the cerebellum hangs down below the hole at the base of the skull, in millimeters. The part of the cerebellum that hangs down are the “tonsils” (not the organs in the back of your throat, but named similarly!) and hanging down below the foramen magnum (hole at the base of the skull) is referred to as “herniation” or “ectopia.” The mention of “Chiari malformation” or “tonsillar ectopia” on a radiologist report does not necessarily mean this is problematic or symptomatic. There is a normal amount the cerebellar tonsils hang, which changes as people get older. For instance, the vast majority of teenagers and young adults with tonsillar ectopia of 5  mm of less are normal and asymptomatic. As the amount of tonsillar ectopia increases beyond 5  mm, patients are more and more likely to be symptomatic. Tonsils sagging beyond 12 mm are almost always symptomatic. Some patients will get fluid collections in the spinal cord with Chiari malformations, which usually indicates the Chiari is symptomatic. Interestingly, sagging cerebellar tonsils can also be a result of IIH. We think that, in certain patients, high intracranial pressure (ICP) can actually “push” the cerebellar tonsils downward, causing the imaging findings of Chiari malformation. Other patients with lumbo-peritoneal (LP) shunts can develop Chiari malformations by the shunts draining fluid from below the brain, “pulling” the cerebellum downward. Similarly, Chiari malformations may be seen in intracranial hypotension (low pressure) when there are cerebrospinal fluid (CSF) leaks in the spine. Chiari malformations, when symptomatic, usually cause headaches on the back of the head that worsen with straining, lifting, coughing, or putting the head down. In more severe cases, patients can get eye pain, dizziness, difficulties breathing or swallowing, weakness of the arms and legs, tingling and numbness in the arms, and difficulty walking. Most patients with Chiari malformations only have chronic headaches centered in the back of the head or neck. The symptoms are a result of the cerebellar tonsils “squeezing” the back of the brain, called the brainstem. Neurosurgeons perform a procedure to relieve the pressure in the hole at the base of the skull by providing more room. This is called a “decompression” surgery because it opens up the hole at the base of the skull and makes more room. There are two varieties of this surgery, one being less invasive, and one being more invasive. The less invasive surgery is a “bone-only” decompression, where the bone on the back of the skull and the back of the top spine bone (C1) are removed. This allows the membrane outside the brain (the dura) to expand backward, giving more room for the cerebellum and the brainstem. The more invasive surgery involves the

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same bone removal, but the dura (membrane around the brain) is opened and an “expansile duraplasty” is performed. This involves stitching a piece of material to the dura where it is opened to widen the space. Often times this surgery also includes cauterization of the cerebellar tonsils to shrink them. The tonsils have no real use and therefore cauterizing the tonsils almost always causes no problems. Neurosurgeons often disagree with what surgery is better. Most neurosurgeons will perform the more invasive surgery in patients with more severe symptoms, more pronounced tonsillar ectopia (cerebellum hangs down really far), or with fluid collections in the spinal cord. In patients with Chiari malformation and IIH, patients undergoing the more invasive surgery (with opening of the dura) are high-risk for CSF leak after the surgery because intracranial pressure (ICP) is often high. This high pressure often results in CSF leaking through the “duraplasty” and into (and potentially through) the incision. A fluid pocket may accumulate near the base of the skull called a “pseudomeningocele.” For this reason, often times a less invasive “bone-­only” surgery is a better first option. The surgery is painful because it requires that the muscles be moved off the back of the head during the operation. Most patients have a week or so of pretty significant head pain. This usually requires a few days in the hospital for pain management. In patients with Ehlers-Danlos syndrome (EDS) and cranio-cervical instability (CCI), these surgeries can make the CCI worse because they further destabilize the head on the neck.

