What is CTE? Understanding Chronic Traumatic Encephalopathy

Chronic Traumatic Encephalopathy (CTE) is a progressive brain condition believed to be caused by repetitive head injuries. This neurodegenerative disease leads to the gradual deterioration and death of nerve cells within the brain, a process known as degeneration. It’s crucial to understand that CTE is a condition that worsens over time. Currently, the only definitive method for diagnosing CTE is through a post-mortem examination of the brain, specifically during an autopsy.

It’s important to note that CTE is considered a rare disorder, and our understanding of it is still evolving. Unlike conditions resulting from a single traumatic brain injury, CTE is linked to the accumulation of repeated head traumas. These traumas are frequently observed in individuals participating in contact sports and those exposed to military combat situations. The development of CTE has also been associated with second impact syndrome, a dangerous condition where a subsequent head injury occurs before the symptoms of a previous head injury have fully subsided.

Experts are actively engaged in research to fully elucidate how repeated head injuries and other contributing factors trigger the brain changes characteristic of CTE. Ongoing studies are exploring the relationship between the number and severity of head injuries and the subsequent risk of developing CTE.

Significantly, CTE has been identified in the brains of individuals who have participated in American football and other contact sports like boxing. Furthermore, it may also affect military personnel who have experienced explosive blasts. The symptoms associated with CTE are thought to encompass difficulties with cognitive functions, emotional regulation, physical coordination, and alterations in behavior. These symptoms are believed to emerge years, even decades, after the initial head trauma occurred.

Currently, a definitive diagnosis of CTE cannot be made during a person’s lifetime, except in cases with a history of high-risk exposures. Researchers are diligently working on developing diagnostic biomarkers for CTE, but as yet, no reliable biomarker has been validated. When symptoms suggestive of CTE are present, healthcare professionals may diagnose traumatic encephalopathy syndrome, which reflects the clinical presentation associated with CTE.

The precise prevalence of CTE within the general population remains unknown, but current evidence suggests it is a rare condition. The exact causes are still under investigation, and there is currently no cure for CTE.

Symptoms of CTE: Recognizing the Signs and Changes

There are no symptoms that are exclusively indicative of CTE. The potential symptoms associated with CTE can also be observed in a variety of other medical conditions. However, in individuals confirmed to have CTE through autopsy, a range of cognitive, behavioral, mood, and motor changes have been consistently reported.

Cognitive Impairment

Cognitive difficulties are a significant aspect of CTE, manifesting in several ways:

Trouble thinking: Individuals may experience a general slowing down of thought processes and difficulty in processing information.
Memory loss: This can range from mild forgetfulness to significant difficulties in recalling recent events or long-term memories.
Problems with planning, organization, and carrying out tasks: Executive functions are often affected, leading to challenges in planning, organizing daily activities, and completing tasks that require multiple steps.

Behavioral Changes

Behavioral alterations can be disruptive and challenging for both the individual and their families:

Impulsive behavior: Acting without thinking, engaging in risky activities, or having difficulty controlling urges.
Aggression: Increased irritability, outbursts of anger, or even physical aggression.

Mood Disorders

Mood disturbances are common in individuals with CTE, significantly impacting their emotional well-being:

Depression or apathy: Persistent sadness, loss of interest in activities, and a general lack of motivation.
Emotional instability: Rapid and unpredictable shifts in mood, exaggerated emotional responses.
Substance misuse: Turning to drugs or alcohol as a coping mechanism for emotional distress or cognitive difficulties.
Suicidal thoughts or behavior: In severe cases, individuals may experience thoughts of suicide or engage in suicidal actions.

Motor Symptoms

Motor difficulties can affect movement, coordination, and physical function:

Problems with walking and balance: Unsteadiness, difficulty maintaining balance, and an increased risk of falls.
Parkinsonism: Symptoms resembling Parkinson’s disease, including tremors, slow movement (bradykinesia), rigidity, and speech difficulties.
Motor neuron disease: In rare instances, CTE may be associated with motor neuron disease, leading to the degeneration of cells controlling walking, speaking, swallowing, and breathing.

It’s crucial to understand that CTE symptoms do not appear immediately following a head injury. Experts believe that these symptoms develop gradually over years or even decades after the occurrence of repeated head trauma.

Researchers propose that CTE symptoms may present in two distinct forms based on the age of onset. The first form may emerge in early adulthood, typically between the late 20s and early 30s, and is primarily characterized by mental health and behavioral issues. Symptoms in this early-onset form often include depression, anxiety, impulsivity, and aggression. The second form of CTE is thought to manifest later in life, typically around age 60. This later-onset form is characterized by memory and thinking problems that are likely to progress into dementia.

It is important to acknowledge that the complete spectrum of signs associated with CTE, as observed in post-mortem examinations, is still not fully understood. Furthermore, there is limited knowledge about the precise progression and trajectory of CTE over time.

When to Seek Medical Advice

CTE is believed to develop over an extended period following repeated brain injuries, which can range from mild to severe. It is essential to consult a healthcare provider in the following situations:

Suicidal thoughts: Research indicates that individuals with CTE may have an elevated risk of suicide. If you are experiencing thoughts of self-harm, it is crucial to seek immediate help by calling emergency services or a suicide hotline. In the U.S., you can dial 988 to reach the 988 Suicide & Crisis Lifeline.
Head injury: Seek medical attention after any head injury, even if immediate emergency care is not required. If you are concerned about a head injury sustained by your child, contact their healthcare provider promptly. Depending on the symptoms, medical professionals may recommend immediate evaluation.
Memory problems: If you have concerns about your memory or experience other cognitive or behavioral issues, consult your healthcare provider for assessment.
Personality or mood changes: If you notice significant changes in your personality or mood, such as depression, anxiety, aggression, or impulsive behavior, it is important to seek medical advice to determine the underlying cause.

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Causes and Risk Factors of CTE

Concussion

Repeated head trauma is strongly implicated as the primary cause of CTE. Studies investigating CTE have predominantly focused on American football players, ice hockey players, and military personnel serving in combat zones. However, it’s important to recognize that repeated head injuries can also occur in other sports and due to factors such as physical abuse.

A head injury can result in a concussion, which may lead to headaches, memory problems, and other symptoms. However, it’s crucial to understand that not everyone who experiences repeated concussions, including athletes and military personnel, will develop CTE. Some research studies have even indicated no increased incidence of CTE in populations exposed to repeated head injuries. This highlights the complexity of CTE and the fact that not all repeated head injuries lead to this condition.

In brains affected by CTE, researchers have observed an abnormal buildup of a protein called tau around blood vessels. The tau accumulation pattern in CTE is distinct from the tau deposits found in Alzheimer’s disease and other forms of dementia. CTE is believed to cause brain tissue to deteriorate and shrink, a process known as atrophy. This atrophy occurs because damage to nerve cells, which are responsible for transmitting electrical impulses, disrupts 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 (frontotemporal dementia). This overlap underscores the complexity of neurodegenerative conditions and the potential for co-occurrence or misdiagnosis.

Repeated exposure to traumatic brain injury is considered a significant risk factor for CTE. However, experts are still actively researching and refining our understanding of the specific risk factors that contribute to the development of this condition.

Prevention of CTE

Currently, there is no specific treatment or cure for CTE. However, because CTE is strongly linked to recurrent concussions, preventive strategies are crucial. 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 involves implementing safety measures, proper concussion management protocols, and education to reduce the incidence and severity of head injuries, particularly in high-risk groups such as athletes and military personnel.

By Mayo Clinic Staff

Chronic traumatic encephalopathy care at Mayo Clinic