title: Negative and positive predictive values of nerve monitoring in thyroidectomy.
abstract: BACKGROUND
  Recurrent nerve injury is 1 of the most important complications of thyroidectomy. During the last decade, nerve monitoring has gained increasing acceptance in several centers as a method to predict and to document nerve function at the end of the operation. We evaluated the efficacy of a nerve monitoring system in a series of patients who underwent thyroidectomy and critically analyzed the negative predictive value (NPV) and positive predictive value (PPV) of the method.
  
  
  METHODS
  NIM System efficacy was prospectively analyzed in 447 patients who underwent thyroidectomy between 2001 and 2008 (366 female/81 male; 420 white/47 nonwhite; 11 to 82 years of age; median, 43 years old). There were 421 total thyroidectomies and 26 partial thyroidectomies, leading to 868 nerves at risk. The gold standard to evaluate inferior laryngeal nerve function was early postoperative videolaryngoscopy, which was repeated after 4 to 6 months in all patients with abnormal endoscopic findings.
  
  
  RESULTS
  At the early evaluation, 858 nerves (98.8%) presented normal videolaryngoscopic features after surgery. Ten paretic/paralyzed nerves (1.2%) were detected (2 unexpected unilateral paresis, 2 unexpected bilateral paresis, 1 unexpected unilateral paralysis, 1 unexpected bilateral paralyses, and 1 expected unilateral paralysis). At the late videolaryngoscopy, only 2 permanent nerve paralyses were noted (0.2%), with an ultimate result of 99.8% functioning nerves. Nerve monitoring showed absent or markedly reduced electrical activity at the end of the operations in 25/868 nerves (2.9%), including all 10 endoscopically compromised nerves, with 15 false-positive results. There were no false-negative results. Therefore, the PPV was 40.0%, and the NPV was 100%.
  
  
  CONCLUSIONS
  In the present series, nerve monitoring had a very high PPV but a low NPV for the detection of recurrent nerve injury.
authors.affiliation: University of São Paulo Medical School, São Paulo, Brazil; Department of Head and Neck Surgery and Albert Einstein Jewish Hospital, São Paulo, Brazil. cerneamd@uol.com.br
authors.forename: Claudio R
authors.initials: CR
authors.lastname: Cernea
authors.forename: Lenine G
authors.initials: LG
authors.lastname: Brandão
authors.forename: Flavio C
authors.initials: FC
authors.lastname: Hojaij
authors.forename: Dorival
authors.initials: D
authors.lastname: De Carlucci
authors.forename: José
authors.initials: J
authors.lastname: Brandão
authors.forename: Beatriz
authors.initials: B
authors.lastname: Cavalheiro
authors.forename: Adriana
authors.initials: A
authors.lastname: Sondermann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis; D011237:Predictive Value of Tests; D061226:Recurrent Laryngeal Nerve Injuries / Q000175:diagnosis*; D013965:Thyroidectomy / Q000009:adverse effects; D014826:Vocal Cord Paralysis / Q000517:prevention & control; D055815:Young Adult