title: 5-Year imaging sequelae of concussive blast injury and relation to early clinical outcome.
abstract: Current imaging diagnostic techniques are often insensitive to the underlying pathological changes following mild traumatic brain injury (TBI) or concussion so much so that the explicit definition of these uncomplicated mild brain injuries includes the absence of radiological findings. In the US military, this is complicated by the natural tendency of service members to down play symptoms for fear of removal from their unit particularly in combat making it challenging for clinicians to definitively diagnose and determine course of treatment. Questions remain regarding the long-term impact of these war-time brain injuries. The objective of the current study was to evaluate the long-term imaging sequelae of blast concussion in active-duty US military and leverage previous longitudinal data collected in these same patients to identify predictors of sustained DTI signal change indicative of chronic neurodegeneration. In total, 50 blast TBI and 44 combat-deployed controls were evaluated at this 5-year follow up by advanced neuroimaging techniques including diffusion tensor imaging and quantitative volumetry. While cross-sectional analysis of regions of white matter on DTI images did not reveal significant differences across groups after statistical correction, an approach flexible to the heterogeneity of brain injury at the single-subject level identified 74% of the concussive blast TBI cohort to have reductions in fractional anisotropy indicative of chronic brain injury. Logistic regression leveraging clinical and demographic data collected in the acute/sub-acute and 1-year follow up to determine predictors of these long-term imaging changes determined that brain injury diagnosis, older age, verbal memory and verbal fluency best predicted the presence of DTI abnormalities 5 years post injury with an AUC of 0.78 indicating good prediction strength. These results provide supporting evidence for the evolution not resolution of this brain injury pathology, adding to the growing body of literature describing imaging signatures of chronic neurodegeneration even after mild TBI and concussion.
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Mac Donald
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Barber
authors.affiliation: University of Washington, Department of Radiology, Seattle, WA, USA.
authors.forename: Jalal
authors.initials: J
authors.lastname: Andre
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Evans
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Panks
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Sun
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA.
authors.forename: Kody
authors.initials: K
authors.lastname: Zalewski
authors.affiliation: University of Washington, Department of Internal Medicine, Seattle, WA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Elizabeth Sanders
authors.affiliation: University of Washington, Department of Neurological Surgery, Seattle, WA, USA; University of Washington, Department of Biostatistics, Seattle, WA, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Temkin
mesh_terms: D000328:Adult; D016880:Anisotropy; D001753:Blast Injuries / Q000000981:diagnostic imaging*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D055815:Young Adult
keywords: A-P, anterior–posterior; Concussion; DR-BUDDI, Diffeomorphic Registration for Blip-Up blip-Down Diffusion Imaging; DTI, Diffusion Tensor Imaging; Diffusion tensor imaging; EPI, Echo Planar Imaging; EPV, events-per-variable; FA, Fractional Anisotropy; FLAIR, Fluid attenuation inversion recovery; MPRAGE, Magnetization prepared rapid gradient-echo; Neurodegeneration; TBI, Traumatic Brain Injury; TORTOISE, Tolerably Obsessive Registration and Tensor Optimization Indolent Software Ensemble; Traumatic brain injury; US, United States