Intra-operative Neuromonitoring and Neurostimulation of the Recurrent Laryngeal Nerve in Thyroid Surgery: A Randomized Clinical Trial

Introduction: Intra-operative functional testing of the nerve is gaining a wide diffusion, particularly neurostimulation (NS) and introperative neuromonitoring (IONM). The impact of these methods on avoiding recurrent laringeal nerve (RLN) injury is still controversial. The aim of our study was to compare the efficacy of RLN direct stimulation alone to direct stimulation in association to intra-operative neuromonitoring. Materials and Methods: The study was designed as a randomized clinical trial. Between January 2008 and April 2009 were included 250 patients (455 nerve at risk) randomized into 2 groups: control group of 125 patients (229 nerves at risk) assigned to NS with palpatory feedback, and the study group comprising 125 patients (229 nerves at risk) assigned to IONM and NS. The prevalence of RLN palsy and accuracy of the feedback signals were compared between the groups. Results: The overall RLN injury incidence for nerve at risk was 2.7% in the study group and 2.6% in the control group. No statistically significant difference was found between the groups. Either palpatory feedback or IONM feed back to RLN direct neurostimulation obtained an elevated negative predictive value (respectively 98.2% and 99%) and a poor positive predictive value (26.7% and 22.2%). The accuracy of the two methods resulted to be similar (respectively 95.8% and 92.7%). Conclusions: The IONM, compared to NS alone, did not significantly reduce the incidence of nerve injury after thyroid surgery. Furthermore the two methods showed a similar accuracy in predicting postoperative paralysis.