Textbook on MRI Mapping of the Human Deep Brain: Maps and Extended 3D Analysis 9782759825769

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Current Natural Sciences

Jean-Jacques LEMAIRE

Textbook on MRI Mapping of the Human Deep Brain Maps and Extended 3D Analysis

All Illustrations Ó Jean-Jacques Lemaire

Printed in France

EDP Sciences – ISBN(print): 978-2-7598-2575-2 – ISBN(ebook): 978-2-7598-2576-9 DOI: 10.1051/978-2-7598-2575-2 All rights relative to translation, adaptation and reproduction by any means whatsoever are reserved, worldwide. In accordance with the terms of paragraphs 2 and 3 of Article 41 of the French Act dated March 11, 1957, “copies or reproductions reserved strictly for private use and not intended for collective use” and, on the other hand, analyses and short quotations for example or illustrative purposes, are allowed. Otherwise, “any representation or reproduction – whether in full or in part – without the consent of the author or of his successors or assigns, is unlawful” (Article 40, paragraph 1). Any representation or reproduction, by any means whatsoever, will therefore be deemed an infringement of copyright punishable under Articles 425 and following of the French Penal Code. Ó Science Press, EDP Sciences, 2021

Foreword

We are settling our neuronal nodal network knowledge learned from the visualization of the human brain connectivity. However, the understanding of the integration of deep cerebral structures is still lacking. The visualization of these nodal connections and hubs of neurons, represent a major challenge for specialized physicians and neuroscientists alike. It is challenging to unveil the less complex networks, such as motor, sensory, auditive and visual. More so to understand the discrete connections, we still do not realize the existence, for example, the ones responsible for human cognition. Recognition in the living brain of relays learned during years of exhaustive anatomic dissections, using from the most basic to the most complex laboratory techniques of brain fixation and dissection, is the mission of this textbook. We still have not correlated with the necessary detail what we are having the privilege to see in vivo with images of the living brain. Now, we can see and confirm these relays with exquisite details. These need to be cataloged to be available, not only for the understanding of the brain structure and function but also, most importantly, for guiding neuroscientists and physicians to develop novel strategies to treat neurological diseases, minimizing human suffering. While the cerebral cortex is better mapped during awake surgery, we learned recently that plasticity can modify areas of cortical function. This challenges well established neuroscientists’ and physicians’ anatomical knowledge. We are realizing, comparing the findings in open surgery, functional images and the old established maps of the cerebral cortex that functional sites are changing dynamically in the brain of an individual. While we are realizing these cortical dynamisms, we know little about these changes in the depth of the brain. Indeed, understanding the deep cluster of cells’ functions and their cortical connections still limits what physicians offer to abate patients’ suffering and cure diseases. Atlases devised for this purpose exist; however, the correlation of the displayed structures with the most targeted deep brain functional relays to alleviate DOI: 10.1051/978-2-7598-2575-2.c901 © Science Press, EDP Sciences, 2021

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symptoms is still being unveiled. Now with tractography, functional imaging and spectroscopy offered by magnetic resonance imaging (MRI), these mysteries of the brain function are at hand to realize. Aided by molecular imaging and optogenetics, our understanding of the human brain function promises to be fertile grounds for years of study. This understanding depends, however, on detailed anatomical knowledge. This Textbook, hinged on exquisite MRI analyses and painstaking segmentation of structures, brings further knowledge of what is necessary to explore the universe of the functionality of deep brain therapeutic targets. Several of which already alleviating symptoms of diseases for which medicine still do not have the cure. Understanding the anatomical boundaries of a cluster of cells, their connections, and their correlation to the established clinical knowledge is the base for the development of novel therapies. Structures related to motor function, easily correlated to symptoms during surgery, are taken as the main indicators of functionality of certain deep brain cluster of cells. The motor relays of the thalamus, pallidum and subthalamus are explored by Professor Lemaire in this compendium, confirming their boundaries, shapes and correlation with the classic ventricular landmarks, which guided the functional neurosurgeon to approach the brain during the last century. They allowed the transfer of the knowledge acquired in the last century to the live images and probabilistic atlases being developed in the two decades of the past century and now. This became possible, thanks to the advent of the computerized images: computed tomography, magnetic resonance imaging and positron emission tomography, all valued Nobel Prizes. The exquisite three-dimensional compilation presented by Professor Lemaire in various views enhance the knowledge necessary for interpretation of the surgical anatomy, indispensable for our interventions based on images for stereotactic surgery, surgical navigation and guided ultrasound surgery. Beyond the motor targets in the depth of the brain, already applicable to the therapy of several motor cerebral disorders, the reader is greeted with the same detailed definition of structures involved in mysteries of endocrine function, cognition and behavior, including the hippocampus and the hypothalamus. This gift to science presented in this Atlas represents years of dedication of Prof. Lemaire, which I had the privilege to witness for over a decade, correlating settled knowledge of brain anatomy with the detailed visualization offered by images obtained with high tesla MRI technology, always bringing to the anatomical interpretation his exquisite knowledge of functional neurosurgery, acquired during a lifetime experience treating patients with genetic and neurodegenerative diseases of the brain. This Atlas becomes a classic of human brain anatomy. Antonio De Salles Professor Emeritus of Neurosurgery and Radiation Oncology University of California Los Angeles, USA Director of NeuroSapiens, São Paulo, Brazil

Preamble

After more than fifteen years of pure direct targeting of the deep brain in stereotactic functional neurosurgery, i.e. the direct mapping, identification (label and boundary) and targeting of anatomical structures, and considering the amount of knowledge gathered, and the kind requests from students, I have taken the decision to provide this advanced knowledge to all those who are interested in deciphering the architecture of the human brain. From the first report of pure direct targeting in 1999i, this new path was charted progressively, with the conviction that the basic principle of direct identification of the deep brain architecture would be a significant step in advancing neuroscience and medical applications. Clinical MRI was being developed at the same time as the technique of deep brain stimulation was introduced, with the result that they cross-fertilized the concept of direct targeting in my mind. This made it apparent that an atlas of the 3D MRI anatomy of the deep brain would be necessary, allowing the analysis of structural information (i.e. neuroanatomy). Using a high field (4.7 T) MRI research machine, it was possible to obtain high resolution ex vivo images of the deep brainii. The inherent challenge was to fix labels and determine boundaries to structures on the basis of patchy anatomic evidence and using non-dedicated tools. Finally, it took more than ten years to create an atlas usable for clinical practice, research and teaching, and fully MRI based. It was baptized MDBA, for MRI Deep Brain Atlas. The clinical approach to the atlas creation process required a meticulous checking of anatomic and topographic information, structure by structure, bearing in mind i

Lemaire J.J., Durif F., Boire J.Y., Debilly B., Irthum B., Chazal J. (1999) Direct stereotactic MRI location in the globus pallidus for chronic stimulation in Parkinson’s disease Acta Neurochir. 141, 759. https://doi.org/10.1007/s007010050372. ii Lemaire J.-J., Caire F., Bonny J.-M., Kemeny J.-L., Villéger A., Chazal J. (2004) Contribution of 4.7-T MRI in the analysis of MRI anatomy of the human subthalamic area, Acta Neurochir. 146, 906 (Abst.). https://doi.org/10.1007/s00701-004-0301-9.

DOI: 10.1051/978-2-7598-2575-2.c902 © Science Press, EDP Sciences, 2021

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the potential clinical implications. This work was punctuated by the publication of articles. Finally, deep brain mapping provides an advanced atlas gathering historical data and modern imaging. Obviously, the atlas is composed of maps that can be used for the direct identification of the structures, which is what it was designed for. However, it can also be used by those performing indirect identification of structures, as it is also a stereotactic atlas. Neuroscientists should be interested in such data, which are infrequent, and particularly since they are based on clinical practice. This textbook is intended for a wide audience of students and professionals. While compiling it, I noted that known structures are sometimes not so known as thought, talked about or reported. Despite this, it was possible to merge sources, sometimes in oblivion, in an effort to mix several points of view, to clarify the information without oversimplification. Doing so, I pointed to still little-known areas to suggest new maps of certain regions. Today, recent advances in artificial intelligence have revealed that the automatic identification of brain structures, including the deep brain, may be achievable in the next few decades, and advances will be achieved all the more quickly as the ground truth will be available for learning the machine. Therefore, precise and extended databases, linking several terminologies must be built, and the MDBA could participate in this exciting challenge. In summary, the textbook of MRI mapping of the human deep brain gathers advanced clinical knowledge in neuroanatomy, and historical and pioneering anatomical data which were made available to map the deep brain. Mapping was performed by meticulous manual contouring of more than one hundred structures revealed by high geometric resolution, sub millimetric voxels, using MRI images. The MDBA facilitates the direct identification of structures on MRI and enables 3D understanding of the deep brain architecture. Finally, a specific section of the textbook shows examples of real clinical cases of manual contouring of deep brain structures targeted in functional stereotactic neurosurgery. The textbook provides the means to identify anatomic structures of the deep brain on MRI, both in territories studied anatomically since the first pioneering works, some of which going back to the 19th century, and others still not well studied/explored. Indeed, recognizing the structures that make up the human deep brain is difficult. This is true in medicine and research, even with the most recent MRI machine and computing methods. It should be noted at the outset that the term deep brain is somewhat imprecise. It is an attempt to define a region composed of subcortical, deeply seated, structures, white matter territories and gray nuclei. In practice, the deep brain includes, not exclusively, the thalamus, the prethalamus, the hypothalamus, the lenticular and sub lenticular regions, capsules and lamina, and the mesencephalon, so-called “macrostructures”. Most structures making up these macro structures are little known from clinical and anatomical points of view, first and foremost because they are deeply located and imbricated in a complex manner, hence many are merely ignored, incompletely studied, or unexplored. The following structures are examples among the most well-known: the subthalamic nucleus, the zona incerta, the ventrocaudal nucleus of the thalamus, the ventromedial nucleus of the hypothalamus, the thalamic fascicle, the brachium conjunctivum, the ansa

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lenticularis, the substantia innominate, the central tegmental tract and the area of Wernicke. Clinicians or researchers who want to identify structures on MRI must look for fragmented data in books and publications, as well as in free web-based atlases. They must address the difficulty of mastering different sources in a comprehensive and integrated manner. Moreover, reference books are not easy to read because they require advanced knowledge, and some are simply not available in libraries. Furthermore, there are several nouns that refer to the same, or almost the same, structure, e.g. the thalamic fascicle is also called the thalamic fasciculus, the Forel H1 field, H1, the area tegmentalis H, and Forel’s field H. The same fascicle is also called: area subthalamica tegmentalis and pars dorsomedialis (Neuronames); fasciculus thalamicus and nucleus campi dorsalis [H1] (terminologica anatomica and neuroanatomica); field h1 and the nucleus of the dorsal field of the subthalamus (Foundational Model of Anatomy). On the other hand, free web atlases, which are quite easy to download, are often simplified and sometimes include approximations, notably for structures which have not been frequently and recently studied. Finally, there is no precise and detailed MRI atlas of the deep brain. These difficulties are also hurdles for master’s students in search of a synthetic and comprehensive description of the deep brain, facilitating the analysis of MRI anatomy, while giving links to several nomenclatures. More specifically, the textbook addresses three tricky points regarding the structures of the deep brain. ➢ Topography, topology and neighborhood. The topography and topology of the structures of the deep brain are indubitably one of the most difficult 3D anatomic organizations to master in humans. This atlas offers a unique representation in 2D and 3D of structures that greatly facilitate the understanding of the complexity of the brain’s architecture, depicted in a straightforward way. For example, the main routes penetrating the thalamus are easy to explain as soon as you can see its reliefs. ➢ Shape and boundary. It is difficult to explain and imagine the shape of deep brain structures, even for simple ones such as the subthalamic nucleus. The meticulous manual contouring of each structure, with sub-millimetric voxels, according to MRI contrasts and anatomic features, gives very precise real shapes and envelopes. ➢ Terminology. As mentioned above, the terminology of deep brain structures is complex and often confusing. The MDBA offers a large sample of names used in clinical practice and also recommended by anatomical ontologies. Regions not extensively mapped or only partially labelled have been revisited and a new terminology is proposed that merges historical names when available, such as the subthalamic tegmental field, which was subdivided into anterior, central, dorsal, lateral, medial zones and the Forel H field. People eager to recognize the architecture of the deep brain, both clinicians and neuroscientists, have two main options: they can use the historical method which relies on stereotactic landmarks, or the indirect method following a proportional and probabilistic approach, or they can use the more recent and straightforward method based on the direct recognition of structures on MRI. They both have strengths and weaknesses. The indirect method relies on quite a long history of works and is

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efficient in numerous applications; in fact, you do not need to know the precise architectural features of structures, and some are directly visible on the imagery used. For example, if you want to study the putamen of the lenticular nucleus, atlases can confirm or show its location quite precisely, and also it is identifiable on MRI and Pet-Scan. This technique is also relatively well adapted for studying a series of data of different subjects or patients. However, it is difficult to precisely explore structures, for example, the limits of the ventral putamen at the edges of the putamen, the ventral claustrum, caudolenticular gray bridges and innominate substance are complex. In this case, most common knowledge on the topic and atlases are extremely limited. On the other hand, the direct method relies on advanced knowledge of the architectural features of structures, and on the information provided by the most recent imagery used. It is perfectly adapted for the analysis of “difficult” regions and above all gives a unique chance to study individual data. However, it is time-consuming and demands much more effort to study a series of data. Briefly, the first, historical “indirect” method, developed in the 19th century, relies on stereotactic atlases (e.g. Schaltenbrand & Bailey, Talairach, etc.) and enables identifying a structure according to coordinates. The link between the morphological (anatomo-histological) data of atlases (labeled structures) and subject (patients or subjects) imageries (projection or slice imagery) is made through stereotactic coordinates. The most widely used stereotactic coordinate system is based on well-known anatomic beacons, the anterior (AC) and posterior (PC) white commissure, and related geometry landmarks (ACPC line and planes). This is the most widely used technique in the world. You do not have to master deep brain architecture or recognize structures; you look for the structure of interest in your atlas and select the coordinates to obtain probabilistic information on the location of the structure. This is widely used in neurosurgery, and also by the neuroimaging community (e.g. Talairach’s daemon). As more and more specific MRI sequences allow visualizing details thanks to greater geometrical and contrast resolution, teams combine stereotactic coordinates and direct visualization of the architecture; the subthalamic nucleus is very likely the most emblematic example of this mixed approach. Whatever the case, it is still limited to particular structures because they have been targeted for a long time, such as the globus pallidus and the subthalamic nucleus, or they are easily recognizable on MRI images because they are big, like the thalamus, or strongly contrasted, as in the case of striatal structures like the caudate. One must bear in mind that the greater the weight of the indirect method, the more the topographical information is approximated. The direct method is attracting increasing attention with the advances made in MRI acquisition and machines. However, it is still limited by the difficulty of mastering the deep brain architecture and making the link between the structures observed in images and corresponding to anatomical structures; hence mixed techniques are largely used and they rely mainly on the indirect method. The novelty of this textbook is that it associates advanced neuroanatomical nomenclatures connected with several classical terminologies and direct MRI cartography, giving an extensive and realistic overview of the deep brain. It also

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provides clinical examples of the manual contouring of structures commonly targeted in functional neurosurgery. This work was made possible by the coregistration of small scaleiii structural MRI images with contoured and labeled structures, and by merging clinical, historical and academic nomenclatures. The handbook gives graphic representations of the deep brain combining triplanar views of 2D slices (the atlas) and 3D views by regions, giving precise topographical information as close as possible to reality. The contouring is specific as it was done structure-by-structure, manually, according to MRI contrasts. It was performed by region, over 10 years due to the topographical complexity and arid literature, guided by the clinical questioning of the moment. The first important step was the decryption of thalamus MRI architecture leading to a simplified clinical topographic nomenclatureiv, and the second significant step was the analysis of electric contact (used for deep brain stimulation) locations according to the atlas in the remote region at the medial border of brain peduncles close to the hypothalamus and the tegmentumv. The last version of the atlas available in this proposal was completely revised, all the structures were checked, contours refined, notably eliminating overlaps (technical limitations of the previous version), and several nomenclatures were merged. 3D representations of structures and regions have been merged with sections along structures, enabling comprehensive topographical analysis. The novelty also resides in precise mapping of remote areas, paving the way for further research. This textbook is of interest to all those who are interested in neuroscience and medicine as it gives updated and extensive synthetic information, as well as topographically correct data. All aspects are addressed with sufficient detail to help a large audience, ranging from those who are not familiar with deep brain structures to researchers in the domain. Synthetic, extensive and updated data are useful for everyone, from university students to researchers looking for data that they can rely on. Topographically correct data are of interest for those who target the brain, such as neurosurgeons, those who analyze the topography of biomarkers-lesions, such as neurologists and neuroradiologists, and those who work on neuroimaging research, such as neuroscientists and researchers in computer science. In neurosurgery, the atlas gives reliable data enabling people to introduce, according to their own environment and practice, MRI guided stereotactic targeting, ranging from classical indirect targeting to pure direct targeting. I have used it in daily clinical practice for many years. In medicine, the atlas will be useful to neuroradiologists and neurologists, as well as practitioners in neuro-anesthesiology, intensive care units and rehabilitation facilities, and likely very soon psychiatrists. Millimetric approach: manual contouring from 256 images, matrix 512 × 512 pixels, no gap, and 250 µm side isotropic voxels. iv Lemaire J.J., et al. (2010) Anatomy of the human thalamus based on spontaneous contrast and microscopic voxels in high-field magnetic resonance imaging, Neurosurgery 66, 161. v Fontaine D., et al. (2010) Anatomical location of effective deep brain stimulation electrodes in chronic cluster headache, Brain J. Neurol. 133, 1214. iii

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It should prove to be an interesting tool for teaching (I use it in programs for master’s students, most of whom ask me where they can obtain the handbook). In neuroscience, the MRI atlas completes the panoply of documents, and enables everyone to make the link between extensive historical knowledge and MRI cartography, with clinical validation (daily practice in neurosurgery and publications).

