Does extensive dissection of recurrent laryngeal nerve during thyroid operation increase the risk of nerve injury? Evidence from the application of intraoperative neuromonitoring

Abstract

Purpose Extensive dissection of recurrent laryngeal nerve (RLN) is inevitable in some complicated thyroid operations. The study aimed to determine whether extensive dissection of RLN increases the risk of nerve injury. Method Three hundred thirty-one patients (506 nerves at risk) who underwent thyroid operations with intraoperative neuromonitoring were included. The study chiefly focused on the 101 RLNs on which extensive nerve dissection from the thoracic inlet to the entry of larynx was performed and for which the nerve exposure was longer than 5 cm. Electromyographic (EMG) signals were obtained from the RLN and vagus nerve before and after complete RLN dissection, and these were defined as R 1, V 1 and R 2, V 2 signals, respectively. The RLN palsy rates and the change of EMG signals were evaluated and analyzed. Results Among 101 nerves with extensive dissection, 13 nerves were due to the operation for recurrent goiter; 41 nerves, for large goiter with substernal extension; and 47 nerves, for thyroid cancer with paratracheal nodal metastasis. No permanent palsy occurred, but 2 nerves experienced loss of EMG signal after complete RLN dissection from a large recurrent goiter and developed temporary palsy. The palsy rates were 2% (2/101) in the extensive dissection group and 2.5% (10/405) in the nonextensive dissection group ( P = .77). Among 99 nerves with normal vocal function after operation, none experienced weakened signal after complete RLN dissection, and the mean amplitudes of R 2 and V 2 signals were not significantly different from those of R 1 and V 1 signals (R 2 vs R 1; 1038 vs 1030 μV; P = .74; V 2 vs V 1; 824 vs 816 μV; P = .75). Conclusions The results of this study suggest that careful surgical dissection is well tolerated by the RLN.