Association Between Recurrent Laryngeal Nerve Calibre and Body Figure: A Preoperative Tool to Assess Thin-Diameter Nerves in Thyroidectomy

Inadvertent recurrent laryngeal nerve (RLN) injury is a major complication of thyroidectomy. This study aimed to investigate the association between preoperative clinical parameters and RLN size prediction. Total thyroidectomy and thyroid lobectomy data were collected between January 2014 and April 2017. Routine identification of the recurrent laryngeal nerves was performed, while intraoperative findings (nerve diameter, thyroid gland weight, intraoperative neuromonitoring (IONM) use, and signal recording) and demographic data were collected for analysis. A total of 848 patients with 1357 RLNs at risk were enrolled in this study. RLN diameter was thinner in females, those with body height <160 cm, and those with a BMI <25 (all p < 0.001). RLN diameter was directly proportional to age, body weight, height, and BMI. RLN diameter was thinner (1.71 mm vs. 1.55 mm, p = 0.039) and branched nerve incidence was higher (18.5% vs. 29.7%, p = 0.09) in the postoperative RLN injury group. Branched nerves were more frequently encountered in female patients (female vs. male: 28.8% vs. 18.7%, p = 0.004). The risk of RLN palsy in intraoperative IONM loss patients was 27 times higher compared to that in IONM normal patients (1.55% vs. 30%, p < 0.001). Thinner nerves did not yield a higher rate of IONM signal loss. Thinner nerves and higher palsy rates could be anticipated in females, younger age groups, those with shorter stature, and those with low BMI. RLN diameter was not associated with the rate of IONM signal loss.