Microsurgical Resection of a Giant Trochlear Nerve Schwannoma: 2-Dimensional Operative Video

We present the case of a 17-year-old male, who complained of a 1-year onset of pulsatile headache, dysphagia, speech changes, and emotional lability. Neuroimaging revealed a large left-sided contrast-enhancing tumor located at the infratentorial space consistent with a large trochlear nerve schwannoma. The tumor was compressing the brainstem, obstructing the outflow of the third and lateral ventricles causing hydrocephalus, and disturbing the cortico-bulbar pathways bilaterally leading to the diagnosis of pseudobulbar palsy. After the patient consented the surgical procedure, he was operated through a subtemporal transtentorial approach placed in the lateral position. A lumbar drain was used for brain relaxation during the procedure and image guidance to define the limits of surgical exposure. A microsurgical technique was used, aiming to preserve the cranial nerves and the vascular structures running through the perimesencephalic cisterns. Gross total resection was achieved and clinical course remained uneventful aside from a transient third nerve palsy. Symptoms improved and the three-month follow-up revealed an almost complete function of the oculomotor nerve (Video 1). Trochlear nerve schwannomas are the rarest variety of the cranial nerve schwannomas. Depending on tumor size, clinical and neuroimaging signs of mass effect and brainstem compression, treatment can be observation, microsurgical resection through cranial base approaches or radiosurgery.1-5.

Surgical Treatment of Trochlear Nerve Schwannomas: Case Series and Systematic Review

BACKGROUND AND OBJECTIVE

Cranial nerve schwannomas almost always arise from sensory or mixed nerves. Motor cranial nerves, such as the trochlear nerve, are rarely associated with schwannomas. No consensus has yet been made for surgical intervention because of the low number of reported cases of trochlear nerve schwannomas. This study comprises a systematic review of the literature and our experience for surgically treated trochlear nerve schwannomas.

METHODS

Three databases (Web of Science, PubMed, and Cochrane Library) were searched without date restrictions. Studies were included if they were published in the English literature and presented patients of any age who underwent surgical treatment for trochlear schwannoma. Data extracted from the included studies were combined with our experience.

RESULTS

Forty-one studies, presenting 43 patients, met the inclusion criteria. The total number of patients was 45 after our experience was added. The most common symptoms were diplopia (62.2%), headache (46.7%), and motor weakness (37.8%). Mean age during the diagnosis was 45.1 years. Although the subtemporal transtentorial approach (n = 14) is the most preferred method, its application has decreased in recent years. In the last decade, the lateral suboccipital approach (n = 11) has gained popularity. Residual postoperative trochlear nerve deficit was detected in 81% of patients. The probability of neurologic deficit was not statistically associated with tumor volume (P = 0.914), location (P = 0.669), or resection rate (P = 0.554).

CONCLUSIONS

Although trochlear schwannomas are rare and their treatment involves challenges, total resection with the proper approach provides the most desirable results.

Segmental Imaging of the Trochlear Nerve: Anatomic and Pathologic Considerations

BACKGROUND

The trochlear nerve (the fourth cranial nerve) is the only cranial nerve that arises from the dorsal aspect of the midbrain. The nerve has a lengthy course making it highly susceptible to injury. It is also the smallest cranial nerve and is often difficult to identify on neuroimaging.

EVIDENCE ACQUISITION

High-resolution 3-dimensional skull base MRI allows for submillimeter isotropic acquisition and is optimal for cranial nerve evaluation. In this text, the detailed anatomy of the fourth cranial nerve applicable to imaging will be reviewed.

RESULTS

Detailed anatomic knowledge of each segment of the trochlear nerve is necessary in patients with trochlear nerve palsy. A systematic approach to identification and assessment of each trochlear nerve segment is essential. Pathologic cases are provided for each segment.

CONCLUSIONS

A segmental approach to high-resolution 3-dimensional MRI for the study of the trochlear nerve is suggested.

Cavernoma of the trochlear nerve

Here we present the case of a 53-year old man with progressive double vision due to isolated left trochlear nerve palsy. Cranial magnetic resonance imaging (MRI) showed a small tumor within the left quadrigeminal cistern that did not increase in size after several months. Explorative neurosurgical intervention revealed a left trochlear nerve cavernoma. The lesion was microsurgically excised followed by end-to-end anastomosis of the trochlear nerve. After a one-year follow up, double vision totally disappeared and cranial MRI showed no recurrence. Cerebral cavernous malformations usually become symptomatic in seizures or focal neurological deficits after intracerebral hemorrhage. Rarely, cavernomas arise from cranial nerves. To the authors' knowledge, this is the first report on a symptomatic cavernous malformation arising from the trochlear nerve and on its successful surgical management.

Cystic trochlear nerve schwannoma. Case report

BACKGROUND

Twenty-six cases of pathologically verified schwannomas of the trochlear nerve have been reported in the literature. Five of them had a large cystic component and a smaller solid portion. Complex skull base approaches have been usually applied for their removal.

