Abstract
Objectives
1) To evaluate the efficacy of a nerve monitoring(NM) system in a series of patients submitted to thyroidectomy; 2) To critically analyze the negative-predictive-value(NPV) and positive-predictive-value(PPV) of the method.
Methods
NIM® system efficacy was prospectively analyzed in 447 patients submitted to thyroidectomy between 2001 and 2008(366 female/81 male; 420 Caucasian/47 non-Caucasian; 11- to 82-years-old, median: 43 year-old). There were 421 total thyroidectomies and 21 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 postoperatively. 10 paretic/paralyzed nerves (1.2%) were detected (2 unexpected unilateral paresis, 1 unexpected bilateral paresis, 1 unexpected unilateral paralysis, 2 unexpected bilateral paralysis and 1 expected unilateral paralysis). At the late videolaryngoscopy, only 2 permanent nerve paralysis were noted (0.2%), with an ultimate result of 99.8% functioning nerves. NM showed absent or markedly reduced electrical activity at the end of the operations in 25/858 nerves (2.9%), including all 10 endoscopically compromised nerves, with 15 false-negative nerves. There were no false-positive nerves. Therefore, NPV was 40.0% and PPV was 100%.
Conclusions
In the present series, NM had a very high PPV, but a low NPV for the detection of recurrent nerve injury.
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