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At least 19 recordsLinked to original sources
PubMed1981

Fiber contribution from the mesencephalic nucleus of the trigeminal nerve to the trochlear nerve in the cat: a histological quantitative study.

The fiber connections between the trigeminal mesencephalic nucleus and tract and the trochlear nerve root of 15 cats were examined after silver impregnation of the pontomescencephalic region of the brains. The results revealed that: (a) some of the mesencephalic root fascicles join the trochlear root, (b) some of the mesencephalic root cells contribute their processes to the trochlear root, and (c) some mesencephalic cells are found amidst the fibers of the trochlear nerve during its intrabulbar course. The fibers of the trochlear nerve were counted at certain preselected sites before and after crossing the mesencephalic nucleus. The statistical data obtained indicated that the trigeminal mesencephalic root contributes 4-10% of the fibers of the trochlear nerve, before it crosses the mesencephalic nucleus.

Animals↗
PubMed1988

The central-peripheral transitional regions of cranial nerves. Trochlear and abducent nerves.

Unlike all other nerves containing somatic efferent fibres, the trochlear nerve emerges from the dorsal aspect of the brainstem. It generally emerges as a single trunk which resembles a dorsal rather than a ventral spinal nerve rootlet in terms of its size and of the morphology and position of the central tissue projection which it contains. The morphology of the central-peripheral transition of the trochlear nerve is therefore correlated with its dorsal location rather than with the nature of its constituent fibres. By contrast, abducent nerve rootlets emerge from the ventral aspect of the neuraxis, in line with other cranial and with spinal ventral nerve rootlets which also contain somatic efferent fibres. Its rootlets resemble the latter in terms of their size, being much smaller than those of dorsal rootlets or the trochlear nerve. They possess two distinct types of central-peripheral transitional zone: those of the rostral rootlets resemble zones of cervical ventral spinal rootlets. Many of these emerge through a circumscribed thickening of the astrocytic glia limitans. Caudal abducent rootlets emerge through a tongue-shaped glial elevation projecting above the level of the surrounding brainstem surface, resembling Type 1 oculomotor rootlets.

Abducens Nerve↗
PubMed1995

Regenerative axonal sprouting in the cat trochlear nerve.

Following peripheral trochlear nerve axotomy in the cat, the normal number of myelinated axons is restored despite significant motor neuron death, suggesting regulation of the number of myelinated axons in the regenerated nerve. In this study we used light and electron microscopy to examine the production and maintenance of axonal sprouts at different locations in the nerve and at different postoperative intervals. Despite proliferative sprouting and an overproduction of nonmyelinated axons in the regenerating trochlear nerve, the number of myelinated axons was strictly regulated. Only approximately 1,000 regenerated axons were eventually remyelinated, but many nonmyelinated axons were still present 6-8 months postaxotomy. Regenerated axons were remyelinated in a proximal-to-distal direction between 3 and 4 weeks postaxotomy. We also examined the maturation of regenerated myelinated axons by measuring axon diameter and myelin index (an expression of myelin thickness). Mean myelinated axon diameter remained significantly below normal in long-term regenerated nerves. Mean myelin index was not different from normal at 4 weeks postaxotomy but was significantly decreased at long postoperative intervals, reflecting a slightly thicker myelin sheath relative to the axon diameter. This relative increase in mean myelin thickness could serve to restore normal conduction velocity despite the decrease in mean axon diameter. We suggest that the regulation of the number of myelinated axons at the normal number despite cell death and the increase in mean myelin thickness may both be compensatory mechanisms that function to restore preoperative conditions and maximize functional recovery.

Animals↗
PubMed1975

Delayed trochlear nerve palsy in a case of zoster oticus.

A 57-year-old man with herpes zoster oticus developed a delayed fourth nerve palsy followed by transient intermittent sixth nerve weakness. Trochlear nerve lesions occur rarely with zoster, particularly in the absence of zoster ophthalmicus. A knowledge of the wide range of motor manifestations and the chronicity of meningitis with zoster will afford earlier diagnosis without resort to arteriography.

