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PubMed2004

The nerve supply to the orbit of the Bactrian camel.

The Bactrian camel is an important domestic animal in some desert and semi-desert areas of the world, but there is no detailed description of the nervous supply to the orbit in this animal. In this study, 10 heads of adult Bactrian camels were collected and the nerves supplying the orbit were examined grossly. The results showed that the nerves supplying the orbit included the optic nerve, oculomotor nerve, trochlear nerve, abducent nerve, the branches of ophthalmic nerve and the maxillary nerve. The anatomical characteristics of the origins, courses and distributions of the nerves to the orbit in the Bactrian camel were described and compared with those of other domestic animals. These results have importance for further research on the comparative neuroanatomy, neurophysiology and the related clinical surgery of the camel.

Animals↗
PubMed1988

Fibre composition of the feline trochlear and abducens nerves.

Cat trochlear and abducens nerves were studied by electron microscopy at two different levels. Five mm peripheral to the exit from the brainstem, the average number of myelinated axons is 965 in the trochlear nerve and 1901 in the abducens nerve. The size spectrum is unimodal and small myelinated axons predominate. Both nerves contain 16% unmyelinated axons at this level. At the PNS/CNS transition, the nerve fascicles contain few unmyelinated axons, but bundles of such axons are present in the adjacent pia mater. We suggest that the trochlear and abducens nerves may channel unmyelinated sensory and/or autonomic axons to the leptomeningeal blood vessels and the pia mater of the brainstem.

Abducens Nerve↗
PubMed2001

Intracranial distribution of the sympathetic system in mice: DiI tracing and immunocytochemical labeling.

The intracranial distribution of the cephalic branches of the superior cervical ganglion (scg) was studied in mice using indocarbocyanine dye (DiI) anterograde tracing. Two main branches were traced from the scg. The first branch joined the nerve of the pterygoid canal (the vidian nerve), npc, from which several intracranial sympathetic branches passed to the branches of the trigeminal nerve (tgn), abducent nerve (abn), trochlear nerve (trn), and oculomotor nerve (ocn). Most of the second branch joined the abn, from which sympathetic fibers dispersed in the distal region of the trigeminal ganglion (tgg) to form a plexus close to the ganglion's branches. Branches from this plexus joined the branches of the tgn, trn, and ocn. Several minor branches arising from the second branch of the scg were also observed. One formed a sympathetic plexus around the internal carotid artery (ica); a second formed a sympathetic plexus in the proximal region of tgg, close to its root; and a third branch coursed laterally to reach the ear by passing along the greater petrosal nerve (gpn). All of the intracranial trajectories traced from scg were found to be catecholaminergic, and likely sympathetic, using tyrosine hydroxylase (TH) immunocytochemistry.

Abducens Nerve↗
PubMed2004

Visualization of the oculomotor cranial nerves by magnetic resonance imaging.

MRI is the imaging method of choice in patients with cranial nerve palsies. However, the nerves are often not seen on MR images and smaller lesions may not be diagnosed on routine brain MRI. The purpose of this study is to show that the oculomotor cranial nerves can be visualized by standard MR sequences and to present an update on clinical applications of cranial nerve imaging. In MR images of normal subjects, it is demonstrated that the oculomotor nerve, the trochlear nerve and the abducens nerve can be identified not only in the subarachnoid space and cavernous sinus, but also in the orbit. However, a precondition is the use of appropriate imaging sequences and planes (e.g., subarachnoid cisterns: T2-weighted fast spin-echo or T2*-weighted three-dimensional sequences in oblique-axial and sagittal planes; cavernous sinus: contrast-enhanced T1-weighted coronal images; orbit: T1-weighted images without contrast agent in the coronal plane obtained using surface coils). The capability of imaging cranial nerves is clinically important not only for diagnostic purposes in eye muscle palsies but also for planning surgical procedures at the cranio-orbital junction.

Abducens Nerve↗
PubMed1998

[Ocular torticollis].

