Researchers have shown that three novel imaging techniques can detect mild brain damage not visible using traditional methods. The findings will help scientists better define the type of damage that can lead to long-lasting memory and emotional problems, as well as help identify those who are most vulnerable to further trauma.

Such tools are of great interest to the military, which needs ways to distinguish traumatic brain injury from post-traumatic stress disorder. Both are common in veterans returning from Iraq and Afghanistan, and they have similar symptoms, but they require different types of treatment. The new imaging methods may also shed light on the effect of repeated mild brain trauma, such as concussion, for which soldiers and professional athletes are at risk. Anecdotal reports about ex-football players who developed early dementia, as well as concern for thousands of military troops exposed to repeated explosions, have made the long-term consequences of these types of injury an important and controversial issue.

"Right now, a football coach has no way of knowing who can go back on the field and who shouldn't, a military officer doesn't know who should be removed from the battlefield, a lawyer doesn't know who has a real injury and who is faking," says David Brody, a neurologist and scientist at Washington University, in St. Louis.

Mild traumatic brain injury is notoriously difficult to diagnose. The brains of concussion patients often look normal on CT scans, the most common test after head trauma, and "cognitive deficits can be subtle, even to a neurologist," says Michael Selzer, a neuroscientist at the University of Pennsylvania. Fortunately, most people with concussions recover within days or weeks. But about 10 to 15 percent have persistent problems, including headaches, nausea, memory deficits, and emotional abnormalities that can linger for months or years.

Scientists hypothesize that mild head trauma damages the brain's white matter--the long projections, called axons, that ferry messages between neurons. White matter is invisible to CT scans and magnetic resonance imaging (MRI). One of the most promising techniques for detecting subtle brain injury, called diffusion tensor imaging (DTI), is a variation of MRI that tracks water molecules in the brain's white matter. In research presented this week at the Society for Neurosciences conference in Washington, DC, Brody and his colleagues found that DTI analysis of brain-injury patients revealed signs of white-matter damage not visible with normal MRI. The damage seemed to correlate with cognitive deficits, including slowed reaction time.