Routine neuroimaging techniques (CT and MRI) do not usually reveal abnormalities after mild TBI, so extensive research is being conducted to find methods with greater sensitivity and specificity. White matter tracts such as the corpus callosum, internal capsule, and corona radiata appear to be the most vulnerable to injury. Diffusion tensor imaging (DTI) is able to detect damage to axonal tracts by using a measure of directional water diffusion (fractional anisotropy). Both positive and negative findings have been reported (2, 6). Some studies analyzed whole brain areas while others focused on specific regions of interest. Unfortunately, there has been no methodological uniformity among studies in defining abnormality. Since abnormalities are often calculated based on differences from healthy comparison subjects, the question arises as to what is the most appropriate control. As individuals with mild TBI may also have posttraumatic stress disorder (PTSD), depression, anxiety, headaches, sleep disturbance, and other symptoms, researchers need to compare individuals with TBI with those who have psychiatric symptoms but no injury. A recent study found DTI abnormalities in combat-exposed soldiers, which normalized after 1.5 years, but the soldiers had neither PTSD nor TBI (7).