Key Points 1. Chiari malformations or “tonsillar ectopia” is often reported on brain MRI or CT scans in patients with IIH. 2. Sometimes the Chiari malformation is a result of IIH from high-pressure “pushing” the cerebellum downward or from lumbo-peritoneal (LP) shunts “pulling” the cerebellum downward. 3. Some degree of tonsillar ectopia is normal and usually does not cause symptoms. As the amount of cerebellar sag increases, the more likely patients are to be symptomatic. 4. There are two variants of the surgery to “decompress” the back of the brain: a less invasive “bone-only” surgery and a more invasive procedure that involves bone removal, opening the dura (membrane outside the brain), and a “duraplasty.” 5. Patients with IIH are high-risk for leaking cerebrospinal fluid (CSF) after the more invasive procedure. Often times, patients with IIH are better first treated with the less invasive surgery to avoid this risk. 6. Patients who have Ehlers-Danlos Syndrome (EDS) may also have cranio-­ cervical instability (CCI) causing abnormal movement of the head on the neck, which is often worsened following Chiari decompression surgery.

Reference

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Reference Alsuhaibani AH, Carter KD, Nerad JA, Lee AG. Effect of optic nerve sheath fenestration on papilledema of the operated and the contralateral nonoperated eyes in idiopathic intracranial hypertension. Ophthalmology. 2011;118(2):412–4.

Glossary

Abdominal pseudocyst  An infected collection of fluid in the abdomen around the peritoneal shunt catheter that causes abdominal swelling and the shunt to stop working. Acetazolamide (Diamox)  A common medication prescribed for IIH that reduces the amount of fluid the brain makes, reducing intracranial pressure. Acetaminophen (Tylenol) Over-the-counter medication that reduces inflammation in the body and helps with pain. Acute  Happens suddenly over a short period of time (hours to a few days). Addiction  Occurs with opiate pain medications where withdrawal symptoms occur if the medication is stopped. Angiogram  A procedure where catheters are placed in blood vessels in the body and contrast dye is injected in blood vessels. X-ray machines are used to make movies of the blood traveling through vessels. In this book, we use the term to describe a procedure where a catheter is placed into arteries and veins to and from the brain and pressures are measured in the veins. Angioplasty  Use of a retrievable balloon delivered through a blood vessel to stretch open a blood vessel or stent. Antisiphon device  A part of a shunt system or valve that prevents more fluid from draining through the shunt than what is supposed to. Aplastic (aplasia)  Did not form during development and is missing. Arachnoid granulations  Small organs in the brain that absorb cerebrospinal fluid that is made by the brain. Arteriogram  A procedure where a catheter is placed into an artery and contrast dye is injected. X-rays machines are used to make movies of the blood traveling through the arteries. Arteriovenous malformations or fistulae  Abnormal connections between arteries and veins where arteries directly connect to veins leading to high-pressure blood traveling in veins. Aspirin  Over-the-counter mild blood thinner and anti-inflammatory medication. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0

