This is the largest study on apraxia in HD. Ideomotor limb apraxia is a common sign in HD patients, occurring in a high percentage. In contrast to the opinion of several authors, occurrence of apraxia in HD is independent from neuropsychological decline and the severity of most neurological symptoms.

Background: Although ideomotor limb apraxia is often considered to occur only in dementia with cortical involvement like Alzheimer’s disease (AD), it is also frequently seen in dementia with subcortical degeneration like Huntington’s disease (HD). Methods: To assess the occurrence of ideomotor limb apraxia, 46 patients with HD (27 men) and 37 patients with AD (16 men), matched for cognitive performance, were assessed with an apraxia test battery containing tests of the imitation of meaningless hand and finger gestures, the performance of meaningful gestures and of pantomimic movements. Results: There was a high frequency of ideomotor limb apraxia in both AD and HD patients. For the assessment of hands’ imitation 13.5% of the AD patients and 41.3% of the HD patients were apraxic, for fingers’ imitation 21.6% (AD) and 41.3% (HD) were apraxic, for gestures 27.0% (AD) and 32.6% (HD), and for the assessment of pantomimic movements 24.3% (AD) and 52.2% (HD) showed apraxia. In the AD patients, disease severity was related to the occurrence of apraxia. Conclusions: Ideomotor limb apraxia is a common sign in both groups of patients, occurring in a high percentage. For particular neuropsychological deficits, including ideomotor limb apraxia, a division of dementia in a subcortical and cortical subtype seems to be clinically not meaningful.