Distal-proximal differences in limb apraxia in corticobasal degeneration but not progressive supranuclear palsy

Limb apraxia is an important diagnostic sign of cortico-basal degeneration (CBD), although it is also found in progressive supranuclear palsy (PSP). We investigated whether the severity of apraxia differed between proximal and distal arm movements in the two diseases, as suggested by their differing patterns of motor impairment. We studied 24 CBD patients, 25 PSP patients, and 19 healthy controls using a battery of cognitive tests and an ideomotor apraxia test that examined imitation of hand and of whole arm gestures separately. CBD and PSP patients did not differ in general characteristics or disability and were similarly impaired in cognitive performance. Within-group differences between distal and proximal gesture scores were significant only for CBD patients ( p=0.007), in whom distal movements were more compromised. This finding suggests the presence of limb kinetic apraxia in CBD, perhaps in association with ideomotor apraxia.