• Michael Hermann, Christa Hellebart, and Michael Freissmuth.
• Department of Surgery, Kaiserin-Elisabeth-Spital, University of Vienna, Vienna, Austria.
• Ann. Surg. 2004 Jul 1; 240 (1): 9-17.

ObjectiveWe evaluated the ability of neuromonitoring to predict postoperative outcome in patients undergoing thyroid surgery for different indications.Summary Background DataNeuromonitoring has been advocated to reduce the risk of vocal cord palsy and to predict postoperative vocal cord function.MethodsThree hundred twenty-eight patients (502 nerves at risk) were studied prospectively at a single center. Neuromonitoring was performed with the Neurosign 100 device by transligamental placement of the recording electrode into the vocalis muscles. Cumulative distribution of stimulation thresholds was determined by stepwise decreases in current (1 mA to 0.05 mA) for both the vagus and the recurrent nerve. Patients were grouped according to surgical risk (benign and malignant disease, reoperation for benign and for malignant disease).ResultsIf the electrophysiological response was correlated to postoperative vocal cord function, the sensitivity of neuromonitoring was modest (86% in surgery for benign disease) to low (25% in reoperation for malignant disease); the positive predictive value was modest (overall rate 62%) but acceptable (87%) if corrected for technical problems. Specificity and negative predictive values were high (ie, overall >95%). Stimulation thresholds were not augmented in 11 patients, in whom postoperative palsy developed despite normal intraoperative recordings. Similarly, an electrical field response was elicited in 14 of 21 patients with preoperative vocal cord palsy. Electromyographic recordings did not reveal an abnormal amplitude or a decline in nerve conduction velocity.ConclusionsNeuromonitoring is useful for identifying the recurrent laryngeal nerve, in particular if the anatomic situation is complicated by prior surgery, large tissue masses, aberrant nerve course. However, neuromonitoring does not reliably predict postoperative outcome.

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