Chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) results from blows to the head over a period of time that cause concussion (mild traumatic brain injury). These injuries lead to difficulties with thinking (cognition), emotions and behaviors that do not become noticeable until many years later. CTE can lead to physical problems as well. Not everyone who has one or more concussions develops CTE.

CTE involves progressive damage to nerve cells (neurodegenerative disease). The damage results in visible changes to the brain. Some of these changes can be seen with brain imaging, but a diagnosis at this time can be made only on inspection after death (autopsy). Researchers are working to find a way to diagnose CTE in those who have the disease while the individuals are still alive.

Originally called punch drunk syndrome (dementia pugilistica), CTE was first demonstrated in boxers. Doctors now know that other individuals who play a wide variety of sports that involve repeated blows to the head, such as football players, can develop CTE. Military personnel who have had blast injuries also are at risk.

Researchers do not yet fully understand CTE's prevalence and causes. There is no cure for CTE.

Symptoms Causes Risk factors Prevention

Symptoms of CTE are like those of other conditions that involve progressive loss of function or structure of nerve cells (neurodegenerative diseases), including:

  • Alzheimer's disease
  • Parkinson's disease
  • Frontotemporal dementia
  • Amyotrophic lateral sclerosis (ALS) — also known as Lou Gehrig's disease

Overall, people with CTE first have problems with thinking (cognition), mood and behavior. Later, they may also develop physical problems.

Military personnel who have experienced traumatic brain injury may experience post-traumatic stress disorder.

Signs and symptoms of CTE usually begin eight to 10 years after repetitive mild traumatic brain injury. These include:

  • Difficulty thinking (cognitive impairment)
  • Impulsive behavior
  • Depression or apathy
  • Short-term memory loss
  • Difficulty planning and carrying out tasks (executive function)
  • Emotional instability
  • Substance abuse
  • Suicidal thoughts or behavior

Over time, memory and executive function may become worse, and other signs and symptoms may develop, including:

  • Irritability
  • Aggression
  • Speech and language difficulties
  • Motor impairment, such as difficulty walking, tremor, loss of muscle movement, weakness or rigidity
  • Trouble swallowing (dysphagia)
  • Vision and focusing problems
  • Trouble with sense of smell (olfactory abnormalities)
  • Dementia

Researchers use the following stages to describe the progression of CTE symptoms:

  • Stage I. Headache, loss of attention and concentration
  • Stage II. Depression, explosivity and short-term memory loss
  • Stage III. Decision-making (executive) dysfunction and cognitive impairment
  • Stage IV. Dementia, word-finding difficulty and aggression

They have also created four stages to describe the process of damage to brain tissue.

CTE causes ongoing pathological changes that once are started, continue to have an effect for years or decades after the original traumatic brain injury or after an individual retires from a sport. Symptoms progress throughout an individual's life.

CTE progresses in two patterns. In younger people, it may begin with behavior and mood changes, whereas in older people, it may begin with cognitive problems that progress and may lead to dementia. It's not known whether there are two different disease processes or if the process changes over time.

When to see a doctor

CTE develops over many years, long after repeated mild traumatic brain injury occurs.

However, see your doctor in case of the following:

  • Suicidal thoughts. Some studies report 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 have 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.

Initial injury

The main cause of CTE is repetitive head trauma. Football players have been the focus of most CTE studies. However, athletes participating in other sports, including soccer, ice hockey, rugby, boxing, wrestling, basketball, field hockey, cheerleading, volleyball and lacrosse, may experience repeated head impacts and also have high rates of concussion.

Blast injuries to military personnel also can result in CTE.

However, not all athletes and not everyone who experiences repeated concussions, including military personnel, go on to develop CTE.

Effect of injury

CTE causes the wasting away (atrophy) of many parts of the brain. Injuries to the section of nerve cells involved in conducting electrical impulses (axons) interfere with cell-to-cell communication. Other changes include deposits of the proteins tau and TDP-43, and changes in white matter — the part of the brain made up of nerve fibers. Unlike in Alzheimer's disease, deposits of beta-amyloid, another protein, are not common.

More than one-third of people with CTE also have signs of another neurodegenerative disease, including Alzheimer's disease, motor neuron disease, Parkinson's disease or frontotemporal lobar degeneration.

Researchers believe that repetitive mild traumatic brain injury must occur in order for someone to develop CTE. But other factors are needed as well, since not everyone with repetitive head injury develops thinking (cognitive), emotional or behavioral problems later in life. These factors could include the type of injury, total numbers of injuries, how severe the injuries are or other medical factors. Although researchers believe tau proteins are involved, other proteins may play a role as well.

Research has focused on genetic risk factors, in particular the presence of specific apolipoprotein E (APOE) genotypes, which have been established as a risk factor for Alzheimer's disease. So far, APOE has not been found to be a risk factor for the development of CTE.

Age, sex, stress, alcohol and substance abuse may also contribute to the development of CTE.

There is no treatment for CTE or other neurodegenerative disease. However, because CTE is associated with recurrent concussions, it can be prevented. Also, individuals who have had one concussion are more likely to have another head injury. Therefore, the key to prevention of CTE is to reduce mild traumatic brain injuries and prevent additional injury after a concussion.

The following equipment can help reduce head injury:

  • Sports-specific helmets. Helmets have reduced injury for baseball, ice hockey, rugby, alpine skiing and snowboarding. However, it's possible that people choosing to wear a helmet also take fewer risks. Helmets have not reduced injury for soccer players. And helmets cannot eliminate the occurrence of concussions.
  • Bicycle and motorcycle helmets. These reduce head injury in case of accident.

Coaches and players need to be familiar with current guidelines for sports-related injuries. It's difficult to evaluate concussion during play, and coaches and players should err on the side of caution by keeping injured athletes out of the game.

The following signs and symptoms of concussion may be visible to coaches or to the athlete:

Danger signals:

  • Loses consciousness, even briefly
  • One pupil larger than the other
  • Is drowsy or cannot be awakened
  • A headache that gets worse
  • Weakness, numbness or decreased coordination
  • Repeated vomiting or nausea
  • Slurred speech
  • Convulsions or seizures
  • Unable to recognize people or places
  • Becomes increasingly confused, restless, agitated or has other unusual behavior

Signs someone might observe in another person:

  • Appears dazed or stunned
  • Is confused about assignment or position
  • Forgets an instruction
  • Is unsure of game, score or opponent
  • Moves clumsily
  • Answers questions slowly
  • Loses consciousness, even briefly
  • Shows mood, behavior or personality changes
  • Can't recall events prior to or after hit or fall

Symptoms someone might self-report:

  • Headache or pressure in head
  • Nausea or vomiting
  • Balance problems or dizziness
  • Double or blurry vision
  • Sensitivity to light
  • Sensitivity to noise
  • Feeling sluggish, hazy, foggy or groggy
  • Concentration or memory problems
  • Confusion

If you suspect a concussion in yourself or someone else, follow the four-step action plan:

  • Remove the athlete from play for the day.
  • Have a health care professional evaluate the athlete.
  • Inform the athlete's parent, guardian or significant other.
  • Keep the athlete out of play until health care professional OKs a return.

Follow the gradual five-step plan to return to play:

  • Light aerobic exercise, no weightlifting
  • Moderate exercise, weightlifting OK
  • Heavy, noncontact exercise
  • Practice and controlled full contact
  • Competition
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