Objective: Adductor Laryngeal Dystonia (AdLD) is a rare neurological voice disorder. It is characterized by task specificity, with selective impairments in speaking but not when whispering or doing other innate vocal behaviors. AdLD can cause individuals to have a dysphonic voice with auditory-perceptual features of strain and roughness, which negatively affects voice-related quality of life. It is unclear how AdLD and the severity of dysphonia of these speakers affect intelligibility (how well a speaker’s message is being understood). This study aimed to investigate the difference in intelligibility of individuals with AdLD compared to those without AdLD (controls), and to characterize the relationship between the overall severity of dysphonia of the AdLD speakers and their intelligibility.
Methods: Speakers were 44 individuals with AdLD, and 44 age- and sex-matched controls. Each speaker read out a unique set of six Sentence Intelligibility Test sentences. Overall severity of dysphonia was assessed by five experienced Speech-Language Pathologists using the Consensus Auditory Perceptual Evaluation-Voice. Five inexperienced listeners listened and orthographically transcribed all six sentences for each participant. An analysis of variance was performed to determine the effects of group, sentence length, and their interaction on intelligibility. A Pearson’s correlation was used to assess the strength of the linear relationship between intelligibility and overall severity of dysphonia.
Results: Individuals with AdLD had significantly lower intelligibility than controls. As sentence length increased, intelligibility significantly decreased. Intelligibility significantly decreased as overall severity of dysphonia increased.
Conclusion: AdLD has a negative impact on a speakers intelligibility, and intelligibility decreases as overall severity of dysphonia increases.