Ben C. Watson Rick Roark Steven Schaefer
Dept. of Otolaryngol., Munger, Rm. 170, New York Medical College, Valhalla, NY 10595
Perceptual ratings of vocal abnormality in spasmodic dysphonia (SD) are confounded by high variability in the severity, quality (strain-strangle versus aspirate), and task sensitivity of symptoms. Perceptual ratings are also relatively distant from the physiologic source of vocal disruption. Investigations at the neuromuscular level are closer to the source of disruption and may be informative. Thyroarytenoid myoelectric activity was recorded while SD and normal control subjects produced multiple tokens of sustained vowel, word repetition, and sentence tasks. Quantitative amplitude measures were submitted to several principal components analyses to develop models of neuromotor abnormality in SD. Analyses yielded quantitative indices of the magnitude and task-sensitivity of thyroarytenoid activity. A between-group model that included one measure across the three tasks achieved 100% discrimination of normal control and SD subjects on one component. The within-group model failed to separate perceptually different subgroups of SD subjects along either component considered separately. Models challenge the validity of the traditional clinical distinction between abductor and adductor SD and the validity of perceptual ratings of vocal spasms in spasmodic dysphonia. [Work supported by NIH Grant No. DC-00410.]