Chronic Traumatic Encephalopathy

Repetitive mild head traumas lead to permanent brain changes

Soccer players battling to head the ball
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Repetitive mild head injuries can lead to progressive degenerative brain disease.  This disease is called “Chronic Traumatic Encephalopathy” or CTE.

It is a disease that is found primarily in athletes and individuals who experience repeated mild head trauma. Football players, soccer players and boxers are particularly at risk.

Head trauma leading to CTE can be so mild that there is no loss of consciousness, and no symptoms are felt.

It’s just experienced as a “knock on the head”.  Athletes exposed to these types of traumas usually just return to regular play, or perhaps sit on the sidelines for a few minutes to regain their focus.

When they return to play they risk another mild head trauma during the same sporting event, which further contributes to the ongoing damage.

What Happens to the Brain

Chronic Traumatic Encephalopathy gradually causes structural changes in the brain. In the early phases, tests such as MRIs and CT scans may not show any changes. However, over time the brain begins lose some of its weight.

In addition, small fluid filled areas inside the brain called “ventricles” become larger. This most often happens to the lateral and third ventricles. As the disease progresses, something called atrophy sets in. Atrophy is a wasting away of tissues and organs.

Some of these structural changes are also common as the brain ages, and may happen with other neurological diseases such as Alzheimer's and Amyototropic Lateral Sclerosis (ALS).

However, with CTE the changes are related to abnormal protein buildup that is caused by the repetitive head trauma. This can only be seen when the athlete's brain tissue is analyzed under a microscope.

Tau Proteins

On microscopic examination, there is an abnormal buildup of “tau” proteins.

Tau proteins are a natural part of the brain’s structure and are found in nerve cells where they stabilize microtubules which run up and down the nerve cell.

In CTE the tau proteins build up in a way unique to this particularly neurodegenerative disease. They become entangled, and get in the way of normal cellular communication.

Signs and Symptoms of CTE

Researchers are still learning which signs and symptoms are specifically associated with CTE. Medical providers look for changes in key areas: behavior, cognition, mood and movement. Signs include:

  • Difficulty remembering
  • No longer being able to solve complex problems as well as before
  • Feeling depressed
  • Having suicidal thoughts, or a suicide attempt
  • Experiencing anxiety
  • Acting aggressively
  • Feeling impatient, and becoming angry much faster
  • Trembling (similar to Parkinsons symptoms)

Some individuals with traumatic encephalopathy also develop muscular symptoms that mimic the neurodegenerative disease called Amyotrophic Lateral Sclerosis (ALS). At first, scientists believed that ALS could be caused by repetitive mild head trauma, but now it’s believed that these individuals are instead developing Chronic Traumatic EncephaloMyopathy (CTEM). The word "myopathy" in this case indicates there is a problem with controlling ones muscles.

CTEM is primarily characterized by problems with maintaining one’s balance, difficulty walking and slowly progressing muscle weakness.

Diagnosing CTE

Right after a mild head injury such as being hit in the head with a ball, or crashing into another athlete, there are no obvious, signs of damage on radiologic tests. This is because the damage is occurring at the cellular level, and through the buildup of tau proteins.

Diagnosis can be made by medical professionals experienced in understanding the risk factors for CTE, and piecing together the physical signs and symptoms. New research is exploring emerging ways to identify excess buildup of tau in the brain. However, as of now, a definitive diagnosis of CTE occurs during an autopsy and examination of brain tissues to look for abnormal tau protein buildup.


McKee AC1, Cantu RC, Nowinski CJ, Hedley-Whyte ET, Gavett BE, Budson AE, Santini VE, Lee HS, Kubilus CA, Stern RA. Chronic traumatic encephalopathy in athletes: progressive tauopathy after repetitive head injury. J Neuropathol Exp Neurol. 2009 Jul;68(7):709-35. doi: 10.1097/NEN.0b013e3181a9d503.

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