Manual of Neuro Ophthalmogy

Manual of Neuro-ophthalmology Manual of Neuro-ophthalmology Amar Agarwal MS FRCS FRCOphth Athiya Agarwal MD DO Dr Ag...

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Manual of Neuro-ophthalmology


Amar Agarwal MS FRCS FRCOphth Athiya Agarwal MD DO Dr Agarwal’s Group of Eye Hospitals and Eye Research Centre 19, Cathedral Road, Chennai - 600 086, India

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JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD New Delhi • Ahmedabad • Bengaluru • Chennai • Hyderabad Kochi • Kolkata • Lucknow • Mumbai • Nagpur

Published by Jitendar P Vij Jaypee Brothers Medical Publishers (P) Ltd Corporate Office 4838/24, Ansari Road, Daryaganj, New Delhi 110 002, India Phone: +91-11-43574357 Registered Office B-3, EMCA House, 23/23B Ansari Road, Daryaganj, New Delhi 110 002, India Phones: +91-11-23272143, +91-11-23272703, +91-11-23282021, +91-11-23245672 Rel: +91-11-32558559 Fax: +91-11-23276490, +91-11-23245683 e-mail: [email protected] Visit our website: www.jaypeebrothers.com Branches • 2/B, Akruti Society, Jodhpur Gam Road Satellite Ahmedabad 380 015 Phones: +91-79-26926233, Rel: +91-79-32988717 Fax: +91-79-26927094 e-mail: [email protected] • 202 Batavia Chambers, 8 Kumara Krupa Road, Kumara Park East Bengaluru 560 001 Phones: +91-80-22285971, +91-80-22382956, +91-80-22372664 Rel: +91-80-32714073 Fax: +91-80-22281761 e-mail: [email protected] • 282 IIIrd Floor, Khaleel Shirazi Estate, Fountain Plaza, Pantheon Road Chennai 600 008 Phones: +91-44-28193265, +91-44-28194897, Rel: +91-44-32972089 Fax: +91-44-28193231 e-mail: [email protected] • 4-2-1067/1-3, 1st Floor, Balaji Building, Ramkote Cross Road Hyderabad 500 095 Phones: +91-40-66610020, +91-40-24758498 Rel:+91-40-32940929 Fax:+91-40-24758499, e-mail: [email protected] • No. 41/3098, B & B1, Kuruvi Building, St. Vincent Road Kochi 682 018, Kerala Phones: +91-484-4036109, +91-484-2395739, +91-484-2395740 e-mail: [email protected] • 1-A Indian Mirror Street, Wellington Square Kolkata 700 013 Phones: +91-33-22651926, +91-33-22276404, +91-33-22276415 Rel: +91-33-32901926 Fax: +91-33-22656075, e-mail: [email protected] • Lekhraj Market III, B-2, Sector-4, Faizabad Road, Indira Nagar Lucknow 226 016 Phones: +91-522-3040553, +91-522-3040554 e-mail: [email protected] • 106 Amit Industrial Estate, 61 Dr SS Rao Road, Near MGM Hospital, Parel Mumbai 400012 Phones: +91-22-24124863, +91-22-24104532, Rel: +91-22-32926896 Fax: +91-22-24160828, e-mail: [email protected] • “KAMALPUSHPA” 38, Reshimbag, Opp. Mohota Science College, Umred Road Nagpur 440 009 (MS) Phone: Rel: +91-712-3245220, Fax: +91-712-2704275 e-mail: [email protected] USA Office 1745, Pheasant Run Drive, Maryland Heights (Missouri), MO 63043, USA Ph: 001-636-6279734 e-mail: [email protected], [email protected] Manual of Neuro-ophthalmology © 2008, Jaypee Brothers Medical Publishers All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the authors and the publisher. This book has been published in good faith that the material provided by authors is original. Every effort is made to ensure accuracy of material, but the publisher, printer and authors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only.

First Edition: 2009 ISBN 978-81-8448-411-3 Typeset at JPBMP typesetting unit Printed at Ajanta

This book is dedicated to a lovely couple

Marguerite Mcdonald and Stephen Klyce

Contributors Amar Agarwal MS FRCS FRCOPHTH Dr. Agarwal’s Group of Eye Hospitals and Eye Research Centre 19, Cathedral Road Chennai-600 086, India [email protected] Athiya Agarwal MD DO Dr. Agarwal’s Group of Eye Hospitals and Eye Research Centre 19, Cathedral Road Chennai-600 086, India [email protected] Garrett Smith MD Moran Eye Center Salt Nake City, UTAH USA Jeyalakshmi Govindan DO DNB Consultant Ophthalmologist Dr. Agarwal’s Eye Hospital 19, Cathedral Road Chennai, India Nick Mamalis MD Moran Eye Center Salt Nake City, UTAH USA P Ramesh MBBS DMRD DNB MNAMS FRCR Director, Liberty Scans Chennai, India Priya Narang MS Narang Eye Hospital Ahmedabad, Gujarat, India

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Reena M Choudhry MD DO DNB FRCS Icare Eye Hospital and Postgraduate Institute Noida, Uttar Pradesh India Sameer Narang MS Narang Eye Hospital Ahmedabad, Gujarat India Saurabh Choudhry MD DO DNB Icare Eye Hospital and Postgraduate Institute Noida, Uttar Pradesh India S Soundari DO DNB FRCS Consultant Ophthalmologist Dr. Agarwal’s Eye Hospital 19, Cathedral Road Chennai India

Foreword Neuro-ophthalmology is a complex subspecialty which requires keen skills of clinical observation, attention to detail, and intricate thought processes in order to formulate the appropriate diagnostic and therapeutic plan for the patient. What makes the field even more challenging is our limited knowledge of the intricate neurological pathways between the eye and the brain; many of which are still being discovered, as long as our understanding is evolving. To concisely and accurately explain the basics of neuroophthalmology is a difficult task, as it requires a thorough understanding of the subject as well as a natural gift for simplifying and organizing the material so that it appeals to a wide audience. Through the process of teamwork, the Agarwals’ have succeeded in creating an outstanding book for neuro-ophthalmology that will prove to be an excellent reference for a full spectrum of readers, from medical students to practising ophthalmologists. Prof Amar Agarwal once explained to me that for any challenging situation, “The battle is in the brain”. Whether the task is climbing Mount Everest or writing a complete library of ophthalmology texts, the true challenge is in mind. Having the drive and determination to succeed, no matter the situation, is the mark of a true pioneer, and a characteristic of one of my strongest mentors, Prof Amar Agarwal. Uday Devgan MD FACS Chief of Ophthalmology Olive View-UCLA Medical Center UCLA School of Medicine Private Ophthalmic Practice Maloney Vision Institute Los Angeles, California, USA

Preface Understanding Neuro-ophthalmology is a challenge. It took us a long time to comprehend the basics in this field when we were residents. That is the notion why we have written Manual of Neuro-ophthalmology. The idea is that you dear reader can go through the text and figures and never have difficulty in understanding this subject like we did. We would like to thank our consultant Dr S Soundari for helping us. Shri JP Vij and his full team of M/s Jaypee Brothers Medical Publishers have always supported our writing endeavors. Our sincere thanks to them. Finally, dear reader we hope this book will change your outlook to Neuro-ophthalmology. Amar Agarwal Athiya Agarwal

Contents 1. Supranuclear Pathways for Eye Movements ..................................... 1 Athiya Agarwal, Amar Agarwal 2. Supranuclear Disorders of Eye Movements ....................................17 Athiya Agarwal, Amar Agarwal 3. Nystagmus .............................................................................................32 Athiya Agarwal, Amar Agarwal 4. The Pupil ................................................................................................54 Athiya Agarwal, Amar Agarwal 5. Visual Pathway .....................................................................................73 Athiya Agarwal 6. Anatomy of the Optic Nerve ............................................................ 103 Athiya Agarwal 7. Oculomotor Nerve ............................................................................. 109 Athiya Agarwal 8. Lesions of the Oculomotor Nerve ................................................... 118 Athiya Agarwal 9. Trochlear Nerve and its Lesions ..................................................... 123 Athiya Agarwal 10. Abducent Nerve and its Lesions ..................................................... 132 Athiya Agarwal 11. Trigeminal Nerve .............................................................................. 140 Athiya Agarwal 12. Facial Nerve and its Lesions ............................................................ 145 Athiya Agarwal 13. Congenital Optic Nerve Anomalies ................................................ 150 Priya Narang, Sameer Narang, Amar Agarwal 14. Optic Nerve Tumors ......................................................................... 157 Nick Mamalis, Garrett Smith 15. Abnormalities of Optic Nerve Head .............................................. 185 Reena M Choudhry, Saurabh Choudhry, Amar Agarwal 16. Ocular Myopathies ............................................................................ 197 S Soundari 17. Miscellaneous .................................................................................... 204 Jeyalakshmi Govindan, S Soundari 18. Examination of a Neuro-ophthalmology Case .............................. 219 S Soundari 19. Imaging in Neuro-ophthalmology .................................................. 226 P Ramesh Index ..................................................................................................... 253

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Supranuclear Pathways for Eye Movements Athiya Agarwal, Amar Agarwal

