'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.