Cystic trochlear nerve schwannoma. Case report

Imaging of trochlear nerve schwannomas: a case series and systematic review of the literature

Purpose Trochlear nerve schwannomas are rare tumors. So far, only 121 cases have been published. We present four new cases, discuss the imaging characteristics and summarize all previously published cases through a systematic review.Methods Four cases, all treated in AZ Sint-Jan Hospital Brugge-Oostende (Belgium), were collected, including their demographic, clinical and radiological data. All MR imaging was performed with the three-dimensional fluid-attenuated inversion recovery (3D-FLAIR), turbo spin echo T1 high-resolution (TSE T1 HR), three-dimensional balanced fast-field echo (3D b-FFE) and three-dimensional T1 black blood (3D T1 black blood) sequence. We compared our findings with the present literature through a systematic literature review in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.Results Screening with routine unenhanced 3D-FLAIR imaging could identify all schwannomas as hyperintense lesions on the course of the trochlear nerve. The use of 3D T1 black blood sequences was superior in depicting the lesions, while high-resolution 3D b-FFE images enabled us to visualize the anatomic boundaries of the lesions in detail. Most trochlear schwannomas are located in the ambient cistern, at or just below the free edge of the tentorium.Conclusion The majority of trochlear nerve schwannomas are located cisternal and display variable enhancement on contrast administration. 3D-FLAIR imaging is superior in detecting these lesions. Comparison with data collected from previous cases demonstrates the importance of early diagnosis and treatment. Generally, patients with trochlear nerve schwannomas have a good prognosis.

Hemorrhagic schwannoma of the trochlear nerve: Case report and a review of the literature

Background

Schwannomas of the trochlear nerve with the absence of systemic neurofibromatosis are considerably uncommon, especially complicated by intra-tumoral hemorrhage. Due to the lack of typical clinical manifestations and imaging findings, a definite diagnosis of trochlear schwannomas before surgery is particularly difficult.

Case presentation

We report the case of a 64-year-old female patient who presented with a unilaterally intermittent headache of 2-month duration and without a remarkable neurological deficit at admission. Imaging studies revealed a well-demarcated cystic-solid lesion with mixed signals beside the brainstem and suprasellar cisterna. The patient underwent a surgical operation with total resection of the tumor by a subtemporal surgical approach. The tumor was intraoperatively found to originate from the trochlear nerve and was pathologically confirmed as a hemorrhagic schwannoma with cystic degeneration.

Conclusions

We describe this case in detail and conduct a concomitant survey of the literature, summarizing the clinical presentations, radiological features, surgical treatment, and the possible mechanisms of hemorrhage in relevance to trochlear nerve schwannoma.

Schwannomas of Brain and Spinal Cord

Schwannomas are benign tumors originating from the Schwann cells of cranial or spinal nerves. The most common cranial schwannomas originate from the eight cranial nervevestibular schwannomas (VS). VS account for 6-8% of all intracranial tumors, 25-33% of the tumors localized in the posterior cranial fossa, and 80-94% of the tumors in the cerebellopontine angle (CPA). Schwannomas of other cranial nerves/trigeminal, facial, and schwannomas of the lower cranial nerves/are much less frequent. According to the World Health Organization (WHO), intracranial and intraspinal schwannomas are classified as Grade I. Some VS are found incidentally, but most present with hearing loss (95%), tinnitus (63%), disequilibrium (61%), or headache (32%). The neurological symptoms of VSs are mainly due to compression on the surrounding structures, such as the cranial nerves and vessels, or the brainstem. The gold standard for the imaging diagnosis of VS is MRI scan. The optimal management of VSs remains controversial. There are three main management options-conservative treatment or "watch-and-wait" policy, surgical treatment, and radiotherapy in all its variations. Currently, surgery of VS is not merely a life-saving procedure. The functional outcome of surgery and the quality of life become issues of major importance. The most appropriate surgical approach for each patient should be considered according to some criteria including indications, risk-benefit ratio, and prognosis of each patient. The approaches to the CPA and VS removal are generally divided in posterior and lateral. The retrosigmoid suboccipital approach is a safe and simple approach, and it is favored for VS surgery in most neurosurgical centers. Radiosurgery is becoming more and more available nowadays and is established as one of the main treatment modalities in VS management. Radiosurgery (SRS) is performed with either Gamma knife, Cyber knife, or linear accelerator. Larger tumors are being increasingly frequently managed with combined surgery and radiosurgery. The main goal of VS management is preservation of neurological function - facial nerve function, hearing, etc. The reported recurrence rate after microsurgical tumor removal is 0.5-5%. Postoperative follow-up imaging is essential to diagnose any recurrence.

