The relationship between the vagus nerve and the common carotid artery in thyroid surgery: an ultrasonographic study

To evaluate the positional relationship of the cervical vagus nerve with the common carotid artery (CCA) and internal jugular vein (IJV) using high-resolution ultrasonography and to identify anatomical variations relevant to vagus nerve localization during intraoperative neuromonitoring (IONM) in thyroid surgery.

This prospective observational study included 97 individuals aged 20-30 years, providing 194 cervical sides for analysis. The vagus nerve was evaluated bilaterally using high-resolution ultrasonography and classified into six positional patterns according to its relationship with the CCA and IJV. Positional distributions were compared according to side and sex.

Position 1 was the most frequent configuration (n = 128, 66.0%), followed by Position 2 (n = 59, 30.4%). Positions 3 and 4 were observed in 5 (2.6%) and 2 (1.0%) sides, respectively. Positions 5 and 6 were not observed in any case. Thus, the vagus nerve was predominantly located between the great vessels, while superficial and medial-superficial variants were uncommon. No statistically significant association was found between vagus nerve position and side or sex (all p > 0.05).

The cervical vagus nerve exhibits positional variation within the carotid sheath, although it is predominantly located between the CCA and IJV. High-resolution ultrasonography allows identification of these anatomical variations and may facilitate preoperative localization of the vagus nerve, potentially supporting safer IONM and reducing the risk of iatrogenic neural injury during thyroid surgery.