Enigma Military Brain Injury: A Preliminary Meta-Analysis Of Diffusion Mri Measures

Objective: To identify reproducible differences in diffusion MRI (dMRI) measures in military brain injury, using a meta-analysis of multiple cohorts. Background: Traumatic brain injury (TBI) is one of the most common injuries affecting members of the United States military and armed services worldwide. Injuries can affect combat readiness in the immediate post-injury phase, and can also lead to long-term cognitive impairments and adverse health consequences. Diffusion MRI (dMRI) offers sensitive metrics of brain injury, and is complementary to more traditional imaging modalities. Only a few studies have used dMRI in military brain injury and they have found mixed results, partly due to limited power in small samples. Design/Methods: Participants were assessed from 4 different projects for a total of 369 TBI/concussion participants and 202 comparison participants never diagnosed with TBI. All cohorts included participants who were either United States Veterans or Active Duty Service Members. All sites processed dMRI brain scans locally with a standard protocol (http://enigma.usc.edu). FA (fractional anisotropy) was averaged within 63 ROIs from the JHU (Johns Hopkins University) atlas. TBI/control effect sizes were calculated within each cohort, and statistical results were pooled across cohorts to conduct a meta-analysis of the individual regression parameters. Results: We found significantly higher FA in TBI in the superior longitudinal fasciculus (SLF p =0.0011). The external capsule (EC) and posterior thalamic radiation (PTR) showed borderline effects. Conclusions: Some studies have shown higher FA in concussed individuals even months post-injury, when edema, which could lead to increased FA calculations initially, has already resolved. Animal studies have indicated that higher FA after mild injury could be a marker of fiber reorganization and remyelination. Identifying imaging biomarkers of brain injury in the military will help us better understand injury and recovery processes, and ultimately may assist in the assessment of more effective treatments. Study Supported by: ELD is supported by a grant from the NINDS (K99 NS096116). ELD and PT are also supported by NIH grants to PT: U54 EB020403, R01 AG040060, and R01 NS080655. DoD ADNI is supported by the NCIRE (DoD W81XWH-12-2-0012). The Chronic Effects of Neurotrauma Consortium is supported by grants PT108802-SC104835 and W81XWH-13-2-0095 from the Department of Defense and grant 5I01RX002174 from the VA. A Longitudinal Study of Chronic TBI in OEF/OIF/OND Veterans and Service Members is supported by grant funding from the VA (study number O1062-I; grant number: 5I01RX001062). Funding for the iSCORE study was provided by the Defense and Veterans Brain Injury Centers, U.S. Army Medical Research and Materiel Command (USAMRMC; W81XWH-13-2-0025). This material is based in part upon work supported by the U.S. Army Medical Research and Material Command and from the U.S. Department of Veterans Affairs. The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the U.S. Government, the U.S. Department of Veterans Affairs, or the U.S. Department of Defense, and no official endorsement should be inferred. Disclosure: Dr. Dennis has nothing to disclose. Dr. Wilde has nothing to disclose. Dr. Scheibel has nothing to disclose. Dr. Troyanskaya has nothing to disclose. Dr. Velez has nothing to disclose. Dr. Wade has nothing to disclose. Dr. Drennon has nothing to disclose. Dr. York has nothing to disclose. Dr. Bigler has nothing to disclose. Dr. Abildskov has nothing to disclose. Dr. Taylor has nothing to disclose. Dr. Jaramillo has nothing to disclose. Dr. Eapen has nothing to disclose. Dr. Belanger has nothing to disclose. Dr. Newsome has nothing to disclose. Dr. Levin has nothing to disclose. Dr. Hinds has nothing to disclose. Dr. Walker has nothing to disclose. Dr. Thompson has nothing to disclose. Dr. Tate has nothing to disclose.