Aerodynamic Phonatory Pattern as a New Sign of Superior Laryngeal Nerve Injury

Abstract

Objectives: Reduced quality of life after thyroid surgery is multifactorial and may include the need of lifelong different treatments. About 1 in 20 patients experience voice changes, and it is very frequent that these changes may not be caused by neural lesions. The purpose of this study is to describe aerodynamic phonatory features in thyroidectomized patients in order to determine what mechanisms are involved in voice changes in these patients and what are the best rehabilitative options. Methods: We studied 58 thyroidectomized patients with neither apparent neural cause of thyroidectomy-related dysphonia nor recurrent laryngeal nerve injury nor external branch of the superior laryngeal nerve (EBSLN) injury. The patients were asked to produce sustained vowels, syllables, and sentences. Three items were recorded in upright and sitting positions. Afterward, acoustic and aerodynamic measurements were made: fundamental frequency, jitter, shimmer, intensity, harmonic/noise ratio, spectrographic analysis, subglottic pressure, mean transglottic flow, and laryngeal resistance. All measurements were made using Voice Plus from Alamed Corporation software. STATA software was used to analyze variables. Results: We describe 2 different groups of patients with different aerodynamic pattern in voice production that correlate with voice quality. In 66% of patients there was no change and in 34% the glottal pressure and laryngeal resistance decreased as a result of lower tension in the vocal fold as a consequence of an injury of the EBSLN. Conclusions: This aerodynamic phonatory pattern that may be understood by objective aerodynamic measurements could be another new sign of EBSLN injury.