Electrophysiologic analysis of injury to cranial nerve XI during neck dissection.

BACKGROUND Despite preservation of the accessory nerve, a considerable number of patients report partial nerve damage after modified radical neck dissection (MRND) and selective neck dissection. METHODS Accessory nerve branches for the trapezius muscle were stimulated during neck dissection, and the M wave amplitude was measured during distinct surgical phases. RESULTS The accessory nerve was mapped in 20 patients. The M wave recordings indicated that major nerve damage occurred during dissection at levels IIa and IIb in the most proximal segment of the nerve. The M waves evoked from this nerve segment decreased significantly during surgery (analysis of variance; p = .001). CONCLUSION The most significant intraoperative injury to the accessory nerve during neck dissection occurs at anatomic nerve levels IIa and IIb. © 2015 Wiley Periodicals, Inc. Head Neck 38: E372-E376, 2016.