Size of recurrent laryngeal nerve as a new risk factor for postoperative vocal cord paralysis

Recurrent laryngeal nerve paralysis (RLNP) is a frequent and serious complication following esophageal cancer surgery. Therefore, this study aims to evaluate the correlation between recurrent laryngeal nerve (RLN) size and RLNP. This was a retrospective study of esophageal cancer patients who underwent thoracoscopic esophagectomy from January 2012 to December 2014. Eighty-four patients were included in the primary analysis. Diameter of the RLN was measured using the digital video recording of surgical procedures by the ratio between scissor and RLN. For evaluation of vocal cord paralysis or paresis, indirect laryngoscopy was performed. Because RLNP more frequently occurs on the left side than the right, we evaluated the correlation between size of the left RLN and left RLNP. The median size of the left RLN was 1.51 mm. We found that the incidence of postoperative left RLNP (Clavien-Dindo classification >= 1) was significantly higher (71% vs. 24%; P < 0.001) in thin RLNs (<= 1.5 mm) than in thick RLNs (>1.5 mm). Thin RLN (P < 0.001), female sex (P = 0.025), and being overweight (P = 0.034) were identified as significant independent risk factors for postoperative RLNP. RLNP more easily occurred when the RLN was thin. It is difficult to confirm occurrence of postoperative RLNP before and at extubation. Therefore, it is helpful to know its risk factors including size of RLN.