Normative intra-operative electrophysiologic waveform analysis of superior laryngeal nerve external branch and recurrent laryngeal nerve in patients undergoing thyroid surgery.

Background: Injury to the external branch of the superior laryngeal nerve (EBSLN) can occur during superior pole dissection in thyroid surgery; the EBSLN injury rate is reported as high as 28 % (Cernea et al., Head Neck 14:380-383, 1992). Injury to the EBSLN leads to variable symptoms that may be overlooked, but that can be significant, especially to professional speakers and singers.