Almost a century ago, a rare but serious form of dementia was linked to repetitive head injuries in boxing. The dementia was aptly named, “Boxer’s dementia.” Lately, this “punch drunk” dementia has been found to affect athletes in other sports, such as American football and soccer, where athletes' heads take repeated blows, so a broader term for this condition was needed.

Chronic traumatic encephalopathy (CTE), is a related brain disorder that has been shown to affect other kinds of athletes, and more rarely, non-athletes who sustain head injuries. It has been in the news lately because of two high-profile cases.

After having suffered symptoms for years, Boogaard died of a drug overdose at 28. An autopsy revealed that CTE had been the cause of his neurological problems.

Dave Duerson, a former Chicago Bears player, committed suicide last year, after having suffered from memory problems, erratic and uncontrolled emotions, and violent behavior. He left a note requesting that his brain be donated to the Boston University Center for the Study of Traumatic Encephalopathy so that it could be studied. These brain tests confirmed what he suspected: that he had suffered from CTE.

Professional hockey player Derek Boogaard was one of the youngest known athletes to be affected. After having suffered symptoms for years, Boogaard died of a drug overdose at 28. An autopsy revealed that CTE had been the cause of his neurological problems.

Brain traumas, especially chronic injuries such as those sustained in sports can, over time, lead to irreversible brain damage. There is just so much jarring and shaking the brain can take. The difficulty is that the most serious, long-term symptoms often don't show up until later in life, but clearly CTE can develop almost any age. Here, we’ll discuss the symptoms, brain changes, and prevention of CTE in athletes and in all of us.

The Symptoms of CTE

Chronic traumatic encephalopathy affects many areas of a person’s functioning, including mood, emotional regulation, cognitive capacity, memory, and personality. It often doesn’t develop for years after the traumas occurred, and can present with a different constellation of symptoms in each person it affects.

Some experts have suggested that there are actually three phases of the disease.

Its prevalence in boxers continues. One recent review study of athletes who were diagnosed with CTE found that of the 51 confirmed cases of CTE, 46 were in athletes – and of these, 39 were boxers. Five football players, a soccer player, and a wrestler made up the remainder of the athletes affected by chronic brain trauma.

The most common initial symptoms of CTE are a variety of psychological and behavioral changes. Some experts have suggested that there are actually three phases of the disease. The first includes problems with attention, concentration, memory, and confusion; the second stage may bring with it more exaggerated behavioral symptoms like changes in social behavior, “erratic” behavior, and problems with judgment. Finally, the third stage can carry more severe cognitive deficits, full-blown dementia, and Parkinsonism.

Two Case Studies
A classic example is that of a retired NFL football player (all study subjects are anonymous), who started showing symptoms at age 40, when his family “began to notice minor impairments in his short-term memory, attention, concentration, organization, planning, problem solving, judgment, and ability to juggle more than one task at a time.” His memory also suffered. He “repeatedly asked the same questions over and over, he did not recall why he went to the store unless he had a list, and he would ask to rent a movie that he had already seen.”

Another CTE sufferer was a boxer whose short career began at 17 and ended at 22. He’d had an unrelated head injury in his teens. He started having problems with memory in his mid-20s, and in the next decade he had occasional falls and problems with confusion. His symptoms remained fairly steady for the next several decades, but they became more pronounced at the end of his life, at the age of 80.

Other research has shown that blows to the head in soccer, can over time, produce changes similar to those of CTE. The same is true for other head traumas, like head banging and repeated blows to the head from domestic abuse (more on this later). Although athletes appear, at least at the this point, to make up the majority of CTE patients, there’s no reason that other types of recurrent head traumas would not pose similar risks.

What’s Happening in the Brains of CTE Patients

The brain changes accompanying all forms of dementia are still being worked out. Amyloid-beta plaques and the accumulation of tangled bundles of protein filaments (which include deposits of the protein, tau) are hallmarks of Alzheimer's disease. Interestingly, amyloid-beta accumulation is not so widespread a phenomenon in CTE as it is in Alzheimer’s. But like Alzheimer’s and other forms of dementia, CTE is marked by the accumulation of tau in certain regions of the brain. Researchers are still working hard to determine just why tau accumulates in the first place, and what can be done to stop it.

Tau accumulation is present in higher concentrations in certain areas of the brain in CTE, particularly around blood vessels.

Autopsies of CTE patients’ brains show a distribution of large and small band-shaped and small flame-shaped, tangles of tau protein inside cells. These tau tangles can accumulate in the brain, similar to those seen in other dementias, but in CTE the shape of the tangles appears to be quite different from those in Alzheimer’s. Tau accumulation is present in higher concentrations in certain areas of the brain in CTE, particularly around blood vessels.

About 30% of people show higher levels of amyloid-beta proteins after having head injuries. More research is needed to determine the fundamental neurological differences among the dementias.

Why Trauma Leads to Tau (and Other Changes)

When the head undergoes a trauma, the brain takes a hit. Brain tissue may be insulated by layers of bone and fluid, but severe or repeated injuries disrupt the neural communication in the brain. Recent research on the long-term effects of concussion offers a picture of the lasting effects a brain injury can have. Lateral, or side-to-side, traumas are more damaging to than sagittal, or front-to-back, motion.