Acknowledgements

Jean-Marie Bonny, Jean-Yves Boire, Louis Boyer, François Caire, Rémi Chaix, Jean Chazal, Jérôme Coste, Antonio De Salles, Franck Durif, Denys Fontaine, Youssef El Ouadih, Andrew Frew, Jean Gabrillargues†, Simone Hemm, Laurent Hermoye, Paolo Jelmoni, Ferenc Jolecz†, Ron Kikinis, Nikos Makris, Lemlih Ouchchane, Jean-Pierre Renoux, Robert Schmidt, Thomas Schwann, Séverine Siadoux, Anna Sontheimer, François Vassal and Abdelrahim Zerroug.

†

Deceased.

Contents Foreword . . . . . . . . Preamble . . . . . . . . Acknowledgements Introduction . . . . . .

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. III . V . XI . XV

CHAPTER 1 Mapping the Human Deep Brain . . . . . . . . . . . . . . . . . . . . . 1.1 What is the Deep Brain? . . . . . . . . . . . . . . . . . . . . . . 1.2 MRI Mapping or Cartography . . . . . . . . . . . . . . . . . . 1.3 From the Anatomical Material to the MRI Deep Brain and 3D Rendering . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Atlas ............

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CHAPTER 2 Analysis of Deep Brain Regions . . . . . . . . . . . . . . . . . 2.1 The Thalamus . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 The Subthalamus or Prethalamus . . . . . . . . . . . 2.3 The Telencephalic Structures of the Deep Brain 2.4 The Hypothalamus . . . . . . . . . . . . . . . . . . . . . .

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The MRI Deep Brain Atlas – MDBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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CHAPTER 3

CHAPTER 4 Clinical MRI Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 The Intern Pallidum . . . . . . . . . . . . . . . . . . . . . . . . 4.2 The Subthalamic Nucleus . . . . . . . . . . . . . . . . . . . . 4.3 The Ventral Intermediate Nucleus of the Thalamus .

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125 126 128 131

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Introduction

The complexity of the deep brain architecture is a major impediment for its utilization in the field of neurosciences, including clinical neurosciences. At the same time, it must be acknowledged that, when taking everything into account, mastering the deep brain architecture also remains challenging. The very first attempt to describe the deep brain dates back to the 17th century with Willis and Crone1, while 300 years later, in the 19th century, Luys provided the first photographic atlas showing the deep brain2 (figure 1). The textbook provides an advanced description of the human deep brain based on the architecture revealed by magnetic resonance imaging (MRI). This modern approach is fully complementary to those of histological and anatomical works. It also provides tricks and tips enabling the identification of structures according to spatial beacons and MRI contrasts, intended notably for those interested in

FIG. 1 – From Luys, photograph (left) and drawing (right) of an axial section of the human brain showing the emblematic “centre médian”.

DOI: 10.1051/978-2-7598-2575-2.c903 © Science Press, EDP Sciences, 2021

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identifying these structures directly in MRI images. The terminology is intrinsically complex; hence, we provide homonyms and references; Latin and French words are in Italic. The readers should find useful data to complete their desire for knowledge on the human deep brain in numerous documents (see an open-ended list hereafter) and references3–11. Throughout the textbook, the orientation of the structures of the deep brain is given with the position of the head of a standing person, and if necessary the rostrocaudal system is specified; hence, superior means toward the vertex; inferior means toward the feet; posterior means toward the occipital region; anterior means toward the frontal region; accounting for the relative location along the curvature of the diencephalon-mesencephalic junction, dorsal can be superior (diencephalon) or posterior (mesencephalon); ventral is inferior (diencephalon) or anterior (mesencephalon); rostral is toward the frontal polar region and caudal is toward the lower brainstem. The anterior commissure (AC) – posterior commissure (PC) plane (ACPC horizontal or axial plane) is also used as a reference because it is widely used in clinical stereotaxy. All in all, the textbook aims to help researchers and clinicians, students and seniors, to master the terminology used and to identify the deep structures of the human brain on MRI. Open-ended list of relevant references-sources

❖ Ford D.H., Schadé J.P. (1971) Atlas of the human brain. Elsevier Pub. Comp. ❖ Mai J.K., Majtanik M., Paxinos G. (2016) Atlas of the human brain, 4th edn. Academic Press. ❖ Mai J.K., Majtanik M. (2017) Human brain in standard MNI space: a comprehensive pocket atlas. Elsevier Inc. ❖ Flatau E. (1894) Atlas of the human brain: and the course of the nerve fibres. S. Karger. ❖ Jakob C. (1901) Atlas of the nervous system, an epitome of the anatomy, pathology, and treatment. W.B. Saunders & Company. ❖ Talairach Daemon: https://www.talairach.org/daemon.html. ❖ The MNI Brain and the Talairach Atlas: https://imaging.mrc-cbu.cam.ac.uk/ imaging/MniTalairach. ❖ Talairach J., Tournoux P. (1988) Co-planar stereotaxic atlas of the human brain/3-dimensional proportional system: an approach to cerebral imaging. Thieme. ❖ Talairach J., Tournoux P. (1993) Referentially oriented cerebral MRI anatomy: an atlas of stereotaxic anatomical correlations for gray and white matter. Thieme. ❖ Brain Atlas: Montreal Neurological Institute: https://www.mcgill.ca/ bic/software. ❖ Subcortical Atlases in MNI Space: https://www.lead-dbs.org/helpsupport/ knowledge-base/atlasesresources/atlases/.

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❖ Atlas of Brain MRI: https://w-radiology.com/atlas_brain_mri.php. ❖ Morel A. (2007) Stereotactic atlas of the human thalamus and basal ganglia. CRC Press. ❖ Vanderah T., Gould D. (2020) Nolte’s the human brain, 8th edn. Elsevier ed. ❖ Duvernoy H.M. (2005) The human hippocampus: functional anatomy, vascularization and serial sections with MRI, 3rd edn. Springer, Berlin Heidelberg New York. ❖ Yushkevich P.A., Avants B.B., Pluta J., Das S., Minkoff D., Mechanic-Hamilton D., Glynn S., Pickup S., Liu W., Gee J.C., Grossman M., Detre J.A. (2009) A high-resolution computational atlas of the human hippocampus from postmortem magnetic resonance imaging at 9.4 T, NeuroImage 44, 385. https://doi.org/10.1016/j.neuroimage.2008.08.042.

Chapter 1 Mapping the Human Deep Brain

1.1

What is the Deep Brain?

The deep brain is a catch-all term, which comes from the clinical field, enabling the description of numerous deep-seated structures belonging to different anatomical regions, however topographically and functionally highly related. The structures are anatomical elements, of which nuclei, cortices and white matter components are known. Here the deep-seated structures refer essentially to prosencephalic (diencephalon and telencephalon) gray nuclei and neighboring structures, which include rhinencephalic [olfactive system] structures and the amygdalo-hippocampal complex partially composed of cortices, and most elements of the upper (mesencephalon) brainstem. Although of extremely frequent usage in neuroscience, the term nucleus deserves some explanations. Basically, it is a gray matter territory essentially made up of neuron bodies assembled in a cluster, as opposed to cortices where the neuron bodies are roughly arranged in columns and layers at the surface of hemispheres. All gray matter territories are traversed, by construction, by neurites, including the axons or nerve fibers. Neuron bodies are also present in white matter zones, notably neighboring the gray matter, such as intralaminar territories of the thalamus and the subthalamic tegmental field. There is no capsule around the nuclei, but often a high density of nerve fibers surrounding them, and which looks like a capsule. This explains why the name capsule was used in pioneering works, e.g., the capsula nuclei rubris tegmenti, the capsula centri median thalami and the capsula corporis subthalamici6,12 (figure 1.1). The macroscopic gray matter clusters of the deep brain identified over time were named the noyaux gris centraux [central gray nuclei] by Luys13. They were composed of the couche optique (thalamus) and the corps strié [striate body], which can be assimilated as the opto-striate bodies [corps opto-striés]5,13. The somewhat ambiguous term basal ganglia is nowadays accepted as a group of highly functionally related nuclei, the striatum (caudate and putamen), the pallidum, the substantia nigra and the subthalamic nucleus14,15. DOI: 10.1051/978-2-7598-2575-2.c001 © Science Press, EDP Sciences, 2021

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Textbook on MRI Mapping of the Human Deep Brain

FIG. 1.1 – From Sabin, drawing of a dissection of the upper brain stem of the human brain showing capsules of nuclei.

The white matter structures of the deep brain have different names. A fascicle is a white matter bundle of microscopically delineated nerve fibers6, such as the mammillothalamic fascicle. A zone, an area, a capsule or a corona are crossed by fascicles, such as the zone of Wernicke, the tegmental area, the internal capsule and the corona radiata. The peduncle, radiation, brachium and stratum are so called because of their specific shapes, such as the brachium conjunctivum, the inferior thalamic peduncle or radiation and the stratum intermedium pedunculi. The fields of Forel, studied by A Forel in the nineteenth century16, are typical mixed territories, paucicellular and crossed by numerous nerve fibers and fascicles, with several of them named for each structure; for example, the lenticular fascicle, H2 field, area tegmentalis H2, pallido-thalamic fascicle, dorsal division of the ansa lenticularis, ventral field, fasciculus lenticularis, and nucleus campi ventralis17. As mentioned above, the deep brain is composed of diencephalic, mesencephalic and telencephalic structures. The diencephalon [interbrain] occupies the central position of the deep brain, and is composed of four elements: the thalamus; the epithalamus [pars epithalamica diencephalic] with the habenula, the inter habenular commissure, the retroflexed fascicle and the pineal gland; the metathalamus [pars metathalamica diencephali]; the subthalamus; the hypothalamus. The pretectum (posterior commissure) has been differentiated from the epithalamus18. The mesencephalon of the upper brainstem is placed caudally and ventrally to the diencephalon, and the telencephalon is placed rostrally and forms the two hemispheres. The segregation of the human deep brain structures is very likely not definitively settled, as suggested by works on the ontology of the mouse brain19, which has not been definitively settled (see e.g.,20): the diencephalon lying between the hypothalamus and the midbrain is made up of the pretectum (including the posterior commissure), the thalamus (including the habenula and the lateral geniculate body) and the prethalamus (including the reticular nucleus, the zona incerta and the

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pregeniculate nucleus); the subthalamic nucleus belongs to the hypothalamus as a part of the forebrain. Hence, we propose to use a condensed architectural topographical organization of the human deep brain, on top of which advanced users can add their own knowledge: (1) telencephalic structures; (2) the hypothalamus; (3) the thalamus to which has been assigned the metathalamus or geniculate bodies and the epithalamus; (4) the subthalamus or prethalamus, to which has been assigned the tectum and the pineal gland (figure 1.2).

FIG. 1.2 – The deep brain regions.

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Textbook on MRI Mapping of the Human Deep Brain

The thalamus was one of the very first large deep structures identified between the hemispheres. It was named the optic thalamus [Thalami Nervorum Opticorum1] as it spreads to the hypothalamus and the optic tract (figure 1.3). Later, the optic thalamus was split into dorsal thalamus located dorsally (superior), and ventral thalamus or subthalamus [prethalamus] located ventrally (inferior). The thalamus, in the broad meaning [couche optique; thalamus dorsal; dorsal thalamus; optic thalamus; sensory thalamus; interbrain], is nowadays subdivided into dorsal thalamus or thalamus as such, and the metathalamus. Structures are associated by some authors, the epithalamus (historically named olfactory thalamus), the posterior white commissure and the stria medullaris. The prethalamus [subthalamus; ventral thalamus; motor thalamus; région sous-optique; region sous-thalamique] is composed of numerous structures belonging to the diencephalo-mesencephalic junction, and notably to the tegmentum. The difference between subthalamus and prethalamus, and consequently the association of structures with the subthalamus or the prethalamus, is still a matter of debate18. This region is composed of nuclei such as the subthalamic nucleus, and white matter structures such as the brachium conjunctivum and the subthalamic tegmental field.

FIG. 1.3 – From Willis and Crone, posterior view of the brain showing the thalamus.

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The tegmentum [pars tegmentalis mesencephali and isthmi], also named calotte5, is placed between the brain peduncles (pes pedunculi) and the substantia nigra ventrally, and the tectal plate posteriorly (or dorsally; an artificial vertical frontal plane along the brain aqueduct separates the tegmentum and the tectum). The tectal plate [tectum, pars tectalis mesencephali] is composed of the superior (lateral and anterior) colliculi and the inferior (medial and posterior) colliculi, and the immediately adjacent structures. Again, one must bear in mind that it is somewhat artificial to segregate the deep brain structures according to different ontologies, for instance, the stria medullaris thalami should belong to the epithalamus, the thalamus, the hypothalamus6,21 and the prethalamus18.

1.2

MRI Mapping or Cartography

The different MRI signals of the deep brain structures enable mapping. Mapping or cartography needs a priori knowledge of the architecture (shape, composition, and location) of these structures at millimetric scale. Usually, this mapping is carried out manually for clinical applications, using common drawing tools, slice by slice. The clinician maps directly by visual analysis of images, or indirectly using any useful tool or knowledge, i.e., they label, localize and determine the boundary of structures in 2D or 3D. The type and quality of information resulting from cartography depends on the voxel size, i.e., the geometric resolution, usually between 1 and 3 mm per side, down to sub millimetric, and on the contrast range. The latter is related to the signal-to-noise ratio, the type of MRI sequence and the millimetric architecture of the tissue: mapping is easier, providing much information, with high geometric resolution and high contrasts between structures, or mapping is difficult, providing little information, with low geometric resolution and low contrasts. A priori knowledge of structures is mandatory and is based on skills acquired from experimental and/or clinical works. The literature is abundant, however the vocabulary is often challenging. In the textbook, the signal of voxel is described and displayed according to a gray scale, ranging from white, high intensity, to black, low intensity. This gray scale is the reflection of the microarchitecture, i.e., cell density, the density and anisotropy of bundles of axons, and the biochemical content of the tissue. The ferromagnetic charge, which is non-negligible in neurons and glial cells, particularly influences the MRI signal (see e.g.,22). However, as an initial approximation, all things being equal, the whiter the signal, the higher the density of neuronal cell bodies, with the classical “gray matter” aspect; the darker the signal, the higher the density of axons, with the classical “white matter” aspect (figure 1.4). This range of contrasts is the opposite of common clinical T1-weighted imaging, where white matter is pale gray, and gray matter is dark gray.

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FIG. 1.4 – Coronal MRI slice (inversion-recovery sequence) showing the gray signal of the gray matter and the dark signal of the white matter.

1.3

From the Anatomical Material to the MRI Deep Brain Atlas and 3D Rendering

The anatomical material used for building the MRI Deep Brain Atlas (MDBA) was an adult brain specimen imaged at 4.7 T, resulting in isotropic voxels of 250 µm per side. Post processing consisted of ACPC reorientation, resampling at 0.125 × 0.125 × 0.256 mm3, and image filtering (sharping and sigmoid intensity remapping). This enabled, slice by slice, to visually determine the boundaries between the structures and to manually contour each structure according to the spontaneous MRI contrasts and a priori knowledge, aided by tri planar and 3D approaches17. The contours enabled building and displaying 3D structures (triangular approximation from the labelled voxels) (figure 1.5). The nomenclature of structures is a mixture of clinical practice, historical terms, and international standard ontologies5–8,10,18,23–31. In the following sections, for each structure is given: (1) the acronym, the name and the rounded volumes (mm3; of the voxel objects) of the MDBA; (2) NeuroNames [NN]30; (3) the Terminologia Anatomica 1998 [TA98]31; (4) the terminology of the Foundational Model of Anatomy; National Center for Biomedical Ontology [FMA]32; (5) the Terminologia neuroanatomica 2017 [TA2017]18; (6) complementary Data, French terminology of Laget8, Talairach et al.9, Déjerine5, Duvernoy23, Guillain & Bertrand10, and English terminologies of Riley6, Olszewski & Baxter27, Schaltenbrand & Bailey33 and Nieuwenhuys, Voogd & Van Huijzen7. The terminologies are presented in the following forms, each [acronym] is separated by /, and n.a. means that the data were not available: e.g., CAULEN-gray-b; caudolenticular gray bridges; 232 mm3/[NN] pontes striatales/[TA98] pontes grisei caudatolenticulares; transcapsular grey

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FIG. 1.5 – Workflow: ACPC alignment of brain specimen (A) and MRI dataset (B); post-processed sagittal MRI slice going through the subthalamic nucleus (C); 3D rendering (top) and contouring (stair-case like aspect due to voxel labelling, bottom left; smoothed lining after probabilistic triangulation and filtering, bottom right) of the subthalamic nucleus (D).

bridges; A14.1.09.525/[FMA] set of caudolenticular gray bridges; 77 813/ [TNA2017] pontes grisei caudatolenticulares/gray laminae bridging the caudate and lenticular nuclei; n.a.; pontes striatales; pontes grisei lenticulares. One hundred and nineteen structures were labelled from meticulous, step-by-step, and test-end-retest processes. The MDBA, built over time, is provided in detail (chapter 3). In parallel to the analysis of the 4.7 T data set, the result of the visual mapping was compared to clinical practice in functional deep brain surgery, progressively enabling the use of the MDBA in clinical routine17. The dataset of objects enabling the 3D analysis is exposed region by region in the following sections, accompanied by illustrational plates.

