1. In a prospective cohort study of over 800 military service members, brain magnetic resonance imaging (MRI) of patients with military traumatic brain injuries (TBI) demonstrated a significant increase in pituitary abnormalities and T2-weighted white matter hyperintensity as compared to control subjects.
2. Cerebral microhemorrhages were an uncommon finding among those with TBI, and did not colocalize with regions of white matter hyperintensity, but did correlate with increased TBI severity.
Evidence Rating Level: 2 (Good)
Study Rundown: Blast exposure among military service members is a common cause of TBI within this population. Although post-TBI brain changes have been studied in patients in sports-related injuries or motor vehicle collisions, there has been a paucity of evidence of specific radiopathologic findings among military members who have experienced blast-related TBI. The purpose of this study was to describe and characterize the findings on brain MRI among this cohort.
The current study prospectively recruited over 800 military service members who underwent multi-sequence brain MRI examination. At the conclusion of the study, patients with blast-related TBI demonstrated a significantly higher incidence of pituitary abnormalities and gliosis as represented by T2 hyperintensity as compared to control subjects. Notably, fewer than 10% of subjects with TBI demonstrated cerebral microhemorrhages likely due to the chronicity of findings surveyed among this population, though they did correlate with an increased severity of TBI when present. This was the first large scale study to characterize potential neuroimaging markers for blast-related TBI in military personnel. However, this study was limited by a small control group. Of the over 800 patients recruited, only 42 reported no previous history of TBI, which may reduce the validity of the results. Additionally,T2-weighted white matter postcontrast enhancement is a non-specific feature that is commonly seen in other chronic conditions, but here may represent chronic inflammatory changes. Additional prospective trials are needed to confirm these findings as neuroimaging markers for military or blast-related TBI.
Relevant Reading: Military TBI during the Iraq and Afghanistan wars
In-Depth [prospective cohort]: This study prospectively performed multi-sequence brain MRI scans on military service members from 2009 to 2014 at a single institution in the United States. Scanning protocols included standard T1- and T2-weighted anatomical imaging, gradient-recalled-echo sequences and pre- and post-contrast T2 FLAIR sequences, the latter of which are an uncommonly used imaging protocol, but may highlight blood-brain barrier integrity. Functional imaging sequences including diffusion-tensor imaging, perfusion imaging, and MR spectroscopy were also included. Patients were excluded if they had a previous history of neurological or psychiatric conditions. Severity of traumatic brain injuries were evaluated clinically based on the Department of Defense and Veteran Affairs Criteria. Images were interpreted by one of four fellowship trained neuroradiologists. Overall, 876 military service members were recruited. There were 834 participants that reported a previous history of TBI and 42 reported no previous history of TBI. At the conclusion of the trial, the TBI group demonstrated significantly higher frequency of cerebral microhemorrhage (OR: 6.64; 95% CI: 0.4 to 109.2; p<0.001) though these remained uncommon among the affected group, with only 7.2% demonstrating microhemorrhages. The most common findings among those with TBI were pituitary abnormalities (OR: 16.76; 95% CI: 2.29 to 122.52; p<0.001), and gliosis as represented by focal white matter T2 hyperintensities (OR: 10.57; 95%CI: 1.44 to 77.42; p<0.001), with all odds ratios compared to the non-TBI group.. There was a trend within the TBI group of T2-weighted hyperintensity compared to the non-TBI group (OR: 1.75; 95% CI: 0.92 to 3.30; p=0.057). Cerebral microhemorrhage was significantly associated with more clinically severe TBI (p<0.001).
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