The author presents an account on different causes of ophthalmological torticollis and rotational nystagmus in paresis of the trochlear nerve and abducent nerve, in Duan's syndrome I or acute Brown's syndrome or in bilateral ptosis combined with paresis of the levators. He recommends different surgical techniques and prefers combined operations performed with a single anaesthesia in pareses of the levators, the abducent nerve and trochlear nerve. For release of the horizontal direct muscles within the framework of paretic affections of the eye he recommends adjustable elongations as described by Gonin-Hollwich. In ptosis he uses frontotarsal suspension as described by Fox, using lyophilized fasciae. The paper contains also a family history of congenital fibrous syndrome.

Adult↗
PubMed1979

Trochlear-oculomotor nerve interactions in Xenopus laevis tadpoles: a temporal study.

When the trochlear nerve (NIV), which innervates the superior oblique muscle (SOM), is crushed or cut at stages 48-49 in Xenopus tadpoles, fibers from the oculomotor nerve (NIII) sprout and invade the SOM. The maximal percentage of specimens having at least one oculomotor nerve fiber on the SOM on a given day increased from 9.1% following a single crushing of NIV to 84.2% following three successive severings of NIV and the average number of silver-impregnated NIII fibers per specimen increased from 0.23 +/- 0.16 (mean +/- S.E.M.) in the single-crush experiment to 7.35 +/- 1.33 in the triple-cut experiment. This increase directly reflects the delay in the return of NIV. As NIV returns to the SOM, a portion of the inappropriate innervation is lost; while another portion appears to be stable and is in evidence 90 days after a single sectioning of NIV. The more rapidly NIV returns to the SOM, the more complete is the displacement of the NIII fibers. This suggests that the association between NIII and the SOM changes with time so that easy displacement of the inappropriate innervation is likely only when the reinnervation by the appropriate nerve fibers is rapid.

Animals↗
PubMed2003

Prospective analysis of diplopia after anterior temporal lobectomy for mesial temporal lobe sclerosis.

OBJECT: In this prospective study the authors investigated the incidence and natural history of postoperative diplopia in patients undergoing anterior temporal lobectomy (ATL) and amygdalohippocampectomy for medically intractable mesial temporal lobe epilepsy. METHODS: Forty-seven patients scheduled for ATL for medically refractory seizures were examined preoperatively, 2 to 7 days postoperatively, and 3 to 6 months postoperatively. Ophthalmological examination including pupillary measurements, stereoacuity measurements, palpebral fissure measurements, vertical fusional amplitudes, Lancaster red green testing, visual field testing, and alternate cover testing was performed. Antiepileptic drug levels were monitored. Nine (19%) of 47 patients developed diplopia postoperatively. The diplopia was caused by trochlear nerve palsy in every case. No oculomotor nerve dysfunction was documented. Trochlear nerve function recovered completely in all patients within 3 to 6 months postoperatively. CONCLUSIONS: Postoperative diplopia following ATL occurs more often than previously thought and is primarily due to trochlear nerve dysfunction. Awareness of this transient complication is important in preoperative patient counseling.

Adolescent↗
PubMed1992

Neurinoma of the third, fourth, and sixth cranial nerves: a survey and report of a new fourth nerve case.

A rare case of trochlear nerve neurinoma is described. Including this case, the number of reported intracranial tumors arising from the sheaths of the third, fourth, and sixth cranial nerves is 38. By site and relationship to the nerve segment, they fall into three groups: cisternal, cisternocavernous, and cavernous. In cisternal tumors of the third and sixth nerves, paresis of the nerve hosting the tumor is the unique nerve deficit; by contrast, in those of the fourth nerve, paresis of the trochlear nerve can be absent and that of the third nerve present. In the latter tumors, a peculiar ataxic hemiparesis syndrome is produced by midbrain compression. Cisternocavernous neurinomas often cause symptoms of intracranial hypertension, while cavernous neurinomas bring about two clinical features: paresis of one or more nerves of the cavernous sinus and a clinicoradiological orbital apex syndrome. At surgery, generally cisternal neurinomas are totally removed and the nerve source of the tumor identified; in cisternocavernous and cavernous neurinomas, total removal of tumor and identification of the parent nerve have been reported in only half of the cases. In the majority of parasellar neurinomas, clinical differences can be found between those arising from the nerves governing eye movement and those arising from the gasserian ganglion.

Abducens Nerve↗
PubMed2000

Anatomical study of the lateral wall of the cavernous sinus, emphasizing dural construction and neural relations.

