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DTI shows long-term impact of blast-induced brain injuries in veterans

By 11th February 2014No Comments

Using Diffusion Tensor
Imaging MRI, researchers have found that soldiers who suffered mild traumatic
brain injury (MTBI) induced by blast exposure exhibit long-term brain
differences, according to a study presented at the recent RSNA annual meeting.
Recent wars have resulted in many veterans with blast-induced MTBI, or trauma
resulting from mortar fire and improvised explosive devices. Diagnosis can be
challenging, especially in mild cases. “Mild traumatic brain injury is
difficult to identify using standard CT or MRI,” said study co-author Dr P.
Tyler Roskos, a neuropsychologist and assistant research professor at the Saint
Louis University School of Medicine in St. Louis, Mo. USA. “One of those
methods is diffusion tensor imaging (DTI), which identifies microstructural
injury to white matter, the part of the brain that consists mostly of
signal-carrying axons. Damage-associated changes in water movement along the
axons are comparable in certain respects to what might happen with a garden
hose “As water passes through the hose from the tap to the sprinkler, it goes
in the same direction, but if the hose was punctured, the water would shoot out
the sides.” 

In the study, researchers
compared DTI-derived fractional anisotropy (FA) values in 10 veterans of
Operations Iraqi Freedom and Enduring Freedom who had been diagnosed with MTBI
with those of 10 healthy controls. FA measures the uniformity of water
diffusion throughout the brain, with low FA values tending to indicate areas of
axonal injury. The average time elapsed between the blast-induced injury and
DTI among the patients was 51.3 months. “The time since injury is a novel
component in our study,” Dr. Roskos said. “Most other blast-related MTBI
studies examine patients in the acute phase of injury.”


Comparison of FA values
showed significant differences between the two groups, and there were
significant correlations between FA values and attention, delayed memory and
psychomotor test scores. Since the victims were, on average, more than four
years removed from their injuries, the results suggest the presence of a
long-term impact of blast injury on the brain. The results also indicate that
DTI is sensitive to group differences in blast-related MTBI even in the
post-acute phase. “DTI shows promise in enhanced sensitivity for detecting MTBI
compared to MRI/CT, even in the chronic phase,” Dr. Roskos said.
“Identification of changes in specific brain regions may help in diagnosis and
treatment of MTBI among veterans.”

The study was different from others in that it studied victims of blast-induced injuries as much as four years on average  after the trauma.