W. Geoffrey Wright, director of neuromotor science programs and associate professor in the Department of Physical Therapy, published the results of a study exploring postural control and stress reactivity in active duty coast guard personnel in the March/April supplement to Military Medicine.
For the study, researchers used a custom-designed virtual reality-based device to assess postural stability combined with startle response and neurocognitive assessments on coast guard members who previously experienced mild traumatic brain injury (mTBI).
“Because of better armor, helmets, and overall protection, more soldiers are surviving combat in recent military conflicts,” said Wright. “This, of course, is very happy outcome for our military, veterans, and their families. The only downside is that there are hidden injuries that go unrecognized by the soldier and undetected by the clinician, yet can have serious long-term negative effects on the soldier's well-being.”
The 36 participants had no deployment-limiting medical condition but had a history of brain injury, including 39% of participants who had a previous mTBI and some who had experienced more than one. Participants were recruited by experimenters at coast guard boat stations at Port Canaveral and Port Lauderdale in Florida. The mTBI came from a variety of sources: blasts, falls, sports and vehicle injuries, and other blunt force traumas. The study built on Wright’s previous work with the Virtual Environment TBI Screen (VETS) in Temple’s Motion-Action-Perception lab.
Researchers found that the number of mTBI incidents had a significant effect on posture, and lifetime mTBI was associated with a suppressed acoustic startle response; neurocognitive performance did not seem to be affected. Specifically, Wright says, a notable difference was found (between those with a history of mTBI and those who reported no history) when participants were required to maintain balance standing on an unstable foam surface while viewing a dynamically moving virtual scene.
Researchers found another critical outcome through an acoustic startle test, where the magnitude of response to audio stimuli was reduced in those with a history of mTBI. These deficits were detected despite those participants self-reporting no symptoms.
“In other populations, the two deficits — startle reactivity and balance on unstable surfaces with conflicting visual stimuli — may not only go unnoticed but may be easily dismissed as having little functional impact,” Wright wrote. “Yet, the operational demands confronting coast guard personnel may at times draw on such otherwise subtle capabilities for mission success.”
A further challenge — and one that Wright has also explored, in research with a colleague at the U.S. Department of Veterans Affairs (VA) — is separating the effects of mTBI from the effects of PTSD, which impacts somewhere between 10 and 20 percent of veterans of the conflicts in Iraq and Afghanistan, according to the VA.
“The research we’ve been doing initially focused on detecting lingering signs of mTBI, which could help guide clinical decision-making, rehabilitation, and return-to-duty decisions,” said Wright. But, he added, “the symptoms of mTBI and PTSD] often co-occur and are sometimes difficult to dissociate.”