Publication:

Superior laryngeal nerve dysfunction following thyroid surgery: assessment of incidence and long-term effect

Background Importance of Sentinel lymph node (SLN) in thyroid surgery has received little attention compared to Recurrent laryngeal nerve (RLN). Injury to the external branch of the superior laryngeal nerve (EBSLN) is a voice-altering complication of thyroid surgery that has significant implications for professional voice users. The symptoms can be nonspecific and the subtle laryngoscopic manifestations are often overlooked.

Methods This study involved 50 patients of thyroid disease with no prior voice pathology who subsequently underwent thyroid surgery. All patients underwent voice analysis pre-operatively, including video laryngoscopy, voice analysis and Grade of hoarseness, roughness, breathiness, asthenia, and strain (GRBAS) scale. Voice analysis was repeated at 2 weeks, 4 weeks, 3 months and 6 months post operatively. Patients with no change in voice after 04 weeks were not followed up subsequently.

Results Of 50 patients, 20 (40%) patients underwent hemithyroidectomy, 18 (36%) total thyroidectomy, 11 (22%) subtotal thyroidectomy and 1 (2%) Near total thyroidectomy. Based on voice analysis, patients were categorized into four different groups namely - normal with no laryngeal nerve injury (N=45, 90%), RLN palsy (N=2, 4%), SLN palsy (N=3, 6%). Patients with SLN palsy showed bowing of vocal cords persisting till 06 months post operatively. There were changes in fundamental frequency also, which appeared at 02 weeks and gradually improved on subsequent follow up.

Conclusions The prevalence of SLN injury and dysfunction is unknown as many cases go undiagnosed. Further research is needed to improve the index of suspicion in patients with poor voice quality and reduced vocal range post operatively. On improved diagnostic accuracy, early treatment of this complex disorder may lead to significant recovery.