[1]Division of Thyroid Surgery, China-Japan Union Hospital, Jilin University, 126 Xiantai Blvd, Changchun City, Jilin Province, China.
Background: During monitored thyroidectomy, recurrent laryngeal nerve (RLN) injury often occurs after complete nerve dissection as detected by loss of EMG signal. Continuously monitoring nerve function during RLN dissection might be helpful and useful to earlier detect adverse EMG change and prevent imminent nerve injury. Methods: A total of 120 patients with 208 RLNs at risk were enrolled in this study. A standardized IONM procedure was strictly followed. The RLN was continuously stimulated at the lower exposed end with a handheld stimulating probe and the quantitative change of EMG amplitude was watched during RLN dissection. Once the EMG amplitude decreased >50% as compared with the initial signal, the surgical maneuver was stopped immediately. The nerve was retested to determine the amplitude recovery at the time points of 2, 4, 6, 8 and 10 minutes. After 10 minutes, the operation was restarted with meticulous dissection and gentle thyroid retraction. Results: 19 RLNs experiencing EMG amplitude reduction > 50% were identified by this procedure, 18 nerves (16 were caused by traction injury and 2 by compression injury) showed progressive gradual amplitude recovery, and 1 nerve caused by thermal injury showed persistent decrease after 10 minutes. Among the 18 nerves with amplitude recovery, the recovery rate was >90% in 8 nerves, 80-90% in one, 70-80% in 6, 60-70% in 1 and 50-60% in 2. No complete loss of signal was encountered in this study, but two nerves with substantial amplitude decrease developed postoperative temporary vocal cord palsy. Conclusions: During monitored thyroidectomy, continuously monitoring nerve function during RLN dissection is a necessary procedure to earlier detect adverse EMG change and prevent imminent nerve injury.
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