Neural Monitoring of the Superior Laryngeal Nerve in Thyroid Surgery

Thyroid surgeons place an enormous amount of importance and rightly so to the preservation of the recurrent laryngeal nerve (RLN) during thyroidectomies. A good knowledge of the anatomy of the nerve and meticulous dissection technique and intraoperative identification of the nerve are crucial to the anatomic and functional integrity of the nerve. The use of intraoperative neural monitoring to aid the surgeon in the identification of the RLN has gained acceptance and is considered standard practice in several units. However, lesser emphasis has been placed historically on the identification and preservation of the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery. The EBSLN supplies the cricothyroid muscle that controls pitch variation during phonation. Unlike damage to the recurrent laryngeal nerve which manifests readily as vocal cord paralysis, intraoperative damage to EBSLN is difficult to assess postoperatively as visual assessment of the larynx is not indicative of the integrity of the nerve. Injury of the EBSLN can cause weakness or complete paralysis of the ipsilateral cricothyroid muscle. Patients may report a deeper voice or an inability to produce high pitched sounds. Patients may also complain of weakness, tightness of the voice, and require extra effort to speak. Of note, voice changes with EBSLN injury are subtle in the general population but can be devastating in patients who depend on their voice for a living. Importantly, EBSLN injury is reported in upto 50% of thyroid surgery in contrast to 12% of recurrent laryngeal nerve injury during thyroid surgery. The new guidelines published in the Laryngoscope recommend routine intraoperative neural monitoring of EBSLN. The Investigators have a functional system in use currently for monitoring recurrent laryngeal nerve intraoperatively and propose to study the impact of monitoring the EBSLN using the same neural monitoring device to improve voice results following thyroid surger