This study aims to determine the microscopic anatomy of the layers of the lateral wall of the cavernous sinus (CS) and, in particular, intends to examine the location and relations of the dural openings on the deep layer. Forty sides of 20 formalin-fixed and fresh cadavers were dissected and their CS examined. In 12 cases we found an opening on the deep dural layer; however, in four of them the inferolateral trunk of the internal carotid artery (ICA) was identified through these dural openings. We noticed the trochlear nerve making a curve (5% of cases) or lying close to the ophthalmic nerve (12.5%) on the lateral wall. In one case, the triangular area described by Parkinson could not be exposed surgically. Our findings indicate the importance of the heterogeneous courses of the cranial nerves lying on the lateral wall and point to the significance of the dural openings, which can influence the etiology of neoplastic invasions originating from the CS.

Cavernous Sinus↗
PubMed1992

Oculomotor and sensory mesencephalic trigeminal neurons in lungfishes: phylogenetic implications.

The location and number of neurons in the brainstem with projections to the eye muscles were investigated by means of fluorescent tracers in the African lungfish Protopterus dolloi. The oculomotor nucleus (M III) projects bilaterally with a ratio of 3:1 (70 ipsilateral, 20 contralateral neurons). Three subdivisions of this nucleus can be differentiated: one projects exclusively ipsilaterally, another projects exclusively contralaterally, and a third component projects bilaterally. The trochlear nucleus (M IV) is located caudally, distinct from M III, and projects predominantly to contralateral eye muscles with a ratio of 6:1 (18:3 neurons). The abducens nucleus (M VI) contains about 30 neurons with ipsilateral projections only. There is no evidence for an accessory abducens nucleus in Protopterus. Intraocular injections of tracers do not reveal any retinopetal projections in Protopterus. The mesencephalic trigeminal nucleus (Mes V) of Protopterus and Neoceratodus contains about 540-590 neurons on each side. In juvenile Protopterus, up to 75 Mes V neurons are located caudally in a ventral projection of the tectum above the velum medullare anterius. Fifty-five Mes V neurons (10% of the total number) have processes that exit the brain with the trochlear nerve. The relatively large number of Mes V neurons in lungfishes correlates with the well developed jaw musculature. The present study provides the first conclusive evidence for the location of oculomotor subdivisions in the brain of a lepidosirenid lungfish. The organization of the oculomotor nucleus is consistent with the observation that lungfishes possess the pattern of eye-muscle innervation seen in elasmobranchs and supports the unconventional view that lungfishes may be the sistergroup of elasmobranchs.

Abducens Nerve↗
PubMedDate not supplied

[Microsurgical anatomy of the area of the superior orbital fissure].

The microsurgical anatomy of the upper rima palpebrarum region was studied in 7 specimens of the base of the skull. The basic indicators in preparing specimens of the upper rime palpebrarum region are the upper and lower tendons of the lateral rectus, the upper orbital vein, the frontal and trochlear nerves. These indicators allow one to dissect cavernous sinusal formations to the rear and orbital formations to the front.

Abducens Nerve↗
PubMed1985

Development of the trochlear nucleus in quail and comparative study of the trochlear nucleus, nerve, and innervation of the superior oblique muscle in quail, chick, and duck.

The present study was undertaken to examine the development of the trochlear nucleus in quail and to compare the mature trochlear nucleus, nerve, and their sole target of innervation, the superior oblique muscle, in quail, chick, and duck. Study of the trochlear nucleus in quail from embryonic day 5 through hatching shows a maximum of 1,248 neurons on embryonic day 10 followed by spontaneous degeneration of 40% of the neurons between days 10 and 16. Previous studies have shown that although the initial and final number of neurons is different in chick and duck, the magnitude of trochlear cell loss in both species is about 40%. This study shows the average number of neurons in the nucleus of quail, chick, and duck, 2 weeks post-hatching, to be 658, 743 and 1,459, respectively. Fiber counts in the trochlear nerve from electron micrograph montages at the same period indicated a ratio of about 1:1 between neurons and axons. While a majority of the fibers in these nerves are myelinated, an average of 3-6% of the fibers are unmyelinated. The nucleus in the quail not only contains the smallest number of neurons but it also innervates the smallest muscle in terms of total number of muscle cells and endplates. However, the opposite relationship does not hold true. The nucleus in duck contains the largest number of neurons, yet the largest number of muscle cells and endplates were found in the chick. The ratios between the neurons and muscle cells as well as between neurons and endplates are about the same in quail and duck. These ratios are much higher in the chick, reflecting the relatively small neuron pool destined for a relatively large target. In spite of variations in the number of neurons, muscle fibers, and endplates the average number of endplates per muscle fiber is relatively constant among the three species.

