Study of Glottal Attack Time and Glottal Offset Time in Neurogenic Voice Disorders During Sustained Phonation

Neurogenic voice disorders like adductor laryngeal dystonia (AdLD), vocal tremor, and vocal paresis/paralysis impact the neuromuscular control of the phonatory system, which might lead to an impaired phonation onset/offset. Utilizing laryngeal high-speed videoendoscopy (HSV), this study investigates the glottal attack time (GAT) and glottal offset time (GOT) during soft, habitual, and hard glottal attack modalities in sustained phonation for several neurogenic voice disorders.

HSV data and audio recordings were obtained simultaneously from 14 participants with neurogenic voice disorders and 14 normophonic participants during two productions of the /i/ vowel at soft, habitual, and hard glottal attacks. Using HSV, GAT, defined as the time interval between the first oscillation and the first contact of the vocal folds at phonation onset, and GOT, the time interval between the last oscillation and the last contact of the vocal folds at phonation offset, were measured. GAT and GOT for different glottal attack modalities were compared within each group, also among the different disorders and normophonic participants. Additionally, these values were compared between sustained phonation and connected speech for the normophonic participants and those with AdLD.

The neurogenic disorders group exhibited significantly higher GAT values than the normophonic participants during the hard glottal attack modality. Habitual GOTs for vocal tremor were significantly different than those of unilateral vocal fold paralysis and AdLD. Moreover, the normophonic participants shared similar trends between connected speech and sustained phonation across glottal attack modalities for GAT, while the AdLD group did not. AdLD participants shared the same trend for GOT, while normophonic participants did not.

This study provides evidence of differences in GAT and GOT values during sustained phonation across different neurogenic voice disorders, contributing to the understanding of their pathophysiology. These findings may inform the development of strategies and speech tasks for clinical assessment of neurogenic voice disorders.