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Glossary

Atrium  A chamber of the heart. The right atrium is the chamber of the heart where veins return blood to. Bariatric surgery  Surgeries designed to induce weight loss. Barometric pressure  The force exerted by the atmosphere on the earth. Basal metabolic rate  The rate at which the body uses energy while at rest to keep vital functions going, such as breathing. Benign intracranial hypertension  Another term for IIH, not used very often. Blood patch  A procedure where blood is injected into the space around the cerebrospinal fluid space in the back to treat an ongoing leak of fluid after a spinal tap. Blood thinners  Medications given to make the blood clot less easily. Body mass index (BMI)  Standard calculation that takes your height and weight into consideration and classifies patients into normal weight, overweight, and obese. Bolt An intracranial pressure monitoring device implanted through a hole in the skull used to continuously monitor intracranial pressure. Brain fog Difficulty with thinking, attention, memory, or doing complex tasks like math. Burr hole  The hole made in the skull through which a shunt catheter is passed into the brain. C1 bone  Also called the “atlas;” the top bone of the spine just below the skull. Catheter  A small tube. Central venous pressure (CVP)  The pressure in the large veins near the heart. Cerebellum  The back of the brain behind the brainstem that sits just above the hole at the base of the skull. Cerebral Brain. Cerebrospinal fluid (CSF)  The clear fluid that is made by the brain and bathes the brain and the spinal cord. Certas valve  A programmable valve that is commonly used in shunts and has eight settings, ranging from 1 (pressure of about 3 cm of water) to 7 (about 25 cm of water), with an “off” setting of 8 (40 cm of water). Chiari malformation  Abnormality where the back of the brain (cerebellum) sags down below the hole at the base of the skull (foramen magnum). Choroid plexus  Small organs in the brain that make cerebrospinal fluid. Chronic  Long-lasting or constantly recurring. Clopidogrel (Plavix) A strong blood thinning medication used in most patients who undergo stenting to prevent blood clotting on the metal. Closing pressure  The cerebrospinal fluid pressure measured at the end of the spinal tap after draining fluid. Closure device  A plug placed into the artery or vein puncture site after an angiogram or stent procedure to seal the hole so that bleeding does not occur. cm of water  Centimeters of water. A unit of measure when describing intracranial pressure. Co-dominant  Same size on both sides. Usually refers to the transverse sinuses, indicating they are both large and about equal in size.

Glossary

239

Collaterals Side branches of vessels that develop or enlarge to re-route blood around a blockage. Compression  Being squished down, made smaller, or pressed together. Computed tomography (CT) scan  Type of imaging that uses X-rays to see the body. Best at looking at bone, blood, and implanted devices. Computed tomography venogram (CTV)  Type of CT scan where contrast dye is given through the IV to show the veins of the head and neck. Congestion  An abnormal or excessive buildup of a body fluid. Conscious sedation  Use of IV medications to block pain and help patients relax during procedures. Conservative therapies  Nonsurgical (medical) treatments. Contrast dye A substance injected into the bloodstream with imaging to better show specific anatomical structures. Cranio-cervical  Head and neck. Cranio-cervical (occipito-cervical) fusion A surgery performed by neurosurgeons to rigidly fix the skull to the upper spine bones with rods and screws to allow the bones to grow together (fuse), no longer allowing abnormal movement between the skull and spine. Cranio-cervical instability  Abnormal movement of the head on the spine that can cause neck or head pain and neurological symptoms. Decompression  A surgical procedure that relieves excessive pressure on an internal part of the body by creating more room. Distal catheter  The shunt tubing that travels from the valve to its destination somewhere else in the body. Diuretic  Fluid or water pill that makes the body urinate out excess water. Dominant  The larger of the two. Usually refers to the fact that one transverse sinus or jugular vein is much larger than the one on the other side. Dura  The tough membrane that surrounds the brain and spinal cord and contains cerebrospinal fluid. Duraplasty  Part of a Chiari malformation decompression surgery where the membrane outside the brain (dura) is opened and expanded. Eagle’s syndrome  Condition where the styloid bone compresses nearby structures in the neck, causing symptoms. Ehlers-Danlos Syndrome  Condition defined by loose ligaments and joints. Patients with this problem are hypersensitive to pressure and frequently develop IIH. Empty sella  Imaging finding where the sella (place pituitary gland sits) is full of cerebrospinal fluid and the pituitary gland appears squished due to high intracranial pressure. Endoscopic trans-nasal surgery  A procedure performed by an otolaryngologist (ear, nose, and throat surgeon) through the nose with cameras that is used to repair cerebrospinal fluid leaks at the base of the skull. Equilibrium  A state of physical balance. Extramural stenosis  Narrowing of the vein due to pressure on the vein from the outside. Fixed valve  A shunt valve that has a pressure setting that cannot be changed.

