DOCSLIB.ORG

Anatomical Note the Superficial Origin of the Trochlear Nerve with Special

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Anatomical Note the Superficial Origin of the Trochlear Nerve with Special J. Anat. (1990), 170, pp. 199-201 199 With 4 figures Printed in Great Britain Anatomical Note The superficial origin of the trochlear nerve with special reference to its vascular relations K. K. BISARIA*, I. C. PREMSAGARt, P. K. LAKHTAKIAt, R. C. SAXENA* AND S. D. BISARIA§ * Department of Anatomy, t Department of Neurosurgery, $ Department of Orthopaedic Surgery, K. G. Medical College, Lucknow, U.P. and § Department Of Ophthalmology, Vivekananda Polyclinic, Lucknow, U.P. India (Accepted 14 November 1989) INTRODUCTION A full description of the roots of the trochlear nerve is not commonly found in the literature. Gardner, Gray & O'Rahilly (1960), Hamilton (1976), Romanes (1964), Snell (1981), Hollinshead & Rosse (1985) and Williams, Warwick, Dyson & Bannister (1989) do not mention the possibility of two roots of origin of this nerve. Crosby, Humphrey & Lauer (1962) and Truex & Carpenter (1969) have mentioned that the nerve may emerge as a single root while Paturet (1964) and Nathan & Goldhammer (1973) have mentioned the possibility that more than one root may be present. The relations of the trochlear nerve to the adjoining blood vessels have not been described. MATERIALS AND METHODS For the present work 162 trochlear nerves of 90 formalin-fixed brains were studied (in 18 brains only one of the two nerves could be studied as the other was torn during the removal of the brain from the cranial cavity). The origin of the nerve and its relationships with neighbouring blood vessels was noted. RESULTS In all the 90 brains, the trochlear nerves arose in the usual situation. In 111 nerves out of 162, the nerve had a single root; in 51, double rootlets were present, the rootlets being up to 4 mm apart (Fig. 1). In 14 nerves out of the 51 with double nerve roots, the two roots were of different thickness while in the remaining 37 nerves, the rootlets were almost equal in diameter. When two rootlets were present they were usually orientated alongside one another in the transverse plane but occasionally they lay one behind the other or were arranged obliquely. The distance from the point of origin of each rootlet to its union with the other varied from 1 to 7 mm. Fifty nerves were closely related to the superior cerebellar artery which ran anteroposteriorly over the nerve before ramifying on the superior surface of the cerebellum (Fig. 2). In 20 cases the superior cerebellar artery divided into two branches (Fig. 3) while in 60 cases the superior cerebellar artery was deep to the nerve (Fig. 4). ........: ::.... :. :....: :.: ...:;.: ..i ..... 1 .: r .... Fig. 1. The rootlets of the trochlear nerve on the right side are of different thickness (arrows) and on the left side of equal thickness (arrows). Note that the rootlets arise along an oblique line. Fig. 2. The superior cerebellar artery (arrow) crossing over the trochlear nerve on the left side. Fig. 3. The right trochlear nerve (arrow) passing in between the two branches of the superior cerebellar artery. Fig. 4. The left superior cerebellar artery (arrow) lying deep to the trochlear nerve. Origin of trochlear nerve 201 DISCUSSION Sano (1941), Huber et al. (1943) and Crosby et al. (1962) have demonstrated that the nucleus of the fourth nerve is split into two, a main cranial nucleus and a smaller accessory one more caudally located. Pearson (1943) has mentioned that the accessory nucleus is inconstant and may be bilateral or unilateral. Tozier (1912), Pearson (1943) and Crosby et al. (1962) have commented that sensory as well as proprioceptive fibres may be present and it may be that these separate nuclei account for the double roots outside the brain in the specimens studied. The relationship of the trochlear nerve with the superior cerebellar artery is very variable. The most important relationship, from a functional