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From the Rotman Research Institute (B.L., N.K., E.I.N., S.E.B.) Baycrest Centre for Geriatric Care, Toronto; Departments of Psychology (B.L.), Medicine (Neurology) (B.L., S.E.B.), and Surgery (Neurosurgery) (M.L.S.), University of Toronto; and Departments of Diagnostic Imaging and Radiology (G.C.), Medicine (Neurology) (F.G., S.E.B.), L.C. Campbell Cognitive Neurology Research Unit and Heart and Stroke Foundation Center for Stroke Recovery (F.G., S.E.B.), Surgery (Neurosurgery) (M.L.S.), and Imaging Research (S.E.B.), Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
Address correspondence and reprint requests to Dr. Brian Levine, The Rotman Research Institute at Baycrest, 3560 Bathurst St., Toronto, ON M6A 2E1, Canada blevine{at}rotman-baycrest.on.ca
Objective: To assess the relationship between regional brain volume changes and traumatic brain injury (TBI) severity in patients with and without focal lesions.
Methods: Sixty-nine chronic-phase TBI patients spanning the full range of severity were recruited from consecutive hospital admissions. Patients received high-resolution structural MRI a minimum of 1 year after injury. Multivariate statistical analyses assessed covariance patterns between volumes of gray matter, white matter, and sulcal/subdural and ventricular CSF across 38 brain regions and TBI severity as assessed by depth of coma at the time of injury. Patients with diffuse and diffuse plus focal injury were analyzed both separately and together.
Results: There was a stepwise, dose–response relationship between parenchymal volume loss and TBI severity. Patients with moderate and severe TBI were differentiated from those with mild TBI, who were in turn differentiated from noninjured control subjects. A spatially extensive pattern of volume loss covaried with TBI severity, with particularly widespread effects in white matter volume and sulcal/subdural CSF. The most reliable effects were observed in the frontal, temporal, and cingulate regions, although effects were observed to varying degrees in nearly every brain region. Focal lesions were associated with greater volume loss in frontal and temporal regions, but volume loss remained marked even when analyses were restricted to patients with diffuse injury.
Conclusions: Patterns of parenchymal volumetric changes can differentiate among levels of traumatic brain injury (TBI) severity, even in mild TBI. TBI causes a spatially extensive pattern of volume loss that reflects independent but overlapping contributions of focal and diffuse injury.
Abbreviations: DAI = diffuse axonal injury; FCC = focal cortical contusion; FOV = field of view; GCS = Glasgow Coma Scale; IQR = intraquartile range; LOC = loss of consciousness; LV = latent variable; NEX = number of excitations; PLS = partial least squares; PTA = post-traumatic amnesia; sCSF = sulcal/subdural CSF; TBI = traumatic brain injury; TE = echo time; TR = repetition time; TSI = time since injury; vCSF = ventricular CSF.
Supplemental data at www.neurology.org
Supported by grants from the Canadian Institutes of Health Research (grants MT-14744, MOP-37535, and MOP-108540 to B.L. and grant MT13129 to S.E.B.) and the NIH–National Institute of Child Health and Human Development (grant HD42385-01) to B.L.
Disclosure: The authors report no conflicts of interest.
Received March 28, 2007. Accepted in final form August 30, 2007.
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