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Glossary

Foramen magnum  Hole at the base of the skull that the spinal cord travels through. Furosemide (Lasix)  A fluid pill used to treat IIH by reducing central venous pressure by causing removal of extra fluid in the body through urination. Gastric band surgery  Reversible weight loss surgery where an inflatable band is put across the top part of the stomach, making a smaller stomach pouch. Gastric bypass surgery  A weight loss surgery wherein a small pouch of stomach is separated from the rest of the stomach and then connected to the intestine, bypassing the rest of the stomach and the first part of the intestine. General anesthesia  Medication administered through mask or IV that makes the patient unconscious and unable to remember procedures. Involves the use of a breathing tube and ventilator. Gradient  The pressure buildup across a narrowed vein. Calculated by taking the pressure upstream of the narrowing and subtracting the pressure downstream of the narrowing. Hakim valve A programmable valve that is commonly used in shunts and has many settings ranging from 30 mm of water (3 cm of water) to 200 mm of water (20 cm of water). Heparin  An intravenous blood thinner given during angiogram or stenting procedures to further thin the blood. This medication is also given to patients in the hospital by injection into the skin to prevent blood clots in the legs. Hydrocephalus Condition where cerebrospinal fluid builds up under pressure (“water on the brain”), usually after bleeding in the brain, brain surgery, or infection. The reabsorption of fluid is impaired unrelated to venous sinus pressures. Hypertension  Pressure too high. Hypoplastic (hypoplasia)  Developed small. Hypotension  Pressure too low. Idiopathic  Of unclear cause. Idiopathic Intracranial hypertension Pressure too high inside the skull of an unclear cause. Inguinal crease A line between the abdomen and the thigh, which creates a V shape toward the groin. Internal jugular vein  Large vein that travels through the neck from the base of the skull through the neck to the chest. Interventional radiology suite A procedure room with X-ray machines where angiograms and stent procedures are performed. Intracranial  Inside the skull. Intracranial pressure (ICP)  Pressure within the skull. Means the same as cerebrospinal fluid pressure. Intramural stenosis  Narrowing of the vein due to arachnoid granulations or other structures within the vein itself. Laparoscopic  Surgery on the abdomen that is performed by making small incisions on the belly, inflating the abdomen with air and using cameras. Lateral ventricles  Fluid-filled chambers on each side of the brain that are the usual place where shunt catheters are placed.

Glossary

241

Local anesthetic Numbing medication injected into the skin that burns when placed but shortly thereafter numbs the skin to make procedures less painful. Lumbar  Low back. Lumbar drain  A catheter inserted into the cerebrospinal fluid space in the spine to continuously drain fluid. Lumbar puncture  Spinal tap. Lumbo-peritoneal (LP) shunt A shunt that drains cerebrospinal fluid from the spine to the cavity in the abdomen around the intestines and liver. Magnetic resonance imaging (MRI) scan  Type of imaging that uses magnets to see body tissues. Best at looking at the brain tissue and brain fluid. Magnetic resonance venogram (MRV)  Type of MRI scan that specifically looks at the veins of the head and neck. Manometer  A tall, skinny plastic or glass column that has measurement markings on the side used to measure fluid pressure. Manometry  The act of measuring pressure. Mast cell activation syndrome A condition associated with Ehlers-Danlos Syndrome that causes heightened allergic reactions to medications or other substances. Meta-analysis/systematic review  Type of scientific study that compiles the results of smaller studies to better understand the outcomes related to a treatment. Metformin A common medication for diabetes that often needs to be stopped around the time of procedures that use contrast dye. Methazolamide (Neptazane)  A less common medication prescribed for IIH that reduces the amount of fluid the brain makes, reducing intracranial pressure. Microcatheter  A tiny catheter that is used to measure pressures in veins in the head and body. mmHg  Millimeters of mercury. A unit of measure when describing pressures in arteries or veins. mm of water  Millimeters of water. A unit of measure when describing intracranial pressure. Non-diagnostic procedure  Data obtained from a procedure is not helpful in making decisions, because the procedure was not performed correctly or measurement error made the results hard to interpret. Non-dominant  The smaller of the two. Usually refers to the fact that one transverse sinus or jugular vein is much smaller than the one on the other side. Nonsteroidal anti-inflammatory medications (NSAIDs)  Over-the-counter medications like ibuprofen and naproxen that relieve inflammation in the body and help pain. Normal weight  Defined as a body mass index of 19–24. Nuclear medicine shuntogram  Imaging study where radiotracer is injected into a shunt and a machine monitors the radiotracer as it travels through the shunt tubing to see if the shunt is working. Obesity  Defined as a body mass index of 30 or higher. Occluded  Previously present but now blocked.

