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.

Trocleítis bilateral corticodependiente / Corticodependent bilateral trochleitis

La trocleítis es habitualmente una inflamación transitoria, unilateral y no incapacitante de la tróclea del oblicuo superior. Presentamos el caso de una trocleítis bilateral en mujer de 29 años de evolución tórpida. Tras estudio etiológico exhaustivo con pruebas de neuroimagen, análisis de autoinmunidad e infeccioso no se encontró ninguna causa subyacente. Precisó múltiples infiltraciones en ambos ojos con efecto parcial. Finalmente se decidió intervención quirúrgica para exploración visual de la tróclea, toma de biopsias e infiltración de metilprednisolona que resultaron eficaces en el alivio sintomático. Este caso es excepcional por su bilateralidad y severidad, suponiendo un desafío terapéutico para el equipo clínico (AU)

Trochleitis is usually a transient and non-disabling inflammation of the trochlea of superior oblique. The case is presented of a difficult to manage bilateral trochleitis in a 29-year-old woman. After an exhaustive aetiological study with neuro-imaging tests, as well as an analysis of autoimmunity and infection, no underlying cause was found. Multiple injections of corticosteroids were required in both eyes, with a partial effect. Surgical intervention was finally decided in order to visually examine the trochlea, take biopsies, and inject methylprednisolone. These were effective in relieving the symptoms. This case is exceptional due to it involving both eyes and its severity, and represented a therapeutic challenge for the clinical team (AU)

Lateral Supracerebellar Infratentorial Approach for Superior Oblique Myokymia: A Case Series.

BACKGROUND: Few reports have shown that superior oblique myokymia (SOM) may result from vascular compression of the trochlear nerve and may be curable using microvascular decompression (MVD). OBJECTIVE: To report the clinical characteristics and surgical treatment of 2 cases of SOM and provide a review of the related literature. METHODS: Two patients with SOM were treated using MVD with the lateral supracerebellar infratentorial approach. The patients underwent diagnostic magnetic resonance imaging and three-dimensional fusion imaging preoperatively. A lateral suboccipital craniotomy was performed in the park-bench position. The trochlear nerve and branches of the superior cerebellar artery were confirmed after opening the cerebellomesencephalic fissure over the tentorial surface of the cerebellum. The vessel, which compressed the root exit zone of the trochlear nerve, was transposed far from the nerve and attached to the surface of the midbrain using Teflon felt and fibrin glue. RESULTS: The first case showed compression on both the ventral and rostral sides of the trochlear nerve root exit zone, and the second showed compression only on the ventral side. Large bridging veins on the tentorial surface of the cerebellum complicated the approach in the second case. Postoperatively, both patients had immediate and complete resolution of symptoms without recurrence at the 24-mo and 17-mo follow-ups, respectively. Five previous reports described the complete resolution of SOM after MVD. CONCLUSION: A presentation of an intermittent fluttering ocular sensation should prompt magnetic resonance imaging for ipsilateral trochlear nerve compression. The lateral supracerebellar infratentorial approach allows safe and efficacious MVD for SOM.

Surgical Technique and Nuances of Resection of a Trochlear Schwannoma: Operative Video.

Cranial nerve schwannomas accounts for around 8% of all benign intracranial tumors, arising most commonly from the vestibular nerve, followed by the trigeminal nerve and other lower cranial nerves. However, trochlear schwannoma in a patient without neurofibromatosis-2 are extremely rare and to date, fewer than 100 cases have been reported in the literature. They are either asymptomatic or present with ophthalmologic or neurologic symptoms. Diplopia is the most common initial symptom. As the tumor grows, it can compress the surrounding brainstem and other cranial nerves, causing neurologic symptoms. Asymptomatic lesions are detected incidentally following imaging for some other reason. There are no clear guidelines for the management of these tumors. In general, small asymptomatic tumors are closely observed by serial imaging and symptomatic or larger tumors are managed by surgical excision and/or stereotactic radiosurgery.1-7 Here we present a 41-year-old female patient with incidentally detected left trochlear schwannoma during the follow-up magnetic resonance imaging (MRI) scans. She was followed up regularly with multiple repeat MRI. Recently she started complaining of occasional headaches, and MRI showed a left peimesencephalic cistern tumor causing mass effect on the ipsilateral midbrain. There was also significant brainstem edema. Hence she underwent left retromastoid suboccipital craniectomy, lateral supracerbellar approach, and complete excision of the tumor. Postoperatively the patient had an uneventful recovery without any new neurologic deficits. At 6 months' follow-up the patient is doing well.

