Functional nerve preservation in extracranial head and neck schwannoma surgery

Abstract

IMPORTANCE A schwannoma is an uncommon, benign neurogenic tumor of Schwann cells. Tumor enucleation is the recommended surgical method to preserve function of the original nerve, although enucleation does not guarantee completely intact nerve function after the operation. OBJECTIVE To establish a strategy for functional preservation in extracranial head and neck schwannoma treatment by using an electromyographic (EMG) system during tumor resection. DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort studywas conducted of 15 patients who underwent surgery for removal of schwannoma tumors between April 1, 2006, and March 31, 2015, at an academic tertiary referral center. Data analysis was conducted from April 3, 2006, to September 15, 2015. Neurogenic tumors were diagnosed according to preoperative findings, and during surgery tumors were exposed and given EMG-controlled electrical stimulation to analyze their origins. In motor nerve cases, the electrical activity of the muscle was measured and recorded by EMG. The tumor was then enucleated by incision along tumor fibers mapped using EMG stimulation. If a nerve bundle was visible, we incised along there and enucleated the tumor. INTERVENTIONS A strategy using electrical stimulation to improve preservation of nerve function in extracranial head and neck schwannoma operations. MAIN OUTCOMES AND MEASURES Frequency and duration of postoperative neurologic complications associated with functional preservation surgery with tumor enucleation was evaluated using EMG monitoring according to tumor origin. RESULTS Of the 15 patients with extracranial schwannoma, 9 (60%) were women (mean [SD] age, 36.3 [15.3] years). All 15 patients underwent surgery using a transcervical approach. The most common nerves of origin were the vagus nerve and the sympathetic chain. In sensory or sympathetic nerve cases, the EMG response was absent. Two of 5 patients with vagus schwannoma had postoperative temporary vocal nerve palsy. These symptoms showed improvement after 1 year. There was no tumor recurrence during the follow-up period in any patient. CONCLUSIONS AND RELEVANCE The strategy used here demonstrated amethod of diagnosis and nerve preservation surgery for extracranial schwannomas. Nerve functionality was preserved in all vagus schwannoma cases. However, preservation of nerve function in sympathetic nerve schwannoma cases remains problematic and needs further investigation.