Gesture comprehension, knowledge and production in Alzheimer's disease

Although apraxia is a typical consequence of Alzheimer's disease (AD), the profile of apraxic impairments is still subject to debate. Here, we analysed apraxia components in patients with AD with mild-to-moderate or moderately severe dementia.

Thirty-one patients were included. We first evaluated simple gestures, that is, the imitation of finger and hand configurations, symbolic gestures (recognition, production on verbal command and imitation), pantomimes (recognition, production on verbal command, imitation and production with the object), general knowledge and complex gestures (tool-object association, function-tool association, production of complex actions and knowledge about action sequences). Tests for dementia (Mini Mental State Examination and the Dementia Rating Scale), language disorders, visual agnosia and executive function were also administered.

Compared with controls, patients showed significant difficulties (P ≤ 0.01) in subtests relating to simple gestures (except for the recognition and imitation of symbolic gestures). General knowledge about tools, objects and action sequences was less severely impaired. Performance was frequently correlated with the severity of dementia. Multiple-case analyses revealed that (i) the frequency of apraxia depended on the definition used, (ii) ideomotor apraxia was more frequent than ideational apraxia, (iii) conceptual difficulties were slightly more frequent than production difficulties in the early stage of AD and (iv) difficulties in gesture recognition were frequent (especially for pantomimes).

Patients with AD can clearly show gesture apraxia from the mild-moderate stage of dementia onwards. Recognition and imitation disorders are relatively frequent (especially for pantomimes). We did not find conceptual difficulties to be the main problem in early-stage AD.