Limb apraxia in corticobasal syndrome

Corticobasal syndrome (CBS) is a progressive neurodegenerative disorder with asymmetric presentation and course characterized by degeneration of basal ganglia and cortical structures. Limb apraxia is a commonly observed deficit in CBS. Few studies have examined comprehensively the nature of deficits in limb apraxia. The goal of our study was to investigate the severity of deficits in various conceptual and gesture production task modalities. CBS patients were divided in two groups based on the side of brain that was initially affected by the disease. Ten patients with right hemisphere presentation (RHP) and seven with left hemisphere presentation (LHP) were included. The results showed that while selective conceptual tasks deficits were present in both groups, the overall picture suggests preserved conceptual representations of tools and actions in CBS patients with either LHP or RHP. Both groups were impaired relative to controls on gesture production tasks. Performance on transitive gestures was more severely affected in both groups than intransitive gestures. Imitation was more severely affected than pantomime, suggesting deficits in visuomotor transformations. The addition of verbal cuing during concurrent imitation affected only the LHP patients, rendering them more impaired relative to controls in their imitation with verbal cuing as opposed to their imitation only performance. Imitation of non-representational gestures was least accurate and intransitive gestures were most accurate. Patients were more severely impaired relative to controls when holding the object and when they were shown pictures of tools to pantomime.