Long-term effect of soldiers’ blast injuries revealed by DTI

CHICAGO--Soldiers who have sustained a blast-induced mild traumatic brain injury (mTBI) exhibit long-term brain differences identifiable with diffusion tensor imaging (DTI), according to a study presented Dec. 2 at the annual meeting of the Radiological Society of North America (RSNA).

Since standard MRI or CT lacks sensitivity to mTBI, Thomas M. Malone, research associate at Saint Louis University School of Medicine, and colleagues used DTI, an MRI technique used to identify microstructural injury to white matter, to examine fractional anisotropy (FA) values in a group a veterans with mTBI.

“TBI is the signature wound of the Iraq War and there’s a significant number of subjects that continue to have persistent symptoms weeks, months, even years post-injury,” said Malone.

A total of 10 veterans with post-acute blast mTBI were included in the study and imaged on a 3T scanner an average of 51.3 months post-injury. The researchers noted that the timing of the veterans’ scans is novel because most blast-related mTBI studies have looked at patients in the acute phase. Ten healthy controls were also imaged. Hand-traced regions of interest included the genu and splenium of the corpus collosum and the anterior and posterior limbs of the internal capsule.

Malone and colleagues found significant differences in the FA values between the two groups, indicating that DTI remains sensitive to group differences in the post-acute phase.

“We did find that when we increased the number of subjects in our phase II study and removed the outliers, the DTI results were perhaps indicative that there is fiber damage, and that might help explain some of the chronic deficits that we’re seeing from blast injury, indicating also that these veterans haven’t completely recovered.”

Significant correlations between FA values and attention, delayed memory and psychomotor test scores were also noted. Higher FA values and lower neuropsychological scores were found among veterans with mTBI.

The research is aimed at further differentiating mTBI from post-traumatic stress disorder and thus improving treatment. Veterans returning from operations Iraqi Freedom and Enduring Freedom have an exposure rate of approximately 20 percent to blast-induced mTBI, stemming from mortar fire and improvised explosive devices.