title: Diffusion tensor imaging in chronic head injury survivors: correlations with learning and memory indices.
abstract: Diffusion tensor imaging (DTI) provides a unique insight into the cellular integrity of the brain. While conventional magnetic resonance imaging underestimates the extent of pathology following closed head injury, diffusion-weighted imaging has been shown to more accurately delineate the extent of cerebral damage. There have only been a few case studies of DTI in chronic head injury survivors. This study used DTI to investigate changes in anisotropy and diffusivity in survivors of head injury at least 6 months after their injury. The relationship between cognition and diffusion abnormality was also investigated. The voxel-based analysis revealed significant bilateral decreases in anisotropy, in major white matter tracts and association fibers in the temporal, frontal, parietal and occipital lobes. Statistically significant increases in diffusivity were also found in widespread areas of the cortex. A significant positive correlation was found between diffusivity and impairment of learning and memory in the left posterior cingulate, left hippocampal formation and left temporal, frontal and occipital cortex. The common pattern of abnormality despite heterogeneous injury mechanism and lesion location in the group suggests that these cellular changes reflect secondary insults. The importance of diffusion abnormalities in head injury outcome is emphasized by the significant correlation between a learning and memory index and diffusivity in areas known to subserve this cognitive function.
authors.affiliation: Wolfson Brain Imaging Centre, Box 65, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 2QQ, UK. chs20@wbic.cam.ac.uk
authors.forename: C H
authors.initials: CH
authors.lastname: Salmond
authors.forename: D K
authors.initials: DK
authors.lastname: Menon
authors.forename: D A
authors.initials: DA
authors.lastname: Chatfield
authors.forename: G B
authors.initials: GB
authors.lastname: Williams
authors.forename: A
authors.initials: A
authors.lastname: Pena
authors.forename: B J
authors.initials: BJ
authors.lastname: Sahakian
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
mesh_terms: D000293:Adolescent; D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology; D002908:Chronic Disease; D003071:Cognition / Q000502:physiology; D003072:Cognition Disorders / Q000209:etiology / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D016489:Head Injuries, Closed / Q000473:pathology* / Q000523:psychology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007858:Learning / Q000502:physiology*; D007859:Learning Disabilities / Q000209:etiology / Q000473:pathology; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009412:Nerve Fibers; D009483:Neuropsychological Tests; D017741:Survivors