INTRODUCTION One is always confused about supranuclear pathways. We understand the pathways of the III, IV and VI cranial nerve nuclei. We would be able to trace it from the brain to the superior orbital fissure, but we fail to remember that these pathways we are discussing are the infranuclear pathways which extend from the cranial nerve nuclei to the ocular muscle. We need to also understand the anatomy of the supranuclear pathways.1,2 SUPRANUCLEAR AND INFRANUCLEAR PATHWAYS Anatomical pathways, which extend from the cortical centers of the brain to the cranial nerve nuclei, are called the supranuclear pathways. From the cranial nerve nuclei to the ocular muscle exist the infranuclear pathways (Fig. 1.1). In peripheral nerves, the nerve starts from the brain and reaches the anterior horn cell in the spinal cord. This is the upper motor neuron. From the anterior horn cell of the spinal cord, the nerve moves to the peripheral muscle. This is the lower motor neuron. If there is a lower motor neuron disease the limb is flaccid and if there is an upper motor neuron disease the limb is spastic. The cranial nerve nuclei are like peripheral nerve nuclei. From the cortex of the brain the nerve extends to the cranial nerve nuclei and this is the upper motor neuron (UMN) pathway. From the cranial nerve nuclei the nerve extends to the ocular muscle and this is the lower motor neuron (LMN) pathway. In peripheral nerves if the anterior horn cell gets involved as in poliomyelitis, the patient has a LMN disease and so the limb is flaccid. The anterior horn cell is akin to the cranial nerve nuclei of cranial nerves. So, if the cranial nerve nuclei gets involved the lesion produced will be a LMN lesion.

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Fig. 1.1: Supranuclear pathway

SUPRANUCLEAR EYE MOVEMENT SYSTEMS There are five supranuclear eye movement systems. They are: 1. Saccadic system 2. Pursuit system 3. Vergence system 4. Non-optic reflex system 5. Position maintenance system. SACCADIC SYSTEM The saccadic system is otherwise known as the fast eye movement system or rapid eye movement system. This is because the saccadic system controls the fast eye movements. These are command movements. For example if we say, look to the right, the eyes turn to the right. This occurs rapidly and is a rapid eye movement. The system, which controls this command pathway, is the saccadic system. The saccadic system originates from the frontal lobe of the brain. The impulses then move to the mesencephalic system and so the anatomical pathway subserving the fast eye movements is the

Supranuclear Pathways for Eye Movements

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frontomesencephalic pathway. When you watch someone watching a game of tennis or table tennis, you will notice the eyes move rapidly from one end of the court or table to the other. The eyes keep on darting from one end to the other. These are fast eye movements controlled by the frontomesencephalic pathway. Horizontal Saccades The saccades can in turn be horizontal or vertical. In horizontal saccades, the eyes move horizontally and in vertical saccades, the eyes move up and down. Let us now understand the pathway of the horizontal saccades (Fig. 1.2).

Fig. 1.2: Horizontal saccade pathway LR- Lateral rectus; MR- Medial rectus; LE- Left eye; RE- Right eye; Occ.LobeOccipital Lobe; Fron.lobe- Frontal lobe; III- III Cranial nerve nucleus; VI- VI Cranial nerve nucleus; PGC- Pontine gaze center; MLF- Medial longitudinal fasciculus; UMN Pathway- Upper motor neuron pathway; LMN Pathway- Lower motor neuron pathway

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If the eyes have to look to the right, then the command for this movement is given by the left frontal lobe in area 8 of the cortex. The nerves cross over to the opposite side and reach the right pontine gaze center. From here the nerves pass to the same side (in this case the right) VI nerve nuclei. From the right pontine gaze center nerves also pass to the opposite III nerve nuclei. In this case this will be the left III nerve nuclei. All the cranial nerve nuclei are connected with each other through the medial longitudinal fasciculus or medial longitudinal bundle. In other words from the right pontine gaze center, the nerves pass through the medial longitudinal bundle to the left III cranial nerve nuclei. Till here is the supranuclear pathway. This is why this is also called the frontomesencephalic pathway. From the right VI nerve nucleus nerves then pass to the lateral rectus muscle of the right eye. From the left III nerve nucleus nerves pass to the left medial rectus muscle. These are the infranuclear pathways and both the eyes move to the right. At this stage it is important to understand a bit more on the medial longitudinal bundle. As just explained, the nerves pass from the pontine gaze center to the VI and III nerve nuclei through the medial longitudinal bundle. If there is a lesion in the medial longitudinal bundle, these fibers are cut and there would not be a correlation between the III nerve and the VI nerve. This leads to the condition called internuclear ophthalmoplegia. Vertical Saccades The pathway for the vertical saccades is still doubtful. Vertical saccades depend on simultaneous bilateral activity within the frontal lobes in Area 8 (Fig. 1.3). This means that the horizontal saccades are unilaterally controlled whereas the vertical saccades are bilaterally controlled. If one has to look up or down, impulses travel from both the frontal lobes in Area 8. The impulse travels via the basal ganglia to the pretectal area or the pretectal center for vertical gaze. This is the vertical gaze center. From the vertical gaze center impulses pass to the III nerve nuclei. Till here is the supranuclear pathway. Now, the infranuclear pathway starts and impulses go via the III cranial nerve to the vertical muscles and the patient looks up or looks down. Because of the fact that vertical saccades require bilateral cortical activity, cerebral hemisphere lesions rarely produce deficits in the vertical saccades. Such deficits are seen only with massive hemispheric lesions producing bilateral damage to both frontomesencephalic


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Fig. 1.3: Vertical saccade pathway LE- Left eye; RE- Right eye; Occ.Lobe- Occipital Lobe; III- III Cranial nerve nucleus; VI- VI Cranial nerve nucleus; PGC- Pontine gaze center; MLF- Medial longitudinal fasciculus; UMN Pathway- Upper motor neuron pathway; LMN Pathway- Lower motor neuron pathway

pathways. Disturbances of vertical saccades are much more common with midbrain disorders. Characteristic of the Saccade The characteristic of the saccades is shown in Table 1.1 compared to the other supranuclear eye movements. From the onset of the stimulus, which is voluntary to the beginning of the recorded saccade, the latent period is about 200 to 250 msec. The velocity of the fast eye movement is 30 to 700 degrees/second.

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PURSUIT SYSTEM The smooth pursuit system is utilized when the eyes follow targets that move smoothly and relatively slowly. It maintains a fixed relationship between the movements of the eyes and the target. As smooth pursuit movements directly relate eye position to target position, they are also termed as following or tracking movements. As these movements are slow, they are called slow eye movements. Imagine a person walking and you are watching that person. When your eyes follow the movement of the person, they will be using the pursuit system. The pathway for the pursuit system starts from the occipital lobe and hence is known as the occipitomesencephalic pathway. There are different pathways for horizontal pursuits and for vertical pursuits. Horizontal Pursuit System Pathway If a target is moving to the right (Fig. 1.4), the first step is that the eyes have to visualize the object. So the pathway starts from the retina

Fig. 1.4: Horizontal pursuit pathway (slow phase) LR- Lateral rectus; MR- Medial rectus; LE- Left eye; RE- Right eye; Occ.LobeOccipital Lobe; Fron.lobe- Frontal lobe; III- III Cranial nerve nucleus; VI- VI Cranial nerve nucleus; PGC- Pontine gaze center; MLF- Medial longitudinal fasciculus; UMN Pathway- Upper motor neuron pathway; LMN Pathway- Lower motor neuron pathway


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of both eyes. The impulses pass through the optic nerve, optic chiasma, and optic tract and reach the right occipital lobe in area 19. This area subserves the pursuit movements. It is important to note that the occipital areas mediate horizontal pursuit movements to the ipsilateral side. In other words, the right occipital lobe mediates horizontal pursuit movements to the right. From the occipital lobe, impulses go to the same side pontine gaze center. In this case, impulses from the right occipital lobe go to the right Pontine gaze center. From here impulses go to the right VI nerve nucleus and the left III nerve nucleus. Till here is the supranuclear pathway. From the right VI nerve nucleus and the left III nerve nucleus impulses go via the infranuclear pathway to the lateral rectus and the medial rectus. The characteristics of the pursuits are shown in Table 1.1. Corrective Saccade When the target is moving away from the field of vision the eyes which were moving slowly to that side have to come back to their original position. A fast eye movement does this, in other words a saccade. This is the corrective saccade. If a stream of cars are going in front of our vision, then we keep on following one car and when it goes out of the field of vision our eyes would come and fixate back to the car in the center of our field of vision. This would be done by the corrective saccade. As the impulses from the target moving to the right reaches the occipital lobe (Area 19) and the object is going out of the field of Table 1.1: Characteristics of eye movements

Type

Stimulus (msec)

Latency Velocity (Deg./Sec)

Amplitude Conjugacy (Degrees)