Diagnosis, Differential↗
PubMed2002

Infratentorial lateral supracerebellar approach for trochlear nerve schwannoma.

Schwannomas of the trochlear nerve are very rare. Only 25 cases without associated neurofibromatosis were reported in the literature, only 15 of which were surgically verified. We report an unusual case of a 31-year-old man who presented with isolated unilateral trochlear nerve palsy due to a left sided trochlear nerve schwannoma. The tumor was totally resected without additional morbidity using an infratentorial lateral supracerebellar approach.

Adult↗
PubMed1980

Trochlear nerve regeneration in Xenopus laevis larvae.

The trochlear nerve of Xenopus laevis larvae was sectioned in the orbit, and the nerve distal to the section was removed, so that it could not serve to guide the return of the regenerating nerve to the superior oblique muscle (SOM). In a second series, in addition to removing the distal nerve segment, the SOM was removed or damaged. The regeneration pattern of the trochlear nerve fibers was recorded in situ at 1 to 5-day intervals with the aid of methylene blue staining. The early growth or regenerating fibers was multidirectional; only some fibers encountered the SOM by day 6 or 7; others reached nerves, inappropriate muscle, and other tissues. Ultimately, the fibers that reached the SOM persisted and were reinforced, while those that reached other locations were withdrawn. By 20 days or so, the regenerated trochlear nerve usually had an appearance that was close to that of an uncut nerve. In the second series, in which the SOM was removed or damaged, the multidirectional character of the growth persisted through 20 days after section. these data suggest that: 1) Trochlear nerve regeneration is not guided by cues that closely control fiber growth along a direct path to the SOM, and 2) The SOM acts as a trap for regenerating trochlear nerve fibers, promoting the maintenance and the fasciculation of the trochlear nerve fibers that reach it, and the degeneration of the fibers that do not.

Animals↗
PubMed1994

[Two cases of trochlear nerve neurinoma].

Two cases of trochlear nerve neurinoma without Recklinghausen's disease are described. A 60-year-old male had a left-side sensory disturbance and a hemiparesis. Computed tomography (CT) scan and magnetic resonance image (MRI) showed a cystic enhancing mass in the right tentorial incisura. A 57-year-old male had a gait disturbance and a left-side facial numbness. CT scan and MRI showed a solitary enhancing mass in the right tentorial incisura. These tumors were subtotally removed, and the intraoperative diagnosis of two patients was trochlear nerve neurinoma. Unique clinical manifestations of trochlear nerve neurinoma are discussed with a brief review of 11 cases reported in the literature.

Aged↗
PubMed2004

Cystic trochlear nerve neurinoma mimicking intrinsic brainstem tumour.

Trochlear nerve neurinomas are very rare with less than 20 surgically proved cases reported in the literature. A case of histologically proved cystic trochlear nerve neurinoma, which was mimicking an intrinsic brainstem tumour is reported here. The tumour was totally excised. The clinical features and surgical management are described and the literature reviewed.

Brain Stem Neoplasms↗
PubMed1999

Schwannoma in patients with isolated unilateral trochlear nerve palsy.

PURPOSE: To describe the clinical features of patients with isolated unilateral trochlear nerve palsy secondary to imaging-defined schwannoma of the trochlear nerve. METHODS: A chart review of all patients seen at the Neuro-Ophthalmology Unit at Emory University since 1989. Of 221 patients with trochlear nerve palsy, six had a lesion consistent with a trochlear nerve schwannoma. RESULTS: The six patients had isolated unilateral trochlear nerve palsy. Duration of diplopia before diagnosis averaged 6 months. Magnetic resonance imaging demonstrated circumscribed, enhancing lesions along the cisternal course of the trochlear nerve, all measuring less than 5 mm in greatest dimension. Five of the patients were seen in follow-up, over periods ranging from 11 to 26 months from initial presentation (mean, 15.6 months; standard deviation, 6.0 months). All of these patients remained stable except one, who was slightly worse at 15 months by clinical measurements and magnetic resonance imaging. None of these patients have developed additional symptoms or signs of cranial nerve or central nervous system involvement. CONCLUSIONS: The differential diagnosis of an isolated unilateral fourth cranial nerve palsy should include an intrinsic neoplasm of the trochlear nerve. Magnetic resonance imaging is useful, both for diagnosis and follow-up. These patients can remain stable and may not require neurosurgical intervention.

