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Original Investigation |

Functional Nerve Preservation in Extracranial Head and Neck Schwannoma Surgery

Kei Ijichi, MD, PhD1; Daisuke Kawakita, MD, PhD1; Shinichiro Maseki, MD, PhD1; Shintaro Beppu, MD1; Gaku Takano, MD1; Shingo Murakami, MD, PhD1
[+] Author Affiliations
1Department of Otolaryngology–Head and Neck Surgery, Graduate School of Medical Sciences, Nagoya City University Nagoya, Japan
JAMA Otolaryngol Head Neck Surg. 2016;142(5):479-483. doi:10.1001/jamaoto.2016.0113.
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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 study was 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 a method 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.

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Figure.
Treatment Plan for Extracranial Head and Neck Schwannomas

Preoperative and intraoperative diagnosis of tumor nerve of origin (upper portion) and surgical method for tumor resection according to the nerve of origin type (lower portion). CT indicates computed tomography; EMG, electromyographic; MRI, magnetic resonance imaging; +, positive; and −, negative.

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Mapping of Electrical Stimulation With Electromyography System on Vagus Schwannomas and Identification of Incision Area According to Electrical Stimulation Response

A, Vagus schwannoma with visible nerve bundle. B, Vagus schwannoma with no visible nerve bundle. A hypoglossal nerve lies on the tumor.

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