A study done by investigators at the Boston University Center for the Study of Traumatic Encephalopathy (CSTE) and the Veterans Affairs Boston Healthcare System, in collaboration with the Sports Legacy Institute (SLI), describes 68 cases of chronic traumatic encephalopathy (CTE) among deceased athletes and military veterans whose brain and spinal cords were donated to the VA CSTE Brain Bank. Of the 68 cases, 34 were former professional football players, nine had played only college football, and six had played only high school football. The results, which will be published in the December issue of the scientific journal, Brain, represent the largest case series of CTE published to date, doubling the number of published CTE cases internationally.
Ann McKee, MD, professor at Boston University School of Medicine (BUSM), director of the Neuropathology Service for VA New England Healthcare System and co-director of the CSTE, led this clinicopathological study, which is the first to characterize the pathology of the disease into four stages of severity.
CTE is a degenerative brain disease associated with repeated brain trauma, including concussions and multiple subconcussive exposures such as those in contact sports and military combat, and appears to be slowly progressive in most individuals. In early stages, CTE is characterized by the presence of abnormal deposits of a protein called tau in the form of neurofibrillary tangles, glial tangles and neuropil threads throughout the brain. These tau lesions eventually lead to brain cell death. Currently, CTE can only be diagnosed postmortem.
In the study, the 68 cases of CTE were found in males between the age of 17 and 98. The cases represented 64 athletes, 18 of whom were also military veterans, as well as three additional veterans who did not have a sports background and one individual who engaged in self-injurious head-banging behavior. The development of CTE in an individual in whom self-injurious head banging was the sole environmental exposure, which has been previously published by other groups, suggests that repetitive brain trauma alone is sufficient to trigger CTE in some cases.
There were 50 football players who had evidence of CTE, including 33 who played in the National Football League (NFL), one in the Canadian Football League (CFL), one semi-professional player, nine college and six high school football players. In addition, CTE was found in four National Hockey League (NHL) players, one amateur hockey player, seven professional boxers, one amateur boxer, and one professional wrestler. Veterans with CTE included marines, soldiers and sailors from World War II, the Vietnam and Gulf Wars, as well as the Wars in Iraq and Afghanistan.
The report provides specific pathological criteria for the diagnosis of CTE and divides CTE into four stages of disease (Stages I-IV). The families of all deceased brain donors were interviewed extensively about their loved one's history and medical records were reviewed when available. Eighty-nine percent of individuals pathologically diagnosed with CTE showed clinical symptoms involving cognitive, behavioral, or mood impairments. Headaches and issues related to attention and concentration were common in Stage I. In Stage II, the symptoms expanded to include depression, explosivity and short-term memory impairment. In Stage III, reported symptoms included cognitive impairment and problems with executive functions, specifically planning, organization, multitasking and judgment. Full-blown dementia (i.e., memory and cognitive impairments severe enough to impact daily living) was characteristic of Stage IV. Although CTE appeared to be slowly progressive in most individuals, CTE may not progress, or may not progress at the same rate in all persons.