Just when we thought it was safe to rejoice in our warfighters' safe return, here's something new to worry about.

Traumatic brain injury.

Traumatic brain injury, or TBI, is the signature injury of the Iraq and Afghan Wars. Why? Because the improvised explosive device, or IED, is the enemy's signature weapon. IEDs are the single greatest cause of American deaths and injuries over there.

When an IED explodes, it literally rattles the brains of everyone nearby. If the explosion cracks or shatters the skull, the TBI wound is obvious. But even people who walk away without any apparent injury are at risk, especially if they were knocked unconscious for any period of time. A blast bangs the brain hard against the skull. That may cause damage you can't see on the outside -- an invisible but very real injury. If the brain is later exposed to another explosion, the damage piles on. Accidents and falls can also lead to TBI.

The symptoms can be subtle and include:
• excessive sleepiness,
• difficulty concentrating,
• impaired memory,
• faulty judgment,
• depression,
• irritability,
• emotional outbursts,
• disturbed sleep,
• diminished interest in sex,
• difficulty switching between two tasks,
• and slowed thinking.

All these symptoms can also be caused by other things, so closed brain injury without an external wound is often hard to diagnose. Fortunately, the symptoms usually get better as the brain slowly heals itself. But if the brain can't adapt to the injury, the symptoms get worse. That often brings on other psychological problems.

As a result, TBI affects everyone around the injured servicemember. According to braininjury.com, "The effects of brain injury on the patient may be equaled or even surpassed by the effect on the patient's family. Brain injuries are known for causing extreme stressors in family and interpersonal relationships."

These families and their injured servicemembers need more help. ABC News anchor Bob Woodruff, who wound up with a brain injury after a bomb blast in Iraq, is using his fame to raise public awareness of TBI. The Pentagon is now spending $14 million to research blast injuries. They're also giving medics in combat zones evaluation forms to help them diagnose mild brain injury. The Department of Veterans Affairs is making plans to help veterans needing TBI care. But a former Air Force doc thinks we need to look even further down the road.

Dr. Dale Fuller, an oncologist, is an ordinary citizen with a good idea. He recently sent me the following email:

"Remember Mohammed Ali? His Parkinsonism was attributed to recurrent head trauma sustained in the ring, and other athletes in boxing and other sports have similar stories. I am thinking that we are going to be seeing, in years to come, similar 'late effects' in that population of soldiers who have experienced traumatic brain injuries.

"In my line of work, which is oncology, we have long been aware of the development of 'late effects' as a result of radiation therapy, and more recently as a consequence of chemotherapy. The Institute of Medicine, in 2005, put out a 600-plus page report in which they urge lifetime follow-up for patients who are survivors of cancer and its treatment. I think that the same sort of systematic follow-up for TBI patients needs to be demanded and funded. For cancer patients in approved cancer programs (there are over 1400 such programs in the United States.) we use 'tumor registries' in which we demand a 90 percent follow-up, recognizing that some people simply fall out of the system. We need to do even better than 90 percent for our TBI patients."

I agree with Dr. Fuller. The problem is, the very nature of a brain injury makes it that much more likely that someone suffering from TBI will fall through the cracks -- and the active-duty and VA medical systems are riddled with cracks. Recent scandals have demonstrated all too clearly how hard it can be for injured servicemembers to navigate the military medical bureaucracy. The VA is already short on money and staff, making it unlikely that they're ready to handle a flood of TBI patients. And then there are the TBI sufferers who are never diagnosed in the first place.

When a servicemember with TBI falls through the cracks, it hits the family hard. The blast wave rolls out through the children, spouses, and parents, just as it does with the psychological injuries that result from combat trauma. They've already sacrificed a lot for this country. They shouldn't also be asked to sacrifice their family life to an untreated brain injury. For the sake of the families, more must be done to catch these injuries early and track and treat them long term.