The Function of Cricothyroid Muscle and Its Impaction on Mandarin Lexical Tones in Unilateral Vocal Fold Paralysis

Overview

Mandarin Chinese phonemically distinguishes four tones, with Tone 1 having high-level pitch, Tone 2 high-rising pitch, Tone 3 low-dipping pitch, and Tone 4 high-falling pitch The same segmental context carries different meanings depending on the tone. The function deficit of cricothyroid (CT) muscle, innervated by external branch superior laryngeal nerve (eSLN), would impair the speech tone adjustment. The defect in tone adjustment may interfere with the communication function in Mandarin Chinese speaker more than other language users. This may explain while peripheral unilateral vocal fold paralysis (UVFP) patients with eSLN injury had worse outcomes than those with sole recurrent laryngeal nerve paralysis. The neuromuscular control of laryngeal muscle can be evaluated by laryngeal electromyography (LEMG). The investigators have utilized a quantified LEMG (denoted Q-LEMG) in their previous research to measure the neuromuscular control of thyroarytenoid- lateral cricoarytenoid (TA-LCA) adductor complex. However, the task to measure the CT muscle function by Q-LEMG has not been developed yet. It is of thus of utmost interest to develop a standardized task to measure the neuromuscular function of CT muscle in Mandarin speakers. In Mandarin speaking patients with UVFP, the lexical tone influence from CT muscle can be discovered by the technique. The investigators also want to measure the lexical tone correction by conventional laryngoplasty and its influence in CT muscle activity. The data of lexical tone and its correlation with CT contractile activity is important in attempting pitch adjust artificial electrolarynx.

Purposes: 1. Searching for a standard task to measure CT function by Q-LEMG. 2. Correlate the data among Q-LEMG activity of CT muscle, lexical tone in Mandarin and vocal cord position and its impaction on vocal functions. 3. Detect the influence of lexical tone from conventional laryngoplasty for peripheral UVFP with eSLN injury. Study designs: The current research is a two-year study. In the first year, the investigators will develop a standardized task for quantified LEMG analysis for CT muscles which were controlled by eSLN. In the second year, patients with acute UVFP will be enrolled into the study. By comprehensive evaluation including Q-LEMG analysis, the impact of injection laryngoplasty on tone adjustment can be identified. The results between UVFP with or without CT muscle damage will also be compared. Predictive outcomes: 1. Developing a standard tool, Q-LEMG, to measure the function CT muscles. 2. Achieve the correlation of the neuromuscular control of lexical tone and CT muscle. 3. Analyze the impaction of early temporary injection on speech modal tone in Mandarin speakers and neuromuscular control in CT muscles. 4. Applying the data of tone and CT signals to future pitch controlled artificial electrolarynx animal models.