242

Glossary

Opiate medications  Narcotic pain medications that block pain receptors and tell the body that you are not in pain. Opening pressure  The initial cerebrospinal fluid pressure measured during a spinal tap. This is the best measurement of intracranial pressure. Optic hydrops  Imaging finding where the cerebrospinal fluid space around the optic nerves is dilated from high intracranial pressure. Optic nerve The nerve traveling from the eye to the brain that contains visual information. Optic nerve sheath fenestration (ONSF)  Procedure that is rarely performed today by eye surgeons to open the optic nerve sheath and allow cerebrospinal fluid to drain out, taking pressure off the back of the eye. Otorrhea  Leakage of cerebrospinal fluid out the ear. Overweight  Defined as a body mass index of 25–29. Papilledema  Swelling of the optic disc at the back of the eye from elevated intracranial pressure. Peritoneal cavity  Space in the middle of the abdomen around the organs like the intestines and the liver. Pneumocephalus  Air seen inside the skull on brain imaging. Positive feedback loop  When the product of a reaction leads to an increase in that reaction; when a change in a given direction causes additional change in the same direction. Postanesthesia care unit (PACU)  Recovery room where patients are monitored immediately after a procedure involving general anesthesia. Postural orthostatic tachycardia syndrome (POTS)  A condition that leads to an abnormal heart rate and blood pressure response to changes in body position, often leading to racing of the heart and low blood pressure when standing. Programmable valve  A shunt valve that can be adjusted using a magnet outside the skin. Proximal catheter  The shunt tubing that travels from the cerebrospinal fluid space in the brain or spine to the valve. Pseudotumor cerebri  An old term for IIH. Pseudo means “fake” or “false” and cerebri refers to the brain. This term defined the condition as “like having a tumor in the brain, but without the tumor.” Pulsatile tinnitus  Whooshing sound in the ear that sounds like the heartbeat, usually related to narrowing of the transverse sinus. Quality of life The standard of health, comfort, and happiness experienced by a person. Radio-opaque  Blocks X-rays traveling through the body and therefore are visible on X-ray images. Radiotracer  Substance injected into a shunt that mixes with cerebrospinal fluid, and its position in the shunt and body can be monitored by a nuclear medicine scanner to see if fluid is traveling through each component of the shunt. Re-equilibration phenomenon An observation where some patients have recurrence of IIH symptoms after a 8-week-6-month period of feeling better after

