Fourth nerve palsy opposite a black eye. Two patients simulating orbital blowout fractures.
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Adult↗
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Results for “Trochlear Nerve Injuries”
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The injury response of nerve fibres in the anterior medullary velum of the adult rat.
The injury response of myelinated central nervous system (CNS) axons was documented in the anterior medullary velum (AMV) of the adult rat. Study of silver-stained AMV whole-mounts revealed sprouting of injured axons as early as 14 h post-lesion (hpl), with a complex network of fibres formed by 48 hpl. Signs of fibre degeneration were also apparent from 48 hpl, increasing in extent until 15 days post-lesion (dpl). Fragmentation was largely confined to specific fibre bundles, constituted by the distal portions of severed axons. Although some degeneration of regenerated axons was evident from 15-20 dpl, many remained intact beyond this time, particularly in the area adjacent to the exit of the trochlear nerve, where most regenerated fibres penetrated the ipsilateral trochlear nerve. Counts of HRP filled neurons in the trochlear nucleus after injection of the superior oblique muscle showed that axons entering the IVth nerve rootlet were exclusively ipsilateral trochlear fibres. Less than 50% regenerated; most other severed axons degenerated. The few axons remaining in the AMV may have been fibres, undamaged by the original lesion, which normally course longitudinally through the ipsilateral AMV. These results show that IVth nerve fibres preferentially enter IVth nerve rootlets and, in so doing, survive the effects of injury. Most other CNS axons in the AMV which do not enter the trochlear root probably degenerate.
Animals↗
Hypertropia following trochlear trauma.
Hypertropia following trauma to the trochlea is rare. The more widely recognized response of the trochlea to trauma is hypotropia or acquired Brown syndrome. We observed three cases of hypertropia following penetrating trauma to the trochlea. Each had computerized tomography and/or magnetic resonance imaging to assist in the understanding of the mechanism of the observed superior oblique dysfunction. The clinical course of these cases was variable. Awareness of the damaged trochlea's capacity to respond as a hypertropic as well as a hypotropic syndrome will allow for improved management of these unusual patients.
Adolescent↗
Diplopia following head injury.
Two cases of traumatic fourth cranial nerve palsy are described. The treatment is discussed.
Aged↗
[Catalog of direct eye muscle injuries].
Eye muscle injuries may occur in isolation or concomitantly with orbital fractures. Depending on their mechanical cause they may be encountered in the form of contusions, overextensions or injuries caused by stabbing or cutting. The authors present case histories from their own patient collective in this order, supplemented by a number of cases described in the literature. Particular attention is paid to the superior oblique, injuries to which are almost without exception trochlear or pretrochlear. The special anatomy of the tendon is a factor that may explain restrictions in motility in upward and downward gaze (dysfunctions). Certain severe cases are described and the principles of reconstructive surgery are discussed.
Adult↗
Degenerative and regenerative changes in the trochlear nerve of goldfish.
The features of unlesioned and lesioned trochlear nerves of goldfish have been examined electron microscopically. Lesioned nerves were studied between 1 and 107 days after cutting or crushing the nerve. Unlesioned nerves contained, on average, 77 myelinated axons and 19 unmyelinated axons. The latter were found in 1-2 fascicles per nerve. A basal lamina surrounded each myelinated axon and fascicle of unmyelinated axons. The numbers of myelinated axons, fascicles of unmyelinated axons and basal laminae varied by less than 5% over the intraorbital extramuscular segment of the nerve. Following interruption of the nerve, by either cutting or crushing, all of the axons and their myelin sheaths began to degenerate by 4 days in the distal nerve-stump. Both abnormally electron-dense and electron-lucent axons were observed. Both Schwann cells and macrophages appeared to phagocytose the myelin sheaths. Following a lesion, the Schwann cells and their basal laminae persisted in the distal nerve-stump. In crushed nerves, the basal laminae surrounding myelinated axons formed 97%, on average, of the Schwann tubes in the distal stump. The perimeters of the basal laminae were of similar size to those in the proximal stump, at least for the first 8 days after crush. In crushed nerves, single myelinated axons in the proximal nerve-stump gave rise to multiple sprouts, some of which reached the site of crush by 2 days, the distal stump by 4 days and the superior oblique muscle by 8 days. The regeneration of the unmyelinated axons was not examined. In both crushed and transected nerves, nearly all of the sprouts in the proximal and distal stumps were found within the basal laminae of Schwann cells, even though the spouts were disorganized in the transected region where there were no basal laminae. The growth cones of the regenerating axons were always found apposed to the inner surface of the basal laminae, which may have provided an adhesive substrate that directed their growth. Terminal sprouts from the ends of myelinated axons in the proximal stump accounted for the majority of the regenerating axons in the distal stump, as only a few collateral sprouts were found in the proximal stump, and only a small amount of axonal branching was found within the distal stump itself. The largest axons in the distal stump were remyelinated first, and the number of remyelinated axons increased progressively between 8 and 31 days after crush, at which time there were about twice as many as in unlesioned nerves.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Transitory fourth cranial nerve palsy due to foramen ovale electrode placement.