point of view, is that in which the nerve lies between two branches of the superior cerebellar artery. Sunderland (1948) has stressed that even a normal vessel which is congenitally displaced in position may compress the nerve. Such contact may produce a defect in the conduction of impulses in the nerve which in turn, might be expected to produce a superior oblique palsy. This paper was presented at the first Afro-Asia Oceania Congress of Anatomists, 29 August to 3 September 1988, New Delhi, India. REFERENCES CROSBY, E. C., HUMPHREY, T. & LAUER, E. W. (1962). Correlative Anatomy of the Nervous System, pp. 113; 221. New York: Macmillan. GARDNER, E., GRAY, D. J. & O'RAHILLY, R. (1960). Anatomy. A Regional Study ofHuman Structure, p. 714. Philadelphia: W. B. Saunders Co. HAMILTON, W. J. (1976). Text Book of Human Anatomy, 2nd ed., p. 549. London: Macmillan Press. HOLLINSHEAD, W. H. & RossE, C. (1985). Text Book ofAnatomy, 4th ed., p. 932. New York: Harper & Ross Publishers Inc. HUBER, G. C., CROSBY, E. C., WOODBURNE, R. T., GILILAN, L. A., BROWN, J. 0. & THAMTHAI, B. (1943). The mammalian midbrain and isthmus region. 1. The nuclear pattern. Journal of Comparative Neurology 78, 129-354. NATHAN, H. & GOLDHAMMER, Y. (1973). The rootlets of the trochlear nerve. Anatomical observations in human brains. Acta anatomica 84, 590-596. PATURET, G. (1964). Traite d' Anatomie Humaine, vol. iv, Systeme Nerveuse, pp. 718; 730. Paris: Masson. PEARSON, A. A. (1943). The trochlear nerve in human fetuses. Journal of Comparative Neurology 78, 29-43. ROMANES, G. J. (1964). Cunningham's Textbook of Anatomy, 10th ed., pp. 691-692. London: Oxford University Press. SANO, F. (1941). Division of trochlear nucleus into two or more parts in man and in certain mammals. Tokyo igakkai zasshi 55, 490-491. SNELL, R. S. (1981). Clinical Neuroanatomy for Medical Students, 2nd ed., p. 404. Boston: Little Brown & Co. SUNDERLAND, S. (1948). Neurovascular relations and anomalies at the base of brain. Journal of Neurology, Neurosurgery and Psychiatry 11, 243-257. TOZIER, F. M. (1912). On the presence of ganglion cells in the roots of III, IV and VI cranial nerves. Journal of Physiology 45, 15-16. TRUEX, R. C. & CARPENTER, M. B. (1969). Human Neuroanatomy, pp. 301; 372-377. Baltimore: Williams and Wilkins Co. WILLIAMS, P. L., WARWICK, R., DYSON, M. & BANNISTER, L. H. (1989). Gray's Anatomy, 37th ed., p. 1098. Edinburgh: Churchill Livingstone..
Load more

Recommended publications
  • Cranial Nerve Palsy
    Cranial Nerve Palsy What is a cranial nerve? Cranial nerves are nerves that lead directly from the brain to parts of our head, face, and trunk. There are 12 pairs of cranial nerves and some are involved in special senses (sight, smell, hearing, taste, feeling) while others control muscles and glands. Which cranial nerves pertain to the eyes? The second cranial nerve is called the optic nerve. It sends visual information from the eye to the brain. The third cranial nerve is called the oculomotor nerve. It is involved with eye movement, eyelid movement, and the function of the pupil and lens inside the eye. The fourth cranial nerve is called the trochlear nerve and the sixth cranial nerve is called the abducens nerve. They each innervate an eye muscle involved in eye movement. The fifth cranial nerve is called the trigeminal nerve. It provides facial touch sensation (including sensation on the eye). What is a cranial nerve palsy? A palsy is a lack of function of a nerve. A cranial nerve palsy may cause a complete or partial weakness or paralysis of the areas served by the affected nerve. In the case of a cranial nerve that has multiple functions (such as the oculomotor nerve), it is possible for a palsy to affect all of the various functions or only some of the functions of that nerve. What are some causes of a cranial nerve palsy? A cranial nerve palsy can occur due to a variety of causes. It can be congenital (present at birth), traumatic, or due to blood vessel disease (hypertension, diabetes, strokes, aneurysms, etc).