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The high geometric and contrast resolution has so far enabled characterizing unprecise or still unnamed structures, and proposing names for these segregated structures, according to location and appearance, for instance: the retrolenticular reticularoid zone (reticular appearance, apparent low density of cells, low signal intensity) was observed laterally to the zone of Wernicke; the subthalamic tegmental field covering the historical Forel’s H field, was segregated into anterior, central, dorsal, lateral, medial zones and the Forel H field; the area of reticular appearance placed posteriorly and below the pallidum was named the posterior subpallidal area. The double approach, triplanar slice by slice, or sectional, and 3D rendering, is particularly helpful for mastering the spatial organization and shapes of structures.

Chapter 2 Analysis of Deep Brain Regions

2.1

The Thalamus The thalamus can be partitioned into six regions. The posterior region is occupied by the pulvinar with its free posterior surface. The medial region is occupied by the medial nucleus. The anterior group of nuclei forms the anterior or rostral pole (region). The superior region is composed of the dorsolateral and the dorsomedial nuclei and the superior thalamic peduncle or radiations. The lateral region is composed of an intermediate lateral nucleus and the ventrolateral group of nuclei. The laminar region is placed roughly on the sagittal midline and contains the centromedian-parafascicular nuclear complex. The lateral surface is coated by the superficial lateral thalamus, a reticular nucleus, and the underlying external lamina. The medial surface is coated inferiorly by the superficial medial thalamus, which continues ventrally with the interbrain central gray.

The name thalamus has a Latin root34, meaning couche (FR), thus, couch, lay or bed (noun and verb). The organization of the nuclear and white matter components of the thalamus is particularly complex when accounting for its spatial organization, and often destabilizing regarding the classical nomenclatures, such as the dorsomedial nucleus, which is merely medial and coated by the nucleus dorsal superficialis, which is dorsomedial. Hence, in an attempt to simplify the terminology, we propose a parcellation based on spontaneous contrasts35, accounting for the spatial location of each nucleus, in line with pioneering works and usable in routine stereotactic functional neurosurgery36,37. Thus, for instance, the classical, dorsomedial nucleus is named the medial nucleus of thalamus, and the dorsal superficialis is named the dorsomedial nucleus of thalamus. Table 2.1 summarizes different nomenclatures of thalamic nuclei. The pulvinar, the biggest nucleus of the thalamus, was individualized a long time ago because its posterior (dorsal) surface is visible. It is flanked, anteriorly, laterally and inferiorly, by the geniculate bodies. DOI: 10.1051/978-2-7598-2575-2.c002 © Science Press, EDP Sciences, 2021

Location

Nomenclatures of thalamic nuclei

Nucleus

Riley H.A., 1943

AMD-nu; AMI-nu; AMV-nu

antero-ventralis, N av th; medialis, N m th

Talairach J. et al., 1957 (Walker E./ Kuhlenbeck H./ Talairach et al.)

Anterior (/oral)

Groupe nucléaire antérieur, Na th

Schalentenbrand G. & Bailey P., 1959 (Hassler R./Vogt C. & Vogt O.) Anterior principalis, A.pr or Anteroventralis, AV Fasciculous, Fa

Hirai T. & Jones E.G., 1989/Morel et al., 1997 (Hassler R./Jones E. G.) Anteroventral, AV

Parent (Olszewski J., Monkey related…) Anterior ventral, AV

Medioventral, MV (partially)

Anterior medialis, A. m; anterior inferior, A.if Anterior dorsalis, A.d

Anteromedial, AM

VL medial, VLm (partially) Anterior medial, AM

Anterodorsal, AD

Anterior dorsal, AD

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TAB. 2.1 – Nomenclatures of thalamic nuclei. Hirai T., Jones E.G. (1989) A new parcellation of the human thalamus on the basis of histochemical staining, Brain Res. Rev. 14, 1–34; Riley H. (1943) An atlas of the basal ganglia, brain stem and spinal cord. Williams & Wilkins, Baltimore; Talairach J., David M., Tournoux P., Corredor H., Kvasina T. (1957) Atlas d’anatomie stéréotaxique. Repérage radiologique indirect des noyaux gris centraux des régions mésencéphalo-sous-optiques et hypothalamiques de l’homme [in French], Masson et Cie, Paris; Hassler R. (1959) Anatomy of the Thalamus, Introduction to Stereotaxis with an Atlas of the Human Brain. Stuttgart, pp. 230–290; Schaltenbrand G., Bailey P. (1959) Introduction to stereotaxis with an atlas of the human brain. Georg Thieme Verlag, Stuttgart; Morel A., Magnin M., Jeanmonod D. (1997) Multiarchitectonic and Stereotactic Atlas of the Human Thalamus, J. Comp. Neurol. 387, pp. 588–630; Parent A. (1996) Carpenter’s human neuroanatomy, Williams & Wilkins. ed. Baltimore; Olszewski J. (1952) The thalamus of Macaca mulata. An Atlas for use with the Stereotactic Instrument. Karger, Basel, New York.

Dorsal

AL-nu

Lateralis, N l th

DL-nu

Lateralis, N l th

Supranucleus lateropolaris, L.po (magnocellularis, L.po.mc)

Latéral postérieur, lateralis posterior

Dorso-oralis, D.o Dorso-intermedii, D.im

Intermediate

DM-nu

Antero-dorsalis, N ad th

IL-nu

Lateralis, N l th

Latéral dorsal, lateralis dorsale; possibly Antérieur, Na th (dorsal part) Overlapping latéral postérieur and ventral latéral

Possibly dorso-caudalis, D.c Dorsal superficialis, D.sf

Ventral anterior, VA; (Magnocellular, Vamc, included in the internal medullary lamina) Principal ventral medial, VM (partially) Ventral anterior, VA (partially) Ventral lateral posterior, VLp (dorsal part) Possibly lateral posterior, LP Lateral dorsal, LD

Zentrolateralis oralis, Z.o

Ventral lateral anterior, VLa (partially)

Zentrolateralis intermedius, Z.im Zentrolateralis caudalis, Z.c

VLp + VPLa (partially) Ventral posterior lateral anterior, VPL a (postero-dorsal part)

Ventral anterior (magnocellular, parvocellular), VA (pc, mc)

VA (partially) Lateral posterior, LP

Analysis of Deep Brain Regions

TAB. 2.1 – (continued).

Lateral dorsal, LD

LP

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Thalamic nuclei: MDBA Location

Nucleus

Nomenclatures of thalamic nuclei Riley H. A., 1943

Talairach J. et al., 1957 (Walker E./ Kuhlenbeck H./ Talairach et al.)

Ventral

Lateris ventralis, N lv th

Ventral latéral, lateralis ventralis, L v th

Overlapping Ventral intermédiaire and V.P.L

Schalentenbrand G. & Bailey P., 1959 (Hassler R./Vogt C. & Vogt O.)

Hirai T. & Jones E.G., 1989/Morel et al., 1997 (Hassler R./Jones E.G.)

Ventrooralis anterior, V.o.a (a.b) Ventrooralis medialis, V.o.m Ventrooralis internus, V.o.i

VLa

Ventrooralis posterior, V.o.p (p.b) Ventrointermedius, V.im

VM VLp (antero-medial part)

Parent (Olszewski J., Monkey related…) Ventral lateral oral, VLo VL medial, VLm VL caudal, VLc

VLa

VLp (ventral part)

Cell-sparse zone: Area X (+ VPLo + VLc) ± VPI

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VOA-nu; VOM-nu; VOP-nu; VI-nu

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TAB. 2.1 – (continued).

VCL-nu

Medial Laminar

Ventralis postero-lateralis, N vpl th

Ventral Postérieur Latéral, ventralis posterior lateralis, V.P.L

VCM-nu

Ventralis postero-medialis, N vpm th

Ventral postérieur médian, semilunaire de fleshig, arcuate, ventralis posterior medialis, V.P.M

M-nu

Medialis, N m th

CM-nu

Centri mediani, N cmth

Dorso-médian or medialis dorsalis, m. th Centre Médian de Luys, centralis, Ncm (reticular group)

PF-nu

Parafasciculaire

Ventrocaudalis anterior and posterior externus, V.c.a.e + V.c.p.e Ventrocaudalis parvocellularis externus, V.c.pc.e Ventrocaudalis internus, corpus semilunare, arcuate, V.c.i + V.c.a.i Ventrocaudalis parvocellularis internus, V.c.pc.i Medialis, M

Ventral posterior lateral anterior and posterior, VPLa + VPLp

Ventrobasal complex, ventral posterior, VP, lateral, VPL

Ventral posterior inferior, VPI

VP, inferior, VPI

Ventral posterior medial, VPM, VPLp (partially, the ventral and medial portion) Basal ventral medial, VMb + Submedius Mediodorsal, MD

VP: medial, VPM

Centralis, centre médian, magnocellularis, Ce.mc; parvocellularis, Ce.pc Parafascicularis, Pf

Centre Médian, CM

Analysis of Deep Brain Regions

TAB. 2.1 – (continued).

Dorsomedial, DM, or mediodorsal, MD Intralaminar caudal: centromedian, CM; parafscicular, pf; CMpf complex; subparafascicula

Parafascicular, Pf

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Thalamic nuclei: MDBA Location

Nomenclatures of thalamic nuclei Riley H.A., 1943

LAO-nu

Nuclei of the Lamina medullaris medialis (La mmth)

Talairach J. et al., 1957 (Walker E./ Kuhlenbeck H./ Talairach et al.) Noyaux intralaminaires

Schalentenbrand G. & Bailey P., 1959 (Hassler R./Vogt C. & Vogt O.) Commissuralis, Co (partially) + (i) La.m.o (oralis)

LAC-nu

PUL SFL

SFM

Pulvinaris, N pth Reticularis, N rth Mediani, Nmdth

Pulvinar, posterior Réticulaire, zone grillagée d'Arnold (reticular group) Groupe de la Ligne médianne or substance grise sous épendymaire

Intralamellaris (medialis) caudalis, iLa.(m)c; Limitans, Li; Paramedianus principalis, Pm Pulvinaris, Posterior, Pu

Hirai T. & Jones E. G., 1989/Morel et al., 1997 (Hassler R./Jones E.G.) Central Medial, CeM

Parent (Olszewski J., Monkey related…) Intralaminar rostral: paracentral; central lateral, CL; central median

Central Lateral, CL (partially) Posterior CL; Limitans, Li; Paraventricular, Pv

Pulvinar, Pl

Reticulatum, Rt

Reticular, R

Parataenialis, Pt; Endymalis, Reuniens, Edy

Parataenialis, Pt; Medioventral, (Reuniens), MV (partially)

Lateral group: Pulvinar Reticular

Midline

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Nucleus

Cucullaris, Cu (partially)

Posterior (/caudal) Superficial

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TAB. 2.1 – (continued).

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PUL; pulvinar; 1577 mm3/[NN] pulvinar/[TA98] nuclei pulvinares; A14.1.08.610/[FMA] pulvinar; 62178/[TNA2017] pulvinar/nucleus posterior; nucleus pulvinaris thalami; pulvinar; pulvinar thalami; nucleus posterior thalami.

The lateral geniculate body, which looks like a “gendarme hat” (the bicorn hat of gendarmes under Napoleon I) on coronal sections, is coated dorso-laterally by the zone of Wernicke, a zone of “passage” of nerve fibers, notably toward the thalamus. L-GB; lateral geniculate body; 116 mm3/[NN] lateral geniculate complex/ [TA98] corpus geniculatum laterale; A14.1.08.302/[FMA] lateral geniculate body; 62209/[TNA2017] corpus geniculatum laterale/dorsolateral geniculate body; corps genouillé latéral (métathalamus); corps genouillé externe; corpus geniculatum. ZOW; zone of Wernicke; 186 mm3/[NN] triangular area of Wernicke/[TA98] n.a./[FMA] n.a./[TNA2017] n.a./extended triangular area of Wernicke; zone ou champ de Wernicke; area triangularis; area or field of Wernicke; zona lateralis.

The, small, lateral, pre geniculate nucleus surmounts, slightly medially, the lateral geniculate body. The optic tract directly plugs into the lateral geniculate body, anteriorly. P-GB; pregeniculate nucleus; 14 mm3/[NN] pregeniculate nucleus/[TA98] nucleus ventralis corporis geniculati lateralis; A14.1.08.806/[FMA] ventral nucleus of lateral geniculate body; 62215/[TNA2017] nucleus ventralis corporis geniculati lateralis/nucleus pregeniculatum; n.a.; nucleus praegeniculatus; nucleus accessorius; corpus geniculatum externum; griseum praegeniculatum.

The medial geniculate body is posterior, superior and medial relative to the lateral geniculate body. M-GB; medial geniculate body; 70 mm3/[NN] madial geniculate body/[TA98] corpus geniculatum mediale; A14.1.08.303/[FMA] madial geniculate body; 62211/[TNA2017] corpus geniculatum mediale/corps genouillé médian (métathalamus); corpus geniculatum.

The medial nucleus, the 2nd largest nucleus of the thalamus, is dense, and extends from the anterior pole to the pulvinar. It is wrapped medially and inferiorly by the superficial medial nucleus. Its anterior pole is coated, laterally by the laminar oral nucleus, and medially by the anteromedial nuclei. The dorsomedial nucleus surmounts the medial nucleus. M-nu; medial nucleus of thalamus; 957 mm3/[NN] medial dorsal nucleus/ [TA98] nucleus mediodorsalis; A14.1.08.622/[FMA] medial dorsal nucleus; 62156/[TNA2017] nucleus mediodorsalis/mediodorsal or dorsomedial nucleus of the thalamus; nucleus medialis dorsalis; noyau doso-médian; noyau interne du thalamus; nucleus medialis.

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The anterior group is composed of the anteromedial and anterolateral nuclei. The mammillothalamic fascicle runs between the anterolateral nucleus and the laminar anterior nucleus. The anterolateral nucleus is the biggest of the group, with a “cloudy” aspect on MRI (see atlas). AL-nu; anterolateral nucleus of thalamus; 366 mm3/[NN] n.a./[TA98] n.a./ [FMA] n.a.; n.a./[TNA2017] n.a./composed of anteromedial (AM), anterodorsal (AD), and supranucleus lateropolaris (L.po)/ventral anterior (VA); groupe nucléaire antérieur; noyau antérieur du thalamus; nucleus lateralis.

Three (sub)nuclei form the anteromedial nucleus, the anteromedial dorsal which is prominent in the third ventricle (it was named the nucleus anteroprincipalis), the anteromedial ventral posed on the hypothalamus, and the anteromedial intermediate laying between the dorsal and the ventral anteromedial nuclei. AMD-nu; anteromedial dorsal nucleus of thalamus; 132 mm3/[NN] anterodorsal nucleus of the thalamus/[TA98] nucleus anterodorsalis; A14.1.08.604/[FMA] anterodorsal nucleus; 62141/[TNA2017] nucleus anterodorsalis/nucleus anteroprincipalis (A.pr) or anteroventralis (AV); groupe nucléaire antérieur; noyau antérieur du thalamus; nucleus medialis thalami; nucleus anteroventralis (AV); nucleus anteroprincipalis thalami. AMI-nu; anteromedial intermediate nucleus of thalamus; 14 mm3/[NN] anteromedial nucleus of the thalamus/[TA98] nucleus anteromedialis; A14.1.08.605/[FMA] anteromedial nucleus; 62142/[TNA2017] nucleus anteromedialis/anteromedial nucleus (of thalamus); groupe nucléaire antérieur; noyau antérieur du thalamus; nucleus anteroventralis; nucleus anteromedialis thalami. AMV-nu; anteromedial ventral nucleus of thalamus; 29 mm3/[NN] n.a./ [TA98] n.a./[FMA] n.a./[TNA2017] n.a./nucleus fasciculosus (Fa); medioventral partially; groupe nucléaire antérieur; noyau antérieur du thalamus; nucleus medialis; nucleus fasciculosus thalami.