1. Saccade 2. Pursuit 3. Vergence

Volition, reflex Target motion Accommodative, fusional Head movement

200 125 160

30-700 < 50 < 20

0.5-9.0 0-90 Age

10 HU). As a result of the sum of all contrast medium-filled capillaries with an intact blood-brain barrier (BBB), the contrast enhancement of normal brain parenchyma is only 3–5 HU. The BBB represents a property of the pial vessel, where the tight junction of their capillary endothelium prevents a passive diffusion of macromolecules, such as water-soluble contrast medium (Sage and Wilson, 1994). In case of a breakdown of the BBB, whether caused by a tumor or an infection, the continuous endothelial tight junctions are destroyed, and the extravasation of contrast medium into the pathologic process leads to a contrast enhancement (> 5 HU). In CT examination of the orbit, the indication of IV contrast is limited to suspected vascular lesions, as differential diagnosis is mainly led by morphological changes. If indicated, two main contraindications should be considered: 1. A distinct renal impairment may lead to renal failure. The risk of contrast agent-induced renal failure is high in dehydrated patients, in those with a known renal or cardiovascular insufficiency, and in those suffering from plasmocytoma, hypertonus, and hyperuricemia (Katzberg, 1997). Especially in patients with diabetes mellitus and an additional renal insufficiency, the risk of contrastinduced renal failure is about 9 percent (Parfrey et al. 1989). Although no absolute limiting value can be defined, the serum creatinine should not exceed >1.5 mg/dl, and the use of nonionic contrast agent should be standard (Schwab et al. 1989; Uder 1998). 2. In case of a manifest or known history of hyper-thyreosis, an application of iodized contrast material should be avoided. If imperatively necessary, it should be applied only after blockage of the thyroid, in order to avoid a thyrotoxic crisis, still a lifethreatening disease (Kahaly and Beyer 1989). It is recommended to start prophylactic medication at least 2–4 hours before the application and continue it for 14 days, at a dosage of 900 mg perchlorate per day. In patients at risk, a facultative medication with 20 mg Thiamazol per day can be administered additionally (Rendl and Saller 2001). A known allergic reaction to iodine represents a relative contraindication, as short-term medication with H1- and H2-blockers immediately before the exposure to iodized contrast medium can prevent this complication (Wangemann et al. 1988).

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MRI Basic Physical and Technical Principles of Relaxation, Special Sequences Magnetic resonance imaging (MRI) is a method to generate crosssectional images from the interior of the body based on the physical phenomena of nuclear magnetic resonance without using ionizing radiation. Atomic nuclei such as those of 1H, 13C, 14Na, 19F, 23N, and 31P with an odd number of protons and/or neutrons have a magnetic dipole moment. Hydrogen nuclei are abundant in biological tissue, as in the hydrogen atoms of water molecules. This is the reason for the use of hydrogen nuclei in medical MRI. Without the influence of an external magnetic field, the directions of the innumerable single dipoles are randomly arranged such that they cancel each other out, resulting in no macroscopic magnetic dipole moment. However, in the presence of an external static magnetic field, the small nuclear magnetic dipoles tend to align in the direction of the field, like a compass needle to the magnetic field of the earth. The nuclear magnetic dipoles are not aligned statically, rather they are staggering around the direction of the external static magnetic field. This phenomenon can be compared with the tumbling of a top around the direction of the gravitational force. This movement is called precession. The number of revolutions of this precession, designated Larmor frequency, depends on the magnetic moment of the nucleus and the strength of the external magnetic field applied. In case of a 1.5-T MRI scanner, the Larmor frequency of the hydrogen nuclei is 63.87 MHz. This characteristic allows the transfer of energy from an external radiofrequency pulse to the nuclei provided that the frequency is precisely the same. This means that there is a resonance between the transmitter and the macroscopic oscillating magnetic moment, which acts as the receiver. During energy absorption, the precessing nuclear spin axes circumscribe a cone that becomes increasingly flat. This can be illustrated as an exciting nucleus that opens its umbrella. The Brownian motion of molecules leads to a continuous rearrangement of the dipoles, such that statistically only one per million (5 ppm: parts per million) of the hydrogen nuclei are aligned with the direction of an external 1.5-T field at room temperature. After the termination of the applied radiofrequency pulse, the macroscopic magnetic field returns to its prior state by emitting simultaneously decreasing electromagnetic waves with the precessional frequency. These waves emitted during the relaxation are measurable and represent values which are attributed to the brightness of the individual pixels (picture elements) of which the images are composed by the application of sophisticated mathematical reconstruction algorithms.

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There are two types of relaxation. One is the signal decay of the sum vector parallel to the strong external magnetic field, which is termed the longitudinal relaxation or the T1 relaxation. During the T1 relaxation (spin-lattice relaxation), the excess energy is transferred from the nuclei to the environment (the term lattice is derived from crystalline solids and is used here in a broader meaning). The other relaxation is the signal decay of the sum signal vector perpendicular to the strong magnetic field and is designated the transverse or T2 relaxation. In T2 relaxation, there is a dispersion of the primarily synchronized precessional rotation of the spins. One can imagine the spins as an ensemble of ballet dancers, who initially obey the instructions of the maestro and start all in the same position (they are in phase). After this moment, they show a lack of discipline, and each ballet dancer turns a little faster or slower than the others (loss of coherence), resulting in a random distribution of the positions (out of phase). If we return to the spinning direction, at the beginning of this process we can record the net sum vector of all synchronized (in phase) individual spins, with a rapid decay as they go off phase. The loss of coherence is caused by minute local magnetic inhomogeneities around the macromolecules. As the adjacent spins also exchange excitation energy with each other, T2 relaxation is termed spin-spin relaxation. Signals registered from the biological tissue depend on the water or proton concentration that can be excited and on the relaxation characteristics. Pure or so-called free water would show a high concentration of excitable protons and a slow relaxation caused by only slightly restricted tumbling of small molecules. On the other hand, protons bound to macromolecules would show a fast relaxation by dissipating their energy to the environment and a loss of coherence. The MRI characteristics of tissue are defined by the composition of these components, represented in this paper in a simplified manner. Manipulation of the MRI examination parameters enables us to enhance the differences between the local tissues, resulting in a better inherent contrast. The terms T1-weighted (T1w), proton density-weighted (PDw) or T2-weighted (T2w) characterize MRI sequences or images and define the more pronounced biophysical effect of the specific image information. Proton density (PD)–weighted images are similar to T2-weighted images, but have a shorter echo of 10–50 m and are less dependent on the relation than on the concentration of protons, i.e., water concentration in the tissue (Bösiger 1985). The fluidattenuated inversion recovery (FLAIR) sequence combines T2weighting and suppression of the so-called free, not tissue-bound water.

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After intravenous administration of a MRI-specific contrast medium, such as gadopentate dimeglumine (biologically inert as complexly bounded gadolinium, i.e., GD-DTPA® or GD-DOTA®), a different take-up by tissues is seen, analogous to the iodized contrast medium used in CT. The use of contrast medium (in T1-weighted sequences) can further improve the contrast between anatomical details and also between normal and pathological tissues because of its different signal enhancement. If these contrast-enhancing structures are embedded in primarily hyperintense tissue (such as the extraocular muscles, or potential lesions within the retro-orbital fat) the signals will interfere, resulting in a loss of tissue contrast between the anatomical components. This problem can be solved using a pulse sequence that suppresses the high signal of the native hyperintense tissue. In the case of fat, the sequence is designed to be fat-suppressed (FS). Special MRI protocols enable a differentiation of flowing blood from nonmoving tissue (so-called stationary tissue), the basis for MR angiography. In MR angiography, the signal of stationary tissue is suppressed and the signal of flowing blood is enhanced, without any application of contrast material. The so-called diffusion-weighted MRI (DWI) is able to image molecular diffusion. Tissue-bound water has a restricted molecular diffusion compared with free water, due to frequent collisions with macromolecules, in particular proteins. Therefore, tissues with a different viscosity and a different ratio of intra- and extracellular spaces show different diffusion properties. For this reason, diffusionweighted MRI discriminates reliably an arachnoid cyst filled with free water and an epidermoid tumor of solid tissue whereas in conventional sequences, liquor and epidermoid tumor can both give the same signal intensity (Laing et al. 1999; Gizewski 2001). The so-called anisotropic diffusion of water molecules in the fiber pathways, which is much more restricted across the fibers than along them, can also be imaged in different planes (Hajnal et al. 1991). Diffusion-weighted MRI can disclose an acute infarction at a very early stage, and in the case of elderly patients with multiple chronic infarctions, it helps to uncover additional new lesions (Schaefer 2001). It also seems that diffusion-weighted sequences image a cystic tumor different to the central colliquation of an abscess, so offering an additional tool in the differential diagnosis (Kim et al. 1998). Along with a strong and very homogeneous main magnetic field and all devices (antennas or coils) to excite the protons by a radiofrequency pulse and to receive the electromagnetic waves emitted from them, there is a need for a space-encoding system. Temporary,