Animals↗
PubMed1986

Innervation of extraocular muscles in the rabbit.

The innervation of extraocular muscles in the rabbit was studied by using the methods of horseradish peroxidase (HRP) histochemistry, gross dissection, and quantitative morphology. Subdivisions of the oculomotor complex that innervate the superior rectus, inferior rectus, medial rectus, and inferior oblique and levator palpebrae are described, and our results are in agreement with previous accounts of the projections of this nucleus. Our analysis of the innervation of the lateral rectus and retractor bulbi muscles, however, differs from previous descriptions. The axons of approximately 80% of neurons in the abducens nucleus are in the VIth nerve and innervate the lateral rectus muscle, and approximately 15-20% are internuclear neurons both surrounding and intermingling with the motor neurons of the abducens nucleus. The interneurons project to the medial rectus subdivision of the contralateral oculomotor complex via the medial longitudinal fasciculus (MLF). Neurons in both the abducens and the accessory abducens nucleus innervate the retractor bulbi muscles via the VIth nerve. All neurons in the accessory abducens nucleus innervate the retractor bulbi muscles, but gross dissection revealed that the retractor bulbi is also innervated by the IIIrd nerve. The bases for differences between our data and previously published descriptions are discussed. The trochlear nucleus of the rabbit has not been previously studied by methods of axonal transport. The body of the nucleus, its caudal tail, the trajectories of axons entering the trochlear nerve, and soma size distributions are described. The trochlear nucleus contains approximately 900 neurons; most are motoneurons the axons of which travel in the trochlear nerve and decussate in the anterior medullary velum. Approximately 3% of trochlear motor neurons innervate the ipsilateral superior oblique muscle. Their soma size is significantly smaller than that of contralaterally projecting neurons. For comparative purposes, the innervation of extraocular muscles by the trochlear nerve was also investigated in several rodents and carnivores. In all animals studied, the percentage of trochlear neurons innervating the ipsilateral superior oblique muscle was strikingly uniform (2-4%). Gross dissection of the extraocular muscles revealed in the rabbit a muscle, innervated by the trochlear nerve, for which we propose the name "tensor trochleae." In the rabbit, this muscle is innervated by approximately one-third of the trochlear motor neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Abducens Nerve↗
PubMed1996

Meningiomas of the space of the cavernous sinus.

During the years 1985 to 1992, we encountered 59 patients with meningiomas involving the space of the cavernous sinus. In 29 of these patients, meningiomas were primarily located within the space of the cavernous sinus and were operated on without mortality and with low morbidity. A small subtemporal surgical approach was favored, which allowed initial tumor resection from the posterior aspect, where the Parkinson's triangle is wide, thus avoiding the additional morbidity of large-scale approaches. According to the relationships of the all-important cranial nerves passing within the lateral wall of the cavernous sinus, we divided the primary intracavernous meningiomas into four types, which reflected not only the preoperative cranial nerve deficit but also the feasibility of surgical resection. Cranial nerve function deteriorated after operations in 14% of oculomotor nerves, in one abducent nerve, in 58% of trochlear nerves, and in 21% of trigeminal nerves. We encountered improvement of function in 43% of oculomotor nerves, in 50% of abducent nerves, and in approximately 30% of the second and third but in only 7% of the first branches of trigeminal nerves. There was no improvement in trochlear nerve function. Improvement of oculomotor nerve function was observed only in moderately impaired nerves, which indicates that surgery should be undertaken early to preserve or improve oculomotor nerve function.

Cavernous Sinus↗
PubMed2002

Superior oblique myokymia: magnetic resonance imaging support for the neurovascular compression hypothesis.

