Intraorbital abducens nerve schwannoma

Predictors of Surgical Outcomes in Patients with Abducens Nerve Schwannoma: A Comprehensive Systematic Review and a Case Report

BACKGROUND

Abducens nerve (AN) schwannomas are extremely rare tumors. Clinical characteristics and factors that influence postoperative outcomes are not well defined.

OBJECTIVE

To characterize clinical features of AN schwannomas and predictors of surgical outcomes.

METHODS

PRISMA-guided systematic review of the literature on AN schwannomas was performed. Subsequently, univariate and multivariate regression analyses were performed to identify the predictive value of variables that influence postoperative outcomes.

RESULTS

A total of 42 studies with 55 patients were evaluated. The mean age at presentation was 43.9 ± 14.6 years. The most common presenting symptom was cranial nerve VI palsy (69.1%). Cavernous sinus (49.1%) and prepontine cistern (36.3%) were the most commonly involved locations. Complete recovery after surgery was seen in 36.3% at a median follow-up of 28.4 ± 25.8 months. Preoperative AN palsy (P < 0.001), suboccipital approach (P = 0.007), and subtotal resection of tumor (P = 0.044) were significant protective factors for postoperative complications. Prepontine location and postoperative complications were poor prognostic indicators of AN recovery (odds ratio [OR], 0.10, P = 0.030 and OR, 0.10, P = 0.028, respectively). Subtotal resection was significantly correlated with higher odds of AN recovery (OR, 6.06; P = 0.040).

CONCLUSIONS

AN schwannomas are rare but serious tumors that can cause significant morbidity, with only approximately one third of patients showing complete recovery after surgery. The suboccipital approach was a protective factor for postoperative complications, especially when combined with subtotal resection. Knowledge of these factors along with tumor characteristics helps optimize surgical planning and preoperative counseling.

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.

Orbital intraconal abducens nerve schwannoma: An interdisciplinary approach for management

Schwannomas are rare benign tumors arising from Schwann cells of the nerve sheath. Although the head-and-neck region accounts for a large percentage of extracranial schwannomas, those located within the orbit are infrequent. This paper presents an extremely rare case of orbital schwannoma arising from the terminal branch of abducens nerve in a 37-year-old female. The lesion presented as a large intraconal mass causing proptosis and weakness to abduct the left eye. Imaging showed a well-defined, solid-cystic lesion, measuring 2.7 cm and displacing the lateral rectus muscle laterally and the optic nerve medially. A multidisciplinary approach was used for the surgical management of the tumor. Access was attained through lateral rim osteotomy. Histopathological evaluation was diagnostic for schwannoma. A search of English literature revealed only five previously published cases of abducens nerve schwannomas. A review of these cases has also been discussed along with the present report.

Imaging characteristics and surgical management of orbital neurilemmomas

AIM

To review imaging characteristics and surgical outcomes of orbital neurilemmoma.

METHODS

Retrospective review of 21 patients with orbital neurilemmoma managed at the Zhongshan Ophthalmic Center of Sun Yat-sen University from June 2005 to December 2016. All patients underwent surgical excision following preoperative imaging including ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI).

RESULTS

Among these patients, 11 were male and 10 were female, with age ranging from 12 to 75y (average, 40.3y). Ultrasound of the orbit showed a roundish well-demarcated orbital mass with low or middle internal reflectivity in each case. Dark inner liquid fields were detected in 28.6% of these cases. Doppler ultrasound demonstrated blood flow signals in these masses. CT showed that the tumors were either homogeneous or heterogeneous. MRI of T1WI revealed isointense or hypointense tumors, while the T2WI indicated heterogeneous hyperintense lesions. Gd contrast MRI demonstrated heterogenous or homogeneous enhancement initiating from the wide area of the lesion. Six patients underwent lateral orbitotomy and 15 anterior orbitotomy. All tumors were completely removed. After a mean follow-up of 1.8y, 3 patients experienced reduced vision while the remaining 10 patients showed improved vision after surgery. One patient experienced a mild limitation of upward motility. No recurrence occurred.