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superimposed, magnetic gradient fields cause changes of the Larmor frequency and the phase of spin populations in small volumes (voxels), with a precise local attribution. Where the magnetic field is stronger, the precessional frequency is higher, and where the magnetic field is weaker, the frequency is lower. It is possible to identify the location of signal generating spin pools by small space-encoded differences of the frequencies, like distinguishing radio stations. Additional spaceencoded different phases of precessing spin pools are used. For more superficially located structures, such as the orbits, the image resolution can be optimized by using phased-array surface coils instead of the conventional head coil. Surface coils are specially designed antennas, which can be applied near the region of interest and fades out disturbing signals from the environment. In case of an examination of the orbit, they are placed obliquely over both orbits, in order to lighten the orbital apex. It should be emphasized that a relatively small unilateral surface coil (with a diameter of about 4 cm) applied anteriorly over one orbit is only suitable for imaging the ipsilateral globe and does not provide a more posterior “illumination”. Restrictions Ferromagnetic Material, Pacemaker, Neurostimulator, Ventricular Shunts with magnetically adjustable valves. When approaching the temperature of absolute zero, no electrical resistance as e.g., in the coil of the electric magnet is found. For this reason, the most frequently used modern high-field MRI scanners (0.5–1.5 T) today are based on a superconducting coil of the main magnet, a system with a liquid helium-cooled main coil. This strong main magnetic field necessitates a few precautions. Patients with ferromagnetic implants, e.g., older aneurysm or other vessel clips, pacemakers, neurostimulators, and traumatically incorporated metallic-ferromagnetic foreign bodies (e.g. debris arising from working with metal, or old shell splinters), should not be exposed to high-field MRI. In addition to the image quality disturbance caused by the so-called susceptibility artifacts of the ferromagnetic material (Lüdeke et al. 1985) this can endanger the patient (Kanal and Shellock 1993). Whereas metal devices fixed on bone do not present a danger if exposed to MR, ferromagnetic foreign bodies, or clips in the lung, abdomen, eye, and adjacent to vessels can twist due to the strong main magnetic field and lead to a life-threatening complication. Ventricular shunts with transcutaneous magnetically pressureadjustable valves (Medos and Sophy valves) can be maladjusted in MRI, and therefore the systems have to be checked radiologically

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after MRI (Miwa et al. 2001; Ortler et al. 1997). As new magnetcompatible devices (Wichmann et al. 1997) have only been developed in the last decade, MRI is still unavailable to most patients with an implanted pacemaker or neurostimulator. The problems are not only caused because of the fact that these devices are usually magnetically programmable, there is an additional risk from the electrodes, which can act as antennas and interact with the changing electromagnetic fields. One must be always absolutely certain about the individual patient’s magnet compatibility, probably with the result of a rejection of the patient for MRI if there remains any doubt. Claustrophobia, Sedation, Surveillance To perform a MRI examination, it is necessary to bring the entire patient into the narrow shaft of the equipment, as the optimal homogeneity of the magnetic field is in the center of the magnet. Even for an examination of only the head or the orbit, the patient has to be placed deep inside the MRI. This is mainly a problem for claustrophobic patients, and thus they need sedation before the MRI examination. However, a sedated patient placed in this narrow tunnel is not accessible. In case of deep sedation, special magnet-compatible monitoring devices are needed for surveillance, including at least essential peripheral pulse oximetry. In MRI, the acquired data are not separately sampled sections, as for CT, but the data sampling is simultaneous for all sections of one sequence and the acquisition time depends on the examination parameters, e.g., the repetition time chosen. Therefore, one MRI sequence may last only a few minutes or even more than 10 min. If the patient moves during this time, a loss of image quality of all sections results. During MRI of the orbit, the patient should keep the eyes open and try to maintain a midline resting position. Consequently, in the case of uncooperative patients, who are not able to remain motionless, the quality of the images will be impaired. Optic Pathway Pathology • • • •

congenital pathology/infantile presentations acquired optic pathway lesions work-up in systemic diseases unexpected (incidental) fi ndings Any neuroimaging procedure should be based on profound clinical (including ophthalmological if appropriate) examination. This should allow the neuroradiologist to formulate specific questions.


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CONGENITAL PATHOLOGY OF OPTIC PATHWAYS Infantile Presentations Micro-ophthalmos/Anophthalmos Uni- or bilateral micro-ophthalmos/anophthalmos may be seen in various conditions (Albernaz et al. 1997; Nelson et al. 1991). Neuroimaging is performed to assess orbital anatomy, optic chiasm, and posterior visual pathways as well as possible brain malformations Aicardi syndrome, observed only in girls, is considered to result from an X-linked mutation that is lethal in boys. The relevant triad consists of a typical optic disk appearance with “chorioretinal lacunae”, infantile spasms, and agenesis of the corpus callosum (Aicardi 1992; Brodsky et al. 1995). In addition, other central nervous system malformations are always present, in particular migration anomalies (heterotopias, polymicrogyria) and midline arachnoid cysts. Ocular Tumors Retinoblastoma is the most common intraocular tumor in infancy, affecting about 1 in 20,000 infants. The most frequent presenting symptom is leukokoria, also called “cat’s eye reflex”. Leukokoria generally represents an advanced stage of the disease. Computed tomography (CT) (Fig. 19.1) displays punctate or more homogeneous areas of calcification in 95 percent of retinoblastomas (Barkovich 1995). Contrast enhancement of tumor tissue is generally found. Contrast enhancement is also demonstrable with MRI. T1-weighted images reveal the tumor as hyperintense, T2-weighted images usually as a hypointense mass Proton density images may assist in the demarcation of the tumor. MRI can occasionally provide evidence of distal optic nerve infiltration. A large proportion of retinoblastomas are genetically determined, and about a third occurs bilaterally. When tumoros tissue is also demonstrated in the pineal region by neuroimaging, it is termed trilateral retinoblastoma. This may already be present on initial evaluation. Spasmus Nutans So-called spasmus nutans typically presents at 6–12 months with disconjugate nystagmus, torticollis, and findings have been seen in girls.

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Figs 19.1: CT scan showing trilateral retinoblastoma

Other White Matter Disorders Apart from PMD, other dysmyelinating conditions can present with congenital nystagmus. The exact genetic/biochemical basis of these rare conditions is still unknown. Septo-optic Dysplasia Septo-optic dysplasia (SOD) typically presents as congenital nystagmus. Fundus examination reveals bilateral optic nerve hypoplasia. In addition, the syndrome consists of an absence of the septum pellucidum (Hypothalamic-pituitary dysfunction is present in a minority of patients, presenting as neonatal hypoglycemia and/or growth retardation (Sorkin et al. 1996). The prognosis is quite variable, ranging from blindness to useful vision. Affected children may be mentally retarded. In some children, additional CNS malformations can be found, in particular hypoplasia of the corpus callosum and cortical dysplasia (Sener 1996). SOD is unlikely to be a homogeneous entity. Hypoplasia of the optic nerves and absent septum are also seen as part of the holoprosencephaly complex (Barkovich 1995). The septum pellucidum is also mostly missing in rhombencephalosynapsis. It is suggested that SOD is a vascular disruption sequence (Lubinsky 1997).


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Optic Nerve Hypoplasia Hypoplasia of the optic nerves may be unilateral or bilateral (Figs 19.2 and 19.3). It is not a clinical or pathogenetic entity. We have seen several children with unilateral optic nerve hypoplasia presenting to the ophthalmologist with “poor vision” or strabismus. The intracranial anterior optic pathways are usually markedly asymmetric, but additional anomalies are exceptional.

Figs 19.2A and B: (A) Axial, (B) coronal T2-/FSE MRI of a 3-month-old-girl without visual fixation. Absent septum pellucidum and almost no identifiable optic nerves. Diagnosis: septo-optic dysplasia

Figs 19.3A and B: Patient clinically blind at 1 year (A) Axial, (B) coronal T2-/FSE MRI of a 4-year-old boy. Clinically convergent strabismus and bilateral optic nerve hypoplasia. MRI shows absent septum pellucidum. Diagnosis: septo-optic dysplasia

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Periventricular Leukomalacia Periventricular leukomalacia (PVL) is a well-known complication of prematurity before 34 weeks’ gestational age. PVL affects primarily the posterior part of the hemispheric white matter. Clinically, it may go along with spastic diplegia type of cerebral palsy and is often accompanied by delayed visual development (Jacobson et al. 1996; Lanzi et al. 1998; Olsen et al. 1997). MRI allows the detection of specific residual findings: variable reduction of periventricular white matter predominantly involving the posterior aspects, increased size of lateral ventricles, often with an irregular contour (evacuo). The remaining white matter often shows increased T2 signal, presumably corresponding to gliosis. Multiple Sclerosis It is estimated that about 2 percent of patients with multiple sclerosis (MS) present during childhood. Presenting symptoms may be variable such as muscular weakness, gait abnormalities, visual symptoms, and seizures (Ghezzi et al. 1997; Hanefeld 1992). Imaging findings in pediatric MS are not considered to be different from those in adults (Barkovich 1995). Acute Disseminated Encephalomyelitis Acute disseminated encephalomyelitis (ADEM) or parainfectious encephalomyelitis is considered an autoimmune response. This hypothesis is supported by the fact that the gross pathologic and histologic manifestations resemble those of experimental allergic encephalitis. ADEM involves primarily white matter but can also affect cortical and deep gray matter. Children typically develop acute focal neurologic signs and/or seizures late in the course of a viral illness or post vaccination). Neuroimaging reveals usually multiple foci of T2 hyperintensities; these may be circumscribed, confluent, or occasionally affect white matter diffusely (Murthy 1998). Various patterns of contrast enhancement may be found in the acute/subacute phase. Differentiation of MS from ADEM is not always possible in the beginning. The prognosis of ADEM is favorable as a rule, leading to complete clinical recovery, both from the clinical and the neuroimaging points of view. Occasionally, sequelae can be found. Trauma (Nonaccidental Injury) Injuries to the optic pathways due to head trauma will not be discussed here. However, we would like to point to so-called nonaccidental