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.

Frequency of Diplopia after Intraoperative Nerve Disturbance in Trochlear Nerve Schwannoma: A Case Report and Systematic Review

Schwannomas of the trochlear nerve are relatively rare, and most patients present with preoperative diplopia because of trochlear nerve palsy. We describe the case of a 61-year-old male patient with a trochlear nerve schwannoma and no pre- and postoperative diplopia, despite his trochlear nerve being cut during the operation. We aimed to investigate the frequency of postoperative diplopia associated with intraoperative trochlear nerve disturbance by reviewing previous case reports, wherein postoperative diplopia did not occur after the trochlear nerve was cut intraoperatively. We recorded the frequency of diplopia because of intraoperative trochlear nerve disturbance, such as the trochlear nerve being cut, in cases without pre- and postoperative diplopia. We searched the PubMed, Medline, and Google Scholar databases for works published from 1976 to 2020 and followed the preferred reporting items for systematic reviews and meta-analyses guidelines. We reviewed 36 publications and found 92 cases of trochlear nerve schwannoma. Surgical resection was performed for 43 patients, of whom 40 were kept under observation and 9 were treated with radiation therapy. Of the 43 cases, 9 without preoperative diplopia underwent gross total resection. We analyzed ten cases (including ours) without preoperative diplopia to check for postoperative diplopia. In total, four cases, including ours, did not display postoperative diplopia despite the trochlear nerve being cut. This may be attributed to the preoperatively acquired motor and sensory fusion in the patient's vision because of tumor progression. Our findings may benefit neurosurgeons who treat patients with schwannomas and help them predict patients' outcomes.

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.

Schwannoma of the trochlear nerve-an illustrated case series and a systematic review of management

Schwannomas of cranial nerves in the absence of systemic neurofibromatosis are relatively rare. Among these, schwannomas of the trochlear nerve are even less common. They can be found incidentally or when they cause diplopia or other significant neurological deficits. Treatment options include observation only, neuro-ophthalmological intervention, and/or neurosurgical management via resection or sterotactic radiosurgery (SRS). In recent years, the latter has become an attractive therapeutic tool for a number of benign skull base neoplasm including a small number of reports on its successful use for trochlear Schwannomas. However, no treatment algorithm for the management of these tumors has been proposed so far. The goal of this manuscript is to illustrate a case series of this rare entity and to suggest a rational treatment algorithm for trochlear schwannomas, based on our institutional experience of recent cases, and a pertinent review of the literature. Including our series of 5 cases, a total of 85 cases reporting on the management of trochlear schwannomas have been published. Of those reported, less than half (40 %) of patients underwent surgical resection, whereas the remainder were managed conservatively or with SRS. Seventy-six percent (65/85) of the entire cohort presented with diplopia, which was the solitary symptom in over half of the cases (n = 39). All patients who presented with symptoms other than diplopia or headaches as solitary symptoms underwent surgical resection. Patients in the non-surgical group were mostly male (M/F = 3.5:1), presented at an older age and had shorter mean diameter (4.6 vs. 30.4 mm, p < 0.0001) when compared to the surgical group. Twelve patients in the entire cohort were treated with SRS, none of whom had undergone surgical resection before or after radiation treatment. Trochlear schwannoma patients without systemic neurofibromatosis are rare and infrequently reported in the literature. Of those, patients harboring symptomatic trochlear Schwannomas do not form a single homogenous group, but fall into two rather distinct subgroups regarding demographics and clinical characteristics. Among those patients in need of intervention, open microsurgical resection as well as less invasive treatment options exist, which all aim at safe relief of symptoms and prevention of progression. Both open microsurgical removal as well as SRS can achieve good long-term local control. Consequently, a tailored multidisciplinary treatment algorithm, based on the individual presentation and tumor configuration, is proposed.

Trochlear Nerve Schwannoma Treated with Gamma Knife after Excision: A Case Report and Review of the Literature

Trochlear nerve schwannomas are extremely rare. We present a surgically excised case of trochlear nerve schwannoma followed by Gamma Knife (ELEKTA, Stockholm, Sweden) after histologic confirmation. A 52-year-old man presented with diplopia, gait disturbance, and sensory disturbance. Magnetic resonance imaging demonstrated a large cystic mass at ambient cistern on the right side. Subtotal excision followed by Gamma Knife surgery was undertaken. His neurologic symptoms disappeared with radiologic reduction in size at 15-month follow-up. Because Gamma Knife can manage trochlear nerve schwannomas well, surgical excision should be reserved for large ones and limited to subcapsular or subtotal removal with the expectation of possible recovery of neurologic dysfunction.

