Facial Nerve Outcomes After Vestibular Schwannoma Microsurgical Resection in Neurofibromatosis Type 2

Neurofibromatosis Type II and Facial Paralysis: Clinical Evaluation and Management

BACKGROUND

Facial paralysis secondary to neurofibromatosis type 2 (NF2) presents the reconstructive surgeon with unique challenges because of its pathognomonic feature of bilateral acoustic neuromas, involvement of multiple cranial nerves, use of antineoplastic agents, and management. Facial reanimation literature on managing this patient population is scant.

METHODS

A comprehensive literature review was performed. All patients with NF2-related facial paralysis who presented in the past 13 years were reviewed retrospectively for type and degree of paralysis, NF2 sequelae, number of cranial nerves involved, interventional modalities, and surgical notes.

RESULTS

Twelve patients with NF2-related facial paralysis were identified. All patients presented after resection of vestibular schwannoma. Mean duration of weakness before surgical intervention was 8 months. On presentation, one patient had bilateral facial weakness, 11 had multiple cranial nerve involvement, and seven were treated with antineoplastic agents. Two patients underwent gracilis free functional muscle transfer, five underwent masseteric-to-facial nerve transfer (of whom two were dually innervated with a crossfacial nerve graft), and one patient underwent depressor anguli oris myectomy. Trigeminal schwannomas did not affect reconstructive outcomes if trigeminal nerve motor function on clinical examination was normal. In addition, antineoplastic agents such as bevacizumab and temsirolimus did not affect outcomes if stopped in the perioperative period.

CONCLUSIONS

Effectively managing patients with NF2-related facial paralysis necessitates understanding the progressive and systemic nature of the disease, bilateral facial nerve and multiple cranial nerve involvement, and common antineoplastic treatments. Neither antineoplastic agents nor trigeminal nerve schwannomas associated with normal examination affected outcomes.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Management of Central and Peripheral Nervous System Tumors in Patients with Neurofibromatosis

Neurofibromatosis type I (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis represent a diverse group of genetic tumor predisposition syndromes with a shared feature of tumors affecting the peripheral nerve sheaths. PURPOSE OF REVIEW: Many advancements have been made in understanding the biologic underpinnings of these conditions, and in 2016 the first drug was approved by the FDA to treat pediatric symptomatic unresectable plexiform neurofibromas. RECENT FINDINGS: Mek inhibitors have provided a much-needed therapeutic avenue for NF1 patients with unresectable plexiform neurofibromas (PN), both for reduction of tumor bulk and for improvement in symptoms. Selumetinib is the first FDA approved drug for PN, but is only approved for children. Some research suggests that alternative Mek inhibitors and other mixed tyrosine kinase inhibitors may have better efficacy in adults. Vascular endothelial growth factor (VEGF) inhibitor bevacizumab can prolong hearing and delay the need for surgery in NF2 patients with bilateral vestibular schwannomas. This article provides an update regarding considerations and approaches when treating the tumors associated with the neurofibromatoses (NF), including risk and prognosis metrics, clinical trial results, surgical techniques, and radiation therapy recommendations.

Analysis of the effect of neuroendoscopy-assisted microscopy in the treatment of Large (Koos grade IV) vestibular schwannoma

Introduction

This article aimed to investigate the effects of the endoscopic-assisted microsurgery technique on the resection of large (Koos grade IV) vestibular schwannoma (VS) and provide a prognosis analysis of the patients.

Methods

A retrospective analysis of the use of the endoscopic-assisted microsurgery technique in 16 cases of large vestibular schwannoma surgery was carried out. Intraoperative nerve electrophysiological monitoring was conducted to explore the effect of neuroendoscopy on the resection of internal auditory canal tumors, protection of the facial nerve, and minimizing postoperative complications.

Results

Tumors were completely removed in all 16 cases, and the facial nerve was anatomically preserved in 14 cases (87.5%). There was no postoperative cerebrospinal fluid leakage and no intracranial infection complications occurred.Following the House-Brackmann (H-B) grading system, post-operative facial nerve function was grade I in 5 cases, grade II in 6 cases, grade III in 3 cases, and grade V in 2 cases. As a result, the preservation rate of facial nerve function (H-B grade I-II) was 68.8%. All 16 patients were followed up for 3 to 24 months, and no tumor recurrence was found on enhanced MRI.

Discussion

Using the endoscopic-assisted microsurgery technique in the retrosigmoid approach has many advantages over the microscopic-only approach. When compared to the microscopy-only approach, the endoscope can provide a wide-angle surgical field superior to that of a microscope in areas such as the internal auditory canal in the resection of large VS, minimize iatrogenic injuries, ensure complete removal of internal auditory canal tumors, and well as reducing postoperative complications such as cerebrospinal fluid leakage and the loss of facial and auditory nerve functions.

Neuro-Ophthalmic Complications of Vestibular Schwannoma Resection: Current Perspectives

Vestibular schwannomas (VSs), also called acoustic neuromas, are benign intracranial neoplasms of the vestibulocochlear (VIII) cranial nerve. Management options include “wait-and-scan,” stereotactic radiosurgery and surgical resection. Due to the proximity of the VIII nerve to the facial (VII) nerve in the cerebello-pontine angle, the VII nerve is particularly vulnerable to the effects of surgical resection. This can result in poor eye closure, lagophthalmos and resultant corneal exposure post VS resection. Additionally, compression from the tumor or resection can cause trigeminal (V) nerve damage and a desensate cornea. The combination of an exposed and desensate cornea puts the eye at risk of serious ocular complications including persistent epithelial defects, corneal ulceration, corneal vascularization, corneal melting and potential perforation. The abducens (VI) nerve can be affected by a large intracranial VS causing raised intracranial pressure (a false localizing sign) or as a result of damage to the VI nerve at the time of resection. Other types of neurogenic strabismus are rare and typically transient. Contralaterally beating nystagmus as a consequence of vestibular dysfunction is common post-operatively. This generally settles to pre-operative levels as central compensation occurs. Ipsilaterally beating nystagmus post-operatively should prompt investigation for post-operative cerebrovascular complications. Papilledema (and subsequent optic atrophy) can occur as a result of a large VS causing raised intracranial pressure. Where papilledema follows surgical resection of a VS, it can indicate that cerebral venous sinus thrombosis has occurred. Poor visual function following VS resection can result as a combination of all these potential complications and is more likely with larger tumors.