What is CTE? Understanding Chronic Traumatic Encephalopathy

Chronic Traumatic Encephalopathy (CTE) is a progressive brain condition believed to be caused by repeated head injuries. This degenerative disease leads to the gradual death of nerve cells within the brain. It’s crucial to understand that CTE is not linked to a single head injury but rather to the cumulative effect of multiple blows to the head over time. Currently, the definitive diagnosis of CTE can only be made post-mortem through a brain autopsy.

While still considered a rare disorder, our understanding of CTE is continuously evolving. It is not associated with a singular traumatic brain event but is strongly correlated with repetitive head trauma, frequently observed in contact sports and military service. Notably, CTE development has been linked to second impact syndrome, a dangerous condition where a subsequent head injury occurs before the symptoms of a prior concussion have fully subsided.

Researchers are actively investigating the complex relationship between repeated head injuries and the brain changes that characterize CTE. Key areas of study include determining how the frequency and severity of head impacts influence the likelihood of developing CTE.

CTE has been identified in the brains of individuals who participated in American football, boxing, and other contact sports. It is also being studied in military personnel exposed to blast waves from explosions. The symptoms associated with CTE are diverse, potentially encompassing difficulties with cognition, emotional regulation, physical coordination, and behavior. These symptoms are believed to emerge years, or even decades, after the initial head trauma.

Currently, a definitive CTE diagnosis cannot be made during a person’s lifetime, except in cases with a clear history of high-risk exposures. Researchers are dedicated to discovering diagnostic biomarkers for CTE, but no validated markers are available yet. In the presence of CTE-related symptoms, healthcare professionals may diagnose Traumatic Encephalopathy Syndrome, a clinical diagnosis based on symptoms and history of head trauma.

The exact prevalence of CTE in the general population remains unknown, but it is considered to be uncommon. The precise causes are still under investigation, and currently, there is no cure for CTE.

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Symptoms

There are no symptoms exclusively specific to CTE. The symptoms that have been observed in individuals diagnosed with CTE post-mortem are also seen in numerous other conditions. These symptoms broadly fall into categories of cognitive, behavioral, mood, and motor changes.

Cognitive Impairment

• Difficulty in thinking clearly.
• Memory loss, ranging from mild forgetfulness to significant amnesia.
• Challenges with executive functions such as planning, organizing, and executing tasks.

Behavioral Changes

• Acting impulsively without considering consequences.
• Increased irritability and aggression, sometimes manifesting as verbal or physical outbursts.

Mood Disorders

• Persistent feelings of sadness, hopelessness, or loss of interest in activities (depression).
• Lack of motivation or interest in usual activities (apathy).
• Rapid and unpredictable shifts in emotions.
• Development or worsening of substance misuse issues as a coping mechanism.
• Recurring thoughts of suicide or suicidal attempts.

Motor Symptoms

• Difficulties with balance and coordination, leading to unsteady walking and falls.
• Parkinsonism, characterized by tremors, slowed movements (bradykinesia), stiffness, and speech difficulties.
• In rare cases, motor neuron disease, which involves the degeneration of neurons controlling voluntary muscle movement, affecting walking, speaking, swallowing, and breathing.

It’s important to note that CTE symptoms do not manifest immediately after a head injury. It is believed that they develop gradually over many years or even decades following repeated head trauma.

Experts suggest that CTE symptoms might present in two distinct patterns. An early-onset form, appearing typically between the late 20s and early 30s, is often characterized by mental health and behavioral disturbances, including depression, anxiety, impulsivity, and aggression. A later-onset form is thought to emerge around age 60, primarily affecting cognitive functions, leading to memory and thinking problems that can progress to dementia.

The complete spectrum of signs associated with CTE, identifiable through autopsy, is still under investigation. Furthermore, the precise progression and trajectory of CTE remain areas of ongoing research.

When to See a Doctor

CTE is a condition that develops slowly over time, resulting from repeated brain injuries, which may range from mild to severe. It is crucial to seek medical attention in the following situations:

• Suicidal Thoughts: Research indicates a heightened risk of suicide in individuals with CTE. If you are experiencing thoughts of harming yourself, immediately call emergency services (911 in the US) or your local emergency number. You can also reach out to a suicide hotline. In the U.S., dial or text 988 to connect with the 988 Suicide & Crisis Lifeline or use their Lifeline Chat.
• Head Injury: Consult your healthcare provider after any head injury, even if emergency care wasn’t required. If you are concerned about a head injury sustained by your child, contact their pediatrician promptly. Depending on the symptoms, your or your child’s doctor might recommend immediate medical evaluation.
• Memory Problems: If you are worried about your memory, or if you experience other cognitive or behavioral issues, schedule an appointment with your healthcare provider for assessment.
• Personality or Mood Changes: Seek medical advice if you notice persistent depression, anxiety, aggression, or impulsive behavior in yourself or a loved one.

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Causes

Concussion

Concussion

A concussion is a traumatic brain injury caused by a blow to the head or a sudden jolt that causes the brain to move rapidly inside the skull. This movement can stretch and damage brain cells.

Repeated head trauma is considered the primary cause of CTE. Studies on CTE have predominantly focused on American football players, ice hockey players, and military personnel in combat zones, due to their higher risk of repetitive head impacts. However, it’s important to recognize that other sports and factors like physical abuse can also contribute to repeated head injuries.

A head injury can result in a concussion, leading to symptoms such as headaches, memory problems, and confusion. However, not everyone who experiences repeated concussions will develop CTE. Some studies have not found a direct correlation between repeated head injuries and an increased incidence of CTE, suggesting other factors may also be involved.

In brains affected by CTE, a distinctive finding is the abnormal accumulation of a protein called tau around blood vessels. This tau buildup in CTE is different from the tau accumulations observed in Alzheimer’s disease and other dementias. CTE is believed to cause brain atrophy, a wasting away of brain tissue, due to damage to nerve cells and disruption of communication between brain cells.

It’s also possible for individuals with CTE to exhibit signs of other neurodegenerative diseases, including Alzheimer’s disease, Amyotrophic Lateral Sclerosis (ALS), Parkinson’s disease, or Frontotemporal Lobar Degeneration (FTLD), also known as frontotemporal dementia. The interplay between CTE and these other conditions is an area of ongoing research.

Risk Factors

The main identified risk factor for CTE is repeated exposure to traumatic brain injury (TBI). Researchers are still working to fully understand all the risk factors and individual susceptibility to CTE. The number, severity, and frequency of head impacts likely play a significant role, but other genetic and environmental factors may also contribute.

Prevention

Currently, there is no treatment to cure CTE. However, CTE may be preventable since it is linked to recurrent concussions and head trauma. Individuals who have experienced a concussion are at a higher risk of sustaining subsequent head injuries. Therefore, the prevailing recommendation for CTE prevention is to minimize mild traumatic brain injuries and to prevent further injury after a concussion has occurred. This includes strategies such as:

• Promoting safe sports practices: Implementing and enforcing rules in contact sports to reduce head impacts, teaching proper techniques for tackling and collision, and ensuring athletes use appropriate protective equipment.
• Concussion awareness and management: Educating athletes, coaches, parents, and medical professionals about concussion symptoms and the importance of proper concussion management protocols, including adequate rest and gradual return-to-play guidelines.
• Reducing head injuries in military and other high-risk professions: Implementing safety measures and training to minimize exposure to blast waves and head trauma in military settings and other occupations with potential for head injuries.
• Addressing physical abuse and domestic violence: Recognizing and preventing situations that lead to repeated head injuries due to physical abuse.

By Mayo Clinic Staff

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Nov. 18, 2023

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