Powerful scans are letting doctors watch just how the brain changes in American veterans with post-traumatic stress disorder and concussion-like brain injuries — signature damage of the Iraq and Afghanistan wars.

The research could one day allow far easier diagnosis for patients — civilian or military — who today struggle to get help for these largely invisible disorders. For now it brings a powerful message: problems too often shrugged off as "just in your head" in fact do have physical signs, now that scientists are learning where and how to look for them.

'The good news is this neural signal is not permanent. It can change with treatment.'— Dr. Jasmeet Pannu Hayes

"There's something different in your brain," explains Dr. Jasmeet Pannu Hayes of Boston University, who is helping to lead that research at the U.S. Department of Veterans Affairs' National Center for PTSD. "Just putting a real physical marker there, saying that this is a real thing," encourages more people to seek care, he said.

Up to one in five U.S. veterans from the long-running combat in Iraq and Afghanistan are thought to have symptoms of PTSD. An equal number are believed to have suffered traumatic brain injuries, or TBIs — most that do not involve open wounds but hidden damage caused by an explosion's pressure wave.

Many of those TBIs are considered similar to a concussion, but because symptoms may not be apparent immediately, many soldiers are exposed multiple times, despite evidence from the sports world that damage can add up, especially if there's little time between assaults.

Back pain sidelines soldiers

Few U.S. soldiers evacuated from Iraq and Afghanistan because of back pain are likely to return to duty, regardless of treatment, a study suggests.

About 13 per cent of service members who left their units with back pain as their primary diagnosis eventually returned to duty in the field, the team reported in this week's issue of the Archives of Internal Medicine.

"If you have only a 13 per cent success rate, this is a failure," said study leader Dr. Steven Cohen, a professor of anesthesiology at the Johns Hopkins University School of Medicine and a colonel in the U.S. Army Reserves.

"There's a systemic problem," he added in a release.

The study looked at data from 1,410 soldiers evacuated from war zones and who complained of back pain from 2004 through 2007.

Aside from injuries in battle and psychiatric illness, low back pain is responsible for the lowest rate of return for soldiers, the team said.

Taking long marches on unpaved roads while carrying heavy equipment and body armour will inevitably lead to back pain, Cohen said.

Back pain has notoriously low success rates for treatment among civilians as well.

The biggest predictor of a poor outcome is psychosocial factors such as depression, anxiety and stress, said Cohen. In this way, the back pain findings were similar to those of people with psychiatric disorders.

"These similarities should not be surprising, considering that the major determinants for return to work and overall symptom palliation in patients with spinal pain are psychosocial," the study's authors said.

They called for more research to determine whether treating psychological factors "in theatre" can reduce attrition rates.

"My brain has been rattled," is how a recently retired marine whom Hayes identifies only as Sgt. N described the 50 to 60 explosions he estimates he felt while part of an ordnance disposal unit.

Brain's connective tissue compromised

Hayes studied the man in a new way, tracking how water flows through tiny, celery stalk-like nerve fibres in his brain. He found otherwise undetectable evidence that those fibres were damaged in a brain region that explained his memory problems and confusion.

The non-invasive technique is called "diffusion tensor imaging," which merely adds a little time to a standard MRI scan. Water molecules constantly move, bumping into each other and then bouncing away. Measuring the direction and speed of that diffusion in nerve fibres can tell if the fibres are intact or damaged. Those fibres provide a kind of highway along which the brain's cells communicate. The bigger the gaps, the more interrupted the brain's work becomes.

"Sgt. N's brain is very different," Hayes told a military medical meeting last week. "His connective tissue has been largely compromised."

There's a remarkable overlap of symptoms between those brain injuries and PTSD, said Dr. James Kelly, a University of Colorado neurologist tapped to lead the military's new National Intrepid Center of Excellence opening next year to treat both conditions.

Headaches are a hallmark of TBI while the classic PTSD symptoms are flashbacks and nightmares. But both tend to cause memory and attention problems, anxiety, irritability, depression and insomnia. That means the two disorders share brain regions.

And Hayes can measure how some of those regions go awry in the vicious cycle that is PTSD, where patients feel like they're reliving a trauma instead of understanding that it's just a memory.

Changes with treatment

What happens? A brain processing system that includes the amygdala — the fear hot spot — becomes overactive. Other regions important for attention and memory, regions that usually moderate our response to fear, are tamped down.

"The good news is this neural signal is not permanent. It can change with treatment," Hayes said.

Her lab performed MRI scans while patients either tried to suppress their negative memories, or followed PTSD therapy and changed how they thought about their trauma. That fear-processing region quickly cooled down when people followed the PTSD therapy.

The research has implications far beyond the military. About a quarter of a million Americans will develop PTSD at some point in their lives. Anyone can develop it after a terrifying experience, from a car accident or hurricane to rape or child abuse.

More research is needed for the scans to be used in diagnosing either PTSD or a TBI. But some are getting close — like another MRI-based test that can spot lingering traces of iron left over from bleeding, thus signalling a healed TBI. If the brain was hit hard enough to bleed, then more delicate nerve pathways surely were damaged, too, Kelly notes.