Trochlear nerve schwannoma with intratumoral hemorrhage presenting with persistent hiccups: a case report

Trochlear nerve schwannoma without neurofibromatosis is extremely rare. To our knowledge, only 31 surgical cases have been reported to date, and only 2 cases of trochlear nerve schwannoma with intratumoral hemorrhage have been reported. None of those cases presented with persistent hiccups. We report the case of a 44-year-old man with trochlear nerve schwannoma associated with intratumoral hemorrhage who presented with a 10-day history of persistent hiccups. Computed tomography and magnetic resonance imaging revealed a solid tumor with a 3-cm diameter and intratumoral hemorrhage in the left petroclival region that compressed the midbrain and pons. Subtotal removal of the tumor was performed via the zygomatic transpetrosal approach. Intraoperative findings revealed a tumor arising from the trochlear nerve. The histologic diagnosis was schwannoma of Antoni type A cells with intratumoral hemorrhage. Although the patient's left trochlear nerve palsy worsened temporarily, his postoperative course was uneventful. We present this rare case and discuss the mechanism underlying the patient's persistent hiccups.

Intracranial nonvestibular neurinomas: Young neurosurgeons' experience

BACKGROUND AND OBJECTIVES

Neurinoma arising from other than nonvestibular cranial nerves is less prevalent. Here we present our experiences regarding the clinical profile, investigations, microneurosurgical management, and the outcome of nonvestibular cranial nerve neurinomas.

MATERIALS AND METHODS

From January 2005 to December 2011, the recorded documents of operated nonvestibular intracranial neurinomas were retrospectively studied for clinical profile, investigations, microneurosurgical management, complications, follow-up, and outcomes.

RESULTS

The average follow-up was 24.5 months. Total number of cases was 30, with age ranging from 9 to 60 years. Sixteen cases were males and 14 were females. Nonvestibular cranial nerve schwannomas most commonly originated from trigeminal nerve followed by glossopharyngeal+/vagus nerve. There were three abducent nerve schwannomas that are very rare. There was no trochlear nerve schwannoma. Two glossopharyngeal+/vagus nerve schwannomas extended into the neck through jugular foramen and one extended into the upper cervical spinal canal. Involved nerve dysfunction was a common clinical feature except in trigeminal neurinomas where facial pain was a common feature. Aiming for no new neurodeficit, total resection of the tumor was done in 24 cases, and near-total resection or gross total resection or subtotal resection was done in 6 cases. Preoperative symptoms improved or disappeared in 25 cases. New persistent deficit occurred in 3 cases. Two patients died postoperatively. There was no recurrence of tumor till the last follow-up.

CONCLUSION

Nonvestibular schwannomas are far less common, but curable benign lesions. Surgical approach to the skull base and craniovertebral junction is a often complex and lengthy procedure associated with chances of significant morbidity. But early diagnosis, proper investigations, and evaluation, along with appropriate decision making and surgical planning with microsurgical techniques are the essential factors that can result in optimum outcome.

The middle fossa approach for the removal of a trochlear schwannoma

Objectives. Schwannomas originating from the trochlear nerve are extremely rare; only 30 cases have been reported in the literature. Many operative approaches have been utilized for lesion resection, but the advantages of the anterior transpetrosal approach are numerous and include excellent exposure, minimal extradural retraction of the temporal lobe, and minimal cerebrospinal fluid leaks. We report the second case of a trochlear schwannoma resected via the anterior transpetrosal approach. Setting. A 64-year-old male presented with 3-month history of diplopia and headaches. On physical examination, he was found to have a right fourth nerve palsy. Brain magnetic resonance imaging revealed a mass within the right ambient cistern compressing the adjacent midbrain. A right-sided anterior transpetrosal approach was used-which confirmed that the trochlear nerve entered the mass-to achieve gross total resection. Pathological examination confirmed diagnosis of schwannoma. The patient was discharged on postoperative day 3. He experienced a persistent fourth nerve palsy postoperatively with an otherwise normal neurological examination. Follow-up imaging confirmed complete removal of the tumor. Conclusion. The anterior transpetrosal approach is an excellent approach for removal of trochlear schwannomas involving the cisternal course of the trochlear nerve. It affords complete visualization of this anatomical region while introducing minimal morbidity.

