White matter changes in corticobasal degeneration syndrome and correlation with limb apraxia

Background: Data on white matter changes in corticobasal degeneration syndrome (CBDS) are not yet available, whereas cortical gray matter loss is a feature of this condition. The structural abnormalities related to a key feature of CBDS (limb apraxia) are unknown. Objectives: To measure selective structural changes in early CBDS using diffusion tensor imaging and voxel-based morphometry and to evaluate the structural correlates of limb apraxia. Design: Patient and control group comparison. Setting: Referral center for dementia and movement disorders. Participants: Twenty patients with CBDS and 21 matched control subjects. Interventions: Clinical and standardized neuropsychological evaluations, including assessment of limb apraxia. Main Outcome Measures: Gray and white matter changes in early CBDS. Results: Diffusion tensor imaging revealed decreases in fractional anisotropy in the long frontoparietal connecting tracts, the intraparietal associative fibers, and the corpus callosum. Fractional anisotropy was also reduced in the sensorimotor projections of the cortical hand areas. Voxel-based morphometry showed a prevalent gray matter reduction in the left hemisphere (in the inferior frontal and premotor cortices, parietal operculum, superotemporal gyrus, and hippocampus). The pulvinar, bilaterally, and the right cerebellar cortex also showed atrophy. Limb apraxia correlated with parietal atrophy and with fractional anisotropy reductions in the parietofrontal associative fibers (P <. 01). The limb-kinetic component of apraxia correlated with reduction of hand sensorimotor connecting fibers. Conclusions: The present integrative approach to in vivo structural anatomy combines hodologic imaging, describing patterns of white matter connections between cortical areas, with neuropsychological data. This provides new evidence of gray matter and fiber tract abnormalities in early-phase disease and contributes to clarifying the neural basis of apraxia in CBDS.