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injury by shaking infants less than 6 months of age. The typical presentation is impaired consciousness and convulsions, often resulting in status epilepticus. Typically, bilateral retinal hemorrhages are present. Extensive cerebral damage in this condition usually results in permanent neurological sequelae including visual impairment or even cortical blindness (Ewing-Cobbs et al. 1998). The neuroimaging correlation in the acute stage is not spectacular, with evidence of brain swelling and often some interhemispheric blood accumulation. Followup neuroimaging as a rule demonstrates extensive cerebral atrophy. Neurofibromatosis Type 1 Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder due to mutations in the very large NF1 gene at chromosome 17q11. About 50 percent of patients have new germ-line mutations, i.e. they have no positive family history. The prevalence in most populations is about 1:4000 individuals. As is evident from the listing of diagnostic criteria optic pathway glioma (OPG) is such a criterion. OPG are tumors of infancy; in larger series, the mean age at diagnosis is 4–5 years (Figs 19.4A and B). Diagnostic criteria for neurofibromatosis type 1 The presence of two or more of the following is diagnostic: 1. Six or more café-au-lait spots, greater than 5 mm in diameter in prepubertal children and over 15 mm in post-pubertal individuals. 2. Two or more neurofibromas of any type, or one plexiform neurofi broma. 3. Axillary and/or inguinal freckling. 4. Optic nerve glioma. 5. A distinctive osseous lesion, such as dysplasia of the sphenoid wing, thinning of long bone cortex, with or without pseudarthrosis. 6. A first-degree relative (parent, sibling, or offspring) with NF1 according to the above criteria. OPG are pilocytic astrocytomas. It is important to distinguish astrocytomas from benign lesions commonly encountered in NF1: T2 hyperintensities are often found in the basal ganglia (particularly globus pallidus), brainstem, and cerebellum, not enhancing with contrast and not having space-occupying effects. Mild proptosis is not uncommon in NF, even in the absence of an optic nerve glioma. It can be related to sphenoid wing dysplasia, but often no obvious explanation is evident. Neurofibromatosis Type 2 Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder due to mutations at chromosome 22q12. The involvement of the brain

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Figs 19.4A and B: (A) Sagittal T1-weighted, MRI of a 26-year-old patient with NF1. (B) Asymmetrical optic chiasm glioma known for 12 years

structures in NF1 and NF2 are quite different: While NF2 consistently affects the acoustic/vestibular nerve, this is never encountered in NF1. NF2 is not associated with optic pathway gliomas. • Diagnostic criteria for neurofibromatosis type 2. The following are diagnostic: 1. Bilateral vestibular schwannomas; or 2. A first-degree relative with NF2 (Figs 19.5A and B), and either a unilateral vestibular schwannoma or two of the following: meningioma (Figs 19.6A and B), schwannoma, glioma, neurofibroma, posterior subcapsular lens opacity, or cerebral calcification; or 3. Two of the following: unilateral vestibular schwannoma multiple meningiomas either schwannoma, glioma, neurofibroma, posterior subcapsular lens opacity, or cerebral calcification. INTRACRANIAL PATHOLOGY OF THE VISUAL PATHWAY Intrinsic Lesions, Glioma in Adults The term glioma stands for the corresponding three types of glial cells. The three major types of gliomas originate from: astrocytoma oligodendroglioma and ependymoma and the so-called mixed gliomas that contain two or more different cell types in varying proportions, most frequently primarily oligoastrocytoma (Okazaki 1989), whereas intraventricular choroid plexus papilloma and carcinoma are distinct from ependymoma (Kleihues and Cavanee 2000).


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Figs 19.5A to D: T1-weighted, contrast-enhanced MRI of newly diagnosed NF2 in a 14-year-old girl. MRI shows bilateral acoustic neuromas, meningioma at tip of left temporal lobe, mass (presumably a meningioma) in suprasellar/left parasellar/ sphenoid area

Figs 19.6A and B: (A) Axial plain CT, (B) axial CT following administration of contrast medium in a 14-year-old-patient prompted by new onset of diplopia. Plain CT reveals calcifying right optic nerve sheath meningioma. Following contrast: left frontal meningioma

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Extra-axial Tumors Due to the fact that extrinsic (or extra-axial) tumors are frequently benign, the treatment and prognosis are based upon the correct diagnosis of suspected intracranial extrinsic masses. The use of MRI is mandatory for these tumors because it has the ability to differentiate the boundary between the brain parenchyma and the mass itself. The superior contrast resolution and multiplanar imaging capacity of MRI enable the identification of anatomic markers as cardinal features of an extra-axial lesion. Instead of the demonstration of the tissue contrast of extrinsic masses and brain parenchyma, the definition of boundary layers between the tumor and the brain surface permits the diagnosis of an extra-parenchymal intracranial lesion. The boundary layers represent cerebrospinal fluid (CSF), pial blood vessels, and/or the dura. CSF clefts are recognized as crescentic bands, frequently only over a portion of the tumor, with signal intensities similar to those of spinal fluid: low on T1-weighted, isointense on proton densityweighted, and high on T2-weighted images. In SE sequences, both normal anatomic and pathologic vessels are identified as rounded or curvilinear signal voids at specific locations of the lesion margin. The use of i.v. contrast agents enables the demonstration of the compartmentalization of extrinsic lesions, since a large number of tumors show a specific pattern, including extensive signal enhancement (meningioma, metastasis), while others show none (epidermoid and dermoid tumors) (Goldberg et al. 1996). Metastasis Intracranial metastasis or secondary brain tumors are defined as tumors involving the CNS and originate from, but are discontinuous with, primary systemic neoplasms. They account for 15 to 30 percent of all intracranial tumors in pathologic series (Okazaki 1989; Nelson et al. 2000). The most frequent primary malignancies include lung carcinoma (40% metastasize to the brain), breast carcinoma (roughly 25 percent metastasize to the brain) (Figs 19.7 and 19.8), hypernephroma, melanoma, and neuroblastoma, the latter occurring predominantly in children. All areas of the brain may be affected, with preference for the corticomedullary junction as the starting point (Okazaki 1989), possibly due to greater capillarization of this region (Zülch 1986). The sellar region is the preferred location for hematogenous spread of primary carcinoma of extracranial origin. In addition to the convexity of the brain and/or cerebellum, leptomeningeal tumor cells deposit in the recess of the third ventricle but may also invade the parenchyma of the hypothalamus and/or chiasm.


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Fig. 19.7: A 35-year-old woman with acute vision loss, predominantly of the right eye, and a history of breast carcinoma. Diagnosis: intra- and suprasellar metastasis. MRI: Axial T2-weighted FLAIR sequence showing edema of the chiasm and both optic tracts

Figs 19.8A to D: A 38-year-old-woman with chiasm syndrome, diabetes insipidus, and a history of breast carcinoma. Diagnosis: hypothalamic and chiasmal metastasis of breast carcinoma. T1-weighted MRI: (A) Axial native view showing a slightly hypointense lesion dorsal to the chiasm with apparent invasion. (B) Corresponding contrast-enhanced view, identifying invasion of the chiasm and the proximal optic tracts. (C) Coronal native view. (D) Midsagittal contrastenhanced view, demonstrating metastatic spread throughout the hypothalamus and pituitary stalk (D with permission of Müller-Forell 2001)

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SELLAR TUMORS Corresponding to the various tissues, a number of pathologic processes may occur. More than 30 different pathologic entities, primarily extrinsic lesions, involving and affecting structures of the sellar and juxtasellar region have been described (Osborn and Rauschning 1994). These tumors involve the brain parenchyma secondarily and are often cured completely without recurrences even if the lesion has reached a considerable size. Intrinsic brain tumors, which often show a recurrent clinical course even for benign tumors, develop less frequently in the sellar region. Gliomas of the Chiasm Gliomas of the anterior visual pathway, histologically defined as pilocytic astrocytoma are uncommon lesions, but account for approximately 65 percent of intrinsic tumors of the optic nerve. These lesions most frequently occur in children in the first decade of life (Dutton 1994), whereas only 10 percent present in patients older than 20 years (Wulc et al. 1989). As most of these gliomas are located in the intraorbital and intracranial part of the optic nerve (Fig. 19.9), additional involvement of the chiasm is seen in about 75 percent of patients However, only 7 percent occur in the chiasm itself, and 46 percent involve both the chiasm and hypothalamus the latter increasing the mortality rate to over 50 percent, since no specific therapy alters the final outcome (Dutton 1994). They are not associated with NF 1 and uniformly show a fatal course of usually less than 1 year (Rush et al. 1982; Mason and Kandal 1991; Dutton 1994; Hollander et al. 1999). Imaging Characteristics: MRI as the method of choice relaxation times. In macroadenomas, MRI enables a high anatomic resolution and definition of the neighboring tissue, i.e. intracranial optic nerves, chiasm, and cavernous sinus. In most cases, native, non-contrastenhanced images allow accurate and conclusive differentiation of the tumor and deformed, compressed, flattened visual structures of the optic of the pre- and post-contrast images does not routinely enable the definite prediction of tumor invasion of the cavernous sinus. Only a carotid artery encasement or an extension lateral of the cavernous sinus towards the temporal lobe is a reliable indicator of cavernous sinus invasion.


