title: Investigating Microstructural Abnormalities and Neurocognition in Sub-Acute and Chronic Traumatic Brain Injury Patients with Normal-Appearing White Matter: A Preliminary Diffusion Tensor Imaging Study.
abstract: For a significant percentage of subjects, with chronic traumatic brain injury (TBI), who report persisting cognitive impairment and functional loss, the diagnosis is often impeded by the fact that routine neuroimaging often does not reveal any abnormalities. In this paper, we used diffusion tensor imaging (DTI) to investigate the apparently normal white matter (as assessed by routine magnetic resonance imaging) in the brains of 19 subjects with sub-acute (9) and chronic (10) TBI. We also assessed memory, executive function, and visual-motor coordination in these subjects. Using a voxel-wise approach, we investigated if parameters of diffusion were significantly different between TBI subjects and 17 healthy controls (HC), who were demographically matched to the TBI group. We also investigated if changes in DTI parameters were associated with neuropsychological performance in either group. Our results indicate significantly increased mean and axial diffusivity (MD and AD, respectively) values in widespread brain locations in TBI subjects, while controlling for age, sex, and time since injury. HC performed significantly better than the TBI subjects on tests of memory and executive function, indicating the persisting functional loss in chronic TBI. We found no correlation between diffusion parameters and performance on test of executive function in either group. We found negative correlation between FA and composite memory scores, and positive correlation between RD and visuomotor coordination test scores, in various tracts in both groups. Our study suggests that changes in MD and AD can indicate persisting micro-structure abnormalities in normal-appearing white matter in the brains of subjects with chronic TBI. Our results also suggest that FA in major white matter tracts is correlated with memory in health and in disease, alike; larger and longitudinal studies are needed to discern potential differences in these correlations in the two groups.
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Eyesha
authors.initials: E
authors.lastname: Hashim
authors.affiliation: Department of Neurology, University of California at San Francisco, San Francisco, CA, USA; Department of Brain and Behavioral Sciences, University of Pavia, Italy.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Caverzasi
authors.affiliation: Department of Neurology, University of California at San Francisco , San Francisco, CA , USA.
authors.forename: Nico
authors.initials: N
authors.lastname: Papinutto
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Lewis
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Ruiwei
authors.initials: R
authors.lastname: Jing
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Onella
authors.initials: O
authors.lastname: Charles
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Shudong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Radiology, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Lin
authors.affiliation: Sunnybrook Research Institute, University of Toronto , Toronto, ON , Canada.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Graham
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital , Toronto, ON , Canada.
authors.forename: Tom A
authors.initials: TA
authors.lastname: Schweizer
authors.affiliation: Department of Medical Imaging, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada; Department of Medical Imaging and Neurosurgery at the University of Toronto, Toronto, ON, Canada.
authors.forename: Aditya
authors.initials: A
authors.lastname: Bharatha
authors.affiliation: Department of Neurosurgery, St. Michael's Hospital, Toronto, ON, Canada; Faculty of Medicine, Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto, ON, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Cusimano
keywords: chronic traumatic brain injury; diffusion tensor imaging; human; normal-appearing white matter; sub-acute traumatic brain injury; voxel-based analysis; white matter microstructure