An Avoidable Dementia
One tauopathy is entirely man-made, caused by concussions and other types of brain trauma.
One type of tauopathy—chronic traumatic encephalopathy, or CTE—is entirely caused by environmental factors. Back in the 1920s, it’s what afflicted “punch drunk” professional boxers who developed symptoms of dementia, and today CTE is a well-publicized problem for athletes and soldiers. “It develops from repetitive exposure to mild trauma, such as what football players experience in every play of a game, in people who repeatedly bang their heads because of a developmental disorder, or in those whose grand mal epilepsy is poorly controlled,” says Ann McKee, who directs the Neuropathology Service for the New England Veterans Administration Medical Centers and is a professor of neurology and pathology at Boston University.
When you experience a concussion, the gelatinous brain stretches and elongates inside the skull, injuring the fine fibers of the axons extending from neurons in the brain. Massive amounts of calcium surge into the injured cells, triggering enzymes that could damage or kill the neurons. When you recover from a concussion, cells that survive return to normal. “But repetitive injury will overwhelm that process, and you get CTE,” says McKee. In a unique feature of this tauopathy, tau begins accumulating around small blood vessels in the fissures of the brain’s frontal cortex and then tau tangles spread into the hippocampus and amygdala. Initial symptoms of aggression, depression, impulsivity and drug and alcohol abuse may progress to memory loss, cognitive decline and severe dementia a decade or more later. “This tauopathy simmers much more slowly than Alzheimer’s disease,” says McKee.
Especially worrisome are the symptoms of CTE seen in high school and college athletes. Kids who start playing contact sports as early as age nine may be especially vulnerable to CTE because of cumulative exposure for their underdeveloped brains. “Kids have big heads relative to their body size and underdeveloped necks, and they aren’t as coordinated as adults,” says McKee. “Good helmets, which kids often don’t use, can slow down the velocity of a blow, but they don’t prevent CTE. I think we need to think twice about asking our kids to play sports that limit their future potential.”