Temporal speech characteristics of individuals with multiple sclerosis andataxic dysarthria: 'Scanning speech' revisited

'Scanning speech' has been used as a description of a prominent characteris tic of the dysarthria of multiple sclerosis (MS) as well as of ataxic dysar thria in generat. It is thought to be measurable as equalised syllable dura tions. There are seemingly contradictory prosodic-temporal characteristics of ataxic dysarthria: perceptually characterised as prosodic excess as well as phonatory-prosodic insufficiency and acoustic characteristics including signs of isochrony as well as variability. This study investigates the tem poral characteristics at two levels, duration and variability of syllable d urations and the durations of interstress intervals. A group of 14 individu als with MS and ataxic dysarthria as well as 15 control subjects were studi ed. It was concluded that individuals with ataxic dysarthria and MS showed (a) for syllables: significantly increased durations and decreased intrautt erance variability (more isochrony or syllable equalisation) as well as sig nificantly increased interutterance variability; (b) for interstress interv als: significantly increased durations and increased variability (less isoc hrony). The results point to inflexibility as well as instability of tempor al control, which could contribute to the explanation of why the perceptual characteristics are contradictory. Copyright (C) 2000 S. Karger AG. Basel.