A kinematic study of progressive apraxia with and without dementia

BACKGROUND: Prehension is an ideationally simple, cued movement requiring p roximal (transport) and distal (manipulation) limb control. Patients with t his syndrome of progressive apraxia are unable to perform many activities o f dairy living that require prehension. There is little known about how thi s syndrome kinematically disrupts such movements or whether concurrent deme ntia might play a critical role. OBJECTIVES: Using prehension as a paradigm for an ideationally simple. cued functional movement, we sought to (1) characterize the kinematic features of progressive apraxia in general, and (2) contrast the kinematic differenc es between apraxic patients with and without dementia. METHODS: Eight patients with the syndrome of progressive apraxia (including five without dementia, one of whom had autopsy-confirmed corticobasal gang lionic degeneration, and three with dementia, one of whom had autopsy-confi rmed Alzheimer's disease) were compared with eight age-matched normal contr ol subjects on a prehension task using an Optotrak camera system. RESULTS: Compared with control subjects, apraxic subjects had slowed reacti on time, slowed transport and manipulation kinematics, greater lateral devi ation from the linear prehension trajectory, greater intermanual asymmetry, motor programming disturbances, and mild transport-manipulation uncoupling . There were minor differences between the apraxia subgroups such as greate r intermanual differences and impaired grip aperture velocity in the nondem ented group, and overall slower movement in the demented group. CONCLUSIONS: There are major kinematic differences between apraxic and cont rol subjects on a prehension task. The differences between clinical-patholo gic subgroups are more subtle, and the movement disorder itself rather than concurrent dementia is the greatest determinant of motor disability.