WASHINGTON, D.C. — Traumatic brain injury and post-traumatic stress disorder often coexist in the military because a lot of brain injuries happen during traumatic experiences. But how do you tell which symptoms belong to which diagnosis, and how do you fix it?

Some doctors are getting help figuring that out through a big virtual-reality video game.

The computer-assisted rehabilitation environment, or CAREN, at the National Intrepid Center of Excellence is the only virtual reality machine in the Department of Defense that does research and clinical care for TBI and PTSD patients.

The CAREN is basically a big treadmill in front of a huge curved screen. While a harnessed patient walks, the treadmill moves — up, down, right, left, forward, backward — to match the personalized game-like scenario on screen.

“We may put reflective markers on their hands, and they might control a pair of boxing gloves on the screen. Or you might put two markers on their back and then sync them to a boat, so when they step right, the boat turns right on the screen,” said biomedical engineer and CAREN operator Sarah Kruger. 

Each patient is evaluated before using the CAREN, so Kruger has a good idea of what their physical and behavioral weaknesses are so she can work to strengthen them. 

“The therapist might see that a person’s balance is not that great. We’re going to put him down here in a boat scenario and give him a task of going through a course of buoys or hunting sharks,” Kruger said. “The therapist is actually able to watch their movement to see what their strategy is.” 

Hearing loss and inner ear issues are a major focus since a lot of the service members with PTSD and TBI have been around blasts, affecting balance and vision perception. Cognitive functions are also tested. Kruger will briefly flash birds, math problems or rank insignia onto the screen to see how patients handle multitasking. 

“Patients with brain injuries might be OK with a physical task and a cognitive task, but if we combine those two things together, that’s where they might struggle,” she said. 

The scenarios are a way of testing high-functioning patients for a return to their career fields. 

“They might be totally fine when they’re walking, but if you put them out on my system and you get them up to a jog or run … that might be where their headache comes up or where their dizziness comes on,” Kruger said. “You might not see that in the conventional evaluations because they’re not being pushed physically to where they experience those symptoms.” 

Most of the patients are service members who have struggled to get a clear diagnosis in the general health care system. The CAREN’s strength is that it separates their TBI and PTSD symptoms. 

“Sometimes, in order to diagnose the brain injury symptoms — things like memory and headache — you have to get through the PTSD symptoms, which might be anxiousness and hypervigilance,” Kruger said. “So if you can get those PTSD-type symptoms down, that allows the clinicians to focus more on the TBI symptoms. 

The CAREN is used in conjunction with conventional therapies, not in place of them. The doctors assigned to each patient use the CAREN’s research to develop comprehensive rehab plans.

One NICoE patient who has struggled with TBI symptoms since 2001 said he’s been known to get a little angry and struggle grammatically with communications — and his co-workers and wife have noticed.

“It’s been a bit of frustration with me internally when somebody’s saying, ‘Hey, there’s something wrong with you,’ ” said the 21-year active-duty service member, who didn’t want to be identified.

His doctors recommended he go to NICoE to get some answers. On Day 2 when I talked to him, he had high hopes.

“I’m just hoping to identify what is going on with me so I can contribute back to my family and the military. I love what I do and my family, and if I’m neglecting them in some way because I’m either not aware of what’s going on with me, or there’s something physically wrong with me that needs to be fixed — whatever it may be, hopefully they’ll identify it,” he said.

The NICoE CAREN is one of four used by the DoD. Two other machines focus on amputee care, while the fourth at the Naval Health Research Center does predeployment combat-scenario research.