Chronic traumatic encephalopathy (CTE) is a brain condition associated with repeated blows to the head. It is also associated with the development of dementia. Potential signs of CTE are problems with thinking and memory, personality changes, and behavioral changes including aggression and depression. People may not experience potential signs of CTE until years or decades after brain injuries occur. A definitive diagnosis of CTE can only be made after death, when an autopsy can reveal whether the known brain changes of CTE are present.


What causes CTE?

A review of available literature indicates that the greatest risk factor for developing CTE-related brain changes is repetitive brain trauma — repeated, forceful blows to the head (such as those that may occur playing contact sports) that do not, individually, result in symptoms.

What is a concussion?

Mild traumatic brain injury, also known as a concussion, either doesn't knock you out or knocks you out for 30 minutes or less. Short-term symptoms often appear at the time of the injury, but can develop days or weeks later.

Traumatic brain injuries (TBIs) also can be classified as moderate or severe, depending on symptoms and the length of unconsciousness the brain injury causes. 

Learn More

Physical evidence connecting football and CTE was first discovered by Bennet Omalu, M.D., a forensic neuropathologist who performed an autopsy on Mike Webster, the Hall of Fame center for the Pittsburgh Steelers. His story was made into the movie "Concussion," which has heightened awareness of CTE.

Previously, CTE had been associated with boxing and was called dementia pugilistica or "punch-drunk syndrome." The risk of CTE in boxers seems most closely tied to the number of rounds boxed, not to the number of times a boxer was knocked out, suggesting that even repeated blows to the head that don't cause unconsciousness may increase CTE risk.


Physicians and researchers are only beginning to understand many aspects of CTE. More time and research are needed. For that reason, consensus has not yet been reached on the symptoms of CTE. However, based on present knowledge, the signs of CTE may sometimes be similar to those of other conditions that involve substantial loss of brain cells, including Alzheimer's disease and Parkinson's disease. Possible signs include:

  • Memory loss.
  • Confusion.
  • Personality changes (including depression and suicidal thoughts).
  • Erratic behavior (including aggression).
  • Problems paying attention and organizing thoughts.
  • Difficulty with balance and motor skills.

Like Alzheimer’s dementia, CTE is characterized by tangles of an abnormal form of the protein tau in the brain. Unlike Alzheimer’s dementia, these tangles typically appear around small blood vessels, and beta-amyloid plaques are only present in certain circumstances. How the brain changes associated with CTE are linked to cognitive or behavioral dysfunction is unclear.

How many hits to the head does it take?

There's no evidence that a single concussion increases CTE risk, and not everyone with a history of recurring concussions will go on to develop CTE.

Researchers strongly suspect that CTE is most likely to occur following a large number of traumatic brain injuries — even without loss of consciousness, a small number of more severe traumatic brain injuries, or some other pattern of head trauma.

There is evidence linking moderate and severe traumatic brain injuries to a higher risk of developing other brain conditions, such as Alzheimer’s disease. 

Learn More


Currently, there is not a test to determine if someone has CTE. Because CTE is a relatively new area of exploration for researchers and physicians, formal clinical guidelines for diagnosing and managing CTE do not yet exist. A definitive diagnosis can only be made through an autopsy after death. Scientists are working to further understand CTE and to identify ways to diagnose CTE during life.

When CTE is suspected, a thorough medical history, mental status testing, neurological exams, brain imaging and further diagnostic tests may be used to rule out other possible causes.


Today, there is no treatment and no cure for CTE. The only known way to prevent it is to avoid repeated head injuries. Those with potential signs of CTE may benefit from some of the same types of care provided for people with Alzheimer’s disease and other types of dementia (for example, approaches to deal with aggression).

Being a caregiver for someone with CTE — like being a caregiver for someone with dementia — can be overwhelming. People who are caring for someone with signs of CTE can be helped by knowing what to expect as CTE progresses and from having a support network in place. Learn more about dementia caregiving.


Several major research initiatives are underway to gain further insight into the patterns of​ injury and brain changes that may be implicated in CTE, and to develop new strategies for prevention, diagnosis and treatment. To date, the Alzheimer's Association has invested more than $2 million in research on brain injury, including CTE.