Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative disease of the brain found in athletes, military veterans, and others with a history of repetitive brain trauma. Brain trauma can cause a build-up of an abnormal type of a protein called tau, which slowly kills brain cells. Once started, these changes in the brain appear to continue to progress even after exposure to brain trauma has ended. Possible symptoms include memory loss, confusion, impaired judgment, paranoia, impulse control problems, aggression, depression, and eventually progressive dementia. Symptoms can begin to appear months, years, or even decades after trauma has ended. Currently, CTE can only be diagnosed after death by brain tissue analysis.