As the medical community learns more about the brain impairments afflicting troops fighting in Iraq and Afghanistan, concern is growing back home that these battle-weary soldiers may be facing yet another obstacle: misdiagnosis.

Traumatic brain injury has become a high-profile condition, thrust into the national spotlight now that thousands of troops who have left the war zone continue to struggle with the consequences of combat. Better known as TBI, the ailment is a physical wound caused by the head-rattling shockwaves associated with bomb explosions that tear brain cells apart.

But TBI shares many of the same symptoms with a common battlefield psychological condition known as post-traumatic stress disorder. Both are often marked by depression, mood swings, irritability, problems concentrating, and memory dysfunction. The similarities can cause healthcare professionals to overlook mild traumatic brain injuries, especially when a patient lacks visible wounds, according to doctors and veterans advocates familiar with the issue.

"Mild brain injuries are really difficult to evaluate because there are a lot of overlapping symptoms with post-traumatic stress disorders," said Jordan Grafman, a neuroscientist who studies the effects of TBI on Vietnam veterans at the National Institutes of Health. "Doctors are likely to default to psychological diagnoses especially when they see a lot of PTSD."

Officials at the Pentagon and the Department of Veterans Affairs say that misdiagnosing mild TBI as PTSD is especially problematic because the two conditions are treated differently. Stress disorders are usually treated with counseling and anti anxiety or anti depression medications, while brain injuries typically require some combination of occupational, physical, and cognitive therapy.

"The difficulty in sorting the two out is there are common features [between] them," said Dr. Steven Scott, director of the VA's Tampa Polytrauma Rehabilitation Center . "If you have a better idea what's wrong with the individual and make a diagnosis, you will have better outcomes."

The earlier treatment begins, the better the results, Scott said.

When left unchecked, TBI can disrupt the basic functions of everyday life, making it difficult to perform even simple tasks like getting ready for work or grocery shopping. Most TBIs affect the frontal lobes, which account for about 40 percent of the brain and control a person's ability to structure their day-to-day living.

One of the challenges in diagnosing TBI is that mild brain damage is difficult to find, particularly since it can take months for the initial symptoms to manifest, Scott said. Patients with both a psychological disorder and mild brain injury present an even bigger challenge because in these cases, the brain damage may be masked and therefore go undetected, he added.

The same is true in the civilian world, said Dr. Gregory O'Shanick, national medical director for the Brain Injury Association of America. Though there are some differences in TBI and PTSD symptoms, brain injury cases continue to slip through the cracks because the signs are easy to miss, he said.

"Misdiagnosis happens all of the time," said O'Shanick, who has seen dozens of TBI patients originally diagnosed with depression.

"You see somebody in the military when their lives are organized for them, you may not notice mild traumatic brain injury in [its] fullest form when they're on active duty," O'Shanick said. "But when they come back home and their external structure isn't there, that's where you may see things become much more evident in terms of traumatic brain injury."

Exactly how many TBI cases there are among Iraq and Afghanistan veterans is unknown because neither the Pentagon nor the Department of Veterans Affairs has systematically screened returning troops for the disorder. The lack of a comprehensive plan to deal with brain injuries has provoked harsh criticism from lawmakers and veterans advocates, who accuse the government of neglecting the troops they sent into battle.

With troops deploying for their second, third, even fourth tours of duty, head injuries and stress disorders are becoming more widespread, said Representative Bob Filner, Democrat of California, chairman of the House Veterans Affairs Committee. For every year in the war zone, combat units encounter dozens of potentially brain-injuring blasts, each one doing more harm because the damage is cumulative.

"We don't have the resources in place, and they're scrambling now [to deal] with something that could have been predicted and planned for," Filner said. "TBI is one of the major things coming out of the war we haven't taken care of, and it's going to have long-range effects on our society for years to come."

The psychological wounds associated with combat are well documented. However, little is known about how explosions affect the brain, and the military has been slow to address soldiers' medical needs, often leaving ailing troops and their families to sort out the symptoms, Filner said.

Statistics compiled by the VA show that more than 83,000 Iraq and Afghanistan veterans have sought care for psychological disorders. The department does not track the number of TBI cases, according to spokesman Terry Jemison, who noted that they do know of at least 369 traumatic brain injury patients because they've been treated for other acute conditions.

The Defense Department also does not have figures on the number of brain injuries, but Pentagon officials estimated that they have found about 2,500 potential cases so far.

The government's inability to track TBI cases has angered many veterans advocates who say the lack of attention is another example of how the military failed to prepare for the troops who are now coming home injured. Critics point to long waits for appointments and the squalid conditions at Walter Reed Army Medical Center.

"The number of people who have suffered from mild traumatic brain injury could be in the thousands, but we just won't know about it unless we screen everybody who comes back," said Paul Rieckhoff, executive director of Iraq and Afghanistan Veterans of America. "The system as it stands right now really depends on [veterans] to self-diagnose and then navigate the bureaucracy of red tape to get help."

Diagnosing brain injuries requires thorough clinical evaluation that includes memory and response-time tests. Whether the VA and the Pentagon have the resources to do this for the millions of veterans who have deployed remains to be seen, Rieckhoff said.

"Maybe it's politics, maybe it's negligence, maybe it's incompetence," Rieckhoff said. "I don't know. I just know that it's taking too long to take things like brain injury seriously."

Scott and others at the VA believe the department will start finding more cases because of a four-question screening tool that was put into place in April. Every veteran who visits a VA facility for treatment will be asked whether they've been near a blast, and if so, whether they experienced any difficulties afterward .

This month, the Pentagon expects to add similar questions to its post-deployment health questionnaire, which is given to all troops returning from the war zone.

However, the lag in adopting a screening tool has prompted Senator Susan Collins, Republican of Maine, and Senator Hillary Clinton, Democrat of New York, to propose a computer-based test that would assess an individual's cognitive functioning before and after deployment. Their legislation would provide $3.75 million to institute the program.