Intraoperative Electrophysiological Mapping in the Supraclavicular Approach for Thoracic Outlet Syndrome

Objective: Methods for intraoperative electrophysiological mapping in thoracic outlet syndrome have not yet been established, despite the potential severity of surgical complications. A method for intraoperative electrophysiological mapping in the supraclavicular approach for thoracic outlet syndrome was developed. The purpose of the study was to verify the usefulness and validity of this method. Methods:Twelve patients underwent surgery for thoracic outlet syndrome using this mapping method. The region of interest in an operative field was electrically stimulated, and evoked electromyography was recorded from the deltoid, biceps, triceps, and abductor pollicis brevis for the brachial plexus, the diaphragm for the phrenic nerve, and the serratus anterior for the long thoracic nerve. Cathodal stimulation was performed using a monopolar electrode. The stimulus rate was fixed at 3/s, and 0.2‒ms biphasic square waves were applied. The stimulus current ranged from 0.5 mA to 2 mA. Whether this method enabled identification of important anatomical landmarks by referring to the evoked electromyography pattern was retrospectively investigated. Results:In 10 of 12 cases, clinical improvement was obtained. In all cases, important landmarks related to the brachial plexus and phrenic nerve were identified with this mapping method. In 5 of 12 cases, the course of the long thoracic nerve in the middle scalene muscle was identified. Conclusion:This monitoring method was useful for confirming the distribution of important nerves in the surgical field of thoracic outlet syndrome, and has great significance by enabling management of the anatomical variations seen in thoracic outlet syndrome. (Received:October 31, 2016;accepted:May 1, 2017)