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Figs 19.9A to F: MRI: (A) Axial T2-weighted view with a very large, space-occupying, isointense lesion located in a widened suprasellar cistern, depressing and spreading the basal vessels, (B) Coronal T1-weighted native view demonstrating pressure exertion on the widened third ventricle by the central hypointense (necrotic) tumor, (C) Midsagittal, T1-weighted, contrast-enhanced view with demarcation of the entire enhancing tumor, compressing and displacing the brainstem, and extending into the posterior fossa. Note widening of the entrance of the otherwise normally configured sella (arrow), (D) Coronal native view with intra- and suprasellar lesion and inferior chiasmal compression. Note the slightly hypointense signal in the sphenoid sinus, (E) Corresponding contrast-enhanced view with inhomogeneous contrast enhancement of the intra-/suprasellar, apparently encapsulated lesion, but homogeneous enhancement in the sphenoid sinus. CORR = Sponding to sinus inflammation, note the small leptomeningeal enhancement at the base of the left frontal lobe (arrow), (F) Axial contrast-enhanced view with necrotizing, encapsulated tumor and leptomeningeal enhancement of the basal frontal sulci (arrows)

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Meningiomas Meningiomas (Fig. 19.10) associated with hereditary tumor syndrome such as schwannoma (i.e., in patients with NF2) (Woodruff et al. 2000) mainly occur in younger patients. Approximately 20 percent of meningiomas are located in the sellar region, with 50 percent arising from midline structures such as the sphenoid plane tuberculum sellae diaphragm sellae, or the dura of the cavernous sinus Globular meningiomas of the suprasellar or paraclinoid region may produce early ophthalmological symptoms because of optic nerve.

Figs 19.10A to C: MRI: (A) Axial view in the region of the chiasm, visualizing the superior region of the right sphenoid wing meningioma and an ipsilateral temporal meningioma. Note the susceptibility artifacts after left temporal craniotomy. (B) Coronal view at the cavernous sinus, showing the entire circumference of the meningioma of the right anterior clinoid process. Note the left temporobasal parenchyma defect after initial surgery. (C) Coronal view in the region of the chiasm with tumor extension to the right chiasmal region. Another frontal meningioma is demarcated in addition to the known temporal meningioma or chiasmal compression and therefore do not normally exceed 2 cm in diameter


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Imaging Characteristics: Due to their high cell density and psammomatous calcification, meningiomas of the sellar region present on CT as isodense to hyperdense midline lesions. Diffuse hyperostosis is particularly apparent on CT images of en plaque meningioma). A perifocal edema is detected only in the rare cases where the cerebral cortex is destroyed by this tumor Apart from the differentiation of pituitary adenomas, where a trans-sphenoidal approach is the preferred operative procedure, the most important question for neurosurgeons is the possible invasion of the cavernous sinus and/or narrowing of the ICA, which is best addressed by MRI. Craniopharyngioma They are assumed to arise from Rathke’s pouch epithelium and account for 1.2-4.6 percent of all intracranial tumors and thus represent the second most frequent tumors of the sellar region after pituitary adenomas. Craniopharyngiomas (Figs 19.11A to D) show no sex bias but a bimodal age distribution, with one peak involving children and adolescents and another one involving adults (Adamson et al. 1990; Crotty et al. 1995). A clinicopathologic distinction is made between adamantinous and papillary craniopharyngioma. Most adamantinomas are hormone-inactive lesions and present as solid tumors with a variable, at times predominantly cystic component, containing cholesterol-rich, thick, brownish-yellow fluid with the appearance of machine oil. Imaging Characteristics: CT in the axial and coronal views is still justified for the basic and differential diagnosis of craniopharyngiomas, in view of the characteristic calcification of parts of the tumor seen in 50-70% of cases Even in the absence of calcification, the solid tumor parts appear hyperdense with prominent contrast enhancement, whereas the cysts seem isodense to CSF and may show enhancement of the wall MRI enables superior delineation of the tumor extent, especially on the coronal and sagittal views Morphology and signal patterns are marked by great variety: adamantinous craniopharyngioma primarily shows a combination of T1-weighted hypoin-tense and T2-weighted massive hyperintense signal character, (whereas in papillary craniopharyngioma, a hyperintense signal on T1-weighted and hypointensities on T2-weighted sequences may dominate. The solid tumor parts of both types generally show a hyperintense signal on T1-weighted images and prominent enhancement of the tumor and cyst wall).

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Figs 19.11A to D: (A) Coronal, T1-weighted, contrast-enhanced image with caudal depression of the third ventricle by the predominantly suprasellar, cystic tumor. The contrast-enhanced capsule is visualized, while the chiasm is not seen. (B) Midsagittal view with differentiation of the pituitary stalk (star). Note the depression, dislocation, and deformation of the brainstem. (C) Axial T2-weighted image demonstrating the high proton content (high signal) of the oily fluid content of the cystic tumor region. Note the deformed brainstem. (D) Corresponding T1weighted, contrast-enhanced image where a remnant of the chiasm (confirmed on operation) is seen at the medial right tumor surface (arrow)

Astrocytomas Astrocytic tumors, represent the most frequent entity of primary brain tumors with up to 60 percent of all intracranial neoplasms and comprise a wide range of age and gender distribution, growth potential, extent of invasiveness, morphological features, tendency for progression, and clinical course (Okazaki 1989; Cavanee et al. 2000). Astrocytomas primarily manifest in adults and may arise at any site of the CNS, exhibiting a wide range of histopathological features and


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biological behavior. Astrocytomas include, e.g. pilocytic and subependymal giant cell astrocytoma (both WHO I), diffuse low grade astrocytoma (WHO II), anaplastic astrocytoma (WHO III), and glioblastoma (WHO IV). These different entities reflect the type and sequences of genetic alterations acquired during the process of transformation, where the progression from low grade to anaplastic astrocytomas and glioblastomas is associated with the cumulative acquisition of multiple genetic alterations (Cavanee et al. 2000). Pilocytic Astrocytoma (WHO I) Pilocytic astrocytomas (WHO I) should be differentiated from diffuse growing astrocytomas as they are more circumscribed, slow-growing lesions with different location, morphology, genetic profile, and clinical behavior. High Grade Glioma Diffuse astrocytoma (WHO II) is characterized by a high degree of cellular differentiation, slow growth, and diffuse infiltration of the adjacent brain structures. It has a tendency for malignant progression to anaplastic astrocytoma and, ultimately, glioblastoma). Most of these patients are adults (presenting with seizures and clinical symptoms, depending on the localization. Imaging Characteristic: Although most glial tumors arise from a segment of only one gyrus (Yasargil 1994), the affected parenchyma (usually white matter, but an involvement of gray matter is often seen) demarcates an ill-defined area, hypodense on CT. On MRI, astrocytomas mostly present as mildly hypointense on T1-weighted and hyperintense on T2-weighted, due to the fact that they represent a degenerative microcystic formation, filled with clear fluid, and an irregular, not always clearly distinguished perifocal edema. Metastasis Secondary lesions should always be included in differential diagnostic considerations of extrinsic and even intrinsic tumors of the sellar region, particularly with a view to the capacity of some primarily extracranial tumors to involve the skull base (percontinuitatem) or be hematogenous. Metastases involving the cavernous sinus predominantly arise from malignant tumors of the nasal cavity, growing perineurally or perivascularly via the basal foramina.

