Since his own experience with a traumatic brain injury, Kei Kawata has been looking for better ways to effectively diagnose and rehabilitate brain injuries, particularly concussions.
Most concussion research has focused on a single impact that results in a concussion, but many soldiers and athletes are subject to subconcussive head impacts, hits that don't meet the criteria for a concussion diagnosis but still may have long-term effects. These repetitive, subconcussive impacts are the focus of Kawata’s research. In 2018, Kawata received a highly competitive first-place award in the Military Health System Research Symposium Young Investigator Competition for his work “Association of Increased Serum S100B Levels with High School Football Subconcussive Head Impacts.”
Kawata and colleagues tested whether acute increases in the blood biomarker S100B are associated with the frequency and magnitude of subconcussive head impacts in adolescent football players. Using mouthguards installed with sensors along with blood draws, the team determined that increased levels of the S100B biomarker were significantly associated with greater frequency of impacts, leading them to conclude that changes in S100B levels may be a useful tool for real-time brain injury in sports.
Kawata’s research has also found that eyeball and eyelid movement, or oculomotor function, can be impaired by mild, repetitive head impacts in football players. But the function may adapt mid-season, even as athletes continue to incur head impacts.
"Repetitive subconcussive head impacts have quickly become one of the most complex public health issues," said Kawata, assistant professor at the IU School of Public Health-Bloomington, who led the study published in JAMA Ophthalmology. "We still have much more to learn about brain response to trauma."
The goal is to identify a "safe" threshold for subconcussive brain injury that does not necessarily trigger immediate symptoms, such as headache, dizziness and disorientation.
In the study of eyeball and eyelid movement, Kawata and Steve Zonner, a sports medicine physician in Washington Township Medical Foundation, measured the near point of convergence—the measurement of the closest point of focus before double vision occurs—in more than a dozen high school football players over one season.
Players experienced more than 8,000 recorded hits over this period, and the researchers found a significant increase (up to 33 percent) in near point of convergence resulting from subconcussive head impact frequency, up to the middle of the football season.
However, near point of convergence began to move back toward the baseline measurement from mid-season on, even though players continued to experience subconcussive head impacts.
The research team concluded that, while near point of convergence is one of the most prevalent clinical assessments for concussions, further study is necessary to determine whether it is the best tool in tracking long-term subconcussive brain damage.
Overall, Kawata and his research team are pursuing an ultimate goal of establishing brain-injury-specific objective markers that will help protect the health of soldiers and athletes.