ST. LOUIS • Researchers at St. Louis University School of Medicine want to detect and categorize mild brain damage suffered in military combat.

Their target is to analyze as many as 300,000 soldiers who have returned from wars in Iraq and Afghanistan with traumatic brain injury, ranging from severe to mild. Those with mild traumatic brain injury are their main concern.

Dr. Richard Bucholz, director of the St. Louis University Advanced Neurological Innovation Center said, "Traumatic brain injury has been considered to be a single-diagnosis; all types of brain injury lumped into a few categories."

But, "One size doesn't fit all."

Bucholz is leading the Traumatic Brain Injury Research Study, funded by $5.3 million from the Department of Defense.

"What we've learned from Iraq and Afghanistan is our treatment (for mild TBI) has to be more individualized," he said. "These wars are special; we're seeing many more injuries from the improvised explosive devices (roadside bombs and booby-trapped buildings). These injuries can cause disruption in the brain without finding anything penetrating the brain."

The Defense Department reports that soldiers home from Iraq and Afghanistan have survived improvised explosive devices or roadside bombs because their body armor and armored vehicles protected them. Still, they come away with memory loss, headaches, nausea, imbalance, mental problems and seizures.

Complicating a diagnosis of mild traumatic brain injury, symptoms are similar to the mental health problem called post-traumatic stress disorder. Mild traumatic brain injury and post-traumatic stress disorder can exist together or separately.

"There's no lab test to answer that question," said Tyler Roskos, a neuropsychologist and one of the SLU researchers. "So most (soldiers) are diagnosed with one or the other or both, depending on the physician's judgment."

Researchers know, "Acceleration injury from a blast, sudden acceleration or deceleration, can cause tearing of brain tissue," Roskos said.

This can be from one mammoth blast, or dozens of small blasts, he said.

"There are people who are exposed to blasts one or two times, sometimes time and time again," Roskos said. "Repeated exposure ... is going to perpetuate issues from the initial concussion."

The researchers are using a set of brain imaging machines in hopes they can detect damage as small as brain cells.

"There are cellular level changes that affect how effectively the brain can transfer information from one area to another," Roskos said, "like a bad connection."

Retired Master Sgt. Dave Johnson, 47, volunteered for the study. During his tour in Iraq in 2006-2007, he served with combat engineers, called the "Wolfpack," who destroyed roadside bombs. The group's other job was to blow up disabled American war machines left on the battlefields.

"We had heavily armored vehicles, and we had bombs go off right beside us," he said. "We weren't hurt, but you can really feel it on the inside."

He was called to duty from the Army Reserves in the first Iraq War. He estimates his unit destroyed 250 tons of enemy explosives. "In 1991, that's when the memory problems started," he said.

The second war in Iraq was more of the same. "I couldn't tell you how many," he said. "We were protected from the shrapnel, but the blast overpressure gives you a concussion after awhile."

At distances of 50 to 250 meters, "You could see the blast coming across the sand. You still got a pretty good overpressure."

He retired early because of his traumatic brain injury and post-traumatic stress disorder symptoms. He now lives in Deer Park, Wash.

"There are days when I can tell you exactly what happened and there are days I can't recall what I had for breakfast," he said. "When someone asks about my memory, I say, 'She's 5 foot 4 with blue eyes.' " That's his wife. .

Johnson learned about the study at SLU; the university paid for his visit to St. Louis.

Johnson will be among about 200 test subjects.

A byproduct of the study may be an explanation for the overlap of symptoms between TBI and PTSD, researchers said.

"When you've had someone who's been in combat, there's some possibility for PTSD and a potential for TBI," Roskos said.

HELPING ATHLETES WITH CONCUSSIONS

The findings also could help athletes in sports that have high rates of concussions.

Roskos says it's known that athletes sent back into action too soon after a concussion get new concussions more easily and suffer symptoms longer. That's why part of the study examines athletes to compare with soldiers, he said.

Johnson's only combat is fighting his symptoms, and the quiet at his home in Washington state brings him peace.

"Serenity helps," he said. "Lots of animals walk across my back yard. Cougars walk the treeline, moose and their calves, a fawn was born in the front yard. About 75 percent of the people around here are veterans."