Glossary

243

s­urgical treatment even though intracranial pressure is measured to be much lower than before treatment. Re-programming  To adjust the setting of a shunt valve using a magnet placed on the head. Reservoir  Portion of a shunt that can be accessed with a needle to draw off cerebrospinal fluid or inject radiotracer into the shunt system. Rhinorrhea  Leakage of cerebrospinal fluid out the nose or into the back of the nose and mouth. Rickham reservoir  Mushroom-shaped device that is attached to the shunt catheter that can be accessed with a needle to draw off cerebrospinal fluid or inject radiotracer into the shunt system. Secondary intracranial hypertension  A term sometimes used for IIH when there is a cause, like venous sinus narrowing. Sheath  Small tube placed into an artery or vein through which catheters, wires, and stents can be advanced. Shunt  An implanted device that moves cerebrospinal fluid from the brain or spine to another body cavity to lower intracranial pressure. Shunt revision An operation performed to repair a shunt that is not working properly. Shunt series  A collection of X-rays taken over the entire shunt system to evaluate the position of the shunt in the body and to look for breakages, disconnections, or kinking. Shunt tap  A procedure where a needle is inserted into a shunt reservoir in a sterile manner for sampling fluid or for injecting radiotracer. Sigmoid sinus Large vein that receives blood from the transverse sinus and becomes the internal jugular vein at the base of the skull. Siphoning  “To draw off fluid over time, especially illegally or unfairly.” In the context of shunts, siphoning refers to draining more fluid through the shunt than what is supposed to. Sleeve gastrectomy surgery  A weight loss surgery that turns the stomach into a tubular sleeve making the amount of food that can be eaten dramatically smaller. Spinal catheter  The “proximal” shunt catheter that is placed in the fluid chamber of the spine in lumbo-peritoneal shunts. Spinal headache A low-pressure headache that may occur after spinal tap that worsens with sitting up or standing and improves with lying flat. Spinal tap (lumbar puncture) A procedure where a needle is inserted into the back, between the spine bones, and into the spinal cerebrospinal fluid space to measure pressure or draw off fluid. Stenosis  Fancy word for narrowing. Stent A metal implant that is used to open or restore blood flow through a blood vessel. Stent failure  Patient who did not have improvement in symptoms like we would have expected or desired after stenting. Stent pain  Pressure or discomfort that occurs for a few days after stenting that is usually felt behind the eye and ear on the same side as the stent.

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Glossary

Strata valve  A programmable valve that is commonly used in shunts and has five settings, ranging from 0.5 (pressure of about 3 cm of water) to 2.5 (about 15 cm of water). Styloidectomy  A surgical procedure performed by an otolaryngologist (ear, nose, and throat surgeon) to remove the styloid bone and relieve compression on the internal jugular vein. Styloid process  A thin bone arising from the base of the skull that travels next to the spine and can pinch the internal jugular vein. Sulfa allergy Rash or other reaction to sulfa (sulfonamide) medications. The allergy most commonly occurs with sulfa antibiotic medications. Superior sagittal sinus  Large vein that travels in the middle of the head and splits at the torcula to form the transverse sinuses. Thrombosis  Clotting of blood in a blood vessel. Tinnitus  A sound in the ear. Tolerance  Occurs with opiate medications where higher and higher doses of medication are needed to achieve the same pain-relieving effect. Tonsillar ectopia  Sag of the bottom part of the cerebellum (tonsils) through the hole at the base of the skull. Topiramate  A common medication prescribed for IIH that reduces the amount of cerebrospinal fluid the brain makes, functions as a headache medication, and is an appetite suppressant. Torcula  The bottom the superior sagittal sinus where it splits into the two transverse sinuses. Transverse sinus  Large vein that travels from the torcula at the bottom of the superior sagittal sinus toward the ear and becomes the sigmoid sinus. Valve  Shunt device that controls how much fluid flows through a shunt. Venogram  A procedure where a catheter is placed into a vein and contrast dye is injected. X-ray machines are used to make movies of the blood traveling through the veins. Venous sinus  Large veins leaving the brain that are encased in a membrane (dura). Includes the superior sagittal sinus, torcula, transverse sinuses, and sigmoid sinuses. Ventricle  Fluid chamber of the brain. Ventricular catheter  The part of the shunt that is placed in the fluid chamber of the brain in ventriculo-peritoneal, ventriculo-atrial, or ventriculo-pleural shunts; used interchangeably with “proximal” catheter in these shunt types. Ventricular collapse  Decrease in size of the lateral ventricle around the catheter after shunt placement. Ventriculo-atrial (VA) shunt A shunt that drains cerebrospinal fluid from the brain ventricles to the vein near the atrium of the heart. Ventriculo-peritoneal (VP) shunt  A shunt that drains cerebrospinal fluid from the brain ventricles to the cavity in the abdomen around the intestines and liver. Ventriculo-pleural shunt A shunt that drains cerebrospinal fluid from the brain ventricles to the space outside the lungs.