The superior group is formed by two dense nuclei, the dorsomedial and the dorsolateral. The latter is large and extends from the anterior pole to the posterior pole, surmounting the lateral group. DL-nu; dorsolateral nucleus of thalamus; 532 mm3/[NN] lateral dorsal nucleus/[TA98] nucleus dorsalis lateralis; A14.1.08.608/[FMA] lateral dorsal nucleus; 62176/[TNA2017] nucleus dorsalis lateralis/nucleus dorso-oralis, intermedii, possibly dorso-caudalis; VA partially, ventral-lateral posterior (VLp) partially, possibly lateral posterior; noyau latéral postérieur; nucleus lateralis. DM-nu (thalamus); dorsomedial nucleus of thalamus; 56 mm3/[NN] medial dorsal nucleus/[TA98] nucleus mediodorsalis; A14.1.08.622/[FMA] medial dorsal nucleus; 62156/[TNA2017] nucleus mediodorsalis/nucleus dorsal superficialis; noyau latéral dorsal ± antérieur; nucleus antero-dorsalis.

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The lateral group is composed of the intermediolateral nucleus and the well-known ventrolateral nuclei. IL-nu; intermediate lateral nucleus of thalamus; 316 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./[TNA2017] n.a./zentrolateralis (Z); VLa partially, VLp, VPLa partially; n.a.; nucleus lateralis.

The ventrolateral nuclei extends from anterior to posterior as follows: the ventrooral (rostral or anterior position) anterior, medial and posterior nuclei; the ventral intermediate nucleus (VI; intermediate position); the ventrocaudal lateral and medial nuclei (posterior position). The ventrocaudal medial nucleus has a crescent aspect, identified by pioneering works [noyau semi-lunaire de Flechsig; arcuate; cupuliform], and is dense. The VI (Vim) is sparse and thin. The VI is referred to as belonging to the ventrocaudal nuclei and crossed by nerve fibers of the medial lemniscus8,9, or a separate nucleus placed between the oral and caudal nuclei38. The inferior region of VI is penetrated by the prelemniscal radiations33, which correspond to the region of the H and the posterior part of H1, fields of Forel16, or the radiations de la calotte5 or the tegmental radiations4 [radiatio tegmentalis] (see subthalamic tegmental field), where the tractus rubro-thalamicus6,9 [fibres éfferentes de l’olive supérieure2] passes in the extension of the brachium conjunctivum4 (see subthalamus). VOA-nu; ventrooral anterior nucleus of thalamus; 55 mm3/[NN] ventral anterolateral nucleus of the thalamus/[TA98] n.a.; n.a./[FMA] n.a.; n.a./ [TNA2017] n.a./noyau ventral latéral; nucleus ventralis. VOM-nu; ventrooral mediodorsal nucleus of thalamus; 62 mm3/[NN] ventral anterolateral nucleus of the thalamus/[TA98] n.a.; n.a./[FMA] n.a.; n.a./ [TNA2017] n.a./noyau ventral latéral; nucleus ventralis. VOP-nu; ventrooral posterior nucleus of thalamus; 54 mm3/[NN] ventral anterolateral nucleus of the thalamus/[TA98] n.a.; n.a./[FMA] n.a.; n.a./ [TNA2017] n.a./noyau ventral latéral; nucleus ventralis. VI-nu; ventrointermediate nucleus of thalamus; 134 mm3/[NN] ventral intermediate nucleus/[TA98] nucleus ventralis intermedius; A14.1.08.655/[FMA] n.a.; 62205/[TNA2017] n.a./nucleus ventrointermedius (Vim); VLp (ventral part); noyau ventral intermédiare (anterior part of the ventral posterior); nucleus ventralis. VCL-nu; ventrocaudal lateral nucleus of thalamus; 251 mm3/[NN] ventral posterolateral nucleus/[TA98] nucleus ventralis posterolateralis; A14.1.08.641/ [FMA] n.a.; 84350/[TNA2017] nucleus ventralis posterolateralis/ventral posterior lateral or posterolateral nucleus (VPL); ventral posterior medial (VPM), VPLp partially; noyau ventral postérieur latéral; nucleus ventralis postero-lateralis. VCM-nu; ventrocaudal medial nucleus of thalamus; 92 mm3/[NN] ventral posteromedial nucleus/[TA98] nucleus ventralis posteromedialis; A14.1.08.642/ [FMA] n.a.; 62202/[TNA2017] nucleus ventralis posteromedialis/ventral posterior median nucleus (VPM); crescent; basal ventral medial, submedius; VPM, VPL partially; noyau ventral postérieur médian; noyau semi-lunaire de Flechsig; corpus cupuliforme; nucleus ventralis postero-medialis or arcuatus thalami.

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The laminar group is sparse, crossed by numerous nerve fibers, hence the name lamina. The central, intermediate part is enlarged and contains the centromedian-parafascicular complex. The centromedian nucleus, identified since Luys [centre médian]39, is subdivided into two regions, the magnocellular, the biggest, superolateral, and the parvocellular, the smaller, inferomedial. The parvocellular is bordered medially by the parafascicular nucleus, with both coating the inferolateral part of the median nucleus. The anterior part corresponds to the laminar oral nucleus, notably composed of the central lateral and central nuclei. The posterior part corresponds to the laminar caudal nucleus. CMm-nu; centromedian-magno nucleus; 18 mm3/[NN] centromedian nucleus/[TA98] nucleus centromedianus; A14.1.08.618/[FMA] centromedian nucleus; 62165/[TNA2017] nucleus centromedianus/centromedian nucleus, pars magnocellular (anterior) (LaCM, Mg); centre médian de Luys; noyau central, médian, du thalamus; centri median. CMp-nu; centromedian-parvo nucleus; 139 mm3/[NN] centromedian nucleus/[TA98] nucleus centromedianus; A14.1.08.618/[FMA] centromedian nucleus; 62165/[TNA2017] nucleus centromedianus/centromedian nucleus, pars parvocellular (posterior) (LaCM, pv); centre médian de Luys; noyau central, médian, du thalamus; centri mediani. PF-nu; parafascicular nucleus; 28 mm3/[NN] parafascicular nucleus [TA98] nucleus parafascicularis; A14.1.08.620/[FMA] parafascicular nucleus; 62166/ [TNA2017] nucleus parafascicularis/nucleus parafascicularis; noyau parafasciculaire du thalamus; centri mediani. LAO-nu; laminar oral nucleus of intralaminar thalamus; 122 mm3/[NN] intralaminar nuclear group/[TA98] nuclei intralaminares thalami; A14.1.08.616/ [FMA] intralaminar nuclear group of thalamus; 62022/[TNA2017] nuclei intralaminares anteriores/dorsomedial (central lateral, CL, nucleus; cucularis nucleus partially) and ventromedial (central medial, CeM; commissuralis partially); noyau central médial du thalamus & noyau central latéral du thalamus; nuclei of the lamina medullaris medialis. LAC-nu; laminar caudal nucleus of intralaminar thalamus; 54 mm3/[NN] intralaminar nuclear group/[TA98] nuclei intralaminares thalami; A14.1.08.615/ [FMA] intralaminar nuclear group of thalamus; 62021/[TNA2017] nuclei intralaminares posteriores/posterior (CL); limitans (Li); paraventricular (PV); noyaux intralaminiares; noyaux de la lame/strie médullaire interne; nuclei of the Lamina medullaris medialis.

The inferior region of the thalamus is based on the subthalamus, where the subthalamic tegmental field develops (see subthalamus). Two big fascicles penetrate the inferior region, the mammillothalamic fascicle anteriorly, and the medial lemniscus posteriorly . The mammillothalamic fascicle penetrates the anterior pole. The medial lemniscus (see subthalamus) penetrates the thalamus, rear and medial to the ventrocaudal nuclei, and, deeper seated (superior); it continues laterally to the centromedian nucleus. MT-fa; mammillothalamic fascicle; 70 mm3/[NN] mammillothalamic tract/ [TA98] fasciculus mammillothalamicus; A14.1.08.671/[FMA] mammillothalamic tract; 83849/[TNA2017] fasciculus mammillothalamicus/fascicle of Vicq d'Azyr;

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bundle of Vicq d'Azyr; mammillothalamic tract of the hypothalamus; faisceau mamillo-thalamique; faisceau de Vicq d'Azyr; faisceau thalamo-mamillaire; fasciculus mammillo-thalamicus, thalamo-mammillaris; fasciculus of Vicq d'Azyr.

The anterior thalamic radiation, superior, and the inferior thalamic peduncle [radiation] run along the roof and at the anteroinferior pole of thalamus, respectively. A-TH-rad; anterior thalamic radiation; 63 mm3/[NN] anterior thalamic radiation(s)/[TA98] radiatio anterior thalami; A14.1.08.666/[FMA] anterior radiation of thalamus; 76976/[TNA2017] radiatio anterior thalami; thalamo-frontal fibers/rostral peduncle of thalamus; contingent antérieur des radiations thalamiques; stratum zonale; pédoncule antérieur de la couche optique; pedunculus rostralis, anterior, thalami; radiatio thalamo-frontalis. I-TH-ped; inferior thalamic peduncle; 18 mm3/[NN] inferior thalamic peduncle/[TA98] radiatio inferior thalami; A14.1.08.668/[FMA] inferior radiation of thalamus; 76980/[TNA2017] radiatio inferior thalami/ventral thalamic peduncle, stalk/forms the ansa peduncularis combined with the ansa lenticulris; pédoncule thalamique inférieur (part of the ansa peduncularis); pédoncule inféro-interne du thalamus; pédoncule inférieur du thalamus; pedunculus ventralis or inferior or medialis or infero-internus thalami; radiatio thalamo-strialis.

The lateral surface of the thalamus is a two-layer superficial lateral thalamus [reticular nucleus], which other name, Arnold’s net, which recovers the external fibers cross. The medio-inferior surface of thalamus medial nucleus.

coat, the superficial layer or is multiperforated, hence its [lateral] lamina where nerves is coated by the superficial

SFL; superficial lateral nucleus of thalamus; 455 mm3/[NN] reticular nucleus of the thalamus/[TA98] nucleus reticularis thalami; A14.1.08.638/[FMA] n.a.; 62026/[TNA2017] n.a./reticular nucleus of thalamus (of Arnold); reticular nuclear group; zone grillagée d'Arnold & noyau réticulaire du thalamus; nucleus reticularis. SFM; superficial medial nucleus of thalamus; 213 mm3/[NN] reuniens nucleus/[TA98] nucleus reuniens; A14.1.08.632/[FMA] n.a.; 62153/[TNA2017] nuclei periventriculares/midline and massa intermedia/that contains the nucleus endymalis or reuniens or medioventral, and parataenialis, paraventricularis, commissuralis rhomboidalis nuclei/midline nuclear complex of thalamus, or medial or subependymal or para-ependymal thalamus; groupe de la ligne médianne; nucleus mediani thalami. E-Lam-TH; external lamina of thalamus; 292 mm3/[NN] external medullary lamina/[TA98] lamina medullaris lateralis; A14.1.08.660/[FMA] n.a.; n.a./ [TNA2017] lamina medullaris lateralis/external (lateral) lamina of thalamus; lame/strie médullaire externe du thalamus.

The epithalamus is placed posteriorly and medially. The stria medullaris (of thalamus) lines the superior medial border of the median nucleus, bent at the anterior extremity toward the hypothalamus and at the posterior extremity toward the habenula. The habenula is located above the superficial medial thalamus.

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HAB; habenula; 39 mm3/[NN] habenula/[TA98] habenula; A14.1.08.003/[FMA] habenula; 62032/[TNA2017] habenula/habenula (habenular nuclei); habenula; ganglion de l'habenula; nucleus habenularis; ganglion habenulare. STR-med; stria medullaris of thalamus; 41 mm3/[NN] stria medullaris/[TA98] stria medullaris thalami; A14.1.08.106/[FMA] n.a.; 62080/[TNA2017] stria medullaris prethalami/stria medullaris thalami; strie médullaire; taenia thalami; stria habenularis; habenae; stria pinealis; taenia habenulae, thalami.

The prethalamic reticularoid zone is described with the parathalamic, telencephalic, structures of the deep brain. PTH-ret-z; prethalamic reticularoid zone; 38 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./n.a.; n.a.

Plate Thalamus 1 – Lateral view of the thalamus, successive layers from lateral to medial (first series).

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Plate Thalamus 2 – Lateral view of the thalamus, successive layers from lateral to medial (last series); medial view of the thalamus (bottom right).

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Plate Thalamus 3 – Inferior view of the thalamus (top left) and the subthalamic structures that plug in (top right, overview; bottom left, anterior and posterior fascicles; bottom right, subthalamic tegmental field).

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Plate Thalamus 4 – Anterior view of the thalamus, successive layers from posterior to anterior (first series).

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Plate Thalamus 5 – Anterior view of the thalamus, successive layers from posterior to anterior (last series).

Plate Thalamus 6 – Posterior (left) and superior (right) views of the thalamus.

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The Subthalamus or Prethalamus The subthalamus or prethalamus belongs both to the diencephalon and the mesencephalon, and more specifically for the latter to the tegmentum. The tectum and the pineal gland were added. Hence, it is composed of the ventral tegmental area, the substantia nigra, the subthalamic nucleus, the red nucleus, the zona incerta, the nuclei of the reticular formation, the periaqueductal gray matter, fascicles and the white matter subthalamic tegmental field, the posterior commissure, the colliculi and the pineal gland.

The subthalamus forms the arch of the mesencephalo-diencephalic junction. The tectum and the pineal gland were added to simplify the regional MRI mapping. The emblematic structure of the subthalamus is the substantia nigra, which binds the tegmentum ventrally and some consider it is part of the latter18. Its medial border corresponds to the interpeduncular fossa where the oculomotor nerve emerges at the very posterior part. The substantia nigra is crossed by the sagittal pedunculopontin fibrae of the fasciculus obliquus. SN; substantia nigra; 455 mm3/[NN] nucleus substantia nigra/[TA98] substantia nigra; A14.1.06.111/[FMA] n.a.; 67947/[TNA2017] substantia nigra/SN; subtance noire; locus niger; locus or nucleus niger; nucleus pigmentosus subthalamo-peduncularis; substance of Von Soemmering. OM-n; oculomotor nerve [III]; 88 mm3/[NN] oculomotor nerve/[TA98] nervus oculomotorius [III]; A14.2.01.007/[FMA] n.a./[TNA2017] n.a./common oculomotor nerve; nerf moteur oculaire (commun); nervus oculomotorius communis; third cerebral(cranial) nerve. PED-P-fi; pedunculopontin fibrae; 8 mm3/[NN] fasciculus obliquus crucis cerebri/[TA98] n.a./[FMA] n.a./[TNA2017] n.a./part of the fascicle circumligatus; faisceau en écharpe de Féré; fascicle circumligatus; obliquus cruris or crus cerebri.

The red nucleus [n. ruber, n. ruber tegmenti; of Stilling; of Burdach] is placed in the core of the tegmentum. It was also named l’olive supérieure (superior olivary nucleus) by analogy with the other nucleus with a rounded shape and located in the lower brainstem, the inferior olivary nucleus2. The red nucleus is crossed by many white matter fibers, which explains its unusual aspect, at least for a nucleus, i.e., a low signal on T1-weighted MRI, making it easily identifiable in the tegmentum. The retroflexed fascicle leaves a sharp notch at the medial surface of the red nucleus. RN; red nucleus; 242 mm3/[NN] red nucleus (and its capsule)/[TA98] nucleus ruber (magnocellularis, parvocellularis, posteromedialis); A14.1.06.323/[FMA] red nucleus; 62407/[TNA2017] nucleus ruber/noyau rouge; nucleus ruber tegmenti; nucleus rotondus subthalamo-peduncularis. RN-cd; red nucleus, caudal part; 168 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./ [TNA2017] n.a./noyau rouge; pars caudalis. RN-cr; red nucleus, rostral part; 74 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./ [TNA2017] n.a./noyau rouge; pars rostralis.

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RET-fa; retroflexed fascicle; 39 mm3/[NN] fasciculus retroflexus of the interbrain (diencephalon)/[TA98] tractus habenulointerpeduncularis; A14.1.08. 502/[FMA] habenulo-interpeduncular tract; 72400/[TNA2017] tractus habenulointer-peduncularis; bundle of Meynert/habenulointerpeduncular tract; fasciculus, fascicle of Meynert; faisceau rétroflexe (rétrofléchi, rétroflexus) de fasciculus habenuloMeynert; faisceau habénulo-pédonculaire; interpeduncularis; tractus retroflexus; tractus tegmentalis nuclei habenulae.