CASE DESCRIPTION

We report on a rare case of cystic trochlear schwannoma in a 52-year-old female patient. The patient presented with double vision, facial palsy, decreased hearing, hemiparesis on the right side, and severe gait instability. Magnetic resonance imaging revealed a 2.5-cm left-sided extra-axial lesion compressing the brain stem at the lower midbrain and upper pontine level. Total resection was performed via a retrosigmoid craniotomy. After the surgery, the neurological deficit diminished considerably. At 28 months follow-up, her only complaint was mild double vision when walking down the stairs and hypesthesia in the right half of her face.

CONCLUSIONS

This case represents a rare pontomesencephalic lesion removed successfully via the simple retrosigmoid route.

Primary trochlear headache and other trochlear painful disorders

The trochlear region is a source of distinct pain that may give rise to specific primary pain disorders (primary trochlear headache), but also modulate other pre-existing headache disorders such as migraine. The sensory innervation of this region, by a branch of the ophthalmic division of the trigeminal nerve, may explain the modulatory influence of the nociceptive afferents of this region over migraine headache. We propose the term "trochlear migraine" to refer to the coexistence of strictly unilateral migraine and ipsilateral trochleodynia, with the improvement of migraine being dependent on the resolution of the trochleodynia. Trochleitis is an inflammatory trochleodynia, being frequently idiopathic and rarely secondary to usually immunologic and rheumatologic disorders. We postulate that nociceptive afferents from the inner part of the orbit may sustain the activation of trigeminal neurons, thus sensitizing or exacerbating migraine. Decreasing the possible wind-up induced from this nociceptive afferent stimulation may be effective in controlling headache.

Paralysies oculomotrices douloureuses : une approche diagnostique

We review the question of diagnosis of painful and relatively isolated ophthalmoplegia due to diseases affecting the ocular motor nerves. For each clinical setting, we provide an overview of the main causes and a practical way to approach the diagnosis. As vascular malformations should always be kept in mind in patients with painful ophthalmoplegia, emergency neuroradiological investigations may be needed. However, the etiological scope is wide and the rationale for choosing the more appropriate examination and its optimal timing depends exclusively on the clinical evaluation. Despite advances in investigation techniques, diagnosis may remain difficult or even unresolved in a certain number of patients. We discuss successively paralysis of the third, sixth and fourth nerve, paralysis of several ocular motor nerves, recurrent ophthalmoplegia and ischaemic ocular motor palsies, which are the most frequent cause.

Parésie trochléaire transitoire comme signe neurologique inaugural d’une panartérite noueuse

INTRODUCTION

Panarteritis nodosa (PAN) is a systemic vasculitis affecting small and medium-sized arteries. Neuro-ophthalmological complications of PAN are rare but numerous, and may affect the eye, the visual and the oculomotor pathways. Such complications occur mainly in patients previously diagnosed with PAN.

OBSERVATION

A 51-year-old woman presented with an isolated right trochlear (IV) palsy, in the setting of headaches and fluctuating fever of unknown etiology. Erythrocyte sedimentation rate was 13 mm and full blood cell count was normal. Previous chest X-ray and blood studies were negative for an infection or inflammation. Orbital and cerebral CT scan was normal. Spontaneous recovery of diplopia ensued over four days. Two days later, paresthesia and sensory paresis of the dorsal portion of the left foot were present. Lumbar puncture revealed 14 leucocytes (76 percent lymphocytes) with elevated proteins, but blood studies and serologies were negative. A diagnosis of undetermined meningo-myelo-radiculoneuritis was made. Because of a possible tick bite six weeks previously the patient was empirically treated with 2 g intravenous ceftriaxone for 3 weeks. Fever rapidly dropped. Six weeks after the onset of diplopia, acute onset of blindness in her right eye, diffuse arthralgias and fever motivated a new hospitalization. There was a central retinal artery occlusion of the right eye. Blood studies now revealed signs of systemic inflammation (ESR 30 mm, CRP 12 mg/L, ANA 1/80, pANCA 1/40, leucocytosis 12.4 G/L, Hb 111 g/L, Ht 33 percent). Biopsy of the left sural nerve revealed arterial fibrinoid necrosis. A diagnosis of PAN was made.

CONCLUSIONS

Transient diplopia can be the heralding symptom of a systemic vasculitis such as PAN, giant cell arteritis and Wegener granulomatosis. In this patient the presence of accompanying systemic symptoms raised a suspicion of systemic inflammation, but the absence of serologic and imaging abnormalities precluded a specific diagnosis initially. A few weeks later, the presence of a second ischemic event (retinal) and positive blood studies led to a further diagnostic procedure. Oculomotor and abducens palsies have rarely been reported in association with PAN. We report the first case of trochlear nerve paresis as the inaugural neurological sign of PAN. This case highlights the importance of considering inflammatory systemic disorders in patients with acute diplopia particularly when they are young, lack vascular risk factors or cause, and complain of associated systemic symptoms.