There are likely multiple mechanisms by which traumas can lead to brain damage and dementia, and the more traumatic and more repetitive they are, the more likely they are to result in irreversible damage.

One theory is that during injury blood flow to the brain becomes disrupted, which leads to oxygen deprivation (ischemia). Some suggest this phenomenon could lead to too much tau being deposited in the brain This concept is borne out in the distribution of tau, which is often found in the depths of its “wrinkles.” Alternatively, since tau accumulates near the blood vessels, it could be that the physical force from repeated blows to the head lead to damage to the vascular network of the brain, which could lead to the tangles seen in CTE.

The brain trauma associated with CTE may also trigger the death of neurons; inflammation in the brain; and damage to the white matter, the connective fibers in the brain by which neurons “talk” to one another. One team of CTE researchers suggests that there are probably many “pathological cascades” that are occurring over time. These cascades are thought to continue throughout the course of a lifetime. And the worse the initial injury – or injuries – the more severe the brain damage that can follow.

There are likely multiple mechanisms by which traumas can lead to brain damage and dementia, and the more traumatic and more repetitive they are, the more likely they are to result in irreversible damage.

Some Genetic Predisposition
There does seem to be a genetic component of CTE, and there is some overlap in its genetics with other forms of dementia. The same version of the gene that’s often present in Alzheimer’s patients (the apolipoprotein E gene, and specifically, the ApoE ε4 allele) is also more frequently seen in people who have a worse outcome after having a traumatic brain injury: in other words, some people’s brains may be “set up” to be more sensitive to brain injury, while those who lack this genetic makeup may be less likely to be adversely affected by injuries. Supporting this idea is the fact that the ApoE ε4 gene is found in about 50% of CTE patients, which is considerably higher than the general population (in which only about 15% of people carry it).

Brain Changes Lead to Behavioral Changes
In CTE, the different areas of the brain in which tau accumulates can explain the variety of psychological, emotional, and cognitive problems seen in the disorder. One brain network affected is known as the “emotional” or “visceral brain,” and tau accumulation in these areas may explain symptoms like quick emotional changes, aggression, and violent behaviors seen in Dave Duerson.

Other affected areas, like the hippocampus, likely underlie the loss of memory that some patients experience. And neural changes in the frontal cortex, particularly in its white matter, likely explain the deficits in thinking, judgment and decision-making seen in CTE.

CTE in Women and Children

Diagnosis of CTE can be tricky, and it is apparently often misdiagnosed as Alzheimer’s, as are other less common forms of dementia. Clearly, what differentiates CTE is head injury, so mentioning any previous head traumas, particularly those that include concussions or repeated blows, to one’s doctor is crucial to a diagnosis.

The cognitive deficits seen in kids who sustain head injuries, such as lower IQ, can persist for years after the trauma occurs.

While CTE is more common in boxers and other athletes, it is not confined to them. Any kind of head injury could increase one’s risk for permanent damage, including dementia, especially if it is chronic. One woman who had symptoms of dementia had been beaten repeatedly by her husband over the years. Her autopsy showed brain changes that were just like those described in CTE.

Very recent evidence has suggested that young children are less resilient to early brain injuries than previously thought. Shaken baby syndrome is one of the leading causes of traumatic brain injury in infants, and can lead to cognitive deficits over time. The cognitive deficits seen in kids who sustain head injuries, such as lower IQ, can persist for years after the trauma occurs.

What Is Being Done to Protect Athletes?

Since our understanding of chronic traumatic brain injuries' link to irreversible brain damage is still in its infancy, it is not yet clear how to respond. As more and more cases of CTE in professional athletes come to the public’s attention, sports organizations, including players' organizations, will likely do more to protect players. Parents will likely have to spearhead the movement to ensure young athletes are also protected.

Unfortunately, professional sports associations have been slow to adopt policies to protect players against head injuries. On the websites of the National Football League and the Fédération Internationale de Football Association (FIFA), which oversees soccer, there is only scant information on head injuries and concussion.

As more and more cases of CTE in professional athletes come to the public’s attention, sports organizations, including players' organizations, will likely do more to protect players.

There has been some discussion of whether helmets in American soccer should be required, and football helmets are evolving to absorb impact more effectively. Very recent evidence shows that padded boxing headgear can decrease the impact of some – but not all – types of blow to the head. Hopefully, as more cases of CTE in athletes come to the public’s attention, equipment manufacturers and sports organizations will do more to protect professional players – and the young sports fans who look up to them. Recommendations for improving the fit and monitoring the protectiveness of helmets were presented at the American Orthopaedic Society for Sports Medicine meeting in San Francisco on February 11.

CTE reminds us that our brains are more vulnerable than we might like to imagine. Even though not everyone may be at the same degree of risk for chronic traumatic encephalopathy, a blow to the head, and especially repeated head injuries may reverberate in the brain for months or years to come.