Agenesis of the oculomotor and trochlear nerves in a hydrocephalic foal.
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[Contribution to the study of structure substituting the proprioceptive sensibility of the extrinsic ocular musculature: demonstration of unipolar cells in the ganglia and roots of the trochlear nerve].
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Animals↗
Trochlear nerve neuroma manifested with intractable atypical facial pain: case report.
OBJECTIVE AND IMPORTANCE: Trochlear nerve neuromas are extremely rare. Seventeen surgical cases of this pathological condition have been reported in the English literature. The presented case is distinct from previous reports. CLINICAL PRESENTATION: A 26-year-old woman presented with atypical facial pain. The neurological examination results were normal. Magnetic resonance imaging revealed a left parasellar mass. INTERVENTION: A left pterional craniotomy was performed, providing access to the left parasellar area. After incision of the tentorial edge, the tumor was observed to originate from the short segment of the trochlear nerve that runs between the tentorial leaves. The neuroma was totally removed. CONCLUSION: The facial pain resolved immediately after surgery. Although facial dysesthesias have been noted among patients with trochlear nerve neuromas, here the atypical facial pain was the only clinical manifestation. In all previously reported cases, neuromas originated from the cisternal segment of the trochlear nerve (always before the site of nerve entrance into the tentorial leaves) and expanded mainly into the prepontine and interpeduncular cisterns. Subtemporal and suboccipital approaches were used. In this case, the tumor arose from the short segment of the nerve running between the tentorial leaves. The tumor did not extend either into the ambient cistern or into the cavernous sinus but did involve the parasellar area. A pterional approach was appropriate for tumor removal. A trochlear nerve neuroma should be considered as a potential cause of atypical facial pain.
Adult↗
Cavernous portion of the trochlear nerve with special reference to its site of entrance.
In a study of 80 cavernous sinuses in 40 cadavers, the trochlear nerve entered the cavernous sinus in 87.5% of cases before the crossing, in 7.5% at the crossing and in 5.0% after the crossing of the free and the attached margins of the tentorium cerebelli. In 77.5% of specimens the trochlear nerve showed a marked bend with flattening at the site of its entrance into the cavernous sinus. The nerve ran between the superficial and deep layers of dura, partly between them, in the thickness of the deeper layer, or deep to the deep layer but adherent to it. These findings do not conform with the description of its course by other workers in the past. In 72.5% of specimens the size of the trochlear nerve was larger during its course in the cavernous sinuses but in 20.0% of specimens such an increase in thickness was noted even in the posterior cranial fossa. Only in one specimen was the trochlear nerve adherent to the ophthalmic division of the trigeminal nerve. Cases showing the trochlear nerve entering the cavernous sinus after the crossing of the two margins of tentorium cerebelli and the splitting and branching of the trochlear nerve in the cavernous sinus have not hitherto been reported.
Adult↗
Trochlear nerve schwannoma with intratumoral hemorrhage: case report.
OBJECTIVE AND IMPORTANCE: Schwannomas originating from the trochlear nerve without neurofibromatosis are extremely rare. Thirty-four cases have previously been reported in the literature, and only 25 cases were pathologically diagnosed. In addition, intratumoral hemorrhage in intracranial schwannomas is also rare. Approximately 30 cases of intracranial schwannomas with intratumoral hemorrhage have been reported. CLINICAL PRESENTATION: A 42-year-old man presented with left hemiparesis and right trochlear nerve palsy. Magnetic resonance imaging revealed an abnormal cystic lesion beside the brainstem. His symptoms rapidly worsened after enlargement of the mass because of intratumoral hemorrhage. INTERVENTION: Gross total removal of the tumor was performed via the anterior transpetrosal approach. The tip of the trochlear nerve was fanned out and unified with the tumor. The tumor was diagnosed as a schwannoma. CONCLUSION: The patient's hemiparesis improved postoperatively, and he was discharged 1 week after the operation. Magnetic resonance imaging performed 4 months later revealed no regrowth of the tumor. Only right trochlear nerve palsy has persisted. This report is the second case of intratumoral hemorrhage from a trochlear nerve schwannoma.
Adult↗
Localization of post-traumatic trochlear nerve palsy associated with hemorrhage at the subarachnoid space by magnetic resonance imaging.
PURPOSE: To report evaluation of traumatic trochlear nerve palsy using head magnetic resonance imaging. DESIGN: Observational case reports. METHODS: We examined two cases involving trochlear nerve palsy after closed head injury. RESULTS: Using a fluid attenuated inversion recovery pulse sequence, MRI showed a high-intensity lesion consistent with subarachnoid hemorrhage at the trochlear nerve area in the ambient cisterns. CONCLUSION: An impact force directed toward the tentorium can be a mechanism of injury in some post-traumatic trochlear nerve palsies. Fluid attenuated inversion recovery pulse sequence is a sensitive method for detection of abnormalities in cases associated with head injury.