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Electrodes, Implanted↗
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↗
[Decompensated strabismus surso-adductorius].
Strabismus surso-adductorius is a frequent unilateral or bilateral eye movement disorder. Its clinical features include eye elevation with concomitant vertical deviation in adduction, an abnormal head posture from which the patient is unaware (head turned and tilted towards the healthy side), a moderate subjective excyclotorsion, and a positive Bielschowsky head tilt test. Despite its anglo-saxon denomination as "congenital fourth nerve palsy", it is not a paretic disorder. Strabismus surso-adductorius differs from fourth nerve palsy both by etiology and by symptoms. A proper diagnosis is important as neuroradiological examination is mandatory in cases of acquired non-traumatic fourth nerve palsy, whereas decompensated strabismus surso-adductorius can be operated on without any further investigations. Early on, the oculomotor disorder is often well compensated and it does manifest at the adult age. Asthenopia and intermittent vertical diplopia appear as the fusional mechanisms fade out. The best surgical technique for strabismus surso-adductorius is an inferior oblique weakening procedure. In severe cases a combined shortening of the superior oblique tendon may be necessary.
Adult↗
Acquired lesions of the fourth cranial nerve.
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Adult↗
Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa.
Complete return of function has been obtained following neurosurgical repair of a trochlear nerve inadvertently divided during the clipping of a basilar tip aneurysm. To date this is the second case reported in the literature. The technique of repair and the method of recording the return of function is discussed.
Adult↗
Limitations of brain stem auditory evoked potentials for intraoperative monitoring during a posterior fossa operation: case report and technical note.
We have encountered an example of the insensitivity of brain stem auditory evoked potentials (BAEPs) for monitoring the brain stem during a posterior fossa operation. The addition of somatosensory evoked potential recording to conventional BAEP protocols is readily accomplished and is likely to improve the sensitivity of intraoperative electrophysiological assessment of brain stem function.
Brain Stem↗
Clinical analysis of STA-SCA bypass for vertebrobasilar occlusive disease.
In order to clarify the effectiveness of extracranial- intracranial bypass in cases of vertebro-basilar occlusive disease, we investigated the operative complication, clinical course and follow-up study of 30 cases undergoing superficial temporal artery-superior cerebellar artery (STA-SCA) bypass surgery. Postoperative angiogram showed the patency of the anastomoses in all cases. No serious surgical complications were observed. The outcome on discharge was excellent, with no morbidity and one mortality which was due to cardiac infarction. In the follow-up study, there were four cases with ischemic symptoms, two with transient ischemic attack and two with completed stroke, one of which was a supratentorial infarction due to internal carotid artery occlusion and the other was a small infarction of pons. There were also two deaths due to cardiac infarction and diabetes mellitus. Favorable outcomes were obtained for the remaining cases. The present study suggests that, STA-SCA bypass, can be performed without surgical and systemic complications and used as an effective therapy for vertebrobasilar ischemia.
Adult↗
Return of function after intracranial suture of the trochlear nerve. Case report.
An excellent functional result was obtained after microsuture of a trochlear nerve which was inadvertently divided during the course of a craniotomy. Successful intracranial suture of this nerve has not previously been reported. Ophthalmoscopic detection of excyclotorsion of the eye on the side of the trochlear nerve palsy is discussed, along with its value in the differential diagnosis of acquired vertical diplopia.
Adult↗
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↗
[Advancement of the anterior portion of the superior oblique tendon in case of traumatic bilateral trochlear palsy].
The effect of the advancement of the anterior portion of the superior oblique tendon on cyclovertical and horizontal deviation was studied in seven cases of traumatic bilateral trochlear palsy by using a synoptometer (Cüppers) and cyclodevinometer (Kolling). The anterior portion of the superior oblique tendon was disinserted and advanced laterally according to the amount of the cyclodeviation in primary position with 1 degree/mm. Surgery was done in 5 cases on both eyes, in 2 cases on one eye. The age of the patients ranged from 20 to 64 years (mean 45 years). The excyclodeviation was significantly reduced (p less than .01), however overcorrection was found in the upward gaze. The mean reduction of excyclodeviation in diagnostic positions of gaze was approximately 10-12 degrees. The vertical deviation was significantly reduced in up and downward gaze (p less than .05), nevertheless overcorrection was found in the upward gaze. The mean reduction of the vertical deviation differed according to their positions of gaze. V-pattern esotropia could not be reduced significantly. Therefore an alternative operative approach must be found which can avoid overcorrection in the upward gaze and moreover correct V-pattern esotropia in the downward gaze.
Adult↗
[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↗
Trochlear nerve pareses with brainstem lesions.
Three cases of radiographic localization of fourth nerve lesions are reported: case 1--bilateral pareses due to traumatic contusion; case 2--left paresis from a collicular gunshot wound; and case 3--bilateral pareses due to a (cysticercal) cyst in the caudal cerebral aqueduct.
Adult↗