Nick Buoniconti, a tenacious middle linebacker who won two Super Bowls in the 1970s with the Miami Dolphins and in retirement turned his doggedness to finding a cure for his son’s paralysis, died on Tuesday at his home in Bridgehampton, N.Y. He was 78.

The son, Marc Buoniconti, the president of the Miami Project to Cure Paralysis, which his father helped found, announced the death. His said his father had been in hospice care.

In 2015 doctors told Nick Buoniconti that he showed symptoms of dementia. Two years later he agreed to donate his brain to researchers at Boston University. They are to determine if his repeated head injuries as a player caused chronic traumatic encephalopathy, a degenerative brain disease.

As of 2017, the university’s C.T.E. Center had found the disease in 110 of the 111 former N.F.L. players’ brains it had examined.