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

• Localization of the vagus nerve is necessary during thyroid surgery when using neuromonitoring for electromyographic testing of the inferior laryngeal nerve to reduce the risk of postoperative vocal fold paralysis. • The vagus nerve in the neck can be routinely visualized using ultrasound, and is generally in between the common carotid artery and the internal jugular vein. Its location on ultrasound corresponds very closely to that observed in vivo during surgery (95%). • At the level of the thyroid lobe, there is an anatomic variant with the vagus nerve superficial to the common carotid artery which is seen more often on the left than on the right.