Superior oblique myokymia is a rare movement disorder thought to be caused by vascular compression of the trochlear nerve. Direct display of such neurovascular compression by magnetic resonance imaging has been lacking. The goal of this study was to assess the presence of neurovascular contacts in patients with superior oblique myokymia, using a specific magnetic resonance imaging protocol. A total of 6 patients suffering from right superior oblique myokymia underwent detailed neuro-ophthalmological examination, which showed tonic or phasic eye movement. All patients underwent magnetic resonance imaging, using a magnetic resonance imaging Fourier transform constructive interference in steady-state sequence in combination with magnetic resonance imaging time of flight magnetic resonance arteriography both before and after the administration of Gd-DTPA. With this protocol, the trochlear nerve could be visualized on 11 of 12 sides (92%). Arterial contact was detected at the root exit zone of the symptomatic right trochlear nerve in all 6 patients (100%). No arterial contact was identified at the root exit zone of the asymptomatic left trochlear nerve in any of the 5 left nerves visualized. In conclusion, superior oblique myokymia can result from neurovascular contact at the root exit zone of trochlear nerve, and therefore should be considered among the neurovascular compression syndromes.

Adult↗
PubMed1987

Oculomotor system of the weakly electric fish Gnathonemus petersii.

The peripheral and central aspects of the extraocular system were studied in the weakly electric fish Gnathonemus petersii. All six extraocular muscles show a similar composition of large and small fibers grouped characteristically in the proximal and distal regions respectively. The exit of the three extraocular nerves from the brain is similar to that in other vertebrates. However, the intracephalic and intracranial course of the trochlear nerve is unusual, partly because of the extraordinary hypertrophy of the cerebellum. The three nerves course rostrally on the ventral brain surface; the trochlear nerve penetrates the orbital cavity separately from the two other nerves. The fiber-diameter spectrum of each extraocular nerve is bimodal; unmyelinated fibers were not observed in any of the nerves. The location of the extraocular motor nuclei was established by retrograde axonal transport of HRP or cobaltic-lysine complex. The oculomotor nucleus is situated ventral to the posterior pole of the magnocellular mesencephalic nucleus and the trochlear nucleus is found caudal and dorsal to this. The abducens nucleus is situated at the level of the octavolateral efferent nucleus and consists of a single group of cells on each side of the ventral tegmentum. The oculomotor nucleus of G. petersii shows a somatotopic organization. The superior rectus muscle receives a contralateral innervation whereas the inferior rectus and oblique muscles and the internal rectus muscles receive an ipsilateral innervation. The superior oblique muscle is innervated by contralateral trochlear motoneurons and the external rectus by ipsilateral abducens motoneurons. The majority of extraocular motoneurons have piriform perikarya and long beaded dendrites that extend laterally in the oculomotor and abducens nuclei and rostrally in the trochlear nucleus. The terminal dendritic portions of trochlear motoneurons widely overlap with oculomotor dendrites and perikarya. In all three nuclei the axon originates opposite to the main dendrite. Collaterals of the hairpin-bend abducens axons could be identified in a few cases. The oculomotor system of G. petersii appears basically similar to that of other teleosts; the differences observed concern mainly the structure of the abducens nucleus, the intracranial and intracephalic course of the trochlear nerve, and the relatively small number of axons in each nerve.

Abducens Nerve↗
PubMed2001

Vascular compression as a cause of superior oblique myokymia disclosed by thin-slice magnetic resonance imaging.

PURPOSE: To describe a case of superior oblique myokymia in which thin-slice magnetic resonance imaging (MRI) appeared to show vascular compression of the trochlear nerve. METHODS: A 50-year-old woman presented with episodic monocular oscillopsia. Neuro-ophthalmologic examinations showed intermittent intorsional microtremor of her right eye, diagnosed as right superior oblique myokymia. Thin-slice (1.6 mm) MRI, using spoiled gradient recalled acquisition in the steady state, was employed to examine the trochlear nerve in its course through the ambient cistern. RESULTS: Imaging disclosed a branch of the posterior cerebral artery immediately adjacent to the right trochlear nerve. CONCLUSION: These magnetic resonance findings suggest that a cause of superior oblique myokymia may be vascular compression of the trunk of the trochlear nerve.

Cerebral Arteries↗