Index

A Acetaminophen (Tylenol), 113 Acetazolamide, 106, 107 Anti-inflammatory drugs, 113 B Bariatric surgery, 102, 103 Blood, 40, 44, 49, 53, 54, 60 patch, 86 pressure, 9 thinners, 133, 134, 137, 145, 146, 148, 152, 163, 192 Body mass index, 96 Bone dehiscence, 76, 77 Brain fog, 29 Brain imaging bone dehiscence, 76 cerebral edema, 76 chiari malformation, 74 collapsed ventricle, 74 CT scan, 66–68 CTV, 70 empty sella, 70, 71 IIH, 65, 66 metal artifact, 77 MRI scan, 68, 69 MRV, 70 optic hydrops, 71 pneumocephalus, 75 venous sinus stenosis, 71 venous sinus thrombosis, 72, 73 Brain veins, 7

C Central venous pressures (CVP), 59 Cerebral angiography, 115, 116 allergies, 122 anesthesia affects pressure measurements, 119, 120 contrast dye, 122 procedure, 118, 119, 123–128 shunt, 120, 121 Cerebral edema, 76 Cerebrospinal fluid (CSF), 1, 3, 5, 6, 30, 34, 39, 106, 131, 176, 220, 227 blood pressure, 9, 10 brain veins, 7, 8 hydrocephalus, 17 IIH, 15, 16 intracranial pressure, 18–20 reabsorption, brain fluid, 6, 7 venous sinus pressures, 10–14 Cerebrospinal fluid leak repairs, 231, 232 Cerebrospinal fluid shunt, 173–175 blood thinners, 192 catheter migration, 215–217 CT brain, 204, 205 IIH symptoms, 201, 202 incision, 200 life expectancy, 177, 178 lumbo-peritoneal, 186, 187 nuclear medicine shuntogram, 205, 206 numbness, 198 pain, 199 quality of life, 176, 177 re-equilibration phenomenon, 219, 220

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 K. M. Fargen, Idiopathic Intracranial Hypertension Explained, https://doi.org/10.1007/978-3-030-80042-0

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Index

246 Cerebrospinal fluid shunt (cont.) shunt infection, 217, 218 shunt re-programming, 212–214 shunt revision surgery, 220–222 shunt series, 203, 204 shunt tap, 211, 212 shunt valves, 189, 191 surgical procedure, 193–197 swelling, 199 three parts, 179, 180 ventricular collapse, 207–210 ventriculo-atrial, 184, 185 ventriculo-peritonal, 181–183 Chiari malformations, 73, 233, 234 Chronic intracranial venous hypertension syndrome, 39 Clopidogrel, 145, 146, 148 Closing pressure, 79, 85 Closure device, 127, 128, 150 Collapsed ventricle, 74 Contrast dye, 66 Cosure device, 128 Cranio-cervical, 229, 230 Cranio-cervical fusion, 229, 230 Cranio-cervical instability (CCI), 36, 229 D Dehiscence, 231 Dura mater, 3 Dural venous sinuses, 7 E Ehlers-Danlos syndrome (EDS), 23, 31, 35, 36, 229, 234 Empty sella, 71 F Furosemide, 110, 111 H Hydrocephalus, 16, 17 I Idiopathic intracranial hypertension (IIH), 1, 2 aplasia, 56 brain fog, 29 cerebrospinal fluid leak, 30 chronic condition, 62, 63