The subthalamic nucleus, historically named substance grise or bandelette, accessoire, de l’olive supérieure (accessory gray matter of the superior oliva)39, is a flat tilted ovoid nucleus; its superior face turns medially and slightly anteriorly. The lenticular fascicle runs above the subthalamic nucleus. ST-nu; subthalamic nucleus; 143 mm3/[NN] subthalamic nucleus (and its capsule); subthalamic reticular nucleus/[TA98] nucleus subthalamicus; A14.1.08.702/[FMA] n.a.; 62035/[TNA2017] nucleus subthalamicus/body of Luys; corpus Luysi; STN; corps de Luys; noyau sous-thalamique; corpus subthalamicum; body of Forel; nucleus hypothalamicus. LEN-fa; lenticular fascicle; 20 mm3/[NN] Forel’s field H2; area subthlamica tegmentalis, pars ventrolateralis; dorsal division of ansa lenticularis/[TA98] fasciculus lenticularis and nucleus campi ventralis [H2]; A14.1.08.664; A14.1.09.521; A14.1.08.706/[FMA] lenticular fasciculus of telencephalon and nucleus of ventral field of subthalamus; 61976; 77527/[TNA2017] fasciculus lenticularis/lenticular fasciculus; Forel H2 field; H2; area tegmentalis H2; pallido-thalamic fascicle; H2 field of Forel; dorsal division of ansa lenticularis; ventral field; faisceau lenticulaire; champ H2 de Forel; faisceau H2 du champ de Forel; faisceau lenticulaire de Forel; faisceau inférieur des faisceaux de Forel; area subthlamica tegmentalis, pars ventralis, pars ventrolateralis; fasciculus lenticularis hyopthalami; fasciculus pedunculi.

The subthalamic nucleus is surrounded and penetrated by numerous fibers of fascicles, such as the ansa lenticularis, the subthalamic radiations connecting the cortex, and the commissural fibers of the supramammillary commissure5,6. The zona incerta is placed against the thalamus and seems to extend downward to the inferior border of the superficial lateral thalamus, closing the tegmentum with the substantia nigra laterally. It extends from the hypothalamus to the peri peduncular nucleus. Anteriorly, it demarcates the thalamic fascicle and overlooks the lenticular fascicle and, by extension, the subthalamic nucleus. ZI; zona incerta; 165 mm3/[NN] zona incerta/[TA98] n.a.; A14.1.08.707/[FMA] n.a.; 62038/[TNA2017] zona incerta/zona incerta de Forel; nucleus area tegmenti, campi of Forel, infrasensibilis, of Cajal, of zona incerta. TH-fa; thalamic fascicle; 59 mm3/[NN] Forel’s field H1; area subthlamica tegmentalis; pars dorsomedialis; part of ansa lenticulmaris/[TA98] fasciculus thalamicus and nucleus campi dorsalis [H1]; A14.1.08.679; A14.1.08.705/[FMA] n.a.; 62065; 77526/[TNA2017] fasciculus thalamicus/thalamic fasciculus; Forel H1 field; H1; area tegmentalis H1; H1 field of Forel; dorsal field; faisceau thalamique; champ H1 de Forel; faisceau H2 du champs de Forel; faisceau

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supérieur des faisecaux de Forel; area subthlamica tegmentalis dorsalis, pars dorsomedialis; fasciculus thalamicus hypothalami.

The subthalamic tegmental field is the grouping of the tegmental fields of Forel (area tegmentalis, field H; H1; H2) and the area tegmentalis subthalamica (area prerubralis, nucleus reticularis hypothalami, nucleus reticularis subthalami) which includes the nuclei campi of Forel. It can be subdivided into six zones: the anterior zone, the central zone of tegmentum, the dorsal zone, Forel’s H field, the lateral zone and the medial zone. AZ-STF; anterior zone of the subthalamic tegmental field; 50 mm3/[NN] n.a./ [TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] n.a./anteromedial to the H field; n.a.; n.a. CZ-teg; central zone of tegmentum; 54 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./ventral to the H field; it contains the fasciculus (bundle) Q of Sano; n.a.; n.a. DZ-STF; dorsal zone of the subthalamic tegmental field; 16 mm3/[NN] n.a./ [TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./dorsal to the H field; n.a.; n.a. F-H-F; Forel H field; 23 mm3/[NN] Forel’s field H/[TA98] field h and nucleus campi medialis [H]; A14.1.08.704/[FMA] nucleus of field h; 62037/[TNA2017] campi medialis/containing the prelemniscal radiations; medial field; champs H, prérubrique; radiations de la calotte; area tegmentalis subthlamica; prerubral field; H; medial field; area tegmentalis H. LZ-STF; lateral zone of the subthalamic tegmental field; 40 mm3/[NN] n.a./ [TA98] n.a./[FMA] n.a./[TNA2017] n.a./lateral to the H field; n.a.; n.a. MZ-STF; medial zone of the subthalamic tegmental field; 37 mm3/[NN] n.a./ [TA98] n.a./[FMA] n.a./[TNA2017] n.a./medial to the H field; n.a.; n.a.

The Q fascicle40 crosses the central zone of the tegmentum. Q-fa; fascicle Q; 3 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./[TNA2017] n.a./fascicle Q of Sano; fasciculus Q (Sano); fibrae mediales sustantiae nigrae.

The medial region of the tegmentum is limited, posteriorly by the interpeduncular paranigrae nuclei at the bottom of the interpeduncular fossa against the substantia nigra, and anteriorly by the ventral tegmental area placed against the hypothalamus and the interbrain central gray. IPN-NI; interpeduncular nucleus & paranigral nucleus; 36 mm3/[NN] interpeduncular nucleus & paranigral nucleus/[TA98] nucleus interpeduncularis; nucleus paranigralis; A14.1.06.313; A14.1.06.333/[FMA] interpeduncular nucleus; paranigral nucleus; 72439; 77497/[TNA2017] nucleus interpeduncularis; nucleus paranigralis/noyau interpédonculaire & noyau paranigrique; ganglion interpédonculaire; nucleus (corpus, ganglion) intercruralis or interpeduncularis; possibly nucleus medialis tegmento-peduncularis or tegmenti, and area reticulata substantiae nigrae.

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VTA; region of the ventral tegmental area; 35 mm3/[NN] ventral tegmental area; field H2/[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] n.a./ventral tegmental area (VTA) of Tsai/may include the ento(do)peduncular nucleus/nucleus of ansa lenticularis and the H2 field; area hypothalamica dorsalis (nuclei dorsomedialis, endopeduncularis, ansae lenticularis); aire ventrale de la calotte; aire de Tsai (noyau ventral de la calotte) (±noyau interpédonculaire & endopedunculaire); ventral tegmental area; dorsal hypothalamic region or area; area densa.

The posterior commissure and the pineal gland are close to the posterior region of the 3rd ventricle and overlay the tectum composed of the superior and inferior colliculi and the related superior and inferior brachium. PC; posterior commissure; 19 mm3/[NN] posterior commissure/[TA98] commissura posterior; A14.1.08.416/[FMA] posterior commissure; 62072/[TNA2017] commissura posterior/PC; commissure blanche postérieure (CP); commissura posterior or caudalis or dorsalis. P-g; pineal gland (of epithalamus); 220 mm3/[NN] pineal gland/[TA98] glandula pinealis; A11.2.00.001/[FMA] pineal body; 62033/[TNA2017] glandula pinealis/corpus pineale; epiphysis; nervus pinealis; organe (ou glande) pinéal(e); épihyse; conarium. S-COLL; superior colliculus; 223 mm3/[NN] superior colliculus/[TA98] colliculus superior; A14.1.06.015/[FMA] n.a.; 62403/[TNA2017] colliculus superior/anterior colliculus; colliculus, tubercule quadrijumeau, supérieur, antérieur; colliculus superior or caudalis or oralis; corpus quadrigeminium superius or anterius. BR-S-COLL; brachium of superior colliculus; 11 mm3/[NN] brachium of the superior colliculus/[TA98] brachium colliculi superioris; A14.1.06.013/[FMA] brachium of superior colliculus; 72417/[TNA2017] brachium colliculi superioris/visual pathway (lateral geniculate body); bras conjonctival supérieur ou antérieur; brachium (pedunculus) colliculi superioris; rostralis; anterius; superius. I-COLL; inferior colliculus; 94 mm3/[NN] inferior colliculus/[TA98] colliculus inferior; A14.1.06.014/[FMA] inferior. BR-I-COLL; brachium of inferior colliculus; 9 mm3/[NN] brachium of the inferior colliculus/[TA98] brachium colliculi inferioris; A14.1.06.012/[FMA] brachium of inferior colliculus; 71114/[TNA2017] brachium colliculi inferioris/auditory pathway (med-sial geniculate body); bras conjonctival inférieur ou postérieur; brachium (pedunculus) colliculi inferioris; caudalis; posterius; inferius.

The trochlear nerve emerges below the inferior colliculus. TR-n; trochlear nerve [IV]; 14 mm3/[NN] trochlear nerve/[TA98] nervus trochlearis [IV]; A14.2.01.011/[FMA] n.a.; n.a./[TNA2017] n.a./pathetic nerve; nerf pathétique ou trochléaire; nervus trochlearis; fourth cerebral(cranial) nerve.

The periaqueductal gray substance is located immediately under the tectum (ventrally), in continuity downwards and medially with the interbrain central gray.

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PAG; periaqueductal gray substance; 411 mm3/[NN] periaqueductal gray/ [TA98] substantia grisea centralis; A14.1.06.321/[FMA] central gray substance; 83134/[TNA2017] substantia grisea centralis/central grey substance of midbrain; subtance grise périaqueducale (& périventriculaire); substantia centralis grisea; anulus aquaeductus; stratum griseum centrale, mesencephali. IC-gray; interbrain central gray; 165 mm3/[NN] central gray/[TA98] n.a./ [FMA] n.a./[TNA2017] n.a./central gray; substance grise sous-ependymaire; substantia grisea centralis.

The peri peduncular nucleus lies at the lateral surface of the mesencephalon at the boundary between the tegmentum and the cerebral peduncle (pes pedunculi). PER-PED-nu; peripeduncular nucleus; 87 mm3/[NN] peripeduncular nucleus/ [TA98] nucleus peduncularis; A14.1.05.207/[FMA] peduncular nucleus of pons; 77123/[TNA2017] nucleus peripedoncularis/peduncular nucleus; noyau péri-pédonculaire; nucleus peripeduncularis dorsalis (nppd); processus lateralis substantiae nigrae.

The deep region of the tegmentum is retrorubral. The three largest structures are the periaqueductal gray, the tegmental pontomesencephalic reticular formation and the brachium conjunctivum. The periaqueductal gray contains the dorsal longitudinal fascicle, which also runs inside the interbrain central gray. DLON-fa; dorsal longitudinal fascicle; 23 mm3/[NN] dorsal longitudinal fasciculus/[TA98] fasciculus longitudinalis posterior (or dorsalis); A14.1.04.114/ [FMA] dorsal longitudinal fasciculus of medulla; 72617/[TNA2017] fasciculus longitudinalis posterior/dorsal or posterior longitudinal fasciculus; dorsal longitudinal fasciculus of Schultze (Schuetz or Schüts); faisceau longitudinal dorsal; faisceau de Schütz, Schüts; fasciculus longitudinalis periependymalis or periacquaeductalis; tegmentalis dosrsalis; tractus bulbo-thalamicus; periventricular fibre system.

The medial longitudinal fascicle is placed ventrally to the periaqueductal gray. MLON-fa; medial longitudinal fascicle; 30 mm3/[NN] medial longitudinal fasciculus/[TA98] fasciculus longitudinalis medialis; A14.1.04.113/[FMA] medial longitudinal fasciculus of medulla; 72618/[TNA2017] fasciculus longitudinalis medialis/medial longitudinal fasciculus; bandelette longitudinale postérieure; faisceau longitudinal postérieur; tractus longitudinalis medialis; fasciculus commissurae posterioris; fasciculus longitudinalis dorsalis or posterioris.

The tegmental pontomesencephalic reticular formation is placed anteriorly and laterally to the periaqueductal gray substance. TEG-PM-ret-for; tegmental pontomesencephalic reticular formation; 388 mm3/[NN] formatio reticularis/[TA98] formatio reticularis; A14.1.00.021/

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[FMA] n.a.; 77719/[TNA2017] formatio reticularis/tegmental reticular formation of the pons, midbrain and ventral thalamus; formation (substance) réticulaire (réticulée) ponto-mésencéphalique; substance réticulée de la calotte; formatio, substantia, reticularis.

The inferior and anterior (ventral) part of the tegmental pontomesencephalic reticular formation contains the pedunculopontine [tegmental] nucleus with the U area. PED-P-nu; pedunculopontine nucleus; 67 mm3/[NN] pedunculopontine nucleus/[TA98] nucleus tegmentalis pedunculopontinus; A14.1.06.336/[FMA] pedunculopontine tegmental nucleus; 72429/[TNA2017] nucleus tegmentalis pedunculopontinus/pedunculopontine tegmental nucleus. aU; area U; 12 mm3/[NN] n.a./[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] n. a./ventrolateral and inferior region of the tegmental pontomesencephalic reticular formation; and more specifically of the pedunculopontine nucleus; n.a.; U-Field (Riley, Ziehen).

The brachium conjunctivum [superior cerebellar peduncle], also named historically noyau blanc de Stilling5, has its commissure in the tegmentum, the horseshoe commissure of Wernekink. It runs from lateral to medial, and from inferior to superior, in the tegmentum, and terminates at the inferior and posterior region of the red nucleus. BR-CONJ; brachium conjunctivum; 377 mm3/[NN] superior cerebellar peduncle/[TA98] pedunculus cerebellaris superior; A14.1.05.006/[FMA] superior cerebellar peduncle; 72495/[TNA2017] brachium conjunctivum/superior cerebellar peduncle (& commissure of Wernekink, horshoe commissure); pédoncule cérébelleux supérieur; brachium conjunctivum (& commissure de Wernekink, entrecroisement du pédoncule cérébelleux supérieur); tractus cerebello-rubralis; tractus cerebello-tegmentalis cerebralis.

The superior and inferior parabigeminal areas are placed between the colliculi dorsally and the tegmental pontomesencephalic reticular formation ventrally, and represent the cuneiform area. INF-PBG-a; inferior parabigeminal area; 15 mm3/[NN] parabigeminal area; cuneiform nucleus/[TA98] nucleus parabigeminalis; A14.1.06.320/[FMA] parabigeminal nucleus; 72415/[TNA2017] nucleus parabigeminalis/the parabigeminal area (Riley) is contained within the nucleus cuneiformis (Olszewski & Baxter); aire parabigéminale; area parabigemina posterior; area bigemina; area cuneiformis; nuclei cuneiformis and subcuneiformis. SUP-PBG-a; superior parabigeminal area; 12 mm3/[NN] parabigeminal area; cuneiform nucleus/[TA98] nucleus parabigeminalis; A14.1.06.320/[FMA] n. a.; 72415/[TNA2017] nucleus parabigeminalis/the parabigeminal area (Riley) is contained within the nucleus cuneiformis (Olszewski & Baxter); aire parabigéminale; area parabigemina anterior; area bigemina; area cuneiformis; nuclei cuneiformis and subcuneiformis.

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The lateral lemniscus and the medial lemniscus run postero-laterally and ventrally to the tegmental pontomesencephalic reticular formation, respectively. L-LEM; lateral lemniscus; 27 mm3/[NN] lateral lemniscus/[TA98] lemniscus lateralis; A14.1.05.317/[FMA] lateral lemniscus; 72502/[TNA2017] lemniscus lateralis/ruban de Reil latéral, lemniscus latéral; ruban de Reil, portion postérieure; ruban de Reil inférieur; lemniscus acusticus, lateralis. M-LEM; medial lemniscus; 155 mm3/[NN] medial lemniscus/[TA98] lemniscus medialis; A14.1.04.111/[FMA] medial lemniscus; 83675/[TNA2017] lemniscus medialis/ruban de Reil médian; lemniscus médian; ruban de Reil, portion antérieure); lemniscus; lemniscus sensibilis, medialis.

The central tegmental tract runs along the medial border of the tegmental pontomesencephalic reticular formation. The spinothalamic fascicle runs along the lateral border of the medial lemniscus. C-TEG-tr; central tegmental tract; 45 mm3/[NN] central tegmental tract of the midbrain, pons/[TA98] tractus tegmentalis centralis; A14.1.05.325/[FMA] central tegmental tract; 83850/[TNA2017] tractus tegmentalis centralis/ faisceau central de la calotte (thalamo-olivaire); tractus tegmentalis centralis. SPI-TH-fa; spinothalamic fascicle; 44 mm3/[NN] spinothalamic tract/[TA98] spinothalamic tract; n.a./[FMA] n.a.; n.a./[TNA2017] tractus spinothalamicus/composed of the anterior and lateral spinothalamic fibers of the medulla; faisceau spino-thalamique; lemniscus spinalis; tractus spino-thalamicus; tractus spino-reticulo-thalamicus.

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Plate Subthalamus 1A – Coronal sections going through the red nucleus, from top left to bottom left, from Luys, Forel, Dejerine, Metler and the MDBA (CR8).