    [Show full text]
  • MR Imaging of Primary Trochlear Nerve Neoplasms
    707 MR Imaging of Primary Trochlear Nerve Neoplasms Lindell R. Gentry 1 We present the clinical, anatomic, and MR imaging findings in six patients with seven Rahul C. Mehta 1 primary trochlear nerve neoplasms, as well as the MR and clinical criteria that serve to Richard E. Appen2 establish the diagnosis of these rare cranial nerve neoplasms. Three patients had a Joel M. Weinstein2 history of neurofibromatosis and five patients had clinical evidence of a trochlear nerve palsy. Six of seven neoplasms produced localized, fusiform enlargement of the proximal cisternal segments of the trochlear nerves. The lesions that were visible on noncontrast MR scans (T1-, T2-, and proton density-weighted) had signal intensities that were virtually identical to normal brain parenchyma. All lesions showed intense, homogeneous enhancement on contrast-enhanced scans. Contrast-enhanced imaging was necessary for the detection of five of seven lesions and greatly increased the value of the MR study in all six patients. AJNR 12:707-713, July/August 1991; AJR 157: September 1991 Primary neoplasms arising from pure motor cranial nerves such as the trochlear nerve are rare. To our knowledge just nine primary trochlear nerve neoplasms have been reported in the literature [1-7), only one of which was imaged with MR [1). Over the last 6 years, since we began to use MR as the primary imaging method for evaluating patients with cranial nerve palsies , we have noticed a striking increase in the number of primary trochlear nerve neoplasms over those encountered during the CT era. We believe this is due to a much greater sensitivity of MR in detecting these typically small lesions.
    [Show full text]
  • University International
    INFORMATION TO USERS This was produced from a copy of a document sent to us for microfilming. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help you understand markings or notations which may appear on this reproduction. 1. The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure you of complete continuity. 2. When an image on the film is obliterated with a round black mark it is an indication that the film inspector noticed either blurred copy because of movement during exposure, or duplicate copy. Unless we meant to delete copyrighted materials that should not have been filmed, you will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., is part of the material being photo­ graphed the photographer has followed a definite method in “sectioning” the material. It is customary to begin filming at the upper left hand corner of a large sheet and to continue from left to right in equal sections with small overlaps. If necescary, sectioning is continued again—beginning below the first row and continuing on until complete. 4. For any illustrations that cannot be reproduced satisfactorily by xerography, photographic prints can be purchased at additional cost and tipped into your xerographic copy.
    [Show full text]
  • The Nuclear Pattern of the Non-Tectal Portions of the Midbrain and Isthmus in Primates
    THE NUCLEAR PATTERN OF THE NON-TECTAL PORTIONS OF THE MIDBRAIN AND ISTHMUS IN PRIMATES ELIZABETH C. CROSBY AND RUSSELL T. WOODBURNE Department of Anatomy, University of Michigan FOURTEEN PLATES (TWENTY-THREE FIGURES) INTRODUCTION The various nuclear groups in the midbrain of primates show marked resemblances to their homologues in subprimate forms, although certain regions are characterized by a marked increase and others by a definite decrease in development. The literature dealing with special regions is considerable in amount and some of it is of relatively early date. That pertinent to the present consideration of these regions has been reviewed under the account of the general literature placed at the end of this series of papers. Attention is called here to a few contributions that have been particularly helpful in the preparation of the primate descriptions. Among such are the studies of Ziehen on various regions of the midbrain, particularly his account of the periventricular regions, and the descriptive analysis of Ingram and Ranson ('35) of the nucleus of Darkschewitsch and the interstitial nucleus of the medial longitudinal fasciculus, which confirmed Stengel's ( '24) earlier account. There are innumerable figures and descrip- tions of various parts of the oculomotor and trochlear gray in primates. Among these may be mentioned the work of Panegrossi ('04), Ram6n y Cajal ('ll), Brouwer ('18, and elsewhere), Le Gros Clark ( '26) and Mingazzini ( '28). The differences in nomenclature with respect to the periventricular gray of caudal midbrain and isthmus regions are indicated 441 442 G. CARL HUBER ET AL. to some extent on the figures of the human brain as well as considered in the general literature.
