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

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.

June 25, 2025

Living with chronic traumatic encephalopathy?

Connect with others like you for support and answers to your questions in the Traumatic Brain Injury (TBI) support group on Mayo Clinic Connect, a patient community.

Traumatic Brain Injury Discussions

Dawn Pereda
Adult Life after a Traumatic Brain Injury

215 Replies Fri, Aug 29, 2025

duke21
TBI: Will my symptoms get better or worse?

9 Replies Thu, Apr 24, 2025

See more discussions
  1. Ferri FF. Chronic traumatic encephalopathy. In: Ferri's Clinical Advisor 2025. Elsevier; 2025. https://www.clinicalkey.com. Accessed Jan. 11, 2025.
  2. Evans RW et al. Sequelae of mild traumatic brain injury. https://www.uptodate.com/contents/search. Accessed Jan. 11, 2025.
  3. Katz DI, et al. National Institute of Neurological Disorders and Stroke consensus diagnostic criteria for traumatic encephalopathy syndrome. Neurology. 2021; doi:10.1212/WNL.0000000000011850.
  4. Malec JF, et al. The Mayo classification system for traumatic brain injury severity. Journal of Neurotrauma. 2007; doi:10.1089/neu.2006.0245.
  5. Bieniek KF, et al. The second NINDS/NIBIB consensus meeting to define neuropathological criteria for the diagnosis of chronic traumatic encephalopathy. Journal of Neuropathology and Experimental Neurology. 2021; doi:10.1093/jnen/nlab001.
  6. Eapen BC, et al., eds. Complications of traumatic brain injury. In: Brain Injury Medicine: Board Review. Elsevier; 2021. https://www.clinicalkey.com. Accessed Jan. 11, 2025.
  7. Chronic traumatic encephalopathy (CTE). Alzheimer's Association. https://www.alz.org/alzheimers-dementia/what-is-dementia/related_conditions/chronic-traumatic-encephalopathy-(cte). Accessed Jan. 11, 2025.
  8. Halicki MJ, et al. Blood-based biomarkers in the diagnosis of chronic traumatic encephalopathy: Research to date and future directions. International Journal of Molecular Sciences. 2023; doi:10.3390/ijms241612556.
  9. Ruchika F, et al. Understanding the molecular progression of chronic traumatic encephalopathy in traumatic brain injury, aging and neurodegenerative disease. International Journal of Molecular Sciences. 2023; doi:10.3390/ijms24031847.
  10. Chronic traumatic encephalopathy (CTE). Merck Manual Professional Version. https://www.merckmanuals.com/professional/neurologic-disorders/delirium-and-dementia/chronic-traumatic-encephalopathy-cte. Accessed Jan. 17, 2025.
  11. About repeated head impacts. Centers for Disease Control and Prevention. https://www.cdc.gov/traumatic-brain-injury/about/repeated-head-impacts.html#cdc_disease_basics_symptoms-symptoms. Accessed Jan. 19, 2025.
  12. McKee AC, et al. Chronic traumatic encephalopathy (CTE): Criteria for neuropathological diagnosis and relationship to repetitive head impacts. Acta Neuropathica. 2023; doi:10.1007/s00401-023-02540-w.
  13. Wallingford A, et al. Chronic traumatic encephalopathy. Physical Medicine and Rehabilitation Clinics of North America. 2024; doi:10.1016/j.pmr.2024.02.011.
  14. NIH chronic traumatic encephalopathy diagnosis conference. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Current-Research/Focus-Research/Traumatic-Brain-Injury/NIH-Chronic-Traumatic-Encephalopathy. Accessed Jan. 11, 2025.
  15. Kelly JP, et al. Sports concussion and chronic traumatic encephalopathy: Finding a path forward. Annals of Neurology. 2023; doi:10.1002/ana.26566.
  16. McKee AC, et al. Neuropathologic and clinical findings in young contact sport athletes exposed to repetitive head impacts. JAMA Neurology. 2023; doi:10.1001/jamaneurol.2023.2907.
  17. Concussion basics. Centers for Disease Control and Prevention. https://www.cdc.gov/heads-up/about/index.html. Accessed Jan. 19, 2025.
  18. Nimmagadda R. Allscripts EPSi. Mayo Clinic. Dec. 24, 2024.

Related

Associated Procedures

Products & Services