What is CTE? Understanding chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a disease linked to repeated blows to the head. CTE has most commonly been diagnosed in athletes, but it can happen in anyone who has had recurring head injuries.

Defining CTE: What is chronic traumatic encephalopathy?

CTE is a rare form of brain damage that can result from repeated head injuries, even if they are not severe enough to cause concussion. The repeated head injuries are a type of traumatic brain injury, or TBI, but CTE is a progressive brain disorder that affects how the brain works, leading to dementia.

There is no evidence that an occasional blow to the head will lead to CTE. But there is strong evidence connecting CTE to repeated head impacts, whether or not they cause concussions.

Chronic traumatic encephalopathy was first identified in boxers in the 1920s. At the time, it was called "punch-drunk syndrome." Over the following decades, researchers reported similar findings in other victims of brain trauma.

Among the groups most affected by this type of TBI are professional football players. The first evidence of CTE in football players was found in Pittsburgh Steelers player Mike Webster, who died in 2002 at age 50 after years of bizarre behavior that, in retrospect, was a symptom of his dementia. An autopsy showed a specific type of brain damage causing his dementia. CTE can only be definitively diagnosed by performing an autopsy of the brain after someone has died.

Heightened awareness and concerns about CTE have likely led some athletes who have experienced a number of concussions to retire from their sport sooner than they had planned.

Parents of youngsters who play contact sports have also become concerned about the risk of CTE and brain damage. One study found that children ages 6 to 14 who played tackle football had 15 times more head impacts, and 23 times more hard head impacts, than those who play flag football.

Researchers say CTE may be far more widespread in young people who play a lot of contact sports than previously believed. A study of brains from contact sport players who died before they reached age 30 showed that more than 40% had CTE.

Causes of CTE: The role of repetitive head trauma

CTE is caused by repeated blows to the head that injure the brain's cells and blood vessels. This creates areas of microscopic bleeding and abnormal protein deposits called tangles, which kill brain cells.

Most people with CTE have had hundreds or thousands of head impacts from years of playing contact sports such as American football, boxing, rugby, hockey, or lacrosse. In fact, U.S. women's lacrosse ranks second only to American football in the number of concussions experienced by players.

CTE has also occurred in people serving in the military who are exposed to repeated blasts, and in victims of physical domestic abuse. It has been identified in people as young as 17.

Researchers have estimated that about 17% of people with years of repetitive concussions or mild TBIs will develop chronic traumatic encephalopathy. But it's not clear why some people who have repeated head impacts develop CTE and others do not. Scientists are studying the possible role of genetic, environmental, and lifestyle factors in combination with head trauma.

Symptoms of CTE

The effects of CTE on the brain are similar to those of other dementias and include:

• memory loss
• problems with attention and concentration
• mood disturbances such as anxiety, aggression, and depression
• suicidal thoughts
• impulsive or erratic behavior
• impaired judgement
• poor muscle coordination.

These symptoms worsen over time, even if a person with CTE no longer experiences additional head injuries.

Long-term consequences of CTE

CTE can have devastating impacts on an individual and their family. Family members of people who were found to have CTE reported that they had noticed changes in the person's behavior, thinking, and emotions for some time. These problems often became serious enough to get in the way of their loved one's family, social, or work-related activities.

People with CTE are at risk for poor impulse control and, in some cases, suicide. CTE eventually can lead to advanced dementia, Parkinson's disease, and a movement disorder similar to amyotrophic lateral sclerosis, or ALS (formerly known as Lou Gehrig's disease).

Diagnosing and treating CTE

Currently, the only definitive way to diagnose CTE is by autopsy after death. Diagnosis while someone is still alive can be a challenge, because CTE symptoms are similar to those of other conditions such as Alzheimer's disease. In some cases, CTE symptoms can be mistaken for normal aging.

There is hope that advanced imaging studies, such as special types of magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, can one day be used to improve the diagnosis of CTE by observing patterns of proteins in the brain. For now, doctors may make a tentative diagnosis of CTE based on a person's history (such as playing many years of football), symptoms, neurological exam, and brain imaging studies, after as many other conditions as possible have been ruled out.

Unfortunately, there currently is no way to reverse the brain damage that results from CTE. But certain medications, including cholinesterase inhibitors such as donepezil (Aricept), selective serotonin reuptake inhibitors (SSRIs) such as sertraline (Zoloft), and antipsychotics such as risperidone (Risperdal), may be used to treat symptoms like memory loss, problems with thinking, and mood and behavioral changes.

Preventing CTE

To help prevent CTE in people who play contact sports, researchers are investigating the types of head impacts that have the highest risk.

One study found that CTE is linked more closely to the force of blows to the head than to the number of concussions a person has experienced. The study suggests that CTE risk could be lowered by changing the force of head impacts in practices and games.

There also have been efforts in sports, particularly in football, to decrease the number of concussions by creating stricter penalties for blows to the head. In addition, there are stricter return-to-play guidelines, although there is limited information as to the best way to monitor an athlete's cognitive function after a concussion.

Improvements are being made to protective helmets for athletes engaged in contact sports, to help minimize the impact of a blow to the head. For example, better-performing helmets have contributed to a 25% reduction in concussions across the last five NFL seasons.

Brain donations from athletes have helped support research into CTE. More than 1,000 brains have been donated to the UNITE Brain Bank, the largest tissue repository in the world focused on TBI and CTE, to help further research. By studying these donations, researchers hope to learn more about ways to diagnose, treat, and help prevent CTE.