    [Show full text]
  • Lecture (6) Internal Structures of the Brainstem.Pdf
    Internal structures of the Brainstem Neuroanatomy block-Anatomy-Lecture 6 Editing file Objectives At the end of the lecture, students should be able to: ● Distinguish the internal structure of the components of the brain stem in different levels and the specific criteria of each level. 1. Medulla oblongata (closed, mid and open medulla) 2. Pons (caudal and rostral). 3. Midbrain ( superior and inferior colliculi). Color guide ● Only in boys slides in Green ● Only in girls slides in Purple ● important in Red ● Notes in Grey Medulla oblongata Caudal (Closed) Medulla Traversed by the central canal Motor decussation (decussation of the pyramids) ● Formed by pyramidal fibers, (75-90%) cross to the opposite side ● They descend in the lateral white column of the spinal cord as the lateral corticospinal tract. ● The uncrossed fibers form the ventral corticospinal tract Trigeminal sensory nucleus. ● it is the larger sensory nucleus. ● The Nucleus Extends Through the whole length of the brainstem and its note :All CN V afferent sensory information enters continuation of the substantia gelatinosa of the spinal cord. the brainstem through the nerve itself located in the pons. Thus, to reach the spinal nucleus (which ● It lies in all levels of M.O, medial to the spinal tract of the trigeminal. spans the entire brain stem length) in the Caudal ● It receives pain and temperature from face, forehead. Medulla those fibers have to "descend" in what's known as the Spinal Tract of the Trigeminal ● Its tract present in all levels of M.O. is formed of descending (how its sensory and descend?see the note) fibers that terminate in the trigeminal nucleus.
    [Show full text]
  • Cranial Nerve Disorders: Clinical Manifestations and Topographyଝ
    Radiología. 2019;61(2):99---123 www.elsevier.es/rx UPDATE IN RADIOLOGY Cranial nerve disorders: Clinical manifestations and topographyଝ a,∗ a b c M. Jorquera Moya , S. Merino Menéndez , J. Porta Etessam , J. Escribano Vera , a M. Yus Fuertes a Sección de Neurorradiología, Hospital Clínico San Carlos, Madrid, Spain b Servicio de Neurología, Hospital Clínico San Carlos, Madrid, Spain c Neurorradiología, Hospital Ruber Internacional, Madrid, Spain Received 17 November 2017; accepted 27 September 2018 KEYWORDS Abstract The detection of pathological conditions related to the twelve cranial pairs rep- Cranial pairs; resents a significant challenge for both clinicians and radiologists; imaging techniques are Cranial nerves; fundamental for the management of many patients with these conditions. In addition to knowl- Cranial neuropathies; edge about the anatomy and pathological entities that can potentially affect the cranial pairs, Neuralgia; the imaging evaluation of patients with possible cranial pair disorders requires specific exami- Cranial nerve palsy nation protocols, acquisition techniques, and image processing. This article provides a review of the most common symptoms and syndromes related with the cranial pairs that might require imaging tests, together with a brief overview of the anatomy, the most common underlying processes, and the most appropriate imaging tests for different indications. © 2018 SERAM. Published by Elsevier Espana,˜ S.L.U. All rights reserved. PALABRAS CLAVE Sintomatología derivada de los pares craneales: Clínica y topografía Pares craneales; Resumen La detección de la patología relacionada con los doce pares craneales representa Nervios craneales; un importante desafío, tanto para los clínicos como para los radiólogos. Las técnicas de imagen Neuropatía de pares craneales; son fundamentales para el manejo de muchos de los pacientes.
    [Show full text]
  • Clinical Anatomy of the Cranial Nerves Clinical Anatomy of the Cranial Nerves
    Clinical Anatomy of the Cranial Nerves Clinical Anatomy of the Cranial Nerves Paul Rea AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Academic Press is an imprint of Elsevier Academic Press is an imprint of Elsevier 32 Jamestown Road, London NW1 7BY, UK The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands 225 Wyman Street, Waltham, MA 02451, USA 525 B Street, Suite 1800, San Diego, CA 92101-4495, USA First published 2014 Copyright r 2014 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangement with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.
