Diffusion tensor imaging (DTI), a type of MRI, may be able to predict functional post-deployment outcomes for veterans who sustained mild traumatic brain injury (MTBI), or concussion, during combat, according to a new study published in the journal Radiology.
MTBI is a public health problem of increasingly-recognized importance, particularly among military veterans. Recently, there has been a dramatic rise in the incidence of combat-related MTBI. More than 300,000 U.S. service members were diagnosed with MTBI between 2000 and 2015, according to the Armed Forces Health Surveillance Center.
Current assessment of MTBI remains challenging due to the difficulties in establishing the diagnosis, predicting outcomes and separating the effects of MTBI from other conditions like post-traumatic stress disorder (PTSD).
DTI uses measurements of water movement in the brain to detect abnormalities, particularly in white matter. Previous studies have linked DTI metrics to neurocognitive function and short-term functional outcomes in groups of patients. The desire to uncover possible long-term effects spurred Jeffrey B. Ware, M.D., from the Philadelphia VA Medical Center in Philadelphia, Pa., to evaluate combat veterans using this technique.
Dr. Ware and colleagues used brain MRI and DTI to study 57 military veterans who had a clinical diagnosis of MTBI upon return from deployment. The average length of time between injury and post-deployment evaluation was 3.8 years with an average follow-up duration of 1.4 years.
“All conventional MR images were interpreted as normal,” Dr. Ware said. “We retrospectively analyzed the data from the DTI sequence to derive measures of white matter integrity, which we compared to clinical measures and subsequent outcome measures 6 months to 2.5 years after the initial evaluation.”
The results showed significant associations between initial post-deployment DTI measurements and neurobehavioral symptoms, timing of injury, and subsequent functional outcomes. The measurements also correlated with greater healthcare utilization among veterans with MTBI.
Following initial post-deployment evaluation, 34 of the study participants returned to work. Veterans who did not return to work displayed significantly lower fractional anisotropy (FA) and higher diffusivity in a specific brain region, the left internal capsule. These measures imply less structural integrity in that area of the brain. As this region is known to contain important fibers providing motor stimulation to the typically dominant right side of the body, the results may provide a correlation between impairments in fine motor functioning and inability to return to work.
“Our findings suggest that differences in white matter microstructure may partially account for the variance in functional outcomes among this population. In particular, loss of white matter integrity has a direct, measurable effect,” Dr. Ware said. “It was illuminating to see the association between measures of white matter integrity and important outcomes occurring months to years down the road in our study population.”
“Combat-related Mild Traumatic Brain Injury: Association between Baseline Diffusion-Tensor Imaging Findings and Long-term Outcomes.” Collaborating with Dr. Ware on this paper were Rosette C. Biester, Ph.D., Elizabeth Whipple, M.S., Keith M. Robinson, M.D., Richard J. Ross, M.D., Ph.D., and Paolo G. Nucifora, M.D., Ph.D.
Source: Linda Brooks – RSNA
Image Source: The images are credited to Radiological Society of North America.
Original Research: Full open access research for “Combat-related Mild Traumatic Brain Injury: Association between Baseline Diffusion-Tensor Imaging Findings and Long-term Outcomes” by Jeffrey B. Ware, Rosette C. Biester, Elizabeth Whipple, Keith M. Robinson, Richard J. Ross, and Paolo G. Nucifora in Radiology. Published online March 29 2016 doi:10.1148/radiol.2016151013
Abstract
Combat-related Mild Traumatic Brain Injury: Association between Baseline Diffusion-Tensor Imaging Findings and Long-term Outcomes
Purpose
To determine whether functional outcomes of veterans who sustained combat-related mild traumatic brain injury (TBI) are associated with scalar metrics derived from diffusion-tensor (DT) imaging at their initial postdeployment evaluation.
Materials and Methods
This HIPAA-compliant retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. From 2010 to 2013, initial postdeployment evaluation, including clinical assessment and brain magnetic resonance (MR) examination with DT imaging, was performed in combat veterans who sustained mild TBI while deployed. Outcomes from chart review encompassed initial postdeployment clinical assessment as well as later functional status, including evaluation of occupational status and health care utilization. Scalar diffusion metrics from the initial postdeployment evaluation were compared with outcomes by using multivariate analysis. Veterans who did and did not return to work were also compared for differences in clinical variables by using t and χ2 tests.
Results
Postdeployment evaluation was performed a mean of 3.8 years after injury (range, 0.5–9 years; standard deviation, 2.5 years). After a mean follow-up of 1.4 years (range, 0.5–2.5 years; standard deviation, 0.8 year), 34 of 57 veterans (60%) had returned to work. Return to work was associated with diffusion metrics in multiple regions of white matter, particularly in the left internal capsule and the left frontal lobe (P = .02–.05). Overall, veterans had a mean of 46 health care visits per year during the follow-up period (range, 3–196 visits per year; standard deviation, 41 visits per year). Cumulative health care visits over time were inversely correlated with diffusion anisotropy of the splenium of the corpus callosum and adjacent parietal white matter (P < .05). Clinical measures obtained during initial postdeployment evaluation were not predictive of later functional status (P = .12–.8).
Conclusion
Differences in white matter microstructure may partially account for the variance in functional outcomes among veterans who sustained combat-related mild TBI.
“Combat-related Mild Traumatic Brain Injury: Association between Baseline Diffusion-Tensor Imaging Findings and Long-term Outcomes” by Jeffrey B. Ware, Rosette C. Biester, Elizabeth Whipple, Keith M. Robinson, Richard J. Ross, and Paolo G. Nucifora in Radiology. Published online March 29 2016 doi:10.1148/radiol.2016151013
