Radiological Society North America. US: High school football players may develop impact-related brain changes over the course of a single season.
Players who experience higher levels of head impacts show the most changes, even in the absence of concussion.
It remains unclear whether or not these changes will be associated with any negative long-term consequences.
Some high school football players exhibit measurable brain changes
after a single season of play even in the absence of concussion,
according to a study presented today at the annual meeting of the
Radiological Society of North America (RSNA).
"This study adds to the growing body of evidence that a season of
play in a contact sport can affect the brain in the absence of clinical
findings," said Christopher T. Whitlow, M.D., Ph.D., M.H.A., associate
professor of radiology at Wake Forest School of Medicine and radiologist
at Wake Forest Baptist Medical Center in Winston-Salem, N.C.
A number of reports have emerged in recent years about the potential
effects playing youth sports may have on developing brains. However,
most of these studies have looked at brain changes as a result of
concussion. Dr. Whitlow and colleagues set out to determine if head
impacts acquired over a season of high school football produce white
matter changes in the brain in the absence of clinically diagnosed
concussion.
The researchers studied 24 high school football players between the
ages of 16 and 18. For all games and practices, players were monitored
with Head Impact Telemetry System (HITs) helmet-mounted accelerometers,
which are used in youth and collegiate football to assess the frequency
and severity of helmet impacts.
Risk-weighted cumulative exposure was computed from the HITs data,
representing the risk of concussion over the course of the season. This
data, along with total impacts, were used to categorize the players into
one of two groups: heavy hitters or light hitters. There were nine
heavy hitters and 15 light hitters. None of the players experienced
concussion during the season.
All players underwent pre- and post-season evaluation with diffusion
tensor imaging (DTI) of the brain. DTI is an advanced MRI technique,
which identifies microstructural changes in the brain's white matter.
The brain's white matter is composed of millions of nerve fibers
called axons that act like communication cables connecting various
regions of the brain. Diffusion tensor imaging produces a measurement,
called fractional anisotropy (FA), of the movement of water molecules
along axons. In healthy white matter, the direction of water movement is
fairly uniform and measures high in fractional anisotropy. When water
movement is more random, fractional anisotropy values decrease,
suggesting microstructural abnormalities.
The results showed that both groups demonstrated global increases of
FA over time, likely reflecting effects of brain development. However,
the heavy-hitter group showed statistically significant areas of
decreased FA post-season in specific areas of the brain, including the
splenium of the corpus callosum and deep white matter tracts.
"Our study found that players experiencing greater levels of head
impacts have more FA loss compared to players with lower impact
exposure," Dr. Whitlow said. "Similar brain MRI changes have been
previously associated with mild traumatic brain injury. However, it is
unclear whether or not these effects will be associated with any
negative long-term consequences."
Dr. Whitlow cautions that these findings are preliminary, and more study needs to be done.
Co-authors on the study are Naeim Bahrami, M.S., Elizabeth Davenport,
M.S., Jillian Urban, B.S., Fatemeh Mokhtari, M.S., Mark A. Espeland,
Ph.D., Youngkyoo Jung, Ph.D., Daryl A. Rosenbaum, M.D., Gerard A. Gioia,
Ph.D., Alexander K. Powers, M.D., Joel Stitzel Jr., Ph.D., and Joseph
A. Maldjian, M.D.