Surgical management of nonvascular lesions around the oculomotor nerve

Orbital schwannoma management: a case report, literature review, and potential paradigm shift

PURPOSE

To present a case of orbital schwannoma and assess the literature on treatment modalities.

METHODS

A MEDLINE literature search for cases of orbital schwannomas was performed using the PubMed search tool using the search terms "orbital schwannoma" and "orbital neurilemmoma." Papers were included if they were peer-reviewed, published in English, discussed management, and included the search terms. Each article was rated using the scale developed by the British Centre for Evidence-Based Medicine. In addition, we present a case report of an orbital schwannoma.

RESULTS

A total of 428 articles were found. 102 met the criteria for inclusion. Only two articles met Level 1 evidence and 16 were important to the clinical care process. We report a case of a biopsy-proven orbital schwannoma managed conservatively with observation over a 4-year period due to risk of cosmetic disfigurement with tumor removal. There has been no change in tumor size and no associated complications during follow up.

CONCLUSIONS

There is a paucity of data on the natural history of orbital schwannomas. Based on our review of the literature, we recommend observation for asymptomatic or minimally symptomatic orbital schwannomas with minimal growth over an extended period of time. For rapidly growing tumors or large tumors affecting key structures causing visual loss, diplopia, aesthetic disfigurement, or patient discomfort, a more aggressive approach may be necessary.

Oculomotor nerve schwannoma: case series and literature review

Oculomotor nerve schwannomas are rare benign cranial nerve tumors. There are only a limited number of reports on this pathology in the literature, and there are currently no established management guidelines that aid providers in deciding on surgical versus nonsurgical management. We assess the published literature on the topic to identify indications for treatment as well as outcome measures (e.g., local control rates, survival rates, and complication rates) that have been reported as associated with the various treatment modalities. We attempt to develop an algorithm for evaluation and treatment of oculomotor nerve schwannomas in order to establish consensus on how these tumors should be treated.

Outcomes after stereotactic radiosurgery for schwannomas of the oculomotor, trochlear, and abducens nerves

OBJECTIVE

Cranial nerve (CN) schwannomas are intracranial tumors that are commonly managed by stereotactic radiosurgery (SRS). There is a large body of literature supporting the use of SRS for vestibular schwannomas. Schwannomas of the oculomotor nerves (CNs III, IV, and VI) are rare skull base tumors, occurring close to the brainstem and often involving the cavernous sinus. Resection can cause significant morbidity, including loss of nerve function. As for other schwannomas, SRS can be used to manage these tumors, but only a handful of cases have been published so far, often among reports of other uncommon schwannoma locations.

METHODS

The goal of this study was to collect retrospective multicenter data on tumor control, clinical evolution, and morbidity after SRS. This study was performed through the International Radiosurgery Research Foundation. Patients managed with single-session SRS for an oculomotor cranial nerve schwannoma (CN III, IV, or VI) were included. The diagnosis was based on diplopia or ptosis as the main presenting symptom and anatomical location on the trajectory of the presumed cranial nerve of origin, or prior resection confirming diagnosis. Demographic, SRS dose planning, clinical, and imaging data were collected from chart review of the treated patients. Chi-square and Kaplan-Meier analyses were performed.

RESULTS

Seven institutions submitted data for a total of 25 patients. The median follow-up time was 41 months. The median age at the time of treatment was 52 years. There were 11 CN III schwannomas, 11 CN IV schwannomas, and 3 CN VI schwannomas. The median target volume was 0.74 cm3, and the median marginal dose delivered was 12.5 Gy. After SRS, only 2 patients (including the only patient with neurofibromatosis type 2) had continued tumor growth. Crude local control was 92% (23/25), and the 10-year actuarial control was 86%. Diplopia improved in the majority of patients (11/21), and only 3 had worsening following SRS, 2 of whom also had worsened ptosis, both in the context of tumor progression.

CONCLUSIONS

SRS for schwannomas of the oculomotor, trochlear, and abducens nerves is effective and provides tumor control rates similar to those for other cranial nerve schwannomas. SRS allows improvement of diplopia in the majority of patients. SRS should therefore be considered as a first-line treatment option for oculomotor nerve schwannomas.

Early Recurrence of an Infantile Endodermal Oculomotor Nerve Cyst following Surgical Fenestration: A Case Report

INTRODUCTION

Infantile endodermal oculomotor nerve cyst (EONC) is an extremely rare entity. There are very few pediatric cases reported in the literature, and as expected, oculomotor palsy is the most common presenting symptom. To date however, the risk of recurrence of these lesions following surgical intervention is unclear due to a lack of long-term radiological follow-up.

