Author(s)
Sidharth V. Puram, MD PhD
Harold Chow, MD
Che-wei Wu, MD
James T. Heaton, PhD
Dipto Kamani, MD
Gregory W. Randolph, MD FACS FACE
Affiliation(s)
Massachusetts Eye and Ear Infirmary
Abstract:
Educational Objective: At the conclusion of this presentation, the participants should be able to compare post-cricoid and endotracheal tube electromyographic intraoperative nerve monitoring and discuss how each can be used to guide intraoperative surgical decision making. Objectives: Recurrent laryngeal nerve (RLN) injury is a devastating complication of thyroid/parathyroid surgery. Intraoperative neural monitoring (IONM) has been increasingly used to assess for injury. Although the posterior cricoarytenoid muscle (PCA) is one of the primary muscles innervated by the RLN, posterior cricoid electromyographic (EMG) monitoring of the injured RLN remains poorly characterized and post-cricoid EMG parameters of RLN stimulation after compressive injury are unknown. Study Design: Prospective nonrandomized. Methods: We utilized a canine model to identify IONM post-cricoid EMG correlates of postoperative vocal cord paralysis (VCP). Post-cricoid electrodes were placed and recordings were obtained before and after compressive RLN injury associated with VCP. Results: Post-cricoid electrode recordings revealed a mean amplitude of 1288 ± 509.2 µV and a mean latency of 8.20 ms with maximal vagal stimulation, and mean amplitude of 1807 ± 1065.4 µV and mean latency of 3.50 ms for maximal RLN stimulation. After injury, there was a 62.1% decrement in post-cricoid EMG amplitude with maximal stimulation of the vagus and an 80% decrement with the RLN. Threshold stimulation of the vagus increased by 23%, with a corresponding 42% decrease in amplitude at threshold stimulation. For the RLN, latency increased by 17.3% after injury and threshold stimulation increased by 60%. Conclusions: If RLN amplitude decreases by 80% with an absolute amplitude of <300 µV with a latency increase of >10%, then RLN injury is associated with VCP, similar to values with ETT EMG before and after injury. Our results predict postoperative VCP based on post-cricoid EMG IONM and may guide surgical decision making.