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Plate Subthalamus 1B – Coronal sections going through the thalamic fascicle, from Forel (top) and the MDBA (CR4, bottom).

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Plate Subthalamus 1C – Sagittal sections going to the ventrocaudal medial nucleus of the thalamus, according to (from top left, clock-wise), the MDBA, Riley, Talairach et al., and Schaltenbrand and Bailey.

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Plate Subthalamus 2 – Lateral view of the subthalamus, successive layers (first series).

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Plate Subthalamus 3 – Lateral (top and intermediate rows; successive layers, last series) and medial (bottom row) views of the subthalamus.

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Plate Subthlamus 4 – Lateral (top and intermediate rows), superior (bottom row, left) and anterior (bottom row, right) views of the subthalamic tegmental fields.

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The Telencephalic Structures of the Deep Brain The telencephalic structures of the deep brain are composed of the lenticular nucleus, the sublenticular structures, the claustrum, the amygdalohippocampal complex, the paralenticular and parathalamic regions, and the related white matter structures.

The lenticular nucleus is the biggest telencephalic nucleus composed of the putamen, the lateral subpart, and the pallidum [globus pallidus], the medial subpart. The pallidum itself is composed of the extern-lateral globus pallidus, GPe and the internal-medial globus pallidus, GPi. The GPi, also historically named noyau jaune (of the striatum)2, is subdivided into lateral (GPi-l) and medial (GPi-m) subparts. The lateral medullary lamina covers the pallidum and the medial medullary lamina is placed between the GPe and the GPi. An accessory lamina, the accessory lamina of the internal globus pallidus, partially divides the GPi. PUT; putamen; 2663 mm3/[NN] putamen/[TA98] putamen; A14.1.09.507/ [FMA] putamen; 61834/[TNA2017] putamen/putamen; nucleus lenticularis, pars tertius. GPe; lateral globus pallidus; 769 mm3/[NN] lateral globus pallidus/[TA98] globus pallidus lateralis; A14.1.09.509/[FMA] lateral globus pallidus; 61839/ [TNA2017] globus pallidus lateralis/globus pallidus external; GPe; globus pallidus, pars lateralis; pallidum externe; deuxième portion du pallidum; globus pallidus, crus II, pars lateralis, externa. GPi; medial globus pallidus; 353 mm3/[NN] medial globus pallidus/[TA98] globus pallidus medialis (pars lateralis and medialis); A14.1.09.511/[FMA] medial globus pallidus; 61840/[TNA2017] globus pallidus medialis/globus pallidus internal (inner and outer portions); GPi; globus pallidus, pars medialis; pallidum interne; première portion du pallidum; segments superficiel (latéral) et profond (médial); globus pallidus, crus I, pars mediali, interna. L-m-Lam-LEN; lateral medullary lamina; 150 mm3/[NN] lateral medullary lamina/[TA98] lamina medullaris lateralis; A14.1.09.508/[FMA] lateral medullary lamina of globus pallidus; 62469/[TNA2017] lamina medullaris lateralis/external (outer) medullary lamina/between the putamen and pallidum; lame médullaire externe; lamina medullaris lateralis (externa, limitans); stria medullaris lateralis. M-m-Lam-LEN; medial medullary lamina; 115 mm3/[NN] medial medullary lamina/[TA98] lamina medullaris medialis; A14.1.09.510/[FMA] medial medullary lamina of globus pallidus; 62470/[TNA2017] lamina medullaris medialis/mesial medullary lamina/between GPe and Gpi; lame médullaire interne; lamina medullaris medialis or interna; stria medullaris medialis. A-Lam-GPI; accessory medullary lamina of GPi; 3 mm3/[NN] accessory medullary lamina/[TA98] lamina medullaris accessoria; A14.1.09.513/[FMA] accessory medullary lamina of globus pallidus; 62471/[TNA2017] lamina medullaris accessoria/within Gpi; lame médullaire accessoire; lamina medullaris accessoria (palidi), incompleta.

The anterior commissure passes below the lenticular nucleus, above the innominate substance, and toward the temporal stem laterally.

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AC; anterior commissure; 265 mm3/[NN] anterior commissure/[TA98] commissura anterior; A14.1.08.421/[FMA] anterior hypothalamic commissure; 62053/[TNA2017] commissura anterior/commissure blanche antérieure (CA); commissura anterior or olfactoria or rostralis.

The claustrum divides the thick lamina of white matter between the lenticulo-sublenticular region and the insula in two capsules: the extreme capsule laterally against the insula, and the extern capsule medially against the putamen. The claustrum is subdivided into dorsal (superior) and ventral (inferior) parts. D-CLAU; dorsal claustrum; 338 mm3/[NN] dorsal claustrum/[TA98] claustrum; A14.1.09.421/[FMA] n.a.; n.a./[TNA2017] claustrum dorsale/dorsal part of the claustrum; insular claustrum; avant-mur, claustrum; claustrum; claustrum insulare. V-CLAU; ventral claustrum; 137 mm3/[NN] ventral endopiriform claustrum/ [TA98] claustrum; A14.1.09.421/[FMA] n.a.; n.a./[TNA2017] claustrum ventrale/ventral part of the claustrum; endopiriform; avant-mur, claustrum; claustrum; claustrum temporale, substriatale and prae amygdalae.

The striatum is composed of the putamen, the accumbens nucleus and the caudate. The striatum splits into: the dorsal (superior) striatum with the head of caudate and the dorsal (superior) putamen, roughly above the ACPC plane, the ventral (inferior) striatum for the ventral (inferior) caudate (temporal), and the accumbens nucleus, which is also named fundus striati, i.e., the bottom of the striatum. Close neighboring nuclei are associated with the accumbens nucleus, such as the colliculus nucleus of caudate5, the nucleus accumbens septi, the nucleus parolfactorius lateralis, and the bed of the stria terminalis6,7,33. Islands of striatal cells, isolated from the parent nuclei by white matter fibers of cortico-subcortical connections, are widely distributed between the caudate and the putamen, forming a radiating structure, the caudolenticular gray bridges. The same phenomenon of cell islands is also visible between the pallidum and the substantia nigra, known as the pontes grisei peduncularis, interleaved between the fibers of the stratum intermedium pedunculi. ACC-nu; accumbens nucleus; 113 mm3/[NN] nucleus accumbens/[TA98] nucleus accumbens; A14.1.09.440/[FMA] nucleus accumbens; 61889/ [TNA2017] nucleus accumbens/noyau accumbens; pont de substance grise unissant la partie inférieure des noyaux caudé et lenticulaire; involves the “ colliculus du noyau caudé”; fundus striati; involves the colliculus nucleus caudati; nucleus accumbens septi; nucleus parolfactorius lateralis; bed of the stria terminalis. CAU-nu; caudate nucleus; 344 mm3/[NN] caudate nucleus/[TA98] nucleus caudatus; A14.1.09.502/[FMA] caudate nucleus; 61833/[TNA2017] nucleus caudatus/caudate; noyau caudé; nucleus caudatus. CAULEN-gray-b; caudolenticular gray bridges; 232 mm3/[NN] pontes striatales/[TA98] pontes grisei caudatolenticulares; transcapsular grey bridges; A14.1.09.525/[FMA] set of caudolenticular gray bridges; 77813/[TNA2017]

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pontes grisei caudatolenticulares/gray laminae bridging the caudate and lenticular nuclei; n.a.; pontes striatales; pontes grisei lenticulares. PGP; pontes grisei pedunculares; 53 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./gray laminae between the fibers of the stratum intermedium pedunculi (pedunculus substantiae nigrae; kamm system; système en peigne); bridge substantia nigra and globus pallidus; n.a.; fibers = stratum intermedium de Meynert; couche dorsale du pied du pédoncule.

The emblematic structure of the sublenticular region is known by the somewhat anachronic41 term, innominate substance. INNO-sub; innominate substance; 333 mm3/[NN] basal (magnocellular) nucleus/[TA98] substantia innominata; A14.1.09.426/[FMA] substantia innominata; 61885/[TNA2017] substantia innominata/innominate substance of Reichert; nucleus of Meynert; substance innominée de Reichert; subtantia (regio) innominata (sublenticularis); nucleus planun septale; nucleus basalis of Meynert.

The diagonal band interpenetrates the innominate substance anteriorly, below the anterior commissure, behind the caudate and the olfactory tubercle. DIA-band; diagonal band; 66 mm3/[NN] diagonal band/[TA98] stria diagonalis; A14.1.09.422/[FMA] diagonal band; 61973/[TNA2017] area diagonalis; diagonal band area/the diagonal band of Broca is visible at the surface of the ventral brain (diagonal gyrus), located between the optic tract and the antererior perforated substance (olfactory tubercle); it is also described within the sublenticular region and is associated with cells referered as the nucleus of the diagonal band of Broca (Riley); bandelette diagonale de Broca; fasciculus olfactorius; fasciculus substantiae perforatae anterioris; fasciculus septo-amygdalicus; fasciculus hippocampi. OLF-t; olfactory tubercle; 92 mm3/[NN] olfactory tubercle/[TA98] tuberculum olfactorium; A14.1.09.433/[FMA] anterior perforate substance; tubercle; 61891; 75429/[TNA2017] tuberculum olfactorium/tubercule olfactif; substance perforée antérieure; area olfactoria; tuberculum olfactorium.

The posterior subpallidal area continues the innominate substance above the optic tract and the amygdala posterior extension. The posterior para lenticulo-capsular zone borders the posterior arm of the internal capsule, against the pallidum and above the posterior subpallidal area. The amygdala, covered by the innominate substance, is nested in the anterior extremity of the hippocampal formation. P-SUBP-a; posterior subpallidal area; 57 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./posterior subpallidal area of reticular appearance; n.a.; n.a. AMYG; amygdala; 1194 mm3/[NN] amygdala/[TA98] corpus amygdaloideum; A14.1.09.402/[FMA] amygdala; 61841/[TNA2017] corpus amygdaloideum/amygdaloid body or complex; noyau amygdalien; amygdale

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télencéphalique; complex amygdalien; epistriatum; nucleus amygdaliformis; amygdala; striatum olfactorium; archistriatum; amygdaleum. AMYG-pe; amygdala posterior extension nucleus; 26 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./[TNA2017] n.a./could be the posterior extension of the basal nucleus of amygdala, an/or the amygdalohippocampal area; n.a.; n.a. P-PLC-z; posterior para lenticulocapsular zone; 37 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a.; n.a./[TNA2017] n.a./posterior para lenticulocapsular area of reticular appearance; n.a.; n.a. HIPPO; hippocampal formation; 3400 mm3/[NN] hippocampal formation/ [TA98] hippocampus (part); A14.1.09.321/[FMA] n.a./[TNA2017] (most of) the pars retrocommisuralis hippocampi/the hippocampal formation is composed of the hippocampal complex and the subiculum complex, which represent the inferior segment of the intralimbic gyrus.

The hippocampal complex is composed of (1) four gray matter structures, Ammon’s horn and the dentate gyrus partially rolled up on themselves and the two posterior fasciolar structures, i.e., the fasciolar gyrus and the fasciola cinerea (the fasciolar group, Fa-gp), and (2) two white matter structures, the fimbria and the alveus. The four gray matter structures form the hippocampus proper. Ammon’s horn is the biggest part of the intralimbic gyrus. The indusium griseum (with the two longitudinal striae) prolongs Ammon’s horn along the superior side of the corpus callosum; the (possible) anterior rudiment terminates this gyrus anteriorly23,42. The fimbria prolongs the fornix (it is also called the flattened part of the fornix4) covering the hippocampus, then spreads distally (Latin root34, fringe) in the uncus forming a large medial white matter field. The alveus (Latin root34, riverbed, and alveolus notably of a hive) rolls itself up laterally, covering, the surface of Ammon’s horn (Latin root34, ammonite with its remarkable shell looking like the horn of a ram). The distal hippocampus proper, anterior, is recurved forming the posterior part of the uncus; its superior surface is digitate (the hippocampal digitations). The distal part of the dentate gyrus runs at the medial surface of the uncus, forming the band of Giacomini. The Latin root34 of dentate means tooth, but, the dentate was also named circonvolution godronné5 (FR), meaning molded or a pleated braid. AMM; Ammon’s horn; 1435 mm3/[NN] CA (cornu ammonis) fields/[TA98] hippocampus proprius; A14.1.09.327/[FMA] hippocampus proprius; 62493/ [TNA2017] cornu ammonis/corne d'ammon; cornu ammoni. DEN-g; dentate gyrus; 387 mm3/[NN] dentate gyrus/[TA98] gyrus dentatus; A14.1.09.237/[FMA] gyrus dentatus; 61922/[TNA2017] gyrus dentatus/corps, circonvolution, godronné(e); gyrus dentatus; gyrus dentatum; dentate fascia. FA-g; fasciolar gyrus; 58 mm3/[NN] fasciola cinerea/[TA98] gyrus fasciolaris; A14.1.09.233/[FMA] gyrus fasciolaris; 61921/[TNA2017] gyrus fasciolaris/prolonges the Ammon’s horn. FA-c; fasciola cinerea; 22 mm3/[NN] fasciola cinerea/[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] fasciola cinerea/prolonges the dentate gyrus; fasciola cinereum. FIM; fimbria; 307 mm3/[NN] fimbria/[TA98] fimbria hippocampi; A14.1.09.332; A14.1.09.239/[FMA] fimbria hippocampi; 83866/[TNA2017]

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fimbria hippocampi/the flattened part of the fornix (above the body of the hippocampus proper); fimbria of the fornix; fimbria Ammonis. ALV; alveus; 220 mm3/[NN] alveus/[TA98] alveus hippocampi; A14.1.09.333/ [FMA] alveus hippocampi; 83867/[TNA2017] alveus hippocampi. HIP-P; hippocampus proper; n.a. mm3/[NN] hippocampus/[TA98] n.a.; n.a./ [FMA] n.a.; n.a./[TNA2017] pars retrocommissuralis hippocampi/composed of the gyrus dentatus, the Hammon’s horn and the two proximal (posterior) fasciolar. GIA-band; band of Giacomini; n.a. mm3/[NN] tail of the dentate gyrus/[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] limbus fasciae dentatae/the apex portion of the gyrus dentatus; bandelette de Giacomini; band of dentate gyrus. SUBI; subiculum complex; 694 mm3/[NN] subiculum/[TA98] subiculum; A14.1.09.326/[FMA] subiculum; 74414/[TNA2017] subiculum/composed of the different subparts of the subiculum (subiculum, presubiculum, parasubiculum).

The name hippocampus [Latin root34: campe, chenille, caterpillar; hippocampe, cheval marin, sea horse or little sea fish] could take its name from a seahorse look even if this analogy and its history is debatable42–45, and the hippocampus proper, in 3D also looks like a chrysalis (figure 2.1). The hippocampus can be subdivided into three segments18,42: the posterior segment (“tail of the hippocampus”); the middle segment or “body of the hippocampus”; the anterior segment (“head of the hippocampus”). The subiculum complex (subiculum; Latin root34: subicio or subjicio, underneath, subordinated), continues medially the hippocampus proper, toward the cortex of the parahippocampal gyrus, and rolls up distally (anteriorly) within the uncus. The complex 3D volumetric organization of the hippocampus hinders the identification of its substructures on MRI slices. Sections were selected, oriented according to the ACPC axes, facilitating this identification, using a proportional system of 10th of the dimensions of the hippocampus (see Plate Hippocampus 3): nine axial sections, from HI-A1, superior, to HI-A9, inferior (height of the hippocampus = 33 mm); nine coronal sections, from HI-C1, anterior, to HI-C9, posterior (length of the hippocampus = 36 mm); nine sagittal sections, from HI-S1, lateral, to HI-S9, medial (width of the hippocampus = 24 mm). A coronal section named HI-C* (between HI-C3 and HI-C4) was added because of the particular aspect of Ammon’s horn, the dentate gyrus and the subiculum within the uncus. Some sections of the hippocampus being very close (≤0.5 mm) to MDBA sections, hence the names of these quasi-equivalent MDBA slices are provided (see Plate Hippocampus 3). The ansa lenticularis that collects fiber bundles linking, notably, the lenticular nucleus, the amygdalo-pyriform complex, the hypothalamus and the subthalamus6,46, forms a layer of flat white matter between the GPi and the innominate substance. This portion of the ansa lenticularis belongs to the sublenticular segment of the internal capsule. The ansa lenticularis is bordered, along its concavity, by the tip-pallidal fascicle of Talairach9. The ansa lenticularis is also accompanied by the nucleus of the ansa lenticularis. This nucleus is placed medially and inferiorly against the

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FIG. 2.1 – Hippocampal formation. A. drawing from McCulloch (in Fulton). B. Sagittal section and 3D view (MDBA), along the anterior–posterior axis of the hippocampus showing a “seahorse”. C. Depiction from Vannson (in Duvernoy). D. 3D Hippocampus from the MDBA (gyrus dentatus, green; Ammon’s horn, dark haze; hippocampal formation, light haze).