CONCLUSION

Orbital neurilemmoma is a relatively rare, benign orbital tumor. Effective diagnosis requires a combination of ultrasonography, CT and/or MRI. These imaging techniques are also vital to differentiate neurilemmomas from other orbital masses like that of cavernous hemangiomas and meningiomas. Successful treatment requires complete resection of the neurilemmomas as performed either by lateral or anterior orbitotomy. Recurrence is rare after complete removal.

Factors Associated with Abducens Nerve Recovery in Patients Undergoing Surgical Resection of Sixth Nerve Schwannoma: A Systematic Review and Case Illustration

BACKGROUND

Limited or no literature exists identifying factors associated with functional nerve recovery in patients undergoing resection of sixth cranial nerve (CN VI) schwannomas.

METHODS

A systematic review of literature was performed on CN VI schwannomas that were treated surgically. Synthesizing the findings pooled from the literature, we investigated associations of patient demographics and clinical characteristics with postsurgical CN VI functional recovery in multivariable regression models. In addition, we present the findings of an adolescent woman surgically managed for intracavernous CN VI schwannoma. Complete encasement of the cavernous segment of the internal carotid artery is unique to our case.

RESULTS

We synthesized data of 32 patients from 29 studies, and our index case. Overall, the mean age of the patients was 44.0 ± 16.5 years, and approximately 52% (n = 17) were female. Most tumors were left-sided (n = 18; 54.5%), with an average size of 3.46 ± 1.71 cm. The most common location was cisternal (n = 11; 33%), followed by cavernous sinus (CS) proper (n = 9; 27%), cisterocavernous (n = 8; 24%), orbital (n = 4; 12%) and caverno-orbital (n = 1; 3%). CN VI recovery was reported in less than half the cohort (n = 14; 45%). Tumor extension in the CS was significantly associated with lesser likelihood (odds ratio [OR], 0.07; 95% confidence interval [CI], 0.01-0.98; P = 0.048) of postsurgical CN VI recovery. Although female gender (OR, 0.86; 95% CI, 0.07-10.09; P = 0.906), large tumor size (>2.5 cm) (OR, 0.45; 95% CI, 0.07-2.89; P = 0.397), and solid consistency (OR, 0.37; 95% CI, 0.03-4.19; P = 0.421) were associated with lesser odds for recovery, these were not statistically significant. Likewise, although gross total resection (OR, 6.28; 95% CI, 0.33-118.25; P = 0.220) was associated with higher odds of nerve recovery, the estimates were statistically insignificant.

CONCLUSIONS

CS involvement is associated with lesser odds for functional nerve recovery in patients undergoing surgical resection for CN VI schwannoma.

Clinicopathological features of peripheral nerve sheath tumors involving the eye and ocular adnexa

Peripheral nerve sheath tumors (PNSTs) are known to occur in the orbit and comprise 4% of all orbital tumors, but have not been well studied in contemporary literature. Ninety specimens involving the eye and ocular adnexa (1979-2015) from 67 patients were studied. The mean age was 32.5years. Locations included orbit (58.9%), eyelid (60.0%), and other ocular adnexa. Most specimens were neurofibromas (70.0%), followed by schwannomas (11.1%), neuromas (11.1%), granular cell tumors (n=4), nerve sheath myxomas (n=2), and malignant PNST (n=1). Fifty-six (88.9%) neurofibroma cases were neurofibromatosis 1 associated. Among neurofibromas, 31.7% were localized, 38.1% were plexiform, 25.4% were diffuse, and 4.8% were diffuse and plexiform. These tumors involved skin (31.7%), soft tissue (11.1%), skeletal muscle (22.2%), peripheral nerve (63.0%), lacrimal gland (20.6%), and choroid (n=1). Other histologic findings included pseudo-Meissner corpuscles (27%), Schwann cell nodules (4.8%), prominent myxoid component (7.9%), melanin-like pigment (3.2%), and inflammation (14.3%). Available immunostains included S100 (+ in 15/15 cases), EMA (+ in 2/4 cases), CD34 (+ in 4/4 cases), and Ki-67 (<1% in 4/4 cases). Among 10 schwannomas, 8 were conventional and 2 were plexiform. Observed features included capsule (n=5), hyalinized vessels (n=5), Verocay bodies (n=7), and Antoni B pattern (n=5). Immunostaining included S100+ in 4 of 4 cases, and collagen IV+ and Ki-67 <1% in 3 of 3 cases. Neurofibromas are the most common PNST involving the eye and ocular adnexa, and the majority are associated with neurofibromatosis 1. Plexiform and diffuse patterns and the presence of pseudo-Meissner corpuscles are relatively frequent in this area.

