| Abstract | Objective: Neurogenic voice disorders such as adductor laryngeal dystonia, vocal tremor, and vocal fold paralysis have unique influences on the vocal folds during phonation. Laryngeal high-speed videoendoscopy (HSV) allows for the observation of the vocal folds in intricate detail due to its high frame rate. By using HSV, this study investigates the vibratory mechanisms of the vocal folds at the onset and offset of sustained phonation between normophonic speakers and different neurogenic voice disorders at several vocal modalities.
Methods: HSV data and audio recordings were obtained simultaneously from 15 patients with neurogenic voice disorders (ten female and five male) and 15 normophonic participants (10 female and five male) during two productions of the vowel /i/ at habitual pitch and loudness, soft and hard glottal attacks. Five subjects had vocal fold paralysis, six had adductor laryngeal dystonia, and four had vocal fold tremor. Glottal attack time (GAT) and glottal offset time (GOT) were measured at the onset and offset of phonation for each participant by two raters. GAT represents the duration from the first oscillation to the first contact of vocal folds at the phonation onset, while GOT is the duration between the last oscillation and the last contact at the offset of phonation. Parametric and non-parametric statistical tests were used to compare the GAT and GOT between the normophonic and disordered groups considering the different vocal modalities.
Results and Conclusions: The average GATs and GOTs were found to be higher for the disordered group compared to the normophonic group for all vocal modalities. GAT was found to be statistically significantly different between the normophonic and neurogenic group during hard glottal attacks. Significant differences for GOT were found between vocal tremor and both vocal paralysis and adductor laryngeal dystonia based on a multivariate analysis. This study provides evidence that GAT and GOT may be impacted by different types of neurogenic voice disorders during sustained phonation. These findings may serve as useful tools to distinguish the vocal mechanisms of the studied voice disorders.
Acknowledgments: We acknowledge the support from NIH NIDCD K01DC017751, R21DC020003 and R01DC019402, and Michigan State University Discretionary Funding Initiative.
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