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hypothalamus. There is a small anterior part belonging to the nucleus of the ansa lenticularis, known as the anterior part of Riley6. The entopeduncular nucleus extends posteriorly in the subthalamus toward the anterior region of the red nucleus [putamen rubris]33. ALEN; ansa lenticularis; 75 mm3/[NN] a(A)nsa lenticularis/[TA98] ansa lenticularis; A14.1.08.663/[FMA] ansa lenticularis; 62070/[TNA2017] ansa lenticularis/anse lenticulaire; anse du noyau lenticulaire; ansa lenticularis; part of the “système en peigne”; pars pallido-thalamic of radiate fibers of striatum; the lateral part of the basal forebrain bundle. ALEN-TIPP-fa; tip-pallidal fascicle of Talairach; 15 mm3/[NN] n.a./[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] n.a./ansa lenticularis; faisceau pallidal de la pointe or fascicule sous-thalamique (part of the ansa lenticularis emerging at the tip of GPi). ALEN-nu; nucleus of ansa lenticularis; 67 mm3/[NN] nucleus of the ansa lenticularis/[TA98] nucleus ansae lenticularis; nucleus endopeduncularis; A14.1.08.919; A14.1.08.918/[FMA] nucleus of ansa lenticularis; endopeduncular nucleus; 62036; 77691/[TNA2017] n.a./endo-entopeduncular nucleus; noyau entopédonculaire, noyau de la capsule interne (de cajal); noyau de l'anse lenticulaire; nucleus ansae lenticularis, entopeduncularis, peduncularis; nucleus of Meynert; nucleus subtantia innominate; substantia reticulata hypothalamica. ALEN-AP-nu; nucleus of ansa lenticularis, anterior part (of Riley); 4 mm3/ [NN] nucleus of the ansa lenticularis/[TA98] nucleus ansae lenticularis; nucleus endopeduncularis; A14.1.08.919; A14.1.08.918/[FMA] nucleus of ansa lenticularis; endopeduncular nucleus; 62036; 77691/[TNA2017] n.a./ endo-entopeduncular nucleus; noyau entopédonculaire, noyau de la capsule interne (de cajal); noyau de l'anse lenticulaire; nucleus ansae lenticularis, entopeduncularis, peduncularis; nucleus of Meynert; nucleus subtantia innominate; substantia reticulata hypothalamica.

Plate Hippocampus 1 – Contouring of the hippocampal substructures according to the MRI contrasts: coronal section close to the HI-C7 (see Plate Hippocampus coronal 2).

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Plate Hippocampus 2 – 3D views of the hippocampus: A. Overview. B. The substructures. C. The hippocampus proper. D. The band of Giacomini. E. characteristics of Ammon’s horn and the dentate gyrus (left) and the white matter wrap made of the fimbria and the alveus (right).

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Plate Hippocampus 3 – Location of hippocampus sections (aligned with ACPC axes) positioned every 10th of hippocampus dimensions (relative grid, black; absolute grid, pale gray, mm): axial HI-A, coronal HI-C, sagittal HI-S; MDBA sections located closely (≤0.5 mm) to hippocampus sections are specified (red).

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The retrolenticular reticularoid zone is a large structure bridging the superficial lateral thalamus and the sublenticular region. RETROLENT-retic-z; retrolenticular reticularoid zone; 386 mm3/[NN] n.a./ [TA98] n.a.; n.a. [FMA] n.a.; n.a./[TNA2017] n.a./retrolenticular reticularoid zone thah limits laterally the Wernicke zone; segement retrolenticulaire de Déjerine; n.a.

The tail of caudate and the stria terminalis extend to the sublenticular region, under the retrolenticular reticularoid zone posteriorly, toward the inferolateral region anteriorly. STR-ter; stria terminalis; 167 mm3/[NN] stria terminalis (/nuclei)/[TA98] stria terminalis; A14.1.09.275/[FMA] n.a.; 6974/[TNA2017] stria terminalis/mixed structure whith fibers and nuclei; strie terminale; stria terminalis or semicircularis or cornea.

The zone of Wernicke is crossed by the geniculo-calcarine radiations and the temporo-thalamic fascicle [fibres temporo-thalamiques]; it also belongs to the posterior region of the superior gyrus of the temporal lobe18. The thalamic estuary of the zone is flanked anteriorly by the lateral geniculate body and posteriorly by the retrolenticular reticularoid zone. The retro commissural (anterior commissure) region bordering the internal capsule, located against the hypothalamus, anteriorly, up to the subthalamic nucleus, posteriorly, is composed of several structures. Posteriorly, the lenticular fascicle and the thalamic fascicle are placed on the inferior and superior sides, respectively, of the zona incerta. The prethalamic reticularoid zone and the inferior thalamic peduncle overlook the ansa lenticularis (and the tip-pallidal fascicle of Talairach) and the nucleus of ansa lenticularis (and its anterior part). Together, the inferior thalamic peduncle and the ansa lenticularis form the ansa peduncularis6,7. The fornix and the stria terminalis are semicircular structures linking the septo-preoptico-hypothalamic region to the amygdalo-hippocampal complex. The lamina cornea, a structure with a somewhat complex nature6, is placed directly against the ventricle, medially in relation to the stria terminalis, the superficial lateral thalamus and the anterolateral nucleus of the thalamus. The pre commissural fornix [longitudinal] runs continuously with the diagonal band6,46, so closing the circle of white matter structures around the diencephalon. In particular, this set of white matter and gray matter paths subserves rhinencephalic (olfactory) functions, including those of the olfactory tubercle. FO; fornix; 430 mm3/[NN] fornix/[TA98] fornix; A14.1.08.949/[FMA] fornix of forebrain; 61965/[TNA2017] fornix/fornix without the intra hippocampal part; trigone; fornix; tractus cortico-mammillaris. LA-CO; lamina cornea; 45 mm3/[NN] lamina cornea/[TA98] n.a./[FMA] n.a./ [TNA2017] n.a./(Riley); lame cornée (ependymal thickening); lamina cinerea, infrachoroidea.

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Plate Telencephalon l – Anterior (top left and inferior row; successive layers from anterior to posterior), lateral (top right) and superior (intermediate row) views of telencephalic structures.

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Plate Telencephalon 2 – Anterior views of telencephalic structures (successive layers from anterior to posterior; last series).

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Plate Telencephalon 3 – Lateral (top left), medial (top right), anterior (intermediate), and superior (bottom left and right) views of telencephalic structures.

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The supraoptic tract is visible above the optic tract (see hypothalamus). SU-OT; supraoptic tracts; 18 mm3/[NN] n.a./[TA98] n.a.; n.a./[FMA] n.a.; n.a./[TNA2017] n.a./include the supraoptic commissures (commissurae supraopticae; dorsal and ventral); n.a.; n.a.

The frontopontin fascicle crosses the substantia nigra (see subthalamus). FP-fa; frontopontin fascicle; 24 mm3/[NN] frontopontine fibers/[TA98] fibrae frontopontinae; A14.1.06.106/[FMA] set of frontopontine fibers; 75223/ [TNA2017] tractus frontopontinus/tractus fronto-pontin; fasciculus or tractus fronto-pontinus.

2.4

The Hypothalamus The hypothalamus is composed of ten different macroscopic structures, the pre-optic, suprachiasmatic, supra-optic, infundibular, paraventricular, dorsomedial, ventromedial, posterior and tuberomammillary nuclei, and the lateral hypothalamic area. The posterior limit of the hypothalamus is the mammillary body.

The hypothalamus is bilateral, located directly under the wall of the third ventricle. The tuber cinereum is placed between the mammillary body and the infundibulum of the third ventricle4,8,23. The third ventricle communicates with the lateral ventricle through the interventricular foramen [of Monro] bordered infero-laterally and supero-medially by the fornix that forms a kind of arch. The anterior commissure (AC), located below this arch, represents the anterosuperior landmark of the hypothalamus. From the AC, the posterior limit of the mammillary body, the bottom of the preoptic recess, the optic-chiasma angle, the bottom of the infundibular recess and the optic tract, it is possible to make a proportional diagram to partition the hypothalamus into its ten components47. The biggest structures that connect with the hypothalamus are the fornix, the stria medullaris of the thalamus, the mammillothalamic fascicle, the stria terminalis, the ansa lenticularis, the thalamic fascicle, the lenticular fascicle, the optic tract and the dorsal longitudinal fascicle. The supraoptic tract, composed of the components of the dorsal supraoptic commissure6,21, is visible. The median forebrain bundle [fasciculus basalis olfactorius, fasciculus telencephalicus medialis, fasciculus longitudinalis basalis, fasciculus prosencephali medialis, radiations olfactives profondes]5,6 and the hypothalamocortical system5,21,47 are not identified in this book. MB; mammillary body; 93 mm3/[NN] mammillary body/[TA98] corpus mammillare; A14.1.08.402/[FMA] mammillary body; 74877/[TNA2017] corpus mammillare/nucleus lateral, medial, intercalatus; area hypothalamica posterior (A14.1.08.933); area mammillary; corps mamillaire; tubercule mamillaire; corpus mammillare; albicans; candescans; ganglion mammilare.

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OT; optic tract; 232 mm3/[NN] optic tract/[TA98] tractus opticus; A14.1.08.404/[FMA] optic tract; 62046/[TNA2017] tractus opticus/tractus optique; bandelette optique (rétrochiasmatique); tractus opticus; fasciculus opticus.

The hypothalamus is connected with the olfactory system or rhinencephalon, and notably the olfactory tubercle. The olfactory cortices are made up of5,7,18,23: on the frontal side, the subcallosal gyrus [carrefour olfactif de Broca] and the olfactory tubercle; on the temporal side, the piriform lobe (cortex) and the entorhinal cortex, the uncus [circonvolution du crochet] partially, and the anterior part of the parahippocampal gyrus or T5 [the historical “2e circonvolution limbique”]. Table 2.2 summarizes different nomenclatures of hypothalamic nuclei. The ten structures of the hypothalamus are: (1) (2) (3) (4) (5) (6) (7) (8) (9)

The preoptic nucleus of the hypothalamus (PO). The suprachiasmatic nucleus and the supra-optic nucleus (SO). The infundibular nucleus (INF). The dorsomedial nucleus (of the hypothalamus) (DM). The ventromedial nucleus (VM). The paraventricular nucleus (PV). The tuberomammillary nucleus (TM) that contains the mammillary body. The lateral hypothalamic area (LH-a). The lateral intermediate region of the hypothalamus that overlaps the lateral hypothalamic area and the tuberomammillary nucleus of the hypothalamus (IHa). (10) The posterior nucleus (P). PO-nu; preoptic nucleus of hypothalamus; 93 mm3/[NN] preoptic area/[TA98] area preoptica; A14.1.08.407/[FMA] preoptic area; 62313/[TNA2017] area hypothalamica anterior (chiasmatica)/preoptic (medial, lateral, anterior) nucleus of hypothalamus; prothalamus; noyau préoptique de l'hypothalamus; area preoptica (area hypothalamica rostralis, A14.1.08.902). SO-nu; suprachiasmatic nucleus & supra-optic nucleus, of hypothalamus; 7 mm3/[NN] suprachiasmatic nucleus of the hypothalamus/[TA98] nucleus suprachiasmaticus; nucleus supraopticus; A14.1.08.911;A14.1.08.912/[FMA] n. a.; 67883; 62317/[TNA2017] nucleus suprachiasmaticus & nucleus supraopticus/suprachiasmatic nucleus & supra-optic (dorsomedial, dorsolateral, ventromedial) nucleus, of hypothalamus; noyau suprachiasmatique & noyau supra-optique, de l'hypothalamus; nucleus ovoideus or suprachiasmaticus; nucleus supraopticus (hypophyseus, tangentialis) hypothalami; (area hypothalamica rostralis, A14.1.08.902). INF-nu; infundibular nucleus of hypothalamus; 19 mm3/[NN] arcuate nucleus of the hypothalamus/[TA98] nucleus arcuatus; A14.1.08.923/[FMA] arcuate nucleus of hypothalamus; 62329/[TNA2017] nucleus arcuatus; semilunaris; infundibular/arcuate nucleus; infundibular periventricular nucleus; noyau arqué (infundibulaire) de l'hypothalamus; infundibular nucleus. DM-nu (hypothalamus); dorsomedial nucleus of hypothalamus; 47 mm3/ [NN] dorsomedial nucleus of the hypothalamus/[TA98] nucleus dorsomedialis;

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Nucleus

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Nomenclatures of hypothalamic nuclei Talairach et al. (1957)

SO-nu

Nauta, Haymaker (1969)

Supraoptic n.a

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Intermediate

PV-nu DM-nu VM-nu INF-nu L-HYPOTH-a; I-HYPOTH-a; TM-nu: Post-nu; MB

Wahren (1977)

Supraoptic, tangential Ovoid Prothalamus

Suprachiasmatic Preoptic medial Preoptic lateral Anterior Paraventricular Dorsomedial Ventromedial (tuber principal) (Sub part of Infundibular, arcuate ventromedial) Posterior Dorsal

Lateral (including 1; excluding the fornix)

Anatomo functional architecture from Saper (2004) & Toni et al. (2004) Anteroposterior division(region) Preoptic, chiasmatic, anterior

Tuberal, median

Mediolateral zone Periventricular

Suprachiasmatic Preoptic, periventricular

n.a

n.a

Tuber lateral

Caudal

n.a Medial preoptic, paraventricular Paraventricular Posterior Dorsomedial, periventricular ventromedial

Sparse cells n.a n.a

Dorsal hypothalmic area n.a

Lateral area, supraoptic

Tuber lateral n.a Tuberomamillaris Posterior, mammilary

n.a Mamillary n.a Supramamillary n.a

n.a

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n.a

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Arcuate

Lateral or lateral hypothalamic area (including 1,2)

n.a Perifornical (2) Tuberomamillaris, mamilloinfundibularis (1) Intercalatus Mamillary lateral and medial n.a Premamillary n.a Supramamillary n.a Postmammillaris

Medial Supraoptic

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TAB. 2.2 – Nomenclatures of hypothalamic nuclei. Talairach J., David M., Tournoux P., Corredor H., Kvasina T. (1957) Atlas d’anatomie stéréotaxique. Repérage radiologique indirect des noyaux gris centraux des régions mésencéphalo-sous-optiques et hypothalamiques de l’homme [in French], Masson et Cie, Paris; Nauta W.J., Haymaker W. (1969) Hypothalamic nuclei and fiber connections. In The hypothalamus. Springfield, Illinois, USA: Charles C. Thomas, pp. 136–200; Wahren W. (1959) Anatomy of the Hypothalamus, in: Introduction to Stereotaxis with an Atlas of the Human Brain, Georg Thieme Verlag Stuttgart, pp. 119–151; Saper C.B. (2004) The Human Nervous System (Second Edition) Hypothalamus Elsevier., George Paxinos and Jürgen K. Mai; Toni R. et al. (2004) The human hypothalamus: a morpho-functional perspective, Journal of Endocrinological Investigation 27 (6 Suppl), pp. 73–94.

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A14.1.08.922/[FMA] dorsomedial nucleus of hypothalamus; 62331/[TNA2017] nucleus dorsomedialis hypothalami/noyau dorso-médian de l'hypothalamus; nucleus dorso-medialis hypothalami or nucleus hypothalamicus dorso-medialis; nucleus centralis infundibuli. VM-nu; ventromedial nucleus of hypothalamus; 25 mm3/[NN] ventromedial nucleus of the hypothalamus/[TA98] nucleus ventromedialis hypothalami; A14.1.08.928/[FMA] n.a.; 62332/[TNA2017] nucleus ventromedialis hypothalami/ventromedial nucleus; principal tuberis or infundibular medialis; noyau ventro-médian de l'hypothalamus; nucleus hypothalamicus ventro-medialis or ventralis tuberis cinerei; nucleus infundibularis medialis. PV-nu; paraventricular nucleus of hypothalamus; 20 mm3/[NN] paraventricular nucleus of the hypothalamus/[TA98] nucleus periventricularis; A14.1.08.924/[FMA] paraventricular nucleus of hypothalamus; 62320/[TNA2017] nucleus paraventricularis hypothalami/filiformis; noyau paraventriculaire, filiforme, de l'hypothalamus; nucleus paraventricular. TM-nu; tuberomammillary nucleus of hypothalamus; 71 mm3/[NN] tuberomammillary nucleus/[TA98] nucleus tuberomammillaris; A14.1.08.932/[FMA] n.a.; 62335/[TNA2017] nucleus tuberomammillaris/tuberomamillaris; mamilloinfundibularis; noyau tubéro-mammillaire; nucleus tubero-mammilaris. L-HYPOT-a; lateral hypothalamic area; 105 mm3/[NN] lateral hypothalamic area/[TA98] area hypothalamica lateralis; A14.1.08.929/[FMA] lateral hypothalamic region; 62030/[TNA2017] areae hypothalamicae lateralis/lateral area; aire hypothalamique latérale; zone latérale de l'hypothalamus; nucleus hypothalamicus lateralis or area hypothalamica lateralis. I-HYPOT-a; lateral intermediate region of the hypothalamus; 37 mm3/[NN] n.a./[TA98] n.a./[FMA] n.a./[TNA2017] n.a./overlapping of the lateral hypothalamic area and the tuberomammillary nucleus of hypothalamus; n.a.; n.a. POST-nu; posterior nucleus of hypothalamus; 179 mm3/[NN] posterior hypothalamic area(region)/[TA98] nucleus dorsalis hypothalami; A14.1.08.921/ [FMA] dorsal nucleus of hypothalamus; 77685/[TNA2017] nucleus posterior hypothalami/dorsal nucleus; aire hypothalamique postérieure & aire hypothalamique dorsale; nucleus hypothalamicus posterior or area hypothalamica posterior.

