Innervation of the cricothyroid muscle by the recurrent laryngeal nerve

Abstract

Background The recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (SLN) are generally thought to innervate the endolaryngeal muscles and the cricothyroid muscle (CTM), respectively. Meticulous anatomic studies found communication between these nerves (ie, the human communicating nerve). In this study, we report the innervation of the CTM by the RLN. Methods We performed electromyographic studies of 50 patients during thyroidectomy (20 total and 30 hemithyroidectomies). During surgery, the external branch of the SLN, RLN, and vagus nerve were stimulated. Responses were evaluated by visual observation of the CTM and by electromyographies through needle electrodes inserted into the CTM. Results Seventy CTMs were evaluated. The RLN stimulation yielded both visible contractions and clear electromyographic responses (>300 μV) in 27 (39%), either response in 24 (34%), and neither response in 19 (27%) of the CTMs. The vagus stimulation gave similar results. Conclusion The RLN innervated the CTM at least in 39% cases.