Impaired information integration contributes to communication difficulty in corticobasal syndrome.

OBJECTIVE To investigate the cognitive and neural correlates of discourse impairment in corticobasal syndrome (CBS). BACKGROUND Difficulty communicating is a frequent clinical manifestation in patients with CBS. However, the mechanisms underlying this disabling problem are not well understood. METHODS Twenty patients with CBS and 8 healthy seniors narrated a picture story. Narratives were analyzed for maintenance of the narrative theme, identification of the overall point of the story (global connectedness), and connectedness between consecutive events (local connectedness). Discourse measures were correlated with performance on cognitive tasks and with cortical atrophy as determined by magnetic resonance imaging voxel-based morphometry. RESULTS Patients with CBS referred to the narrative theme significantly less frequently than controls. Global connectedness was intact in only 6 of 20 CBS patients (30%), but preserved in all controls. Local connectedness was significantly diminished in patients relative to controls. Discourse performance in CBS was related to tasks requiring higher-order integration of visual material, but not to basic visuospatial/visuoperceptual, language, or memory function. Discourse impairment was directly related to atrophy in the right parietal lobe and bilateral dorsolateral prefrontal cortex. CONCLUSIONS Our findings suggest that impaired information integration in CBS, related to parieto-frontal disease, interferes with patients' ability to narrate a coherent story.