Isolated trochlear palsy as the only presentation of midbrain infarction: a case report.

Trochlear palsy often results from traumatic, congenital and microvascular disorders. An intra-axial lesion as a cause of trochlear palsy is uncommon. Moreover, it usually accompanies other neurological deficits. Isolated trochlear palsy as the only presentation of brainstem stroke is unexpected. This current case report describes a 74-year-old male that presented with trochlear palsy without other neurological signs. Brain magnetic resonance imaging (MRI) revealed an acute midbrain infarction. The case report also reviews recent literature and provides a stepwise algorithm for clinicians to approach patients with trochlear palsy. Despite its rarity, clinicians are advised to consider ischaemic stroke as a cause of trochlear palsy even without other neurological deficits. Early MRI should be performed for prompt and proper management.

Unilateral Isolated Trochlear Nerve Palsy due to Ipsilateral Midbrain Infarction.

Ischemic stroke is a very rare etiology in cases of isolated trochlear nerve palsy, and no reports of ipsilateral trochlear nerve palsy caused by unilateral stroke have so far been published. However, we now report a case of isolated trochlear nerve palsy due to ipsilateral dorsal small midbrain infarction in a 70-year-old woman who presented with acute onset of diplopia. There were no other clinical manifestations, but brain magnetic resonance imaging revealed a small ischemic lesion in the right dorsal midbrain, showing that isolated trochlear nerve palsy can be caused by stroke.

Unilateral Fourth Nerve Palsy due to Presumed Metastatic Melanoma.

ABSTRACT: An 81-year-old man with a history of metastatic melanoma presented with sudden onset of painless, binocular vertical diplopia. The clinical examination was consistent with a right fourth nerve palsy. An MRI of the head revealed a mass dorsal to the right tectum at the level of the inferior colliculus. An MRI just 4 months prior did not show a lesion in that location. An MRA of the head did not show an aneurysm. This is a rare case of an isolated fourth nerve palsy believed to be due to metastatic melanoma compressing the nerve along the dorsal midbrain.

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.

Trochlear Schwannoma Arising from Transition Zone of Nerve Sheath in the Pineal Region: Case Report and Review of the Literature.

BACKGROUND: This report presents the third case of trochlear schwannoma arising from the pineal region and the first case to be resected using a paramedian infratentorial supracerebellar approach. Schwannomas of cranial nerves have traditionally been thought to arise from the transitional point where the axonal envelopment switches from glial cells to Schwann cells; however, recent temporal bone histopathologic evidence from vestibular schwannomas challenges this view. Of the 38 cases of pathology-confirmed trochlear schwannoma in the literature, there are only 2 cases arising from the pineal region, where the nerve sheath transition zone is located. Here, we discuss an unusual case of trochlear schwannoma arising from this transition zone. CASE DESCRIPTION: A 65-year-old man was admitted to our institute after a traffic accident. He complained of headache and dizziness, and a computed tomography scan revealed an isodense mass in the pineal region with obstructive hydrocephalus. Magnetic resonance imaging with contrast showed an enhancing mass in the pineal region. The tumor was subtotally resected using a paramedian infratentorial supracerebellar approach, and pathology confirmed the diagnosis of trochlear schwannoma. CONCLUSIONS: Trochlear schwannoma should be considered when a mass is identified in the pineal region. This diagnosis should still be entertained for mass lesions along the free tentorial edge because the tumor may arise distant from the glial-Schwann transition zone located by the dorsal midbrain. We propose a treatment algorithm for this rare tumor that seeks to maximize functional outcome.

Two-Dimensional Video of Surgery on Trochlear Schwannoma.