Adolescent↗
Relationships of the cisternal segment of the trochlear nerve.
OBJECT: The cisternal portion of the trochlear nerve (fourth cranial nerve) can easily be injured during intracranial surgical operations. To help minimize the chance of such injury by promoting a thorough understanding of the anatomy of this nerve and its relationships to surrounding structures, the authors present this anatomical study. METHODS: In this study, in which 12 cadaveric heads (24 sides) were used, the authors describe exact distances between the trochlear nerve and various surrounding structures. Also described are relatively safe areas in which to manipulate or enter the tentorium, and these are referenced to external landmarks. CONCLUSIONS: This information will prove useful in planning and executing surgical procedures in and around the free edge of the tentorium cerebelli.
Aged↗
Trochlear nerve schwannoma removed by combined petrosal approach.
Trochlear nerve schwannoma is an extremely rare intracranial tumour. It is a benign tumour often presenting late with the involvement of neighbouring structures and potentially life threatening complications. We report a case of this condition, which is the first to be treated by surgery via a presigmoid 'combined petrosal approach' with follow-up by magnetic resonance imaging (MRI) for 6 years. The advantages of the presigmoid combined petrosal approach for this type of tumour are described. Early investigation of patients with unexplained trochlear nerve palsy by MRI will facilitate the management of these rare tumours.
Cranial Nerve Neoplasms↗
MR anatomy of the proximal cisternal segment of the trochlear nerve: neurovascular relationships and landmarks.
PURPOSE: To assess the anatomic features and vascular relationships of the proximal portion of the cisternal segment of the trochlear nerve. MATERIALS AND METHODS: In 30 subjects (60 nerves) and in one patient with right superior oblique myokymia (SOM), the anatomy of the trochlear nerve was depicted with three-dimensional (3D) Fourier transformation constructive interference in steady state (CISS) magnetic resonance (MR) imaging, whereas the adjacent vessels were detected with 3D time-of-flight (TOF) MR imaging before and after gadopentetate dimeglumine administration. The images were evaluated with respect to the identification of the trochlear nerve, the distance between the point of exit (PE) and the midline, the visualized length, the vascular relationships, and the distance between the PE and the point of neurovascular contact. RESULTS: 3D CISS MR imaging depicted the proximal cisternal segment of the trochlear nerve in the transverse, sagittal, and coronal planes in 57 (95%), 51 (85%), and 48 (80%) of 60 nerves, respectively. The distance from the midline to the PE was 3-9 mm, and the maximum visualized length of the trochlear nerve was 1-14 mm. An arterial-trochlear neurovascular contact was seen at the root exit zone (REZ) in eight (14%) nerves and at a mean distance of 3.4 mm distal to the PE in 29 nerves (51%). The patient with SOM had arterial-trochlear neurovascular contact at the REZ. CONCLUSION: Use of 3D CISS sequences and 3D TOF sequences with or without gadopentetate dimeglumine enables accurate identification of the proximal cisternal segment of the trochlear nerve and its neurovascular relationships.
Adult↗
Bilateral trochlear nerve paresis in hydrocephalus.
Three patients with nonneoplastic hydrocephalus had bilateral paresis of the trochlear nerves. Associated signs, including paresis of upgaze, light-near dissociation of the pupils, and convergence-retraction nystagmus, suggested rostral involvement of the mesencephalon. Trochlear nerve paresis and accompanying signs improved after revision of ventricular shunts in two patients. Bilateral trochlear nerve paresis may be a localizing sign of involvement of the superior medullary velum (the anatomic site of trochlear nerve decussation) by a dilated sylvian aqueduct and/or downward pressure from an enlarged III ventricle.
Adolescent↗
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↗
[A case presenting with trochlear nerve palsy and segmental sensory disturbance due to circumscribed midbrain and upper pontine hemorrhage].
We describe a patient presenting with trochlear nerve palsy and segmental sensory disturbance due to circumscribed mesencephalic hemorrhage. A 36-year-old man with no past illness visited our hospital complaining of sudden onset of diplopia, dysesthesia of the left face and upper extremity, and acuphenes of the left ear. Neurological examination revealed left trochlear nerve palsy and segmental sensory disturbance of the left side almost above T11 level. Pain and temperature sensation were disturbed, but vibration, joint position, graphesthesia, kinesthesia, and discrimination sensation were spared. Magnetic resonance imaging of the head, performed 7 days after onset, revealed acute to subacute phase hemorrhage at the right inferior colliculus. No abnormalities were identified on cerebral angiography. Symptoms gradually improved with conservative therapy. After about ten weeks, diplopia disappeared and area of sensory disturbance was reduced (disturbance of pain sensation reduced to about T4 level, temperature sensation to about T9). Segmental sensory disturbance usually accompanies spinal cord lesion. However, several cases of similar symptoms following cerebrovascular disease of the brainstem have been reported. Conversely, some reports have indicated that trochlear nerve palsy due to midbrain hemorrhage accompanies sensory disturbance contralateral to the lesion. The nature of sensory disturbance is thus variable. The present case suggests that segmental sensory disturbance might accompany trochlear nerve palsy caused by hemorrhage of the inferior colliculus, as intramedullary fibers of the trochlear nerve and spinothalamic tract are located nearby and somatotopy of the spinothalamic tract is preserved even at the level of the midbrain.
