Ultrasound visualization of the vagus nerve for intraoperative neuromonitoring in thyroid surgery

Objective Localization of the vagus nerve is required during intraoperative neuromonitoring (IONM) for thyroid surgery in order to electromyographically verify the functional integrity of inferior laryngeal nerve and aim to reduce the risk of postoperative vocal fold paralysis. Classically, the vagus nerve courses within the carotid sheath between the common carotid artery and internal jugular vein, but anatomic variations have been described. Our aim was to compare preoperative ultrasound (US) and intraoperative localization of vagus nerve and to document anatomic variations. Patients and methods Retrospective study of patients undergoing thyroidectomy. The vagus nerve was identified 2 cm below the inferior border of the cricoid cartilage, on US performed 6 weeks prior to surgery; then, vagus nerve was identified surgically. Results For 82 patients, on preoperative US, the right vagus nerve was in between, superficial, or deep to the vessels in 94%, 2.4%, and 3.6%, and on the left in 72%, 24.4%, and 3.6%. Intraoperatively, the right vagus was in between, superficial, or deep in 90%, 4%, and 6%, and on the left in 67%, 27%, and 6%. US correlated with surgery on the right in 79/82 (96%) and on the left in 78/82 (95%). Conclusions To our knowledge, this is the first study directly comparing US and intraoperative findings. The US and surgical findings were identical in 95% on the left and 96% on the right The vagus nerve was superficial in 27% of cases on the left and 4% on the right. Identifying this anatomic variation preoperatively may facilitate IONM.