Limb apraxia in corticobasal degeneration and progressive supranuclear palsy

Abstract

Corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) share pathologic features, and cortical and subcortical signs. Apraxia is frequently described in CBD and sometimes in PSP; however, it is difficult to distinguish ideomotor from limb-kinetic apraxia, and apraxia frequency is unclear. The authors set out to clarify the nature and frequency of apraxia in these diseases. The authors compared probable CBD and PSP patients, matched for motor disability, to healthy age-matched controls on cognitive tests and the De Renzi ideomotor apraxia test. Cognitive impairment was similar, but more CBD (70.8%) than PSP (36%) patients had apraxia. CBD patients committed more apraxic errors of awkwardness and were more compromised on simple gestures; PSP patients committed more sequence errors. While progressive supranuclear palsy (PSP) patients had ideomotor apraxia, the peculiar gesture compromise in corticobasal degeneration (CBD) suggests that limb-kinetic apraxia is dominant. In both illnesses, the movement production system of Roy and Square appears compromised: in CBD defective control of muscle activation seems likely, producing clumsy movements; in PSP, control of motor program activation appears defective, resulting in sequence errors and perseverations. The De Renzi test can reliably estimate apraxia frequency and may be used to distinguish limb-kinetic from ideomotor apraxia.