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Imaging characteristics are nonspecific and similar to those encountered in more common tumors of the sellar region. Cavernoma (Syn. Cavernous Hemangioma) of the Cavernous Sinus They present as well-defined tumorous lesions with a homogeneous, intermediate signal on T1-weighted views, a hyperintense signal on T2-weighted sequences, and homogeneous, massive enhancement after gadolinium administration. The Tolosa-Hunt syndrome The Tolosa-Hunt syndrome (THS) is an inflammatory disease of unknown origin, limited to the superior orbital fissure and the cavernous sinus (Smith and Taxdal 1966). The presentation of cranial nerve paresis of one or several of the cranial nerves passing the cavernous sinus (N III, N IV, N VI, and N V1) may coincide with the onset of orbital pain or follow it within a period of up to 2 weeks. The pain must be relieved within 72 hours after steroid therapy. Although high resolution CT or MRI can neither exclude nor confirm THS when a lesion compatible with an inflammatory process is visualized, other causative lesions as, e.g. a malignant tumor must be excluded. Clinical and neuroradiological follow-up must be done for at least 2 years, even in patients with negative findings on imaging at onset. Cystic Lesions In the differential diagnosis of suprasellar tumorlike lesions, arachnoid cyst and epidermoid cyst play some important role, along with Rathke’s cleft cyst and hypothalamic hamartoma. Rathke’s cleft cyst, a benign epithelium-lined cyst arising from remnants of Rathke’s pouch, may become symptomatic in the case of intra-and suprasellar extension, a rather rare condition (Rose et al. 1992). On MRI, signal intensities vary with cyst content from serous to mucoid (Osborn 1994b). Arachnoid cysts account for about only 1 percent of all intracranial space-occupying lesions, but 10 percent arise in the suprasellar region (Armstrong et al. 1983). Arachnoidal cysts are filled with CSF; the etiology of these mainly congenital lesions remains poorly understood and controversial, but meningeal mal-development is preferred, so that minor aberrations of CSF flow through the loose, primitive, perimedullary mesenchyme are considered to result in a focal splitting of leptomeninges and the formation of a diverticulum or blind pocket


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within the arachnoid membrane (Schachenmayr and Friede 1979; Becker et al. 1991). As an arachnoid cyst is a well-defined, sharply demarcated, extra-axial formation filled with CSF, MRI signal characteristics correspond with hypointense signal on T1-weighted and hyper-intensity on T2-weighted images. Epidermoid cysts probably arise from inclusion of ectodermal epithelial elements at the time of neural tube closure (accounting for 0.2–1% of all primary intracranial tumors, 7 percent of them in the suprasellar region (Osb or n 1994b). Imaging of these well-delineated, tumor-like cystic lesions is not always able to differentiate them from arachnoid cyst, especially since the MRI signal intensities are similar to CSF in every conventional sequence. DWI confirms the diagnosis. Multiple Sclerosis The onset of MS usually occurs in patients aged from 20 to 40 years (15% before 20 years of age, 10 percent after 50 years) with a female predominance. Most often, the first and only clinical symptom consists of impaired vision, presenting as retrobulbar neuritis (RBN), followed or combined with fluctuating periods of sensomotoric or gait disturbances. The clinical course of disease progression can be divided into a relapsing-remitting and a chronic progressive form (Heaton et al. 1985). For the diagnosis of MS recently published new guidelines on diagnostic criteria of MS enable the physician to define the diagnosis for MS, possible MS or nor MS, replacing the diagnostic criteria of Poser et al from 1983 (McDonald et al. 2001). These guidelines include the evidence of dissemination in time and space of lesions typical for MS, objectively determined with clinical and imaging signs. The obtained imaging criteria for MS should require evidence of at least three of the four following findings: 1. One gadolinium enhancing lesion or nine T2-hyperintense lesions if there is no gadolinium enhancing lesion, 2. At least one infratentorial lesion, 3. At least one juxtacortical lesion, 4. At least three periventricular lesions. Additional fi ndings of CSF abnormalities with the presence of autochtone IgG production (oligoclonal bands) (McLean et al. 1990), lymphocytic pleocytosis, and abnormal VEP, typical for MS (delayed but with well preserved wave form) provide supplement information (Halliday 1993) to clinical finding of neurological disturbances typical for MS. Imaging Characteristics: MRI is the imaging tool of choice in suspected demyelinating disorders (Sartor 1992; Osborn 1994f; vander Knaap

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and Valk 1995a; Edwards-Brown and Bonin 1996; McDonald et al. 2001). Although the sensitivity in detecting MS lesions is about 85 percent (Lee et al. 1991), the correlation of neurological symptoms and localization of imaging findings is generally poor as most foci are clinically silent (Barkhof et al. 1992), but in some cases a correlation of clinical and imaging findings is probable The imaging protocol should include axial and sagittal PD/T2-weighted and FLAIR sequences, where the demyelinated areas demonstrate a high signal (Filippi et al. 1999a; Reiche et al. 2000). The sagittal view is best in order to show the characteristic periventricular/ pericallosal, ovoid lesions (so-called Dawson’s finger), caused by the centripetal course of the medullary veins, representing the perivascular inflammation (Horowitz et al. 1989). T1-weighted native and contrast-enhanced sequences demonstrate acute or recurrent inflammatory lesions, which normally enhance contrast media, caused by BBB disruption (Paty 1997; Fazekas et al. 1999; Reiche et al. 2000). involvement including the optic chiasm and nerves is the most common site of affection (Mirfakhraee et al. 1986; Okazaki 1989). Depending on the character of the lesions (solitary, multiple, or diffuse disseminating), imaging findings may resemble multiple sclerosis, systemic lupus erythematosus (SLE), non-Hodgkin lymphoma (NHL) or even inflammatory affections like tuberculous menengitis) (Edwards-Brown and Bonin 1996; Woitalla et al. 2000). As periventricular signal intense lesions are seen in about 50 percent of the patients, the differential diagnosis from multiple sclerosis may be difficult, but a possible additional leptomeningeal involvement makes the diagnosis of sarcoidosis more likely (Hayes et al. 1987; Zajicek et al. 1999; Woitalla et al. 2000). In solitary or multiple lesions which often demonstrate a contrast enhancement and show a preference for the diencephalon (the floor of the third ventricle, hypothalamus) and suprasellar region, solid tumors of the suprasellar region should be taken into consideration in the differential diagnosis, along with multiple metastasis, NHL, or Langerhans’ cell histiocytosis 67 percent of patients with sarcoidosis, leptomeningeal and/or ependymal involvement is found. Toxoplasmosis Corresponding to pathological changes, a “target” appearance of the solitary or multiple ringenhancing masses with perifocal edema is common. Rim or focal nodular enhancement following contrast administration are seen on CT and also on MRI. The most important,


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but sometimes hardly distinguishable differential diagnosis is from primary CNS lymphoma (Dina 1991). While a periventricular location and subependymal spread favor lymphoma, more than one lesion, preferentially adjacent to or in the region of the basal ganglia, make toxoplasmosis likely (Osborn 1994g). Acute Disseminated Encephalomyelitis (ADEM) In contrary to multiple sclerosis, ADEM is characterized by an acute monophasic disorder, predominantly occurring following a viral infection or vaccination with a mean latent period of 4-6 days or several weeks; sometimes it is seen without recognized antecedent. ADEM may occur at any age, but shows a preference for children or young adults (Consequently, the simultaneous occurrence of polytopic neurological symptoms such as hemi-, di- or tetraplegia, cerebellar ataxia or cranial nerve palsies, combined with optic neuritis and bladder dysfunction, may lead to the correct diagnosis. As in all demyelinating diseases, MRI shows best the mainly subcortical, confluent, bilateral but slightly asymmetric hyperintense foci on T2-weighted images. Consequently, along with the monophasic clinical symptoms, if BBB disruption is apparent, a similar enhancement of the lesion is seen, in contrast to MS, where only acute foci show a T1 time shortening with signal enhancement. BIBLIOGRAPHY 1. Aicardi J. Diseases of the nervous system in childhood, (2nd edn) MacKeith, Leeds 1998. 2. Albermaz VS, Castillo M, Hudgins PA, Mukherji SK. Imaging findings in patients with clinical anopththalmos. AJNR Am J Neuroradiol 1997;18:555–61. 3. Alsnall E, Rutka JT, Becker LE, Hoffman HJ. Optic chiasmatic-hypothalamic glioma. Brain Pathol 1997;7:799–806. 4. Arnoldi KA, Tychsen L. Prevalence of intracranial lesions in children initially diagnosed with disconjugate nystagmus (spasmus nutans). J Pediatr Ophthalmol Strabismus 1995;32:296–301. 5. Atkinson J. Human visual development over the first 6 months of life. A review and a hypothesis. Hum Neurobiol 1984;3:61–74. 6. Bajaj SK, Kurlemann G, Schuierer G, Peters PE. CT and MRI in a girl with lateonset ornithine transcarbamylase deficiency: case report. Neuroradiology 1996;38:796–9. 7. Barkovich AJ. Pediatric neuroimaging, (2nd edn). Raven, New York 1995. 8. Krenning EP, Kwekkeboom DJ, Bakker WH, Breeman WA, Kiji PP, Oei HY, van Hagen M, Postema PT, de Jong M, Reubi JC. Somatostatin receptor scintigraphy with (111-INDTPA-D Phe 1)- and (1231– Tyr3)-octreotide: the Rotterdam experience with more than 1000 patients. Eur J Nucl Med 1993;20: 716–31.

