Preoperative ultrasound mapping of the vagus nerve in thyroid surgery

Abstract

Background: Intraoperative neuromonitoring (IONM) in thyroid surgery requires electric stimulation of the vagus nerve to verify correct electrode placement. Classically the nerve is found deep to or in-between the common carotid artery and internal jugular vein, but previous studies have shown that the nerve can sometimes be found superficial to the vessels. Our aim was to determine the incidence of a superficial vagus nerve using ultrasound (US) and study possible clinical factors associated with an anteriorly-located vagus nerve.Methods: Retrospective study of patients undergoing thyroid surgery (lobectomy or total thyroidectomy) with intermittent IONM. Substernal goiters, locally invasive tumors or bulky lymph nodes were excluded.The vagus nerve was identified at the level of the mid-thyroid lobe on each side on preoperative US performed by two specialized radiologists, and its location according to 6 possible positions in relationship to the common carotid artery was recorded. The anatomic variability of the vagus nerve was analyzed in relationship to patient demographics and thyroid pathology.Results: Five-hundred twenty-seven patients were included. The right vagus nerve (n=522) was in-between, superficial or deep to the vessels in 92.3%, 6.1% and 1.5% and of cases, respectively, and the left vagus (n=517) in 80.2%, 18.6% and 1.2% of cases, respectively, with a statistically significant difference between right and left vagus nerves (P<0.001). The type of pathology, size of the dominant nodule or the volume of the thyroid lobe were not correlated to finding a superficial vagus nerve. Conclusions:The vagus nerve was identified in all cases on US and found to be anterior to common carotid artery at the level of the thyroid lobe in 18.6% of cases on the left and 6.1% of cases on the right.Identifying this anatomic variant preoperatively may facilitate IONM and avoid inadvertent trauma to the vagus nerve during thyroid surgery.

Impact of lymphovascular invasion on otherwise low-risk papillary thyroid carcinomas: a retrospective and observational study

“…All the patients participating in this study had total thyroidectomy or lobectomy by high-volume thyroid surgeons, after multidisciplinary discussion. All patients were submitted to a preoperative specialized neck ultrasonographic assessment of the neck [ 17 , 18 ]. Prophylactic lymph node dissection was performed in some patients, according to multidisciplinary tumor board discussion and shared decision making with the patient or in case of patients included in the ESTIMABL3 trial and randomized in the prophylactic dissection arm of the study (NCT03570021).…”