CTE, chronic traumatic encephalopathy, can result from recurrent head injury.

In Concussion by Brainy Days Ahead

While many athletes who suffer concussions do not go on to develop CTE, every time it crops up in an autopsy it’s in someone who “had a history of repetitive hits to the head,” says Robert Stern, director of the clinical core of the Alzheimer’s Disease Center at the Boston University School of Medicine.