The syllable method: proportion of impaired syllables as an indicator of spasmodic dysphonia severity.

We have previously proposed the 'mora method' to evaluate the degree of impairment in spasmodic dysphonia (SD) in Japanese-speaking patients. With this method, impairment is judged as the proportion of impaired morae in a 25-mora sentence in a longer passage read aloud. As the mora is the phonologically isochronic unit in Japanese, the proportion of impaired morae in speech can be used to represent the temporal proportion of impaired Japanese speech. This proportional measure of impairment reflects the perceived severity of the impairment, and is a more reliable measure than a 4-point perceptual rating scale completed either by patients or by voice professionals. In this paper, we propose a 'syllable method' to characterize the severity of impairment in English-speaking SD patients. Instead of morae, the severity of SD was represented by the proportion of impaired syllables. It should be possible to characterize SD impairments more reliably and precisely with this method than using a 4-point rating scale completed by voice professionals. Ultimately, the syllable method should become a simple and effective method for evaluating the severity of SD. Furthermore, such methods can be applied to other languages, using the appropriate phonological unit (either mora or syllable).