common symptoms, 23, 24 CVP, 42, 43 diagnosis, 21 high venous pressures, 57 intracranial pressures, 33, 34 light sensitivity, 28 medications, 59, 60 narrowing, 46–48 normal venous pressures, 41, 42 papilledema, 26 positive feedback loop, 49 presentation, 22 pressure gradient, 51 pulsatile tinnitus, 28 treatment strategies, 61, 62 venous congestion, 53 venous narrowing, 44–46 venous pressures, 40, 41 venous sinus narrowing, 49, 50 venous sinus thrombosis, 54, 55 visual loss, 26, 27 visual symptoms, 25 worsening, 32 Intensive care unit (ICU), 151–152 Internal jugular vein treatments, 225–227 Interventional radiology suite, 115, 124 Intracranial pressure (ICP), 18, 39, 79–81, 154, 228 lumbar drain placement, 87–89 lumbar puncture, 81–86 monitoring, 90–93 L Lifestyle modification, 100, 105 body mass index, 95, 96, 98 calorie change, 100, 101 central venous pressure, 98, 99 cerebrospinal fluid, 104 IIH, 95 intracranial pressures, 99 overweight, 97 stenting, 104 successful, 101, 102 weight loss surgeries, 102, 103 Lumbar drain placement, 87–89 Lumbo-peritoneal shunt, 174, 186, 207 M Manometer, 80, 81, 84 Medications, 105 Metal artifact, 77

Index Methazolamide, 107, 108 Microcatheter, 123, 126 Monitor, intracranial pressure, 90–92 Morbid obesity, 96 N Non-steroidal anti-inflammatory drugs (NSAIDs), 113 Nuclear medicine shuntogram, 202, 205 O Opening pressure, 79, 81, 84, 85 Opiate, 111, 112 Optic hydrops, 71 Optic nerve sheath fenestration (ONSF), 228 Over-the-counter (OTC), 113 P Pneumocephalus, 75 Positional orthostasis tachycardia syndrome (POTS), 110 Positive feedback loop, 47, 49 Post-anesthesia care unit (PACU), 150, 151 Postural orthostatic tachycardia syndrome (POTS), 36 Pressure gradients, 51, 137, 147 Pseudotumor cerebri, 1 Pulsatile tinnitus, 28 Q Quality of life, 132 R Re-equilibration phenomenon, 160, 169, 219, 220 Reservoir, 202, 205 Rhinorrhea, 30 S Shunt malfunction, 178, 203 Shunt re-programming, 212–214 Shunt revision, 220 Shunt series, 201–204 Shunt tap, 189, 211, 212 Stent failure, 156, 158, 159 Stent pain, 154

247 Styloidectomy, 226, 227 Sudden visual loss, 144 Superior sagittal sinus, 7, 13, 16 T Thrombosis, 55–57 Tinnitus, 28 Topiramate, 108, 109 Transverse sinus, 137–139, 151, 161, 168 V Valve, 189, 191, 195, 201–203, 205, 207, 211, 214 Venography, 115 Venous sinus pressures, 13 Venous sinus stenosis, 71 Venous sinus stenting, 132–134, 170 angiogram, 139, 140 blood thinners, 145, 146 candidacy for stenting, 136, 137 cerebral angiography, after stenting, 165, 166 children, 144, 145 CSF pressures, 135 IIH medications, 154, 155 new vein narrowing, 161–163 procedure, 147–153 re-equilibration phenomenon, 169 repeat stenting, 167, 168 spinal taps, 163, 164 stent failures, 157–160 stent pain, 153–157 stenting, 142, 143 sudden visual loss, 143, 144 surgical procedure, IIH, 131, 132 symptom improvement rates, 140, 141 transverse, 138, 139 Venous sinus thrombosis, 54, 72 Venous sinuses, 7, 10, 13 Ventricles, 3, 5 Ventricular collapse, 187, 207–210 Ventriculo-atrial (VA) shunts, 184 Ventriculo-peritoneal (VP) shunt, 173, 178, 181, 190 Visual loss, 33 W Weight loss, 95, 99, 100