Overview
Chronic traumatic encephalopathy, also known as CTE, is a brain disease likely caused by repeated head injuries. It causes the death of nerve cells in the brain, known as degeneration. CTE gets worse over time. The only way to definitively diagnosis CTE is after death during an autopsy of the brain.
CTE is rare and not well understood, but experts don't believe it's related to a single head injury. CTE appears to be related to repeated head injuries, often occurring in contact sports or military combat. CTE also has been associated with second impact syndrome, when a second head injury occurs before symptoms of a previous head injury have fully resolved.
Experts are still trying to understand how repeated head injuries and other factors might contribute to the changes in the brain that result in CTE. Researchers are looking at how the number of head injuries someone experiences and how bad the injuries are may affect risk of CTE. Experts also don't yet know how often CTE occurs in the population.
CTE has been found in the brains of people who played U.S. football and other contact sports, including boxing. It also may occur in military members who were exposed to explosive blasts. Symptoms of CTE are thought to include trouble with thinking and emotions, physical symptoms, and other behaviors. It's thought that symptoms develop years to decades after head trauma occurs.
Researchers are working on developing tests for CTE, but none has been validated yet. Healthcare professionals may diagnose traumatic encephalopathy syndrome when the symptoms associated with CTE occur together. There is no cure for CTE.
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Symptoms
There are no specific symptoms that have been clearly linked to chronic traumatic encephalopathy, also known as CTE. Some of the possible symptoms can occur in many other conditions. In people who were confirmed to have CTE at autopsy, symptoms have included cognitive, behavioral, mood and movement changes.
Cognitive impairment
- Trouble thinking.
- Memory loss.
- Problems with planning, organizing and carrying out tasks.
Behavioral changes
- Impulsive behavior.
- Aggression.
Mood changes
- Depression or apathy.
- Emotional instability.
- Substance misuse.
- Suicidal thoughts or behavior.
Movement symptoms
- Trouble with walking and with balance.
- Shaking, slow movement and trouble with speech, known as parkinsonism.
- Gradual loss of control of movements, such as walking, speaking, swallowing and breathing, known as motor neuron disease.
CTE symptoms don't develop right after a head injury. Experts believe that they develop over years or decades after repeated head trauma.
Experts also 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. Symptoms of this form include depression, anxiety, impulsive behavior and aggression. The second form of CTE is thought to cause symptoms later in life, around age 60. These symptoms include trouble with memory and thinking that is likely to progress to dementia.
The full list of signs to look for in people with CTE at autopsy is still unknown. There's also little known 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. See your healthcare professional in these situations:
- Suicidal thoughts. Research shows that people with CTE may be at increased risk of suicide. If you have thoughts of hurting yourself, call 911 or your local emergency number. Or contact a suicide hotline. In the U.S., call or text 988 to reach the 988 Suicide & Crisis Lifeline or use the Lifeline Chat.
- Head injury. See your healthcare professional if you've had a head injury, even if you didn't need emergency care. If your child has had a head injury that concerns you, call your child's healthcare professional right away. Depending on the symptoms, your child's health professional may recommend seeking immediate medical care.
- Memory problems. See your healthcare professional if you have memory loss or if you have other thinking or behavior symptoms.
- Personality or mood changes. Also see your healthcare professional if you feel depressed, anxious, aggressive or impulsive.
Causes
Concussion
Concussion
A concussion occurs when a blow to the head or a sudden jolt shakes the head and causes movement of the brain inside the bony and rigid skull.
Repeated head trauma is likely the cause of chronic traumatic encephalopathy, also known as CTE. Football players in the United States, ice hockey players and military members serving in war zones have been the focus of most CTE studies. However, other sports and factors such as physical abuse can lead to repeated head injuries. Research also has found that CTE can affect people who played both amateur and professional sports. This was discovered when autopsies were done of the brains of young people who had died and had repeated head injuries during their lives.
A head injury can cause a concussion, which may lead to headaches, trouble with memory and other symptoms. Not everyone who experiences repeated concussions, including athletes and military members, goes 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 tau buildup in Alzheimer's disease and other forms of dementia. CTE is thought to cause areas of the brain to waste away, known as atrophy. This happens because injuries to nerve cells that conduct electrical impulses affect communication between cells.
It's possible that people with CTE may show signs of another neurodegenerative disease, such as Alzheimer's disease, amyotrophic lateral sclerosis (ALS), Parkinson's disease or frontotemporal dementia.
Risk factors
Repeated traumatic brain injuries are thought to increase the risk of chronic traumatic encephalopathy. Experts are still learning about the risk factors.
Prevention
Chronic traumatic encephalopathy, also known as CTE, can be prevented by lowering the risk of getting a concussion. People 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 to prevent additional injury after a concussion.