Speech motor control in Parkinson's disease: a comparison between a clinical assessment protocol and a quantitative analysis of mandibular movements.

Nine individuals with Parkinson's disease (PD) and nine normal control subjects, matched for sex and age, were compared on a standardized assessment protocol for dysarthria. Simple measures of hand and gait motility were also obtained. A kinematic analysis of vertical jaw movements during speech was performed by using an optoelectronic technique. The PD subjects were examined during both induced off L-dopa and on L-dopa states, and their performance was compared between the two conditions. Significant group differences were found for all kinematic measures during a syllable repetition task, as well as for the total dysarthria test scores and certain individual test items. Implications and clinical usefulness of the kinematic approach to the study of oral motor functions are discussed.