    [Show full text]
  • Cranial Nerves
    Cranial Nerves Cranial nerve evaluation is an important part of a neurologic exam. There are some differences in the assessment of cranial nerves with different species, but the general principles are the same. You should know the names and basic functions of the 12 pairs of cranial nerves. This PowerPage reviews the cranial nerves and basic brain anatomy which may be seen on the VTNE. The 12 Cranial Nerves: CN I – Olfactory Nerve • Mediates the sense of smell, observed when the pet sniffs around its environment CN II – Optic Nerve Carries visual signals from retina to occipital lobe of brain, observed as the pet tracks an object with its eyes. It also causes pupil constriction. The Menace response is the waving of the hand at the dog’s eye to see if it blinks (this nerve provides the vision; the blink is due to cranial nerve VII) CN III – Oculomotor Nerve • Provides motor to most of the extraocular muscles (dorsal, ventral, and medial rectus) and for pupil constriction o Observing pupillary constriction in PLR CN IV – Trochlear Nerve • Provides motor function to the dorsal oblique extraocular muscle and rolls globe medially © 2018 VetTechPrep.com • All rights reserved. 1 Cranial Nerves CN V – Trigeminal Nerve – Maxillary, Mandibular, and Ophthalmic Branches • Provides motor to muscles of mastication (chewing muscles) and sensory to eyelids, cornea, tongue, nasal mucosa and mouth. CN VI- Abducens Nerve • Provides motor function to the lateral rectus extraocular muscle and retractor bulbi • Examined by touching the globe and observing for retraction (also tests V for sensory) Responsible for physiologic nystagmus when turning head (also involves III, IV, and VIII) CN VII – Facial Nerve • Provides motor to muscles of facial expression (eyelids, ears, lips) and sensory to medial pinna (ear flap).
    [Show full text]
  • Central Fourth Nerve Palsies Mitchell S.V
    RESIDENT &FELLOW SECTION Pearls and Oy-sters: Section Editor Central fourth nerve palsies Mitchell S.V. Elkind, MD, MS Daniel R. Gold, DO CLINICAL PEARLS Lesions of the fourth (trochlear) Clinical features suggestive of bilateral fourth nerve Robert K. Shin, MD cranial nerve cause vertical or oblique diplopia by impair- palsies include right hypertropia in left gaze, left hyper- Steven Galetta, MD ing the ability of the superior oblique muscle to intort tropia in right gaze, and alternating hypertropia with and depress the eye. This binocular diplopia worsens in head tilt to either side (i.e., right hypertropia with right downgaze and lateral gaze away from the affected eye. tilt and left hypertropia with left head tilt).8 Correspondence & reprint Because intorsion is necessary to maintain fusion in ocu- requests to Dr. Gold: [email protected] lar counter-roll, this diplopia also worsens with head tilt CASE REPORTS Case 1. A20-year-oldmanpresented 1,2 toward the affected eye. to the emergency department complaining of 6 days of Diagnosis of a superior oblique palsy can be made binocular vertical diplopia and a left eyelid droop. He using the Parks-Bielschowsky 3-step test: 1) determine had noted fatigue, bilateral eye pain, and flu-like symp- which eye is hypertropic, 2) determine if the hypertro- toms 2 to 4 weeks prior to presentation. pia worsens in left or right gaze, and 3) determine if the Left-sided ptosis and miosis were present on exam- hypertropia worsens in right or left head tilt. In a supe- ination, along with a left adduction deficit.
    [Show full text]
  • Esting Resemblances Between the Avian and the Reptilian and the Mam- Malian Nuclear Pattern in This Region
    CERTAIN NUCLEAR GROUPS OF THE AVIAX MESENCEPHALON ERWIN JUNGHERR Department of Animal Diseases, Storrs AgI%wltural Experiment Station, Storrs, Connecticut FIVEl PLATJB (TPIN FIGURES) A study of the mesencephalon in the chicken has shown many inter- esting resemblances between the avian and the reptilian and the mam- malian nuclear pattern in this region. The following account attempts to stress those likenesses by an application of mammalian terminology to certain nuclear groups in the avian midbrain. The pertinent litera- ture will be considered in connection with the descriptions of the various areas. TECTAL AND BUBTECTAL REGIONS Superior colliculzls The superior colliculus or optie tectum in the bird is homologous with the similarly designated region in reptiles and mammals. However, in the bird there is a greater degree of layer differentiation than in these other forms. The general pattern of tectal lamination in sub- mammals was first described by Ram& (1896), who differentiated four- teen layers in the lizard. He believed the lamination pattern to be sim- ilar in birds and his observations were confirmed by his brother Ram6n p Cajal ('11). In a restudy of the reptilian optic tectum Huber and Crosby ('33, '33a, '33b, '34) established six fundamental layers, found to be present in a wide range of reptilian forms, which they believed to have phylogenetic as well as functional justification (Huber and Crosby, This study is a partial report on a cooperative project between the U. 8. Regional Poultry Research Laboratory, East Lansing, Mich., and the Storrs (Conn.) Agricultural Experiment Station. It is based upon three Huber ( '27) tolnidin-blue stained sets of serial sections of the brain of the chicken, Gallus domesticus.