CASE PRESENTATION

We present a case of a 13-month-old male patient with an EONC and detail his surgical fenestration and postoperative course. Somewhat surprisingly, re-expansion occurred within 6 months and remained stable 2 years later.

DISCUSSION

A surgical approach to fenestration of an EONC in an infant is possible and should be performed by an expert neurosurgeon. Early recurrence is underreported in the current literature, and we encourage longer term radiological surveillance of these lesions after surgery to optimize primary and recurrent management in the future.

Prognosis Factor in Oculomotor Schwannoma: A Case of Endoscopic Endonasal Approach and Systematic Review of the Literature

BACKGROUND

We report the first case of oculomotor nerve (ON) schwannoma treatment through an endonasal endoscopic approach. We also review the literature to determine prognosis factors of ON function after treatment.

METHODS

A complete MEDLINE search was undertaken for all articles reporting data for oculomotor schwannoma. We divided the patient population into 2 groups; Group I: patients who conserved or recovered good ON function and Group II: patients with either new, worsening, or unchanged third-nerve palsy at the last available follow-up. We conducted a comparative statistical analysis of data between the 2 groups.

RESULTS

We identified 55 reported cases of ON schwannoma, all of whom were treated with open transcranial surgery, stereotactic radiosurgery, or observation. There were 22 patients in group I and 33 in group II. At admission, 29 patients had complete oculomotor nerve palsy (34.7% in group I and 67.7% in group II; P = 0.02). Surgical treatment was performed in 36 cases. Radiosurgery was performed in 3 cases. Among patients with good preoperative ON function, 34.6% worsened at last follow-up (26.6% after surgery and 50% with observation; P = 0.03). In total, 31% of patients with total or near-total palsy at admission had an improvement of their ON function (all after surgical resection; P = 0.05).

CONCLUSIONS

ON function at admission and surgical resection of schwannoma appears to be a predictive factor of favorable prognosis regardless of location and tumor size. The endonasal endoscopic approach can be used to biopsy tumors in cases in which open surgery is considered too risky, such as cavernous sinus schwannomas.

Oculomotor Schwannomas: A Systematic Review and Report of Two Pediatric Cases Treated with Fractionated Cyberknife Stereotactic Radiotherapy

OBJECTIVE

Pediatric oculomotor nerve schwannomas are rare and challenging lesions due to the high morbidity associated with surgical intervention and their proximity to critical structures limiting the opportunity for stereotactic radiosurgery. We aim to report and review the novel use of fractionated Cyberknife (Accuray, Inc., Sunnyvale, California, USA) stereotactic radiotherapy in pediatric patients with oculomotor schwannomas.

METHODS

A systematic review of PubMed, Embase, and Cochrane was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two patients, ages 8 and 10 years, with tumor volumes of 0.1 cm³ and 0.2 cm³, respectively, were treated with fractionated Cyberknife radiotherapy at our institution. A total dose of 45-50 Gy was administered over 25 fractions (1.8-2.0 Gy per fraction) to the 82%-84% isodose line. Serial magnetic resonance imaging was obtained for long-term follow-up (56-58 months).

RESULTS

We found 14 articles published between 1982 and 2018 that reported a total of 18 pediatric patients with intracranial oculomotor schwannomas. No previously described cases of pediatric intracranial oculomotor schwannomas were treated with radiation therapy. In both of our patients, radiographic tumor control was achieved at a mean follow-up of 57 months, with 1 patient displaying a decrease in tumor volume. Neither patient exhibited any worsening of their presenting symptoms, nor did either patient develop any new neurocognitive deficits following treatment.

CONCLUSIONS

Fractionated Cyberknife radiotherapy is an effective and well-tolerated treatment option for intracranial oculomotor nerve schwannomas with excellent tumor control rates, similar to surgical and radiosurgical techniques, while sparing critical surrounding structures.

[Oculomotor nerve schwannoma in a child: Case report and literature review]

An isolated schwannoma of the oculomotor nerve is rare in children without an associated neurofibromatosis. A 13-year-old girl, with a previous medical history of migraine, was admitted for disabling ophthalmic migraine with oblique diplopia. The clinical examination showed a right incomplete ophthalmoplegia with reduced ipsilateral visual acuity (8/10). There was no particular skin reaction. The MRI revealed a right (isosignal-T1 and isosignal-T2) nodular schwannoma located within the cisternal segment of the oculomotor nerve. The angio-CT performed later confirmed the absence of any vascular malformation. The treatment consisted of analgesics and corticotherapy, with complete regression of symptoms three weeks later and a normal MRI follow-up. Therefore, radiosurgery was not performed.