By Brenda L. Mooney
BOSTON – For the first time, researchers have categorized chronic traumatic encephalopathy (CTE), the degenerative brain disease associated with repeated brain trauma in military combat and contact sports, into four stages of severity.
In a recent study from the Veterans Affairs Boston Healthcare System, Boston University Center for the Study of Traumatic Encephalopathy (CSTE) and the Sports Legacy Institute (SLI), 68 cases of CTE were identified among deceased athletes and military veterans whose brain and spinal cords were donated to the VA CSTE Brain Bank. The study, which was published in this month’s issue of the journal Brain, represents the largest case series of CTE published to date.
Of the 68 cases of CTE found in males between 17 and 98 years old, 64 were athletes, and 18 of those were also military veterans. Of the athletes, 34 were professional football players, nine only played college football and six had only played high school football. The group included three additional veterans who did not have a sports background.
Evaluation of one of the study subjects — for whom self-injurious head-banging behavior was the sole environmental exposure — underscored the view that repetitive brain trauma alone is sufficient to trigger CTE in some cases.
“This study extends our knowledge concerning the spectrum of the clinical and pathological abnormalities associated with CTE, although further studies are needed to investigate critical aspects of trauma-induced neurodegeneration, including the incidence and prevalence of CTE; whether the symptoms of CTE are distinctive from other conditions; how genetics influence susceptibility or resistance to CTE; and whether other environmental exposures also play an additive role in the development of CTE,” said lead author Ann McKee, MD, director of the Neuropathology Service for VA New England Healthcare System, professor at Boston University School of Medicine (BUSM) and co-director of the CSTE.
McKee also is director of the CSTE and the Brain Banks for Boston University’s Alzheimer’s Disease Center, which are based at the Bedford, MA, VA Medical Center.
CTE, which appears to be slowly progressive in most individuals, is characterized in early stages 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.
Among the veterans found to have CTE were marines, soldiers and sailors from World War II, the Vietnam and Gulf wars, as well as the wars in Iraq and Afghanistan. Researchers also found evidence of the condition in 50 football players, including 33 who played in the National Football League (NFL), one in the Canadian Football League (CFL), one semi-professional player, nine college players and six high school football players. CTE also was identified in four National Hockey League (NHL) players, one amateur hockey player, seven professional boxers, one amateur boxer, and one professional wrestler.
“While it remains unknown what level of exposure to brain trauma is required to trigger CTE, there is no available evidence that occasional, isolated or well-managed concussions give rise to CTE,” explained co-author Robert Cantu, MD, co-director of CSTE and co-founder of SLI.
The new study provides specific pathological criteria for the diagnosis of CTE and divides CTE into four stages of disease (Stages I-IV). Based on interviews with families of the deceased donors, researchers were able to develop a list of symptoms common to stages of the disease:
• In Stage I, headaches and issues related to attention and concentration were common;
• 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.
• In Stage IV, there was evidence of full-blown dementia (i.e., memory and cognitive impairments severe enough to impact daily living).
While CTE appeared to be slowly progressive in most of the study subjects, it may not progress or progress at the same rate in all patients, study authors noted. Overall, however, 89% of those diagnosed with CTE through pathological studies had demonstrated clinical symptoms involving cognitive, behavioral or mood impairments before death, according to the report.
In addition, one-third of the CTE cases were diagnosed with additional neurodegenerative disease, including:
• Motor neuron disease (12%);
• Lewy body disease (16%;
• Alzheimer’s disease (11%); and
• Frontotemporal lobar degeneration (6%).
Years before the onset of cognitive and behavioral symptoms, most of the individuals with CTE and motor neuron disease (CTE-MND) had suffered symptoms of motor weakness, atrophy and fasciculations, or muscle twitches, the study notes.
The next goal of researchers is developing methods to diagnose CTE during life, according to co-author Robert Stern, PhD, Boston University professor of neurology and neurosurgery.
“The ability to diagnose CTE while someone is alive is an important next step to allow us to address some of these important issues, as well as develop and test treatment and prevention strategies for the disease,” he said.
In addition to raising troubling questions about the safety of contact sports, the research underscores that CTE could have devastating implications for military veterans and the VA’s ability to care for them.
A study released this summer also found CTE indications in brain tissue from blast-exposed military personnel. That study noted that as much as 20% of the 2.3 million troops deployed to Iraq and Afghanistan since 2001 could have suffered a traumatic brain injury (TBI) as a result of exposure to IEDs. In a worst-case scenario, 460,000 veterans could be at risk for CTE.