Preoperative Ultrasound Prediction and Intraoperative Neuromonitoring for Preservation of a Non-Recurrent Laryngeal Nerve During Thyroidectomy: A Case Report

Vocal cord paralysis, one of the most notable complications of thyroidectomy, is primarily caused by injury to the recurrent laryngeal nerve (RLN), with the risk increasing in cases of anatomical variation. To prevent such complications, tools like preoperative CT, ultrasonography, and intraoperative neuromonitoring (IONM) have been widely adopted and studied. We recently encountered a patient scheduled for thyroidectomy was found with an aberrant right subclavian artery identified on CT, suggesting the possibility of a right-sided non-recurrent laryngeal nerve (NRLN). Preoperative ultrasound showed a nerve branch arising directly from the vagus nerve at the level of the cricoid cartilage, supporting the suspicion of NRLN. IONM was used during surgery. The nerve was safely identified, allowing the surgery to proceed without complications such as vocal cord paralysis. This case suggests that preoperative ultrasonographic evaluation can enable the surgeons and radiologists to identify NRLN directly by ultrasonographic imaging.