title: Clinical significance of vagus nerve variation in radiofrequency ablation of thyroid nodules.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  The operator should pay attention to anatomical variations and the resulting vagus nerve injury during RF ablation of bulging thyroid nodules.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Songpa-Gu, Seoul, Republic of Korea.
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Ha
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Baek
authors.forename: Jeong Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Jae Kyun
authors.initials: JK
authors.lastname: Kim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D002417:Cattle; D002648:Child; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011846:Radio Waves; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D016606:Thyroid Nodule / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery*; D014463:Ultrasonography / Q000379:methods; D014630:Vagus Nerve / Q000033:anatomy & histology* / Q000473:pathology