Acute ocular motor mononeuropathies: prospective study of the roles of neuroimaging and clinical assessment

The role for immediate neuroimaging in patients 50 years of age or older with acute isolated third, fourth, and sixth nerve palsies is controversial. We prospectively evaluated 66 patients, aged 50 years and older (median 67 years, range 50-85), with acute isolated ocular motor mononeuropathies. Our purpose was to evaluate both the role of neuroimaging and the role of clinical assessment in determining etiology. We found that clinical features, including time to maximal diplopic symptoms, were not predictive of etiology (median 2 days to maximal diplopic symptoms for both peripheral microvascular and other etiologies). The presence of any common vascular risk factor, including diabetes mellitus, hypertension, hypercholesterolemia, or coronary artery disease, was significantly associated with peripheral microvascular etiology in this cohort (p=0.0004, Fisher's exact test). Despite the high prevalence of peripheral microvascular ischemia as an etiology in this age group, other causes were identified by magnetic resonance imaging (MRI) or computed tomography (CT) scanning in 14% of patients. Diagnoses included brainstem and skull base neoplasms, brainstem infarcts, aneurysms, demyelinating disease, and pituitary apoplexy. Neuroimaging procedures may have a role in the initial evaluation of patients 50 years of age or older with acute ocular motor mononeuropathies.

Transient isolated trochlear nerve palsy associated with Rathke's cleft cyst

We report the case of a 52-year-old woman who developed vertical diplopia of 1-days duration. Neuro-ophthalmological testing revealed left trochlear nerve palsy, and sellar MRI revealed a 1.5 cm-sized pituitary mass lesion, a Rathke's cleft cyst. The diplopia disappeared spontaneously after 6 days.

Trochlear Nerve Palsy after Repeated Percutaneous Balloon Compression for Recurrent Trigeminal Neuralgia: Case Report and Pathogenic Considerations

OBJECTIVE AND IMPORTANCE

Repeated percutaneous balloon compression for the treatment of idiopathic trigeminal neuralgia is infrequent. When a second procedure is performed, the outcome is unknown. A patient developed an isolated trochlear nerve palsy after undergoing percutaneous trigeminal ganglion balloon compression for a second time. The mechanism of diplopia and the complications associated with this technique were studied.

CLINICAL PRESENTATION

The patient was a 67-year-old woman with a history of medically refractory idiopathic trigeminal neuralgia involving all three divisions of the right trigeminal nerve.

INTERVENTION

Percutaneous balloon compression was performed. Despite initial total relief from pain without complications, the patient again displayed manifestations of trigeminal neuralgia 3 months after the procedure. The pain disappeared after she underwent a second balloon compression procedure, but she developed an isolated trochlear nerve palsy, which spontaneously resolved in 2 months.

CONCLUSION

Isolated trochlear nerve palsy is a rare and reversible complication after percutaneous balloon compression for trigeminal neuralgia. This case illustrates that the mechanism of injury to the fourth nerve is the result of an erroneous technique: excessive penetration of the Fogarty catheter in Meckel's cave beyond the porus trigemini and compression of the cisternal segment of the trochlear nerve when the inflated balloon is pushed against the tentorium.

Cystic schwannoma of the anterior tentorial hiatus. Case report and review of the literature

Intracranial schwannomas not arising from the facial, trigeminal, or vestibular nerves in the absence of neurofibromatosis are extremely rare. We report a case of a schwannoma arising in the region of the anterior tentorial hiatus and posterior cavernous sinus. A 17-year old girl presented with headaches and intermittent diplopia. An MRI of the brain revealed a heterogeneously enhancing mass adjacent to the free edge of the tentorium, superior to the cerebellopontine angle. An orbitozygomatic pterional craniotomy was done with complete resection of the tumor. Postoperatively, the patient remained neurologically intact. The clinical presentation and treatment of schwannomas arising in this location are discussed.

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.

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.

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.

Presigmoid transpetrosal approach for the treatment of a large trochlear nerve schwannoma--case report

A 61-year-old man presented with a rare, large trochlear nerve schwannoma manifesting as left-sided weakness and hypesthesia, bilateral bulbar pareses, and trochlear nerve paresis persisting for 3 months. T1-weighted magnetic resonance imaging with gadolinium revealed an intensely enhanced, well-circumscribed lesion with multicystic formation occupying the prepontine and interpeduncular cisterns and compressing the pons and midbrain with greater extension to the right. The mass was completely removed through the presigmoid transpetrosal approach with preservation of the posterior cerebral, superior cerebellar, and basilar arteries and their branches. Neuroradiological examination after 3 years demonstrated no recurrence. Enlargement of a tumor in the cisternal portion is inclined to involve and/or encase the adjacent major arteries and their branches. The presigmoid transpetrosal approach is one of the best surgical routes to remove a large trochlear nerve schwannoma safely and completely.

[Neuroradiological imaging of the 3rd, 4th and 6th cranial nerves]

The ocular motor cranial nerves (III, IV, VI) control the eye movements in a near association with the higher cortical areas. Clinically, the most common presentation of abnormal ocular motility is double vision. Identifying the cause of ocular nerve palsy can be difficult, and a large percentage of such cases still remains undiagnosed, even in a new era of neuroradiological techniques. Close co-operation between the clinician and the radiologist is necessary for the selection of the best imaging methods for the specific clinical problem, in order to set the aetiological and topological diagnosis. This article provides a practical review of advances in neuroimaging of the ocular motor nerves.