Aged↗
PubMed1993

Palsies of the trochlear nerve: diagnosis and localization--recent concepts.

In this review, the anatomy of the trochlear nerve, the diagnosis of palsies of the trochlear nerve, and the localization of lesions of the trochlear nerve are discussed. Paresis of the superior oblique muscle is often not evident on duction testing; therefore, subjective diplopia testing with use of a Maddox rod is often necessary. The torsional component of the deviation may be evaluated by double Maddox rod testing. Palsies of the trochlear nerve must be distinguished from other causes of vertical diplopia, such as oculomotor palsy, skew deviation, myasthenia gravis, and Graves' ophthalmopathy. Trauma is the most common cause of isolated, unilateral or bilateral, acquired palsies of the trochlear nerve when a cause can be determined. The localization of lesions of the trochlear nerve to the nucleus or fascicles (or both), subarachnoid space, cavernous sinus and superior orbital fissure, or orbit depends on the associated damage to neighboring neurologic structures. Myokymia of the superior oblique muscle is usually idiopathic and benign but may rarely be an isolated manifestation of tectal disease.

Cranial Nerve Diseases↗
PubMed1988

Trochlear nerve meningioma in von Recklinghausen's disease.

A trochlear nerve meningioma in a patient with von Recklinghausen's disease is reported. The tumour appeared to have originated from the trochlear nerve itself, having no connection either with the neurinomas present in the adjacent regions, or with the tentorium. Histological examinations revealed that the tumour was a meningotheliomatous meningioma and the trochlear nerve fibres were placed in the periphery of the tumours. It was noteworthy that diplopia was not detected either before or after the resection of the trochlear nerve with the tumour.

Adult↗
PubMed1987

The trochlear nerve of amphibians and its relation to proprioceptive fibers: a qualitative and quantitative HRP study.

The cells of origin of the trochlear nerve of urodeles, anurans and gymnophionans were labelled with HRP in order to compare the location and morphology of trochlear motoneurons and to find evidence for sensory fibers in the trochlear nerve of amphibians. Trochlear motoneuron perikarya were found in a ventral tegmental position predominantly on the contralateral side, but an ipsilateral cell was present in some specimens of urodeles and anurans. About 19 motoneurons were labelled in Ambystoma, about 60 motoneurons in Xenopus, and a maximum of 7 cells in Ichthyophis. Decussation of trochlear nerve fibers showed only in Xenopus a highly variable pattern. In urodeles, selective filling of the trochlear nerve labelled in addition to trochlear motoneurons a caudo-medical tectal group of about 20 neurons of the nucleus of the mesencephalic root of the trigeminal nerve. Gymnophionans showed also labelled cells of the mesencephalic trigeminal root in the caudal midbrain close to the trochlear nerve root. In some frogs, a few cells of the mesencephalic trigeminal root were labelled in the caudal tectum and occasionally in the velum medullare anterius. Comparison of the numbers of trochlear nerve fibers with HRP-labelled motoneurons revealed in Xenopus a proportion of 1.2:1, but of 2.7:1 in Ambystoma. However, counting both labelled motoneurons and cells of the mesencephalic trigeminal root resulted in a trochlear nerve fiber to labelled neuron proportion of 1.3:1 in Ambystoma much like in Xenopus. The numbers of superior oblique muscle fibers and of trochlear nerve fibers, but not of HRP-labelled motoneurons, increased significantly with size in Xenopus laevis. We suggest that increased peripheral branching of individual fibers within the trochlear nerve with size rather than differentiation of additional motoneurons takes place in growing postmetamorphic Xenopus. In contrast to other vertebrates studied so far, the trochlear nerve is a mixed nerve in Ambystoma and perhaps in Ichthyophis. Whether this reflects a primitive or a derived condition is at present unclear.

Ambystoma↗
PubMed1990

[Isolated trochlear nerve paralysis following head trauma].

