Risk factors of paralysis and functional outcome after recurrent laryngeal nerve monitoring in thyroid surgery

Recurrent laryngeal nerve monitoring (RLNM) has been suspected to reduce postoperative RLN paralysis (RLNP). However, functional outcome of RLNM in comparison with no nerve identification and visual nerve identification only has not been analyzed. Analysis of 16,448 consecutive multi-institutional operations resulted in 29,998 nerves at risk. Three groups of different RLN treatment were compared: group 1, no RLN identification; group 2, visual RLN identification; and group 3, visual RLN identification and electromyographic monitoring. RLNM was performed with a bipolar needle electrode that was placed through the cricothyroid ligament into the vocal muscle. Risk factors for permanent RLNP were recurrent benign and malignant goiter (odds ratios, [ORs]), 4.7, and 6.7, respectively), primary surgery in thyroid malignancy (OR, 2.0), lobectomy (OR, 1.8), no nerve identification (OR, 1.4), low or medium volume hospital (OR, 1.3), and low volume surgeons (OR, 1.2). Based on these data, visual nerve identification was identified to be the gold standard of RLN treatment in thyroid surgery. RLNM is a promising tool for nerve identification and protection in extended thyroid resection procedures. However, because of the overall low frequency of RLNP, no statistical difference compared with visual nerve identification only was reached in the setting of this study.