Linebacker Junior Seau spent nearly 20 years in the NFL, earning many honors before his retirement after the 2009 season. His high-energy performances earned him the nickname “The Tasmanian Devil.” He was voted to the Pro Bowl 12 times.
Three years after he retired, Seau died by suicide in 2012, a tragic end to an extraordinary life and career. An examination of his body revealed brain damage caused by chronic traumatic encephalopathy, known as CTE: a degenerative brain disease found in people who have suffered repetitive head trauma.
In a study published in the medical journal JAMA in July 2017, CTE was found in 99 percent of deceased NFL players' brains that were donated to scientific research. Doctors believe CTE contributed to Seau's suicide and to other behavioral and medical issues players have suffered after experiencing repeated head trauma while playing football.
Last April, ex-New England Patriots tight end Aaron Hernandez was serving a life sentence in jail for first degree murder when he was found dead in his cell by hanging. Afterwards, he was diagnosed with severe CTE damage for someone his age. CTE can cause aggressive, impulsive behavior. His fiancee and daughter have sued the NFL in a wrongful death lawsuit based on the CTE diagnosis.
In November, news broke that researchers had finally identified CTE in the brain scan of a then-living patient. Dr. Bennet Omalu confirmed that ex-NFL linebacker Fred McNeill was the subject of that research. McNeill had been examined at UCLA before he passed away in 2015 after showing signs of the disease. Dr. Julien Bailes, who participated in the study, told ABC News, "The importance of this one today is that this is the first time to have a scan which shows brain degeneration of CTE in a living person and then to have that person die and it correlates with the autopsy."
The list of former NFL players with CTE is long, and many former professional football players have announced their plans to donate their brains to science after they die. Hall of Famer Warren Sapp announced in June 2017 that, when he dies, he will donate his brain to the Concussion Legacy Foundation—because "I wanted this game to be better when I left than when I got into it."
Click through the photos below to view the stories and obituaries of 20 former pro football players, including Hall of Fame members Junior Seau, Ollie Matson, Tommy Nobis, Frank Gifford, and Ken Stabler, who were found after their deaths to have been suffering from CTE.