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Index Abducent nerve 132 clinical features deviation 135 diplopia 135 head posture 135 ocular movements 135 course 132 cavernous sinus 134 orbit 134 superior orbital fissure 134 exit from the brain 132 lesions 136 nucleus 132 Aberrant regeneration of oculomotor nerve 121 Acute disseminated encephalomyelitis 236, 251 Adrenaline test 67 Alexander’s law 34 Amaurotic pupil 60 Anatomy of the supranuclear pathways 1 Anophthalmos 223 Aplasia 151 Argyll Robertson pupil 63 Astrocytomas 246

Carotid-cavernous fistula 216 Cavernoma 248 Cavernous sinus syndrome 121, 126, 137 Central Horner’s syndrome 67 Cerebellar disorder 30 Cerebellopontine angle tumor 147 Chronic progressive external ophthalmoplegia 200 Ciliary ganglion 114, 115 Claude’s syndrome 120 Cocaine test 67 Coloboma of optic disk 153 Computed tomography 226 contrast medium 227 principles 226 Conjugated palsies 18 lesions of the basal ganglia overactivity 22 underactivity 22 lesions of the collicular area 22 lesions of the frontal cortex 18 bilateral underactivity 21 overactivity 18 unilateral underactivity 20 Craniopharyngioma 205, 245 Cuneus 83 Cystic lesions 248

B

D

Bell’s palsy 149 Benedict’s syndrome 119 Bergmister’s papillae 152 Behr syndrome 186 Bielschowsky’s head tilting test 127 Blepharospasm 201 Botulinum toxin injection 139 Brainstem syndrome 136 Breughel syndrome 202

Darkness reflex 59 Diplopia 126, 135 Dissociated palsies 23 vertical 27 Doll’s head phenomenon 50

A

C Calcarine sulcus 82 Caloric test 43

E Enophthalmos 66 Examination of a neuroophthalmology case 219 direct light reflex 220 examination 219

254


indirect light reflex 220 near reflex 221 CNS examination 225 confrontation visual fields 221 diplopia charting 222 fundus examination 223 Hess charting 222 nystagmus 223 ocular movements 221 other cranial nerve examination 224 reflexes 225 visual fields 223 past history 219 pupil examination 220 swinging flash light test 220 testing of color vision 220

F Facial anhydrosis 67 Facial myokymia 203 Facial nerve course 145 lesions 147 nucleus 145 Foster Kennedy syndrome 192 Foville’s syndrome 137 Functional visual loss 211

G Geniculate ganglionitis 148 Gliomas 157 of the chiasm 242 high grade 247 Gradenigo’s syndrome 137

H Headache 206 Hemifacial spasm 202 Hess charting 222 Heterochromia iridis 67 Hippus 71 Horner’s syndrome 66 Hummelsheim’s operation 139 Hutchinson’s pupil 65, 120 Hydroxyamphetamine test 67

Hyperdeviation 126 Hypoplasia 151

I Intermediary tissue of Kuhnt 107 International Headache Society 208 Internuclear ophthalmoplagia 4, 23 classification 24 etiology 24 Intracranial aneurysms 214 Intracranial pathology 238 extra-axial tumors 240 glioma 238 metastasis 240 Ischemic optic neuropathy 193 arteritic anterior classic signs 193 differential diagnosis 194 etiology 193 management 195 symptoms 194 posterior 195 Isolated fourth nerve palsy 126 Isolated ipsilateral tear deficiency 149 Isolated sixth nerve palsy 138

J Jensen operation 139 Juvenile pilocytic astrocytoma 157

K Kearns-Sayre syndrome 200 Kjer syndrome 186

L Lateral geniculate bodies 79, 87 Lesions of visual pathways 93 lateral geniculate body lesions 98 optic nerve type field defect 93 arcuate nerve fiber bundle 94 bitemporal hemianopia 96 central bitemporal hemianopia 96 junctional scotoma 96 lower temoporal quantrantic defects 98

Index nasal nerve fiber bundle defects 95 papillomacular bundle 93 upper temporal quadrantic defects 97 optic radiations and visual cortex lesion 99 occipital lobe lesion 100 parietal lobe lesions 100 temporal lobe lesions 99 Lid apraxia 203 Light-near dissociation 64

M Macular fibers 87 Magnetic resonance imaging 228 claustrophobia, sedation, surveillance 232 optic pathway pathology 232 restrictions 231 Malignant gliomas of the optic nerve 169 clinical features 169 pathology 170 prognosis 170 radiology 170 Marcus gunn pupil 61 Meige’s syndrome 202 Meningiomas 244 Metastasis 247 Meyer’s loop 81 Micronystagmus 34 Micro-ophthalmos 233 Migraine 206 Millard-Gubler syndrome 136 Miosis 66 Morning glory syndrome 155 Multiple sclerosis 236, 249 Myelineated nerve fibers 152 Myotonic dystrophy 201

N Nasal fibers 86 Neurofibromatosis 237 Non-optic reflex system disorders 30 Nothnagel’s syndrome 119 Nuclear fascicular syndrome 125

255

Nuclear third nerve paresis 118 Nystagmus 32 central 51 cerebellar 51 deviational 36 hysterical 51 idiopathic congenital 52 jerky 34 neutral zone 34 null zone 34 nystagmus blockage syndrome 52 ocular 35 optokinetic 36-38 pathological ocular amaurotic 41 amblyopic 41 latent 41 Miner’s 41 spasmus nutans 41 pendular 33 rotational 48 vertical vestibular 45 canal paresis 46 directional preponderance 47 vestibular 43 voluntary 51

O Ocular myasthenia clinical features 197 investigations 198 electromyography 199 neostigmine test 198 tensilon test 198 treatment 199 medical 200 optical 19 surgical 200 Ocular tumors 233 Oculomotor (third cranial) 109 blood supply 117 branches 116 cavernous sinus 112 ciliary ganglion 114 course in superior orbital fissure 112 course in the orbit 114 exit from the brain 110 nucleus 109

256


One and one-half syndrome 26 Optic atrophy 185 clinical features 186 differential diagnosis 187 Optic chiasma 75 Optic disk pit 156 Optic nerve 85, 103 blood supply intracanalicular 107 intracranial 107 intraocular 108 intraorbital 108 course intracanalicular 103 intracranial 103 intraocular 104 intraorbital 104 relations intracanalicular 104 intracranial 104 intraocular 105 intraorbital 104 Optic nerve gliomas 157 association with neurofibromatosis 160 clinical features 158 histopathology 162 management 167 microscopic findings 164 presenting signs and symptoms 159 radiographic findings 161 Optic nerve head drusen 152 Optic nerve hypoplasia 235 Optic nerve meningiomas 170 clinical features 171 histopathology 174 management 178 radiology 173 signs and symptoms 171 Optic neuritis 187 clinical features 188 management 189 optic neuritis treatment trial 189 Optic radiation 81, 88 Optic tract 87 Optokinetic nystagmus drum 36 Orbital syndrome 121, 126, 138

P Papilledema 190 clinical features 190 management 193 Paradoxical papillary reaction 71 Paralytic pontine exotropia 26 Parinaud’s syndrome 22 Partial ipsilateral facial palsy 149 Periventricular leukomalacia 236 Petrous apex syndrome 137 Pharmacology of the pupil 68 Phenylephrine test 67 Pilocytic astrocytoma 247 Pituitary tumors 204 Polycoria 72 Posterior communicating artery aneurysm 120 Pseudo-Ishihara’s chart 220 Pseudo-Argyll Robertson pupil 64 Pseudo-Gradenigo’s syndrome 137 Pseudo-ophthalmoplegia 17 Psychosensory reflex 60 Ptosis 66 Pupil abnormalities 71 Pupil cycle time 60 Pupil gaze dyskinesis 121 Pupillary pathways 54 accommodation reflex pathway 57 convergence near reflex pathway 56 papillary dilatation pathway 58 pupulloconstrictor light reflex pathway 54 Pupil-sparing isolated third nerve paresis 121 Pursuit disorders 29

R Raymond’s syndrome 136 Reader’s syndrome 68 Retinoblastoma 233 Retinochoroidal coloboma 153

S Saccadic disorders 17 Secondary optic nerve tumors 179

Index blood-borne metastasis 180 extension from adjacent structures 181 extension from the eye 179 extension from the meninges and brain 181 Sellar tumors 242 Septo-optic dysplasia 234 Spasmus nutans 233 Subarachnoid hemorrhage 214 Subarachnoid space syndrome 126, 137 Superior orbital fissure 112, 113, 124 Supranuclear eye movement systems 2 non-optic reflex system 12 position maintenance system 15 pursuit system 6 saccadic system 2 vergence system 11 Supranuclear lesion 147 Swinging flash light test 61, 220

T Tardive dyskinesia 203 Terson’s syndrome 214 Third nerve fascicle syndromes 119 Tic douloureux 203 Tilted disk 155 Tolosa-Hunt syndrome 248 Tonic pupil 64 Tourette’s syndrome 202 Toxoplasmosis 250 Trauma (nonaccidental injury) 236 Trigeminal nerve exit from the brain 140 mandibular division 143 maxillary division 143 nucleus 140 ophthalmic division 141 frontal nerve 142 lacrimal nerve 142 nasocilliary nerve 142 trigeminal cave 140 Trochlear nerve 123 course cavernous sinus 124 exit from the brain 123

257

exit from the nucleus 123 orbital course 124 superior orbital fissure 124 lesions 125 nucleus 123

U Uncal herniation syndrome 120

V Vergence disorders 29 Vestibular system disorders 30 Visual cortex 83, 88 Visual pathways 73 blood supply 89 lateral geniculate body 92 optic chiasma 91 optic nerve 90 optic radiations 92 optic tract 91 retina 90 visual cortex 92 lesions 93 level 73 lateral geniculate body 79 optic chiasma 75 optic nerve 73 optic radiations 81 optic tract 77 retina 73 visual cortex 82 localization 84 lateral geniculate body 87 optic chiasma 86 optic nerve 85 optic radiation 88 optic tract 87 retina 84 visual cortex 88

W Weber’s syndrome 120 Wernicke’s hemianopic pupil 63 Wolfram syndrome 186

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