Subjective and Quantitative Assessment of Vocal Tremor in Patients With Adductor Laryngeal Dystonia

Purpose: The aims of this study were to subjectively and quantitatively analyze vocal tremor (VT) in patients with adductor laryngeal dystonia (ADLD) using video feature tracking of stroboscopic laryngoscopy recordings, to observe the VT incidence and characterize tremor directionality and kinematic parameters, and to identify differences between the patients with intermittent dystonia tremor (iDT) and regular dystonia tremor (rDT). Method: A retrospective analysis included 55 clinically diagnosed ADLD patients (ADLD group) and 10 normal-voiced controls (normal group). Two blinded laryngologists assessed stroboscopic videos and classified ADLD patients with VT into iDT group and rDT group based on tremor regularity. Video tracking was used to quantitatively measure tremor amplitude, period, and velocity of the epiglottis, bilateral vestibular folds, and bilateral arytenoids in horizontal and anteroposterior directions. Results: VT was detected in 61.82% (34/55) of ADLD patients, all of whom were female (34/49). This incidence was statistically different than for controls (0/10) and for male patients with ADLD (0/6; p < .001). Predominant tremor types were horizontal (52.94%, 18/34) and mixed (41.18%, 14/34). Horizontal tremor parameters did not differ significantly within the ADLD group or between the iDT and rDT groups ( p > .05). Mean horizontal amplitudes were epiglottis, 0.21 vocal fold widths; left/right vestibular folds, 0.14/0.12 vocal fold widths; and left/right arytenoids, 0.16/0.13 vocal fold widths. In the anteroposterior direction, only arytenoid amplitude and velocity showed intergroup differences ( p < .05). The iDT group had smaller epiglottic and bilateral arytenoid oscillation amplitudes than the rDT group ( p < .05). Mean anteroposterior amplitudes were epiglottis, 0.33 vocal fold widths; left/right vestibular folds, 0.12/0.16 vocal fold widths; and left/right arytenoids, 0.17/0.22 vocal fold widths. Conclusions: VT is a key phenotype in female ADLD patients. Video tracking enables quantitative characterization of tremor kinematics and reveals objective amplitude differences between the rDT and iDT, providing a methodological basis for objective diagnosis, subtyping, and treatment evaluation of ADLD. Supplemental Material: https://doi.org/10.23641/asha.34057596