Trochlear schwannoma in the absence of neurofibromatosis is a rare entity.1 These schwannomas originate usually from the intradural cisternal part of the nerve and expand in the ambient and interpeduncular cisterns as well as inferiorly in the upper part of the cerebellopontine cistern.2 This case involves a rare pontomesencephalic lesion removed successfully via the simple retrosigmoid suboccipital route (Video 1). A 49-year-old woman presented to our institute with decreased sensation on the left side of her body for 2 months. Neurologic examination revealed left hemihypoesthesia. Cranial magnetic resonance imaging revealed a lobulated, heterogeneously enhanced cystic tumor within the right ambient cistern compressing the adjacent midbrain and extending to the cerebellopontine angle. After obtaining consent for surgery, the patient underwent a right suboccipital retrosigmoid approach for exploration and resection of the lesion. During the operation, it was determined that the tumor originated from the trochlear nerve. Nerve-sparing surgery was performed with intraoperative neuromonitoring including cranial nerve V, VII, X, XI, and XII electromyography and muscle motor evoked potentials. Gross total resection of the tumor was achieved. In the early postoperative period, the patient's eye movements were normal in all directions. The patient did not have any visual problems and experienced improvement in hemihypoesthesia. She was discharged on the third postoperative day. Pathologic examination confirmed diagnosis of schwannoma. At 2 months after surgery, the patient's eye movements were intact, and trochlear nerve palsy did not occur. The patient gave written informed consent for surgery and publication of this case report.

Cause of acquired onset of diplopia due to isolated third, fourth, and sixth cranial nerve palsies in patients aged 20 to 50 years in Korea: A high resolution magnetic resonance imaging study.

AIMS: This study aimed to describe the etiologies of acquired onset of diplopia due to isolated third, fourth, and sixth cranial nerve palsies in young adults in Korea. METHODS: This retrospective study included 127 patients aged 20 to 50 years with acquired onset isolated third, fourth, and sixth cranial nerve palsies who received care at the Strabismus and Neuro-ophthalmology Department of Samsung Medical Center from 2013 to 2017. The etiologies of the palsies determined by clinical assessment, high-resolution magnetic resonance imaging (MRI) with three-dimensional constructive interference in steady state, and laboratory testing were analyzed. RESULTS: Fifty-nine patients manifested sixth cranial nerve palsy. Forty-six patients had fourth cranial nerve palsy and 22 patients had third cranial nerve palsy. The most common etiologies of the ocular motor nerve palsies were presumed inflammatory lesions (21.3%), followed by presumed microvascular causes (17.3%), and neoplasms involving the central nervous system (15.7%). Neoplasms were the most common cause of sixth cranial nerve palsy (25.4%). The most common cause of fourth cranial nerve palsy was presumed microvascular ischemia (28.3%), and presumed inflammatory lesions was the most common cause of third cranial nerve palsy (36.4%). Other non-traumatic causes included vascular lesions, ischemic brainstem stroke, intracranial hemorrhage, non-aneurysmal neuro-vascular contact, multiple sclerosis, and infection. CONCLUSION: A substantial proportion of young adult patients with ocular motor nerve palsies manifested pathologies other than presumed microvascular ischemia or idiopathic causes. Neuroimaging and laboratory tests have important roles in the evaluation of patients aged 20-50 years with acquired ocular motor nerve palsies.

A case of bilateral fourth nerve palsy associated with pseudotumor cerebri syndrome / Caso de paralisia bilateral de quarto nervo associada com síndrome do pseudotumor cerebral

ABSTRACT Pseudotumor cerebri syndrome is puzzling because it results in elevated intracranial pressure with no identifiable underlying cause. Ocular motor nerve palsies, other than a unilateral or bilateral sixth cranial nerve palsy, are rarely seen in patients with this condition. We report here on a 25-year-old female patient with bilateral fourth cranial nerve palsy caused by pseudotumor cerebri syndrome, whose ocular and systemic signs and symptoms of nerve palsy were completely resolved after medical treatment. We infer that fourth nerve palsy could be associated with pseudotumor cerebri syndrome; therefore, clinicians should consider rare ocular motor nerve palsies, even bilaterally, in patients with pseudotumor cerebri syndrome.

