Chronic traumatic encephalopathy (CTE) is the term used to describe brain degeneration likely caused by repeated head traumas. CTE is a diagnosis only made at autopsy by studying sections of the brain.

CTE is a very rare condition. It has been found in the brains of people who played contact sports, such as football, as well as others. Some symptoms of CTE are thought to include difficulties with thinking (cognition), physical problems, emotions and other behaviors.

CTE is a very controversial condition that is still not well-understood. Researchers do not yet know the frequency of CTE in the population and do not understand the causes. There is no cure for CTE.


Some of the possible signs and symptoms of CTE may include:

  • Difficulty thinking (cognitive impairment)
  • Impulsive behavior
  • Depression or apathy
  • Short-term memory loss
  • Difficulty planning and carrying out tasks (executive function)
  • Emotional instability
  • Substance abuse
  • Suicidal thoughts or behavior

Other suspected symptoms may include:

  • Irritability
  • Aggression
  • Speech and language difficulties
  • Motor impairment, such as difficulty walking, tremor, loss of muscle movement, weakness or rigidity
  • Trouble swallowing (dysphagia)
  • Vision and focusing problems
  • Trouble with sense of smell (olfactory abnormalities)
  • Dementia

The full list of symptoms of people with CTE at autopsy is still unknown. It is unclear what kind of symptoms, if any, it may cause. Little is known right now about how CTE progresses.

When to see a doctor

CTE is thought to develop over many years after repeated brain injuries (mild or severe). However, see your doctor in case of the following:

  • Suicidal thoughts. Research shows that people with CTE may be at increased risk of suicide. If you have thoughts of hurting yourself, call 911, your local emergency number or the National Suicide Prevention Lifeline at 800-273-TALK (800-273-8255).
  • Head injury. See your doctor if you have had a head injury, even if you didn't need emergency care. If your child has received a head injury that concerns you, call your child's doctor immediately. Depending on the signs and symptoms, your doctor may recommend seeking immediate medical care.
  • Memory problems. See your doctor if you have concerns about your memory or other thinking (cognitive) or behavior problems.
  • Personality or mood changes. See your doctor if depression, anxiety, aggression or impulsivity occur.


Initial injury

Repetitive head trauma is likely the cause of CTE. Football players have been the focus of most CTE studies.

However, athletes participating in other sports, including soccer, ice hockey, rugby, boxing, wrestling, basketball, field hockey, cheerleading, volleyball and lacrosse, may experience repeated head impacts and also have high rates of concussion.

CTE has also been found in people who repeatedly bang their heads, people who have been physically abused, and those with epilepsy that has not been well-controlled. Blast injuries to military personnel also can result in CTE.

However, not all athletes and not everyone who experiences repeated concussions, including military personnel, go on to develop CTE. Some studies have shown no increased incidence of CTE in people exposed to repeated head injuries.

Effect of injury

CTE is thought to cause areas of the brain to waste away (atrophy). Injuries to the section of nerve cells that conduct electrical impulses affect communication between cells.

It's possible that people with CTE may show signs of another neurodegenerative disease, including Alzheimer's disease, amyotrophic lateral sclerosis (ALS) — also known as Lou Gehrig's disease — Parkinson's disease or frontotemporal lobar degeneration — also known as frontotemporal dementia.

Risk factors

Repeated exposure to traumatic brain injury is thought to increase the risk of CTE, but experts are still learning about the risk factors.


There is no treatment for CTE. But CTE may be prevented because it is associated with recurrent concussions. Individuals who have had one concussion are more likely to have another head injury. The current recommendation to prevent CTE is to reduce mild traumatic brain injuries and prevent additional injury after a concussion.

The following equipment can help reduce head injury:

  • Sports-specific helmets. Helmets have reduced injury for baseball, ice hockey, rugby, alpine skiing and snowboarding. It's possible that people choosing to wear a helmet also take fewer risks. Helmets have not reduced injury for soccer players. Helmets also cannot eliminate the occurrence of concussions.
  • Bicycle and motorcycle helmets. These reduce head injury in case of accident.

Coaches and players need to understand current guidelines for sports-related injuries. It's difficult to evaluate concussion during play, and coaches and players should be cautious and keep injured athletes out of the game.

The following signs and symptoms of concussion may be visible to coaches or to the athlete.

Danger signals:

  • Loss of consciousness, even briefly
  • One pupil larger than the other
  • Drowsy or cannot be awakened
  • A headache that gets worse
  • Weakness, numbness or decreased coordination
  • Repeated vomiting or nausea
  • Slurred speech
  • Convulsions or seizures
  • Unable to recognize people or places
  • Increasingly confused, restless or agitated or has other unusual behavior

Signs of concussion someone might observe in another person:

  • Appears dazed or stunned
  • Is confused about assignment or position
  • Forgets an instruction
  • Is unsure of game, score or opponent
  • Moves clumsily
  • Answers questions slowly
  • Loses consciousness, even briefly
  • Shows mood, behavior or personality changes
  • Can't recall events prior to or after hit or fall

Symptoms of concussion someone might notice themselves:

  • Headache or pressure in head
  • Nausea or vomiting
  • Balance problems or dizziness
  • Double or blurry vision
  • Sensitivity to light
  • Sensitivity to noise
  • Feeling sluggish, hazy, foggy or groggy
  • Concentration or memory problems
  • Confusion

If you suspect a concussion in yourself or someone else, follow the four-step action plan:

  • Remove the athlete from play for the day.
  • Have a health care professional evaluate the athlete.
  • Inform the athlete's parent, guardian or significant other.
  • Keep the athlete out of play until health care professional OKs a return.

Follow the gradual five-step plan to return to play:

  1. Light aerobic exercise, no weightlifting
  2. Moderate exercise, weightlifting OK
  3. Heavy, noncontact exercise
  4. Practice and controlled full contact
  5. Competition

Chronic traumatic encephalopathy care at Mayo Clinic

April 20, 2016
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