Intraoperative laryngeal nerve monitoring during thyroidectomy

Objective: To determine whether nerve integrity monitor testing during thyroidectomy predicts recurrent larygeal nerve (RLN) function after surgery. Design: Prospective cohort outcomes study Patients: The study included 210 consecutive patients with thyroid abnormalities who underwent thyroidectomy. Methods: All patients were intraoperatively monitored with a nerve integrity monitoring system (Xomed NIM II; Medtronic Inc, Fridley, Minnesota), and their vocal cord function was assessed with fiberoptic laryngoscopy before and after surgery. Normal and impaired vocal cord function were compared using an independent t test with respect to postoperative vocal cord mobility, length of the RLN dissection, and the minimum stimulus needed to generate a response at the completion of surgery. Results: There was a statistically significant difference between the stimulus in milliamperes required to stimulate normal vs abnormal functioning nerves at the completion of the procedure at the cricoarytenoid joint (P=.02) and at the distal end of the RLN dissection (P<.01). A greater length of dissected nerve was associated with normal vocal cord function; however, it was not statistically significant (P=.07). Conclusion: These data suggest that an RLN that responds at lower-intensity stimulation (≤0.5 mA) at the end of thyroid surgery is associated with normal vocal cord mobility.