Prolonged Repetitive Head Trauma Induces a Singular Chronic
Traumatic Encephalopathy-Like Pathology in White Matter Despite Transient
Behavioral Abnormalities

DI, Agnoa-Pérez M, Kuhn DM. The American Journal of Pathology. 2016;ahead of

Take Home Message: Mild
repetitive blows resulted in Alzheimer’s disease and 
chronic traumatic encephalopathy (CTE) like conditions in
mice. Additionally, as number of head impacts increased balance coordination
declined, and depressive symptoms progressed.

mild traumatic brain injuries have been suggested to have cumulative adverse
effects such as chronic traumatic encephalopathy (CTE). These problems are not
detectable during the time when athletes are actively exposed to repetitive
head impacts, and animal studies that attempt to replicate a head impact have
not focused on true repetitive impacts that would mimic those sustained by an
athlete. Therefore, the researchers administered a randomized control trial
implementing 30 head impacts using 2 different weights on 32 males, lightly
anesthetized, unrestrained mice (16 mice received 75 gram impacts, 16 mice
received 95 gram impacts) to stimulate the highly repetitive nature of a
sport-related concussion. The head-impact mice received 1 impact per day for 5
days then the mice were given 2 days rest. This schedule was repeated for 6
weeks. Eight mice in the control group were anesthetized on the same schedule,
but no head impacts were delivered. Researchers evaluated the mice on their level
of consciousness (via reflex recovery, balance and coordination, locomotor
activity, grip strength, depression like behavior, and cognitive performance).
Lastly, researchers used brain tissue analyses to determine presence of neuropathological
conditions (Alzheimer’s disease, CTE). As the number of head impacts increases,
the time to recover consciousness diminished; however, balance and coordination,
and cognition declined, and depressive symptoms progressed in the ensuing
weeks. Brain tissue analysis revealed Alzheimer’s disease and CTE like
conditions. No significant differences existed between controls and impact mice
and locomotion and late stage test strength.

researcher performed a novel and important study focusing on the cumulative
effect of head impacts and the central nervous system’s response. It was
interesting that the researchers found as the number of daily head impacts
increased, the less time mice had to regain consciousness, which suggests that
the brain attempts to adapt to head impact forces. This is alarming because
researchers also found, cumulative effects of the head impacts were
demonstrated within the brain tissue, where the brains looked like those
suffering from Alzheimer’s disease and CTE. Researchers did find that mice
receiving head impacts did display a decline in balance and cognition and
developing depression like symptoms, compared to controls.  Although, these were mild they still resulted
in negative alterations in brain tissue. This study will lead to future
progress on the frequency of head impacts and development of neuropathological
conditions and identification of risk factors for the development of these
chronic diseases. Medical professionals should be aware of the risks associated
with repetitive head impacts, and that athletes with a potential head injury should
be evaluated by a healthcare professional to determine severity and treatment

Questions for Discussion:
When you educate athletes about
concussion, do you mention long-term problems like CTE? Do you think athletes
would be more likely to report head impacts if they knew it could lead to a
long-term disease like CTE?

by: Jane McDevitt, PhD
by: Stephen Thomas


Higher Heading Counts May Impair Memory and Brain Tissue

Barry, G., van Schaik, P., MacSween, A., Dixon, J., & Martin, D. (2016). Exergaming (XBOX Kinect™) versus traditional gym-based exercise for postural control, flow and technology acceptance in healthy adults: a randomised controlled trial BMC Sports Science, Medicine and Rehabilitation, 8 (1) DOI: 10.1186/s13102-016-0050-0