Objectives: To evaluate the types and incidence of vagus nerve variations and to assess factors related to the vulnerability of vagus nerves during the radiofrequency (RF) ablation of thyroid nodules.
Methods: Bilateral vagus nerves of 304 consecutive patients who underwent ultrasound of the neck were assessed. Two radiologists evaluated vagus nerve type (types 1-4; lateral/anterior/medial/posterior), the shortest distance between the thyroid gland and vagus nerve, and thyroid contour. Vagus nerve vulnerability was defined as a vagus nerve located within 2 mm of the thyroid gland through the ex vivo experiments, and factors associated with vulnerability were assessed.
Results: We were unable to find one vagus nerve. Of the 607 vagus nerves, 467 (76.9%) were type 1, 128 (21.1%) were type 2, 10 (1.6%) were type 3, and 2 (0.3%) were type 4, with 81 (13.3%) being vulnerable. Univariate analysis showed that sex, location, thyroid contour and type were significantly associated with vagus nerve vulnerability. Multivariate analysis showed that bulging contour caused by thyroid nodules (P = 0.001), vagus nerve types 2/4 (P < 0.001) and type 3 (P < 0.001) were independent predictors.
Conclusion: The operator should pay attention to anatomical variations and the resulting vagus nerve injury during RF ablation of bulging thyroid nodules.