title: Intraoperative monitoring of the recurrent laryngeal nerve by vagal nerve stimulation in thyroid surgery.
abstract: The aim of the present study was to evaluate the thyroarytenoid muscle response during bilateral thyroid surgery using vagal nerve stimulation. 195 patients (390 nerves at risk) underwent a total thyroidectomy. The recurrent laryngeal nerve's function was checked by analyzing the amplitude and the latency of the thyroarytenoid muscle's responses after a vagal nerve's stimulation (0.5 and 1 mA) using the NIM3 Medtronic system. All patients were submitted to preoperative and postoperative laryngoscopy. 20 patients get no thyroarytenoid muscle response to the vagal nerve stimulation, and 14 postoperative recurrent laryngeal nerve palsies were confirmed (3.8 %). Two palsies were present after 6 months (0.51 %). All the patients with muscle's response have normal mobility vocal fold. The test sensitivity was 100 % and the test specificity was 98 %. Physiologically, the mean latencies of the muscular potentials for the right RLN were, respectively, 3.89 and 3.83 ms (p > 0.05) for the stimulation at 0.5 and 1 mA. The mean latencies for the left RLN were, respectively, 6.25 and 6.22 ms for the stimulation at 0.5 and 1 mA (p > 0.05). The difference of the latencies between the right and the left nerve was 2.30 ms (1.75-3.25 ms) with a stimulation of 0.5 or 1 mA (p < 0.05). Thyroarytenoid muscle's response via a vagal nerve stimulation showed a functional asymmetry of the laryngeal adduction with a faster right response. Surgically, this method can predict accurately an immediate postoperative vocal folds function in patients undergoing a bilateral thyroid surgery.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital St Etienne, St Etienne, France.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Farizon
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital St Etienne, St Etienne, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Gavid
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital St Etienne, St Etienne, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Karkas
authors.affiliation: Department of Pathology, University Hospital St Etienne, St Etienne, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Dumollard
authors.affiliation: Department of Pathology, University Hospital St Etienne, St Etienne, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Peoc'h
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital St Etienne, St Etienne, France. jean.michel.prades@univ-st-etienne.fr.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Prades
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007821:Laryngeal Muscles / Q000294:innervation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011183:Postoperative Complications; D011446:Prospective Studies; D012009:Recurrent Laryngeal Nerve; D061226:Recurrent Laryngeal Nerve Injuries / Q000517:prevention & control*; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000601:surgery*; D055536:Vagus Nerve Stimulation; D014826:Vocal Cord Paralysis / Q000209:etiology; D055815:Young Adult
keywords: Intraoperative monitoring; Recurrent laryngeal nerve; Thyroarytenoid muscle; Thyroid gland; Vagal nerve