| Description |
Adductor spasmodic dysphonia (ADSD) and muscle tension dysphonia (MTD) have voice characteristics that can mimic each other, thus leading to diagnostic confusion. Given the perceptual similarity, specific distinguishing features are needed to objectively compare characteristics of ADSD and MTD. Intraword phonatory breaks, comprising of a complete absence of phonation, are one such acoustic feature that needs further research. This investigation assessed the diagnostic worth of acoustic analysis of phonatory breaks as a possible objective test to distinguish ADSD from MTD. Fifty-nine subjects with MTD and 41 subjects with ADSD were recorded reading an all-voiced consonant sentence: Early one morning a man and a woman were ambling along a one-mile lane running near Rainy Island Avenue. The presence and duration in milliseconds of any within-word phonatory breaks were measured. Estimates of sensitivity, specificity, positive and negative predictive value, and likelihood ratios were calculated to determine the precision and worth of phonatory break analysis as a clinical diagnostic test. Results revealed that (a) individuals with ADSD showed a higher mean number of phonatory breaks as compared to individuals with MTD; (b) phonatory breaks occurred in participants with ADSD, particularly at durations less than 60 ms as compared to the MTD group. Also, the ideal duration of phonatory break measurement was 40 ms; (c) all measures of diagnostic precision were markedly better in males. Males with MTD rarely evidenced phonatory breaks, and no male subject with MTD had a break greater than 70 ms; (d) as the number of phonatory breaks increased, diagnostic precision also increased. For example, when a patient has more than four phonatory breaks, it can be quite confidently concluded that the patient has ADSD. It can be concluded that combining information regarding duration and frequency, along with knowledge of gender, improved diagnostic test performance. Automation of the acoustic analysis procedure should be explored. |