39 cases with isolated trochlear nerve palsies of traumatic origin have been analyzed retrospectively. 18 patients (46%) had had cerebral contusion, 15 (39%) cerebral concussion, and 6 patients (15%) a minor head trauma. 33 patients had unilateral trochlear nerve palsies and 6 (all of them with cerebral contusion) bilateral. The degree of the palsies did not correlate with the severity of the head trauma. Essential pathogenetic mechanisms were frontal or occipital blows. We emphasize a fact hitherto underestimated in the literature, that even a relatively mild head trauma (cerebral concussion or minor head trauma) can cause isolated trochlear nerve palsies. This was the case in 21 of our 39 patients (54%). Simple clinical examination techniques are described (Bielschowsky phenomenon, pencil test), which allow detection of trochlear nerve palsies in most cases.

Adolescent↗
PubMed1998

Intracranial repair of a divided trochlear nerve. Case report.

The authors report the case of a 37-year-old woman in whom the trochlear nerve was transected during removal of a meningioma in the cavernous sinus and subsequently repaired by using microsurgical techniques. This patient presented with a tumor in the posterior part of the right cavernous sinus with expansion over the tentorium. Preoperatively, she suffered from partial deficit of the right trochlear nerve. Intraoperatively, the trochlear nerve was noted to be completely encased by the tumor and was totally divided during removal of the lesion. After tumor resection, the trochlear nerve was repaired by using a sural nerve fascicle secured with sutures and fibrin glue. Six months after the operation, trochlear nerve regeneration became evident as the patient's binocular vision gradually improved. The patient regained normal functioning of the superior oblique muscle 3.5 years after surgery. It is concluded that repair of a divided trochlear nerve is worthwhile and can be followed by successful regeneration and an excellent functional recovery of the superior oblique muscle.

Adult↗
PubMed1993

The trochlear nerve: anatomy by microdissection.

This work is based on the microscopic study of 30 trochlear nerve trunks (15 heads). In 17 cases, the trunk arose from two nerve bundles, in 8 cases from one bundle, and for the other 5 nerves, three or four bundles. The mean total length of the trochlear nerve was 86 mm. The nerve may be separated into the 3 following parts: infratentorial, intracavernous, intraorbital. In all 30 cases studied, the first part of the nerve was infratentorial, thus leading us to suggest the term "infratentorial part" for this segment of the nerve. In 27 cases, contact was found with the superior cerebellar artery, in the infratentorial part. In the intracavernous part of ten nerves we found two rami tentorii and in eight cases fibers were exchanged with the ophthalmic nerve. In the orbit, 18 trochlear nerves crossed the posterior ethmoidal artery. 23 trochlear nerves ended on the medial face of the superior oblique muscle. The remaining 7 ended at the superior border of the muscle.

Adult↗
PubMed2002

The microsurgical anatomy of the cisternal segment of the trochlear nerve, as seen through different neurosurgical operative windows.

OBJECTIVE: To describe the anatomy of the cisternal segment of the trochlear nerve as seen through different neurosurgical approaches. METHODS: The cisternal course of ten trochlear nerves was observed in five cadaveric embalmed heads, through the view afforded by the median infratentorial-supracerebellar, the extreme-lateral infratentorial-supracerebellar, and the combined presigmoid-subtemporal transtentorial approaches. The relationships of the trochlear nerve with the surrounding neuro-vascular structures were analyzed. RESULTS: We identified 3 segments of the cisternal trochlear nerve: quadrigeminal, ambient and tentorial. The median infratentorial-supracerebellar approach allowed exposure of the quadrigeminal segment, including the origin of the nerve. The extreme-lateral supracerebellar and the combined presigmoid-subtemporal transtentorial approaches provided visualization of the ambient and tentorial segments of the nerve. The tentorial segment runs in a dural canal contained in the free edge of the tentorium, surrounded by its own arachnoidal sleeve. CONCLUSION: The trochlear nerve is a very delicate structure that can be easily injured during approaches to the tentorial incisura. Accurate knowledge of its anatomy as seen through different operative windows is helpful in maintaining its integrity during surgery.

Brain Diseases↗