Cisternal trochlear nerve schwannoma: improvement of diplopia after subtotal tumour excision

OBJECTIVE AND IMPORTANCE

Trochlear nerve schwannomas without neurofibromatosis are very rare. No more than 33 cases have been pathologically verified. None of the reported cases showed postoperative improvement of trochlear palsy. The authors present a case of trochlear palsy due to a trochlear nerve schwannoma with subsequent improvement of trochlear palsy after subtotal excision of the tumour.

CLINICAL PRESENTATION

A 65-year-old woman presented with diplopia, vertigo and left arm weakness. There was no history of neurofibromatosis. MR imaging demonstrated a tumour in the right perimesencephalic/ambient cistern.

INTERVENTION

The tumour was operated by a pterional approach, and subtotal excision was achieved preserving the tumour capsule with the trochlear nerve. The tumour was pathologically diagnosed as a schwannoma.

CONCLUSION

At 2-year follow-up, there was no double vision and MR imaging showed a small, stable tumour remnant. To our knowledge, this is the first reported case of a trochlear schwannoma in whom postoperative improvement of trochlear function was achieved.

Surgical and histological observations of trochlear neurinoma: case report

A 47-year-old woman presented with an extremely rare case of trochlear nerve neurinoma manifesting as left hemiparesis. Magnetic resonance imaging demonstrated a cystic tumor, 4 cm in diameter, in the right ambient and cerebellopontine cisterns, compressing the midbrain and upper pons. The preoperative diagnosis was trigeminal neurinoma. However, the tumor was identified arising from the trochlear nerve, and was totally removed via the posterior transpetrosal approach. The histological diagnosis was neurinoma. The patient's hemiparesis improved postoperatively. Preoperative diagnosis of trochlear neurinoma must distinguish the neurological presentations of trochlear and trigeminal neurinomas and to analyze the microanatomy of the tumor and skull base structures on neuroimaging.

Stereotactic radiosurgery in two cases of presumed fourth cranial nerve schwannoma

A 47-year-old woman and a 45-year-old man with gradually progressive fourth cranial nerve palsy underwent stereotactic radiosurgery for presumed fourth cranial nerve schwannomas with the gamma knife at a marginal tumor dose of 14 and 13 Gy, respectively. In one patient, the ocular misalignment disappeared; in the other patient, it stabilized. MRI showed shrinkage of the tumors. These patients represent the second and third reported cases of presumed fourth cranial nerve schwannoma treated with radiosurgery and the first cases with substantial follow-up information.

Gamma Knife surgery for schwannomas originating from cranial nerves III, IV, and VI

OBJECT

Schwannomas from the motor cranial nerves controlling eye movement are rare. The authors evaluated the role of Gamma Knife surgery (GKS) in the management of schwannomas originating from cranial nerves III, IV, and VI.

METHODS

Over a 7-year period, 8 patients with schwannomas originating from the oculomotor (2 patients), trochlear (5 patients), or abducent (1) nerve underwent GKS. The mean patient age was 46.1 years (range 19-59 years). The presenting symptoms included diplopia in 5 patients, ptosis in 1 patient, ophthalmoplegia in 1 patient, and headache in 1 patient. Two patients had a history of neurofibromatosis Type 2. Gamma Knife surgery was performed as primary management in 7 patients and after prior resection in 1 patient. The median and mean tumor volumes were 0.22 and 1.32 cm(3) (range 0.03-7.4 cm(3)). A median margin dose of 12.5 Gy (range 11.0-13.0 Gy) was prescribed to the tumor margin. Clinical and imaging follow-up data were available for all 8 patients.

RESULTS

Magnetic resonance imaging showed tumor regression in all patients. The progression-free period varied from 4 to 42 months, with a mean of 21 months. Over a mean of 23 months, 4 of the 5 patients with a trochlear schwannoma and symptoms of diplopia noted symptomatic improvement. No improvement was noted in the 2 patients with oculomotor nerve palsies. Headache was improved in the 1 patient with an abducent neuroma.

CONCLUSIONS

Gamma Knife surgery is an effective and minimally invasive approach capable of inactivating schwannomas originating from the oculomotor, trochlear, and abducent nerves. Accompanying trochlear function may improve. Longer follow-up and larger patient samples are needed to confirm the authors' initial observations.