Stereotypy and motor control: Differences in the postural stability dynamics of persons with stereotyped and dyskinetic movement disorders

We examined whether dynamic measures of postural stability differentiated p ersons with stereotyped movement disorder from persons with dyskinetic move ment disorder. Participants from three groups (stereotypy, dyskinesia, cont rol) were given a goal-oriented postural stability task, and performance wa s measured using a force platform and computerized posturographic technique s. The results showed that both movement disorder groups differed from the control group in the posture task. Further, the stereotypy and dyskinesia g roups demonstrated markedly different postural movement profiles. The postu ral motion of the stereotypy group was characterized by greater amplitude a nd variability but lower complexity than the dyskinesia group. These result s provide support for a motor control model of stereotypy.