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↗
Trochlear nerve schwannomas occurring in patients without neurofibromatosis: case report and review of the literature.
OBJECTIVE AND IMPORTANCE: Despite their predilection for sensory nerves, intracranial schwannomas have been reported in a number of mixed and purely motor cranial nerves, especially in association with Type 2 neurofibromatosis. We report the rare occurrence of a trochlear nerve schwannoma in a patient without neurofibromatosis and review 17 other case reports from the literature. CLINICAL PRESENTATION: A 35-year-old woman presented with an 8-week history of evolving left hemiparesis, bilateral bulbar paresis, and out-of-character emotional lability. INTERVENTION: She underwent a left temporal craniotomy and a subtemporal, transtentorial approach to the tentorial hiatus, with complete excision of a cisternal trochlear nerve schwannoma. CONCLUSION: Postoperative complications included temporary oculomotor and abducens nerve palsies and temporary right hemiparesis and mild expressive dysphasia, which were resolved at 23-month follow-up. Preoperative symptoms and signs completely resolved, but a postoperative complete trochlear nerve palsy required inferior oblique myectomy for correction of diplopia. A review of the literature showed no preoperative trochlear nerve involvement in at least 45% of cases. The tumor is isointense on T1- and T2-weighted magnetic resonance images and enhances brightly with gadolinium. The most frequently used approach for surgical excision is the subtemporal approach, and the tumor is almost always totally excised. Long-term follow-up suggests recovery of preoperative deficit, and persisting or new trochlear nerve palsy is the rule.
Adult↗
Isolated trochlear nerve palsy in patients with multiple sclerosis.
The authors describe five patients with trochlear nerve palsy and MS to characterize this rare association. In two patients, trochlear nerve palsy was the initial clinical manifestation of MS. In the other three patients, this sign occurred after previous neurologic events. MRI did not identify a lesion of the fourth nerve nucleus or fascicle. Ophthalmoplegia resolved within 2 months in four of the five patients. A reason this association is rare is that the fascicular course of the trochlear nerve is exposed to little myelin.
Adult↗
Trochlear nerve palsy following minor head trauma. A sign of structural disorder.
Trauma-induced superior oblique palsy usually results from contusion or avulsion of the trochlear nerve or from decompensation of a congenital trochlear nerve palsy. Severe craniocerebral trauma is often associated with the former mechanism, whereas more minor closed-head injuries can decompensate a congenital phoria. We report a patient who developed an isolated trochlear nerve palsy following minor head trauma. Investigation revealed an unsuspected tentorial vascular malformation that was compressing the trochlear nerve in its subarachnoid course. In the absence of other features (e.g., documentation of old head tilt, large vertical fusion amplitudes) that support decompensation of a congenital phoria, compressive lesions should be sought in cases of fourth cranial nerve palsies that follow minor head trauma.
Cranial Nerve Diseases↗
[Midbrain hemorrhage presenting with trochlear nerve palsy--a case report].
A case of midbrain hemorrhage with isolated trochlear nerve palsy was reported. A 70-year-old female noticed vertical diplopia of insidious onset. Ouclar motility was normal. But her diplopia increased with right head tilt and in the left downward gaze, and disappeared with left head tilt. She had no other neurological symptoms and signs. CT scan revealed high density spot in the left tectum of lower midbrain. This lesion decreased over months but small high density spot existed five months later, which means calcified lesion, probably vascular anomaly. This is the first stroke case of trochlear nerve palsy without other neurological symptoms and signs. The first reason this patient showed isolated trochlear nerve palsy is that hematoma was small. The second is that hematoma developed slowly.
Aged↗
Bilateral trochlear nerve palsies. A clinicoanatomic correlate.
A patient with bilateral trochlear nerve palsies is presented. Computed tomographic (CT) brain scan localized an anterior cerebellar vermis lesion compressing the area caudal to the inferior colliculi where the fourth nerves decussate and exit the dorsal brain stem. This lesion was probably responsible for the bilateral trochlear nerve dysfunction. Pertinent anatomy and pathologic involvement are discussed.
Adenocarcinoma↗