Overview

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

CTE is a rare disorder that is not yet well understood. CTE is not related to the immediate consequences of a late-life episode of head trauma. CTE has a complex relationship with head traumas such as persistent post-concussive symptoms and second impact syndrome that occur earlier in life.

Experts are still trying to understand how repeated head traumas — including how many head injuries and the severity of those injuries — and other factors might contribute to the changes in the brain that result in CTE.

CTE has been found in the brains of people who played football and other contact sports, including boxing. It may also occur in military personnel who were exposed to explosive blasts. Some signs and symptoms of CTE are thought to include difficulties with thinking (cognition) and emotions, physical problems and other behaviors. It's thought that these develop years to decades after head trauma occurs.

CTE cannot be made as a diagnosis during life except in those rare individuals with high-risk exposures. Researchers do not yet know the frequency of CTE in the population and do not understand the causes. There is no cure for CTE. Researchers are currently developing diagnostic biomarkers for CTE, but none has been validated yet.

Symptoms

There are no specific symptoms that have been clearly linked to CTE. Some of the possible signs and symptoms of CTE can occur in many other conditions. In the few people with proved CTE, signs and symptoms have included cognitive, behavioral, mood and motor changes.

Cognitive impairment

  • Difficulty thinking (cognitive impairment)
  • Memory loss
  • Problems with planning, organization and carrying out tasks (executive function)

Behavioral changes

  • Impulsive behavior
  • Aggression

Mood disorders

  • Depression or apathy
  • Emotional instability
  • Substance misuse
  • Suicidal thoughts or behavior

Motor symptoms

  • Parkinsonism
  • Motor neuron disease

CTE symptoms don't develop right after a head injury, but experts believe that they might develop over years or decades after repeated head trauma. Experts currently believe that CTE symptoms appear in two forms. In early life between the late 20s and early 30s, the first form of CTE may cause mental health and behavioral issues including depression, anxiety, impulsivity and aggression. The second form of CTE is thought to cause symptoms later in life, around age 60. These signs and symptoms include memory and thinking problems that are likely to progress to dementia.

The full list of signs to look for in people with CTE at autopsy is still unknown. It is unclear what kind of symptoms, if any, CTE may cause during life. 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 that may be 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've 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.

Causes

Repetitive head trauma is likely the cause of CTE. Football and ice hockey players, as well as military personnel serving in war zones, have been the focus of most CTE studies, though other sports and factors such as physical abuse also can lead to repetitive head injuries.

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.

In brains with CTE, researchers have found that there is a buildup of a protein called tau around the blood vessels. Tau buildup in CTE is different from accumulations of tau found in Alzheimer's disease and other forms of dementia. CTE is thought to cause areas of the brain to waste away (atrophy). Injuries to the sections 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 (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.

Prevention

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.

Chronic traumatic encephalopathy care at Mayo Clinic

May 25, 2021
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