In 2006, 1.7 million cases of traumatic brain injuries (TBIs) occurred in the US, costing 60 plus billion dollars [CDC data]. There were 2.6 million cases in 2010. After the acute symptoms of concussive TBI subside, chronic traumatic encephalopathy (CTE) may set in and linger. CTE is a long-lasting brain inflammation, incurable at present, and ultimately fatal. Many of its consequences, including memory loss, depression, etc. are related to those in Parkinson’s disease and Alzheimer’s dementia. While symptoms in age-related neurodegenerative disorders typically manifest in the sixth decade of life or later, similar symptoms and neuropathology have been reported in the second and third decades of life in football players. Concussion rate in high school football players is ~15% per player per season. In high school sports played by both sexes, girls sustained a higher rate of concussions than boys.
Our video analysis of knockouts and technical knockouts (KOs) in boxing have shown that the first sign of brain dysfunction in concussions is a generalized and dramatic loss of muscle tone affecting the entire body (head-and-neck, upper and lower limbs as well as axial musculatures). The extensive scope of the muscle tone loss is likely an indication that this process is due to an active inhibition rather than a loss of function. This process is likely to involve the cerebellum, a brain structure responsible for the regulation of muscle tone. This loss of muscle tone can be observed within ~50 msec of impact, compared to a typical eye blink at ~300 to 400 msec. The speed of muscle tone loss suggests that the cellular mechanism of concussion may involve neuronal oscillations, which we have earlier suggested to be responsible for the manifestation of the effects of ethanol on cerebellar motor control.
One in five surviving soldiers wounded in combat in Iraq and Afghanistan also had concussions. Understanding concussions require a multi-disciplinary approach that involves neurobiology, biomechanics, and others. We are currently studying the cellular mechanisms of concussions in order to come up with a sound approach to reduce concussion risks.