title: Results of intraoperative neuromonitoring in thyroid surgery and preoperative vocal cord paralysis.
abstract: BACKGROUND
  Systematic studies of intermittent intraoperative neuromonitoring (IONM) have shown that IONM enhances recurrent laryngeal nerve (RLN) identification via functional assessment, but does not significantly reduce rates of vocal cord (VC) paralysis (VCP). The reliability of functional nerve assessment depends on the preoperative integrity of VC mobility. The present study was therefore performed to analyze the validity of IONM in patients with pre-existing VC paralysis.
  
  
  METHODS
  Of 8,128 patients, 285 (3.5 %) with preoperative VCP underwent thyroid surgery using standardized IONM of the RLN and vagus nerves (VNs). VC function was assessed by pre- and postoperative direct videolaryngoscopy. Quantitative parameters of IONM in patients with VCP were compared with IONM in patients with intact VC function. Clinical symptoms and surgical outcomes of patients with pre-existing VCP were analyzed.
  
  
  RESULTS
  A total of 244 patients revealed negative, and 41 revealed positive IONM on the side of the VCP. VCP with positive IONM revealed significantly lower amplitudes of VN and RLN than intact VN (p = 0.010) and RLN (p = 0.011). Symptoms of patients with VCP included hoarseness (25 %), dyspnea (29 %), stridor (13 %), and dysphagia (13 %); 13 % were asymptomatic. New VCP occurred in five patients, ten needed tracheostomy for various reasons, and one patient died.
  
  
  CONCLUSIONS
  Patients with pre-existing VCP revealed significantly reduced amplitude of ipsilateral VN and RLN, indicating retained nerve conductivity despite VC immobility. Preoperative laryngoscopy is therefore indispensable for reliable IONM and risk assessment, even in patients without voice abnormalities.
authors.affiliation: Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Ernst-Grube-Straße 40, 06120, Halle (Saale), Germany, kerstin.lorenz@uk-halle.de.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Lorenz
authors.forename: Mohammed
authors.initials: M
authors.lastname: Abuazab
authors.forename: Carsten
authors.initials: C
authors.lastname: Sekulla
authors.forename: Rick
authors.initials: R
authors.lastname: Schneider
authors.forename: Phuong
authors.initials: P
authors.lastname: Nguyen Thanh
authors.forename: Henning
authors.initials: H
authors.lastname: Dralle
mesh_terms: D000328:Adult; D000368:Aged; D058070:Asymptomatic Diseases; D004576:Electromyography; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000517:prevention & control*; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011300:Preoperative Care / Q000379:methods; D057234:Preoperative Period; D012009:Recurrent Laryngeal Nerve / Q000502:physiology / Q000503:physiopathology; D061226:Recurrent Laryngeal Nerve Injuries / Q000209:etiology / Q000517:prevention & control*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013959:Thyroid Diseases / Q000150:complications / Q000601:surgery*; D013965:Thyroidectomy / Q000009:adverse effects*; D016896:Treatment Outcome; D014630:Vagus Nerve / Q000502:physiology / Q000503:physiopathology; D014826:Vocal Cord Paralysis / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*