‘Insufficient evidence’ on degenerative brain disease in athletes

Available research does not support the contention that athletes are uniquely at risk of chronic traumatic encephalopathy (CTE) or other neurodegenerative disorders, according to a review in the June issue of Neurosurgery, official journal of the Congress of Neurological Surgeons. The journal is published by Wolters Kluwer.

Widely reported and publicized cases of CTE in retired athletes overlap with other neurodegenerative disorders, while the observed symptoms could result from a wide range of other factors, suggests the review by Dr. Gavin A. Davis of Cabrini Medical Centre in Malvern, Victoria, Australia, and colleagues. They write, “[We] think there is insufficient evidence to establish a causal relationship between sports participation and the existence of modern CTE.”

Experts Question Link between CTE and Sports Over the past decade, a series of reports have described CTE as specific neurodegenerative disorder occurring in football players and other athletes. “Typically, sport-related CTE occurs in a retired athlete with or without a history of concussion(s) who presents with a constellation of cognitive, mood, and/or behavioral symptoms,” according to Dr. Davis and coauthors.

Those reports have linked CTE to a history of concussions and “subconcussive impacts” during the athlete’s playing career. However, because of the limitations of case series analysis, no direct causal link between concussion and CTE has been established.

Autopsy studies of athletes with CTE emphasize the presence of a protein called tau in specific areas of the brain. However, Dr. Davis and colleagues note that similar patterns of tau deposits are found in Alzheimer’s disease and other common neurodegenerative disorders. These include the behavioral forms of frontotemporal dementia - the symptoms of which are “almost identical” to those of CTE.

Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative disease of the brain found in athletes (and others) with a history of repetitive brain trauma. This trauma, which includes multiple concussions, triggers progressive degeneration of the brain tissue, including the build-up of an abnormal protein called tau. These changes in the brain can begin months, years, or even decades after the last concussion or end of active athletic involvement. The brain degeneration is associated with memory loss, confusion, impaired judgment, paranoia, impulse control problems, aggression, depression, and, eventually, progressive dementia.

CTE can only be definitively diagnosed through post-mortem examination of the brain, although efforts are underway to learn how to diagnose CTE in living people, a key step to developing a treatment for the disease.

The authors also note that a wide range of other factors can contribute to brain tau deposits, including genetic mutations, various drugs and toxins, environmental factors, and even normal aging. These factors can lead to conditions similar to CTE in people who are not athletes.

For example, tau deposits have been linked to substance abuse, including strong opiate pain medications—which are widely used by athletes. “It is likely that many of the cases with neuropathological findings represent the normal aging process, the effects of opiate abuse, or a variant of frontotemporal degeneration,” Dr. Davis and coauthors write. They believe that in some cases, the clinical features may reflect depression or other mental health issues.

The term “Chronic Traumatic Encephalopathy” appears in the medical literature as early as 1966 and is now the preferred term. Through 2009 there were only 49 cases described in all medical literature since 1928, 39 of whom were boxers. Many thought this was a disease exclusive to boxers, although cases have been identified in a battered wife, an epileptic, two mentally challenged individuals with head-banging behavior, and an Australian circus performer who was also involved in what the medical report authors referred to as “dwarf-throwing.”

CTE was not well known in sports outside of boxing until a Pittsburgh medical examiner named Bennet Omalu identified CTE in two former Pittsburgh Steelers who died in his jurisdiction in 2002 and 2005 and published his findings in two case reports. The work drew the attention of SLI co-founder Chris Nowinski as we was writing Head Games: Football’s Concussion Crisis, and he began reaching out to families of recently deceased former athletes to accelerate the work. He coordinated three more cases in 2006 and 2007 that Dr. Omalu and others diagnosed with CTE, including SLI’s first case, former WWE wrestler Chris Benoit.

At a time of intense focus on the possible health effects of concussion and sports participation, Dr. Davis and coauthors hope their findings will draw attention to the limitations of the current evidence on CTE. They write, “When a previously undescribed condition, such as modern CTE in retired athletes, is proposed based on neuropathological findings in a small and potentially biased sample, then the complex genetic and environmental variables as well as the normal range of age-related brain degeneration implore us to cautiously review the data related to putative CTE.”


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Connie Hughes
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