    [Show full text]
  • Cranial Nerves. Sensory Organs
    Kharkiv National Medical University, Department of Human Anatomy CRANIAL NERVES. SENSORY ORGANS. The cranial nerves are: CN I - Olfactory Nerve CN II - Optic Nerve CN III - Oculomotor Nerve CN IV - Trochlear Nerve CN V - Trigeminal Nerve CN VI - Abducens Nerve CN VII - Facial Nerve CN VIII - Vestibulocochlear Nerve CN IX - Glossopharyngeal Nerve CN X - Vagus Nerve CN XI - Accessory Nerve CN XII - Hypoglossal Nerve Classification of the Cranial Nerves It is possible to describe a cranial nerve in terms of its function and embryological origin, initially cranial nerves can be subdivided into being either: Motor (efferent) Sensory (afferent) And from there further categorization can occur. Motor (efferent) Cranial nerves -Somatic motor (general somatic efferent) (III, IV, VI, XII) These cranial nerves are so called because they innervate muscles derived from the occipital somites, such as the extra ocular and extrinsic tongue muscles. Sensory (afferent) cranial nerves -Visceral sensory special visceral afferent- (VII, IX, X) general visceral afferent- (IX, X) The name is related to the fact that it detects sensation from visceral organs. They are divided into special visceral, referring to the rostral portion of the nucleus which contributes to the special sensation of taste. Whilst the general visceral portion is named as such due to this caudal portion receiving general sensory impulses such as cardiac, respiratory . - General somatic sensory (general somatic afferent) (V, VII, IX, X) These nuclei detect general sensation, such as touch, pain, vibration from the face, sinuses and meninges - Special somatic sensory (special somatic) (VIII) This carries information from the special sensation of hearing and balance.
    [Show full text]
  • Trochlear Nerve Nucleus in Albino Rat
    IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861. Volume 5, Issue 5 (Mar.- Apr. 2013), PP 65-68 www.iosrjournals.org Trochlear Nerve Nucleus in Albino rat Singh A., Khanna J. & Bharihoke V. Department of Anatomy, University College of Medical Sciences & Guru Teg Bahadur Hospital, Delhi India Abstract: A study of the trochlear nerve nucleus and its course within the brain is reported based on histological and fluorescent tract tracing techniques. Twenty inbred adult Wistar albino rats weighing between 150 to 250 gm of either sex were taken in the study. The localization of the nucleus giving rise to the nerve supplying the superior oblique muscle was done by using fluorescent dyes, Fast blue and Diamidino yellow. Fast blue was applied to the trochlear nerve of the right side and the Diamidino yellow was applied to the nerve of the left side in each animal. Animals were sacrificed after appropriate survival period. The labeled neurons were localized in the fourth nerve nucleus in the midbrain with the help of a Ziess fluorescence microscope .The majority of the fibers of the trochlear nerve cross to the opposite side and a few fibers remain ipsilateral. Many neurons were labeled with both the dyes indicating bilateral innervation. The nucleus was studied in paraffin sections stained with Kluver Barrera and Marshland, Glees and Erikson’s stain to trace the nerve fibers within the midbrain. Key words: Fluorescent tract tracing techniques, midbrain, superior medullary vellum, trochlear nerve nucleus, Diamidino yellow, Fast blue I. Introduction The basis of origin of the trochlear nerve from the posterior aspect of the midbrain and its crossing before exiting from the brain remains an enigma.
    [Show full text]