Soldiers returning from Iraq and Afghanistan with mild traumatic brain injury (TBI) have measurable abnormalities in the white matter of their brains, according to a study published online in December in the American Journal of Psychiatry.

"In the military population we studied, patients with TBI have more alterations, sometimes called 'potholes,' in the white matter of their brains than patients without a history of TBI," Ricardo Jorge, MD, University of Iowa professor of psychiatry and senior study author, said in a press release.

Jorge and colleagues used diffusion tensor imaging (DTI), a MRI technique that can detect subtle white matter changes associated with TBI, to examine white matter integrity in a group of veterans. A total of 93 Iraq and Afghanistan war veterans were included in the study, 72 of whom had mild TBI and 21 with no exposure to TBI during deployment. In addition to DTI, the veterans also underwent psychiatric and neuropsychological assessments.

Results showed that veterans with mild TBI had a significantly higher number of the so-called potholes than those without TBI. These are areas of decreased fractional anisotropy stemming from damage to axons, and represent a measure of lower white matter integrity, according to the authors. In veterans with probable TBI, the mean number of potholes was 98.8, compared with 16.8 potholes on average in unexposed veterans.

The authors also found that the number of potholes was correlated with the severity of TBI and performance on the executive functioning tasks. Differences in the number of abnormalities were not influenced by participant age, time since trauma, history of TBI unrelated to deployment or coexisting psychopathology.

Conventional voxel-based analysis did not reveal differences in DTI parameters between the mild TBI and no TBI groups, according to the authors.

Jorge and colleagues also compared the veterans to a group of civilians with TBI and found potholes were more frequent in the civilian group. The authors speculated that this was likely because the civilians included in the comparison had all been admitted to a hospital, indicating more severe injuries, and they were assessed more quickly following injury before natural repair processes could be completed.

The authors concluded that potholes “may constitute a biomarker of axonal injury that can be identified in mild TBI at both the acute and chronic stages of its clinical course…Future studies will need to replicate these findings in other groups of TBI patients with different etiologies and severity, delineate the longitudinal course of DTI abnormalities, and analyze the effect of repetitive mild TBI.”