Ideomotor apraxia in Huntington's disease.

The pattern of movement errors in ideomotor apraxia suggests an abnormality in selection and sequencing of component movements. Individuals with Huntington's disease were evaluated prospectively for the presence of apraxia, and aspects of motor and cognitive function were correlated with apraxic errors. Based on a conservative apraxia rating, ideomotor apraxia occurred in three (33%) of nine patients with a mean duration of disease of 10.4 years. Only two (22%) individuals made no apraxic errors, however, and the group as a whole made apraxic errors in 26% of movements. Apraxia was associated with errors in imitation of nonsymbolic movements but not with errors in recognition of gestures. It correlated significantly with duration of disease and with progressive abnormalities of posture but not with other individual aspects of elementary motor or cognitive function. These associations indicate that apraxia in Huntington's disease may be due primarily to involvement of subcortical motor structures rather than cerebral cortex.