Vagal schwannomas of the head and neck: A comprehensive review and a novel approach to preserving vocal cord innervation and function

Abstract

Background: Schwannomas, benign tumors arising from neurolemmocytes, are the most common type of peripheral nerve tumors. Extracranial schwannomas are most often found in the parapharyngeal space, commonly involving the vagus nerve to cervical sympathetic trunk. Vagal schwannomas present several unique clinical and therapeutic challenges. Methods: A comprehensive literature review was conducted on 197 articles reporting 235 cases of cervical vagal schwannomas. Presenting symptoms, treatment approach, and postoperative outcomes were recorded and analyzed. Results: Vagal schwannomas commonly present as asymptomatic neck masses. When they become symptomatic, surgical resection is the standard of care. Gross total resection is associated with higher postoperative morbidity compared to subtotal resection. Initial reports using intraoperative nerve monitoring have shown improved nerve preservation. Recurrence rates are low. Conclusion: The combination of intermittent nerve mapping with novel continuous vagal nerve monitoring techniques may reduce postoperative morbidity and could represent the future standard of care for vagal schwannoma treatment. K E Y W O R D S continuous intraoperative nerve monitoring, nerve sheath tumor, neurilemmoma, vagal schwannoma, vagus nerve

Intraoperative mapping and monitoring of sensory vagal fibers during vagal schwannoma resection

“…Although surgical resection for large or symptomatic lesions is the standard of care, nerve sacrifice at the time of resection is associated with significant morbidity. A subcapsular microsurgical technique of schwannoma excision has been developed to improve patient functional outcomes, with schwannoma recurrence rates reportedly similar to traditional en bloc resection techniques . Intermittent intraoperative nerve monitoring with selective stimulation of splayed motor fibers running over the surface of the schwannoma has been used to map and preserve vagal nerve motor fibers prior to subcapsular microsurgical tumor removal .…”

“…A subcapsular microsurgical technique of schwannoma excision has been developed to improve patient functional outcomes, with schwannoma recurrence rates reportedly similar to traditional en bloc resection techniques. 6 Intermittent intraoperative nerve monitoring with selective stimulation of splayed motor fibers running over the surface of the schwannoma has been used to map and preserve vagal nerve motor fibers prior to subcapsular microsurgical tumor removal. 7,8 In this case report of a high vagal nerve schwannoma, the LAR was utilized to identify, map, and monitor sensory (in addition to motor) nerve fibers on the surface of the tumor prior to capsule incision and tumor enucleation.…”

Reply to “Function preservation for resection of vagal schwannoma of the head and neck: Are we talking about the same technique?”

“…by Obholzer et al 1 We thank the authors for their clarifications on our recent review of head and neck vagal schwannomas. 2 In the original manuscript, we describe the intracapsular enucleation technique in which "the nerve fibers are pushed aside, and the capsule of the schwannoma is cut open, allowing for the removal of the schwannoma" and classify this surgical approach as a subtotal resection. 2 However, Obholzer et al highlights a discrepancy in this definition.…”

“…2 In the original manuscript, we describe the intracapsular enucleation technique in which "the nerve fibers are pushed aside, and the capsule of the schwannoma is cut open, allowing for the removal of the schwannoma" and classify this surgical approach as a subtotal resection. 2 However, Obholzer et al highlights a discrepancy in this definition. The authors note that a schwannoma causes the displaced tissue of the surrounding nerve to form a pseudocapsule around the true schwannoma capsule, and propose that an ideal tumor enucleation is performed in the plane between the true schwannoma capsule and the nerve pseudocapsule.…”

“…Indeed, the technique described in our manuscript is extracapsular and preserving of the nerve fibers, consistent with the definition put forth by Obholzer et al In conclusion, we appreciate the thoughtful evaluation of our manuscript by Obholzer et al and value their perspectives on the surgical management of vagal schwannoma. 1 Monica H. Xing BA 1 Mykayla L. Sandler BA 1 Mark L. Urken MD, FACS 2…”