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Plate Hippocampus axial 1 – MRI (left) and colored (right) axial sections of the hippocampus from 1 to 6.

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Plate Hippocampus axial 2 – MRI (left) and colored (right) axial sections of the hippocampus from 7 to 9.

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Plate Hippocampus coronal 1 – MRI (left) and colored (right) coronal sections of the hippocampus from 1 to 5.

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Plate Hippocampus coronal 2 – MRI (left) and colored (right) coronal sections of the hippocampus from 6 to 9.

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Plate Hippocampus sagittal 1 – MRI (left) and colored (right) sagittal sections of the hippocampus from 1 to 3.

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Plate Hippocampus sagittal 2 – MRI (left) and colored (right) sagittal sections of the hippocampus from 4 to 6.

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Plate Hippocampus sagittal 3 – MRI (left) and colored (right) sagittal sections of the hippocampus from 7 to 9.

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Plate hypothalamus 1 – Medial (top left and inferior row; successive layers) and inferior (top right) views of the hypothalamus.

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Plate hypothalamus 2 – Anterior (top row and left intermediate row; successive layers) and lateral (right intermediate row and inferior row) views of the hypothalamus.

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Plate hypothalamus 3 – 3D segmentation of the hypothalamus: top diagram, clock-wise from top left, anterior, lateral, posterior, superior, inferior and medial views; bottom, frontal (a, b, c, d and e), axial (f) and sagittal (g) sections.

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Plate hypothalamus 4 – Anterior (top row) views, successive layers from posterior (left) to anterior (right); medial (bottom row) views, successive layers from lateral (left) to anterior (right) (with a lateral view under the intermediate layer).

Chapter 3 The MRI Deep Brain Atlas – MDBA The MRI Deep Brain Atlas (see plates MDBA 1A, 1B and 2, and axial [n = 19], coronal [n = 19], and sagittal [n = 15] plates hereafter) can be used either to map the deep brain from MRI slices or to determine stereotactic targets using indirect landmarks. The MDBA is oriented along the classical axis going through the anterior and posterior white commissures of the diencephalon, or AC–PC line. The ACPC length, rounded to 27 mm, was subdivided into twelve segments. The twelfth, rounded to 2.25 mm, was used to normalize the distances between slices in the axial (A), sagittal (S) and coronal (C) planes. The midpoint between AC and PC (MI) was rounded to 13.5 mm. The height of the thalamus measured 18 mm. The plates (sections) are displayed with absolute distances in mm (overlay of absolute distance grid; black) and with relative distances in 1/12th of ACPC (overlay of proportional distance grid; dark blue). The axial section going through the ACPC horizontal plane is named A0 [−ACPC]; the sections above are named superior, AS, and below, inferior, AI. The coronal section going through AC (perpendicular to AC–PC horizontal plan) is named C0 [−AC]; the plates in front are named CF, and rear CR; at the MI point, the coronal section is named CR6 [−MI] (the 6th coronal plate behind AC); at PC, CR12 [−PC] (the 12th coronal section behind AC). The sagittal section going through the vertical ACPC plane, is named S0 [−ACPC]. Each plate contains: the raw MRI slice; the overlays of contours and the millimetric grid on the raw MRI slice; the overlays of colored structures with their names and the millimetric and proportional grids (figure 3.1).

DOI: 10.1051/978-2-7598-2575-2.c003 © Science Press, EDP Sciences, 2021

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FIG. 3.1 – Arrangement of the elements on an MDBA plate.

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Plate MDBA 1A – Stereotactic landmarks and grids of the MDBA (lateral projection on the midline ACPC vertical plane): AC, PC, midpoint between ACPC (MI), height of thalamus (HT), millimetric grid (dotted gray) and proportional grid (blue) in twelfth of ACPC; the cuneal point of reference of the Montreal Neurological Institute and the contour of the thalamus are displayed.

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Plate MDBA 1B – Representation of three emblematic stereotactic targets: the subthalamic nucleus (yellow), the intern pallidum (blue) and the ventral intermediate nucleus of thalamus (Vim or VI, purple); lateral (top row) and frontal (bottom row) projections according to (from left to right) the MDBA (3D structures), Talairach et al.9 (probabilistic location with specific lines of reference), Schaltenbrand & Bailey33 (probabilistic location) and Benabid et al.48 (probabilistic location).

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Plate MDBA 2 – Locations of MDBA slices according to the proportional grid (twelfth of ACPC; height of thalamus, HT; midpoint between ACPC, MI): top row, coronal sections from frontal (CF2) to rear (CR16), and axial sections above ACPC from 1 (AS1) to 8 (AS8), and below ACPC from −1 (AI1) to −10 (AI10), projected on the sagittal slice S6; bottom, sagittal sections from 0 (S0) to 14 (S14), and coronal sections projected on the axial slice going through ACPC (A0).

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Axial plates (19) from AS 8 to AI 10.

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Coronal plates (19) from CF 2 to CR 16.

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Sagittal plates (15) from S 0 to S 14.

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Chapter 4 Clinical MRI Mapping

Direct manual mapping can be performed in clinical conditions when MRI images show enough structural details, and if enough a priori knowledge is available. If the conditions of visibility and a priori knowledge are incompletely satisfied, manual mapping can be valuably coupled with indirect mapping, relying on proportional diagrams or classical stereotactic targeting. Three common stereotactic targets are used hereafter to exemplify the direct approach: the pallidum, the subthalamic nucleus and the ventral intermediate nucleus of the thalamus (see plates CLIN GPi, STN and VI here after). The MRI sequence used was an inversion-recovery sequence named WAIR (White Matter Attenuated InversionRecovery) developed specifically for this application36,37. This sequence runs on a 1.5-T machine, the most common magnetic field used for medical applications in the world. The values of the parameters of the sequence, such as voxel size, are the result of a compromise between high contrast, high geometric resolution, and length of acquisition acceptable under local or general anesthesia. Basically, the main challenge is to seek the MRI contrasts of known structures, bearing in mind that the contrasts essentially rely, for each structure, on the ratio of cell bodies/bundles of axons, and on the presence of ferromagnetic compounds, thus iron in practice. The manual contouring was performed on raw coronal slices (pixel = 0.527 mm × 0.527 mm) acquired in clinical conditions, i.e., with the stereotactic frame in place. Therefore, the positioning of the patient’s head in the machine depends on the fixation of the stereotactic frame on the head and on the fixation of the head coil on the table. Although these parameters influence the brain orientation and the orientation of the MRI data set, in practice it is mostly quasi ACPC aligned. We prefer to use raw images, without reorientation of the image data set, and without filtering (the pixels are visible!) to stay as close as possible to the MRI signal of the structures. Another parameter, the geometric resolution of the clinical MRI sequence, limits the precision of structure definition. Indeed, certain structures are rather small in view of the size of the voxels, and consequently the boundaries can be defined roughly. Finally, the stair-case like contours and certain unspecific boundaries show the ground truth of real cases. DOI: 10.1051/978-2-7598-2575-2.c004 © Science Press, EDP Sciences, 2021

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The coronal orientation was preferred for drawing, first and foremost because it is well-suited for the clinical analysis of deep brain structures by “layers”, in recognition of the pioneering works on the layers of the brain. In the following examples, one can see that the MDBA data set can be used as an aid to manual drawing.

4.1

The Intern Pallidum

The GPi is the stereotactic target of the classical pallidotomy and of the chronic deep brain stimulation that are both used in functional neurosurgery for alleviating symptoms of severe dystonia and advanced Parkinson’s disease. The MRI aspect of the pallidum is rather dark (WAIR sequence) because of the high density of the fiber bundles that cross this structure, and iron deposits. The GPi is less dark in the anterior segment than in the posterior segment.

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Plates CLIN GPi 1 and 2 – Raw coronal slices from anterior (C - CLIN-GP 1; retro commissural) to posterior (C - CLIN-GP 6), with the original contouring of GPi, GPe and putamen (planning; Parkinson’s disease; only one side is shown). The nearest sections of the full MDBA dataset are depicted for each slice.

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The Subthalamic Nucleus

The subthalamic nucleus is nowadays one of the most common stereotactic targets used in functional neurosurgery for alleviating symptoms of Parkinson’s disease. There is a high iron charge and high density of fiber bundles, both nonhomogeneously distributed. The subthalamic nucleus is roughly more dense and whiter (WAIR sequence) in the anteromedial part. It is bordered by the internal capsule and the nucleus is surmounted by well-contrasted structures, the lenticular and thalamic fascicles, and the zona incerta. The substantia nigra is easily identifiable below the subthalamic nucleus.

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Plates CLIN STN 1, 2, and 3 – Raw coronal slices from anterior (C - CLIN-ST-nu 1) to posterior (C - CLIN-ST-nu 9), with the original contouring of several subthalamic structures (planning; Parkinson’s disease; only one side is shown). The nearest sections of the full MDBA dataset are depicted for each slice.

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Plate CLIN STN 4 – Anterior (top row) and posterior (bottom row) views (successive layers; clock-wise by row) of the subthalamic nucleus and its environment.

4.3

The Ventral Intermediate Nucleus of the Thalamus

The VI nucleus of the thalamus, or classical Vim for thalamotomy, is the most frequent stereotactic target of functional neurosurgery for alleviating tremor, essential or Parkinsonian or Holmes’s. As already mentioned, the VI nucleus is largely crossed by nerve fibers that give a dark signal on MRI, contrasting with the ventrocaudal nuclei posteriorly, and the ventrooral nuclei anteriorly. The VI is also connected to numerous fiber bundles, notably those of the thalamic fascicle anteriorly, and those coming from the red nucleus within the lateral and superior zones of the subthalamic tegmental field. The subthalamic field is clearly identifiable between the red nucleus and the VI, and it contains the prelemniscal radiations (see Plate Subthalamus 1C, section 2.2 (The Subthalamus or Prethalamus)).

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Plate CLIN VI 1 and 2 – Raw coronal slices from anterior (C - CLIN-THAL 1) to posterior (C - CLIN-THA 4), with the original contouring of thalamic structures (planning; Essential tremor; only one side is shown). The nearest sections of the full MDBA dataset are depicted for each slice.

References [1]

[2]

[3] [4] [5] [6] [7] [8] [9]

[10] [11] [12] [13] [14]

[15] [16]

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Index

A Accessory lamina See pallidum, 38 Accumbens nucleus, 39 Alveus, 41 Ammon’s horn, 41 Amygdala, 40 Amygdala posterior extension, 40 Ansa lenticularis, VI, 26, 42, 47, 51 Ansa peduncularis, 47 Anterior commissure, 38, 40, 51 Anterior part of Riley nucleus ansa lenticularis, 44 Anterolateral nucleus thalamus, 16 Anteromedial dorsal nucleus anteroprincipalis, thalamus, 16 Anteromedial intermediate nucleus thalamus, 16 Anteromedial ventral nucleus thalamus, 16 Area U See pedunculopontine nucleus, 30 B Band of Giacomini, 41 Basal ganglia, 1 Brachium colliculi, 28 Brachium conjunctivum, 4, 17, 29, 30 Brain peduncles, 5 C Capsule around a nucleus, 1 Caudate, 1, 40, 47 Caudolenticular gray bridges, 39

Central gray nuclei noyaux gris centraux, 17 Central tegmental tract, 31 Centromedian nucleus thalamus, 18 Claustrum avant-mur, 39 Colliculi inferior and superior See tectum, 28 Cuneiform area, 30 D Dentate gyrus, 41 Diagonal band of Broca fasciculus olfactorius, 40, 47 Diencephalon interbrain, XVI, 1, 2, 47, 67 Dorsal longitudinal fascicle, 29, 51 Dorsolateral nucleus thalamus, 16 Dorsomedial nucleus hypothalamus, 52 thalamus, 9, 15, 16 E Epithalamus, 2, 4, 5 External lamina thalamus, 19 F Fascicle, 2 Fasciola cinerea, 41 Fasciolar gyrus, 41 Fields of Forel Forel, 2

Index

140 Fimbria, 41 Fornix, 47, 51 Frontopontin fascicle, 51 Fundus striati See accumbens nucleus, 39 G GPe globus pallidus extern, 38 GPi globus pallidus intern, 38 H Habenula, 19 Hippocampal formation, 40 Hippocampus See hippocampal formation, 42 Hippocampus proper, 41 Horseshoe commissure of Wernekink See brachium conjunctivum, 30 Hypothalamus (II.D), 2 I Infundibular nucleus [arcuate] hypothalamus, 52 Innominate substance, 38, 40, 42 Interbrain central gray, 27, 28, 29 Intermediolateral nucleus thalamus, 17 Interpeduncular paranigrae nuclei, 27 L Lamina cornea, 47 Laminar anterior nucleus thalamus, 16 Laminar caudal nucleus thalamus, 18 Laminar oral nucleus thalamus, 15, 18 Lateral area hypothalamus, 52 Lateral geniculate body, 15, 47 Lateral intermediate region hypothalamus, 52 Lateral lemniscus, 31 Lateral medullary lamina lenticular nucleus, 38 Lenticular fascicle H2, Forel, 26, 47, 51 Luys, XV, 1, 18

M Mammillothalamic fascicle, 16, 18, 51 Medial geniculate body, 15 Medial lemniscus, 17, 18, 31 Medial longitudinal fascicle bandelette longitudinal postérieure, 29 Medial medullary lamina lenticular nucleus, 38 Medial nucleus thalamus, 9, 15 Metathalamus, 2, 4 N Nucleus, 1 Nucleus of ansa lenticularis entopedeuncularis, 42, 47 Nucleus ventrocaudal medial thalamus, crescent, arcuate, 17 O Oculomotor nerve, 25 Olfactory cortices, 52 Olfactory tubercle, 40, 47, 52 Optic tract, 4, 15, 40, 51 P Pallidum globus pallidus, V globus pallidus, GP, 1, 8, 38 Parabigeminal area, 30 Parafascicular nucleus thalamus, 1, 18 Paraventricular nucleus [filiformis] hypothalamus, 52 Pedunculopontin fibrae, 25 Pedunculopontine nucleus, 30 Peri peduncular nucleus, 26, 29 Periaqueductal gray, 28, 29 Pineal gland, 28 Pontes grisei peduncularis, 39 Posterior commissure, 2, 28 Posterior para lenticulo-capsular zone, 40 Posterior subpallidal area, 40 Prelateral geniculate body, 15 Prelemniscal radiations, 17 Preoptic nucleus [area] hypothalamus, 52 Prethalamic reticularoid zone, 20, 47 Prethalamus See subthalamus, 4 Pulvinar thalamus, 9, 15 Putamen, 1, 38, 39

Index Q Q fascicle, 27 R Red nucleus, 25, 30 Retroflexus fascicle, 25 Retrolenticular reticularoid zone, 8, 47 S Spinothalamic fascicle, 31 Stria medullaris thalamus, 4, 5, 19, 51 Stria terminalis, 39, 47, 51 Striate body corps striés, 1 Subiculum complex, 42 Substantia nigra, 25, 26, 27, 51 Subthalamic nucleus, 26, 47 Subthalamic tegmental fields, 1, 4, 17, 27 Subthalamus (II.B), 4 Superficial lateral thalamus, 26 reticular nucleus, 19 reticular nucleus, 26, 47 Superficial medial nucleus thalamus, 15 Superior cerebellar peduncle See brachium conjunctivum, 30 Suprachiasmatic nucleus and supra-optic nucleus hypothalamus, 52 Supraoptic tract, 51 T Tectal plate See tectum, 5 Tectum, 28 Tegmental pontomesencephalic reticular formation, 29

141 Tegmentum, 25, 26, 29, 30 calotte, 5 Thalamic fascicle H1, VI H1, Forel, VII, 26, 47, 51 Thalamic radiations peduncles, 19 Thalamus, 11, 67 Thalamus (II.A), 4 Tip-pallidal fascicle of Talairach, 42 Trochlear nerve, 28 Tuber cinereum, 51 Tuberomammillary nucleus hypoythalamus, 52 V Ventral intermediate nucleus vim, thalamus, 17 Ventral tegmental area, 27 Ventrocaudal lateral nucleus thalamus, VII, 17 Ventrocaudal nuclei thalamus, VI Ventrocaudal nucleus thalamus, 17 Ventromedial nucleus hypothalamus, 52 Ventrooral nuclei thalamus, 17 W White matter, 2 Willis and Crone, XV Z Zona incerta, 26, 47 Zone of Wernicke, 8, 15, 47