Surgical strategy during intended total thyroidectomy after loss of EMG signal on the first side of resection

Abstract

Unambiguous identification of the recurrent laryngeal nerve with detection of nerve dysfunction giving rise to postoperative vocal cord palsy (VCP) is the principal objective of intraoperative neuromonitoring (IONM) in thyroid surgery. Because intraoperative loss of the electromyographic (EMG) signal (LOS) does not result in VCP in one third of patients, controversy surrounds the issue of whether a change in strategy is needed in planned total thyroidectomy after LOS on the first side of resection. This was a retrospective institutional study of 1,049 consecutive patients (2,086 nerves at risk) with intended bilateral thyroid surgery who were operated on between April 2010 and July 2012 with the use of IONM. The rates of temporary and permanent VCP were analyzed on the basis of the IONM results of the first side of resection and the extent of contralateral resection for completion: resection without LOS (group1); resection with LOS and contralateral thyroidectomy (group2); resection with LOS and contralateral subtotal resection (group3); resection with LOS without any contralateral resection (group4). LOS on the first side of resection was noted in 27 patients (2.6 %). All VCPs were unilateral. The rates of temporary and permanent VCP were 2.5 and 0.4 %, respectively, overall; specifically: group1: 0.5 and 0 %; group2: 64 and 9.1 %; group3: 100 and 50 %; group4: 83 and 8.3 %, respectively. Because an abnormal intraoperative electromyogram carries an 80 % risk for early postoperative VCP, the initial plan of bilateral surgery needs to be critically reviewed after LOS has occurred on the first side of resection, taking into account the underlying thyroid disease of the patient and surgeon expertise. Since more than 80 % of affected nerves will fully recover after the operation, staged completion thyroidectomy is recommended.