A Retrospective Analysis of Vision-Impairing Tumors Among 467 Patients with Neurofibromatosis Type 2

BACKGROUND

Vision is important for patients with hearing loss caused by neurofibromatosis type 2 (NF2). Tumors adjacent to the anterior visual pathway can potentially impair the vision. Only a few case reports and small-series studies have been reported.

OBJECTIVE

To evaluate the clinical features of tumors adjacent to the anterior visual pathway in a large series of patients with NF2.

METHODS

Seventy-three patients with potentially vision-impairing tumors were carefully screened from among 467 patients with NF2.

RESULTS

Among the 73 patients, 31 had intraorbital tumors, 21 had suprasellar meningiomas, and 21 had medial sphenoid ridge meningiomas. Of the 31 patients with intraorbital tumors, 17 had optic nerve sheath meningiomas, 9 had intraorbital schwannomas, 3 had spheno-orbital meningiomas, 1 had an anterior cranial fossa-orbital meningioma, and 1 had a cranio-orbital schwannoma. To the date of the last follow-up, 43 patients (58.9%) experienced visual loss. In most cases, hearing loss tended to occur earlier than visual loss. Six patients underwent early operations, and they recovered well without any further vision damage. Six other patients underwent operations after having no functional visual ability in the affected eyes, and their visual ability was not saved.

CONCLUSIONS

Tumors adjacent to the anterior visual pathway, although uncommon in patients with NF2, can cause progressive visual loss. Early surgical intervention seems to be the primary treatment strategy, except for in patients' optic nerve sheath meningiomas. If patients adopt a wait and see policy, regular visual examination seems to be mandatory.

Orbital Abducens Nerve Schwannoma: A Case Report and Review of the Literature

Intraorbital schwannoma is a rare tumor which accounts for about 1-2% of all neoplasms of the orbit. Orbital schwannomas most commonly arise from the sensory branches of the trigeminal nerve. On the other hand, intraorbital abducens nerve schwannomas are extremely rare, with a search of the English literature identifying only four cases of intraorbital abducens nerve schwannoma. This is the 5th reported case of an orbital schwannoma arising from the terminal branch of the abducens nerve to the lateral rectus muscle. We report a case of an intraorbital abducens nerve schwannoma in a 51-year-old man with no signs of neurofibromatosis. The tumor was totally excised with functional preservation of the nerve by a zygomatic approach with lateral orbitotomy. With knowledge of these anatomic features, total removal of the tumor with preservation of the abducens nerve function might be possible.

Orbital intraconal abducens nerve schwannoma: A case report and review of the literature

Authors report a case of right orbital intraconal abducens nerve schwannoma in a 32-year lady, who presented with a sense of tightness and discomfort in right eye on looking extreme right side since 4 months. The tumor was totally excised with functional preservation of the nerve by superior orbitotomy. The clinical, radiological features and the management are discussed.

Primary intraocular ancient schwannoma: a case report and review of the literature

BACKGROUND

Schwannomas comprise 8% to 10% of all primary intracranial tumors. Primary intraorbital schwannomas are rare, accounting for 1% to 2% of all intracranial tumors. Schwannomas arise from Schwann cells in the myelin sheaths of sensory and cranial nerves.

METHODS

We present the case of a 56-year-old white man blind since 1970 who presented to an outside hospital for a painful right eye. Physicians identified no clinical or radiologic features of neurofibromatosis.

RESULTS

The patient underwent enucleation; the final pathologic diagnosis was ancient schwannoma.

CONCLUSION

We describe herein a case of intrascleral schwannoma with ancient changes arising within the globe of the right eye occupying the subretinal space and completely replacing the vitreous body.