Head injuries

Cleveland Browns strong safety Damarious Randall (23) catches a pass during warm-ups prior to an NFL game against the Tennessee Titans, Sunday, Sept. 8, 2019, in Cleveland. (Margaret Bowles via AP)

FILE - In this Oct. 20, 2018, file photo, Maxim Dadashev, of Russia, left, hits Antonio DeMarco, of Mexico, during a junior welterweight bout in Las Vegas. Maxim Dadashev has died after suffering a brain injury in a fight in Maryland. He was 28. The Russian Boxing Federation said Tuesday, July 23, 2019, that Dadashev died "as a result of the injuries he sustained" in Friday's, July 19, 2019, light-welterweight fight with Subriel Matias at the Theater at MGM National Harbor in Oxon Hill, Maryland. (AP Photo/John Locher, File)

This image provided by the American Medical Association in July 2019 shows the amount of differences between brain scans of patients, U.S. diplomats who developed concussion-like symptoms after working in Cuba, and a control group. Between late 2016 and May 2018, several U.S. and Canadian diplomats in Havana complained of health problems from an unknown cause. One U.S. government count put the number of American personnel affected at 26. (American Medical Association via AP)

FILE - In this Feb. 4, 2016 file photo, NFL Senior Vice President of Health and Safety Policy Jeff Miller speaks during an NFL health and safety news conference in San Francisco. The NFL's top medical experts are asking college football physicians and trainers to help make the game safer. Dr. Allen Sills and Jeff Miller, the NFL's executive vice president for health and safety initiatives, spent Monday June 17 2019 and Tuesday, June 18, 2019 in Indianapolis sharing data about their findings on the prevention and treatment of injuries. (AP Photo/David J. Phillip, File)

In this Dec. 23, 2018, photo provided by Jodi Robinson, a scooter Andrew Hardy was riding sits near the car that hit him while riding the scooter in Los Angeles. Doctors told Hardy he’d likely be paralyzed for life. Five months later, he has learned to walk again. But he says he’ll never ride another scooter. (Jodi Robinson via AP)

Mark Lenzi, a U.S. State Department security engineer who was among several diplomats evacuated in 2018 from the U.S. Consulate in Guangzhou, China, speaks at a news conference Friday, May 10, 2019, in Boston. Lenzi suffered headaches and memory loss under mysterious circumstances while stationed in China. He has pledged to donate his brain for research. (AP Photo/Rodrique Ngowi)

Attorney Gene Locks, who represents many former NFL players, walks from the federal courthouse in Philadelphia after a hearing, Tuesday, May 7, 2019. The NFL concussion fund has paid out $485 million since 2017, but some players lawyers, including Locks, told a federal judge in Philadelphia on Tuesday that there aren't enough doctors in the fund's network to diagnose dementia cases. They oppose a rule to require that players be evaluated by doctors within 150 miles of home to prevent "doctor shopping." (AP Photo/Matt Rourke)

FILE - In this April 17, 2018 file photo, a man walks beside Canada's embassy in Havana, Cuba. Canada announced Wednesday, Jan. 30, 2019, it is removing up to half of the Canadians at its embassy in Cuba after another diplomat was found to have fallen mysteriously ill. Canada has confirmed 14 cases of mysterious health problems since early 2017. (AP Photo/Desmond Boylan, File)

Miami Dolphins running back Frank Gore (21) is tackled by Minnesota Vikings defensive end Danielle Hunter, left, and middle linebacker Eric Kendricks (54) during the first half of an NFL football game, Sunday, Dec. 16, 2018, in Minneapolis. (AP Photo/Bruce Kluckhohn)