RESUMO A sindrome do pseudotumor cerebral é uma síndrome enigmática caracterizada por aumento da pressão intracraniana sem causa definida. Na síndrome do pseudotumor cerebral, as paralisias de nervo oculomotor além da paralisia unilateral ou bilateral do sexto nervo craniano são raramente vistas. Nós reportamos o caso de uma paciente feminina de 25 anos com paralisia bilateral de quarto nervo craniano como resultado da síndrome do pseudotumor cerebral. Após tratamento médico para síndrome do pseudotumor cerebral, os sinais e sintomas oculares e sistêmicos da paralisia nervosa foram resolvidos. Em conclusão, a paralisia de quarto nervo craniano pode estar associada com síndrome de pseudotumor cerebral, portanto médicos devem considerar paralisias raras de nervo oculomotor, mesmo bilateralmente, em pacientes com síndrome do pseudotumor cerebral.

Trochlear nerve palsy associated with Moyamoya disease.

A 48-year-old woman with intracranial hemorrhage at the right hemisphere and the right midbrain was diagnosed as Moyamoya disease (MMD). While restoring consciousness, she complained of diplopia. The left hypertropia with a compensatory right head tilt was noted. The follow up brain image showed the evidence of past hemorrhage at the level of the right inferior colliculus. In this case, the hemorrhage directly damaged the right trochlear nucleus or intra-axial trochlear nerve before decussation and caused left (contralateral) hypertropia. To our knowledge, no report has been described of the trochlear nerve palsy in hemorrhagic Moyamoya disease. Here, we present a case of the patient with trochlear nerve palsy after hemorrhagic MMD and summarize the characteristics of trochlear nerve palsy according to its lesion sites.

A case of bilateral fourth nerve palsy associated with pseudotumor cerebri syndrome.

Pseudotumor cerebri syndrome is puzzling because it results in elevated intracranial pressure with no identifiable underlying cause. Ocular motor nerve palsies, other than a unilateral or bilateral sixth cranial nerve palsy, are rarely seen in patients with this condition. We report here on a 25-year-old female patient with bilateral fourth cranial nerve palsy caused by pseudotumor cerebri syndrome, whose ocular and systemic signs and symptoms of nerve palsy were completely resolved after medical treatment. We infer that fourth nerve palsy could be associated with pseudotumor cerebri syndrome; therefore, clinicians should consider rare ocular motor nerve palsies, even bilaterally, in patients with pseudotumor cerebri syndrome.

Rapidly Growing and Asymptomatic Skull Base Lesion.

Trochlear schwannomas typically present with diplopia and are extremely rare benign intracranial neoplasms that require the combined expertise of neurotologists and neurosurgeons for surgical excision. A combined petrosal approach offers a surgical route for removal of growing and/or symptomatic tumors. A study of a trochlear nerve schwannoma that demonstrated rapid growth but was otherwise asymptomatic was presented in this study.

Transventricular Transvelar Approach to Trochlear Nerve Schwannoma: Novel Technique to Lesions of Inferior Pineal Region.

OBJECTIVES: The schwannoma of the trochlear nerve is rare and originates mostly from the distal parts in the interpeduncular cistern. A lesion on the proximal segment in the inferior pineal region is extremely rare. Because of the rarity of the disease, the surgical approach to this region for the resection of trochlear nerve schwannoma has not been well documented in the literature. We herein describe a novel approach to successfully resect the trochlear nerve schwannoma. METHODS: A 12-year-old boy presented with occipital headache, abnormal gait, and disturbed conjoined eye movement. He was diagnosed with a lesion in the inferior pineal region compressing the superior medullary velum into the roof of the fourth ventricle. A bilateral midline suboccipital craniotomy was performed, and the fourth ventricle was exposed. The lesion was approached through the fourth ventricle superior medullary velum (transventricular transvelar approach). The lesion was totally resected, and his histopathology examination revealed trochlear schwannoma. RESULTS: The patient's symptoms resolved, and he had no recurrence at 12-year follow-up with normal eye movement and vision. CONCLUSION: The transventricular transvelar approach is feasible and safe to treat a lesion of the lower part of the pineal region being pushed through the superior medullary velum.