Former pro football player Kevin Turner, shown here during a 1998 NFL game,had the most advanced stage of CTE when he died in March at the age of 46. Dr. Ann McKee of Boston University and the Concussion Legacy Foundation said that Turner's CTE brought on amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.
CTE stands for chronic traumatic encephalopathy, a neurodegenerative disease associated with repeated head trauma. Scientists believe repeated head trauma can cause CTE, a progressive degenerative disease of the brain. Symptoms include depression, aggression and disorientation, but scientists can definitively diagnose it only after death.
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BMX star Dave Mirra, who was found dead of a self-inflicted gunshot in February, was found to have CTE.
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Charles "Bubba" Smith, a former football player and actor who died in 2011, was also diagnosed with CTE. Smith played for the Baltimore Colts, the Oakland Raiders and the Houston Oilers.
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Former Minnesota Vikings linebacker Fred McNeill died in November 2015 due to complications from ALS. However, an autopsy confirmed that he suffered from CTE. What makes McNeill's case even more remarkable, though, is that he was potentially the first to be diagnosed while alive. Doctors used an experimental new technology to examine his brain.
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Oakland Raiders quarterback Ken Stabler, a former NFL MVP who died in July 2015, suffered from CTE, researchers at Boston University said.
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Kansas City Chiefs linebacker Jovan Belcher shot and killed his girlfriend before killing himself in December 2012. Pathology reports show he probably had CTE.
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Hall of Fame offensive lineman Mike Webster was the first former NFL player to be diagnosed with CTE. After his retirement, Webster suffered from amnesia, dementia, depression, and bone and muscle pain.
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The death of 36-year-old Pittsburgh Steelers offensive lineman Justin Strzelczyk put the link between football and CTE in the national spotlight. Strzelczyk was killed in a 2004 car crash crash after a 40-mile high-speed chase with police in New York.
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Evidence of CTE was found in the brain of football player Lew Carpenter after his death in 2010 at the age of 78.
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Pro Football Hall of Famer Louis Creekmur, who played for the Detroit Lions from 1950 to 1959, suffered decades of cognitive decline before his death.
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Linebacker John Grimsley of the Houston Oilers died of an accidental gunshot wound to the chest in 2008. Analysis of his brain tissue confirmed damage to the neurofibrillary tangles that had begun to affect his behavior and memory.
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Chris Henry played five seasons for the Cincinnati Bengals before dying at the age of 26. He died after falling from the bed of a moving pickup during a fight with his fiancée. His young age prompted concern over how quickly athletes start to suffer from CTE.
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Offensive lineman Terry Long of the Pittsburgh Steelers committed suicide by drinking antifreeze. Although the antifreeze caused swelling of the brain, football-related brain injuries were a contributing factor to his death.
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Pro Football Hall of Famer John Mackey suffered from dementia for years before dying at the age of 69.
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Ollie Matson, who played 14 NFL seasons starting in the 1950s, suffered from dementia until his death in 2011.
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Andre Waters spent most of his 12 seasons with the Philadelphia Eagles before his suicide at age 44.
Junior Seau took his own life in 2012 at the age of 43. The question of CTE came up immediately after his death; scientists at the National Institutes of Health confirmed the diagnosis in January 2013.
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Pro wrestler Chris Benoit was found dead at his suburban Atlanta home along with his wife, Nancy, and son in an apparent murder-suicide. Testing found that the damage to his brain was similar to that of an elderly Alzheimer's patient.
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Reggie Fleming, who played for six NHL teams, was the first hockey player to be diagnosed with CTE.
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Hockey player Bob Probert was found to have CTE after dying of heart failure at the age of 45.
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Ryan Freel became the first Major League Baseball player to be diagnosed with CTE nearly a year after he committed suicide at age 36.
