SAN DIEGO -- Junior Seau, who committed suicide in May, two years after retiring as one of the premier linebackers in NFL history, suffered from the type of chronic brain damage that has also been found in dozens of deceased former players, five brain specialists consulted by the National Institutes of Health concluded.

Seau's ex-wife, Gina, and his oldest son, Tyler, 23, told ABC News and ESPN in an exclusive interview they were informed last week that Seau's brain had tested positive for chronic traumatic encephalopathy, a neurodegenerative disease that can lead to dementia, memory loss and depression.

"I think it's important for everyone to know that Junior did indeed suffer from CTE," Gina Seau said. "It's important that we take steps to help these players. We certainly don't want to see anything like this happen again to any of our athletes."

She said the family was told that Seau's disease resulted from "a lot of head-to-head collisions over the course of 20 years of playing in the NFL. And that it gradually, you know, developed the deterioration of his brain and his ability to think logically."

CTE is a progressive disease associated with repeated head trauma. Although long known to occur in boxers, it was not discovered in football players until 2005. Researchers at Boston University recently confirmed 50 cases of CTE in former football players, including 33 who played in the NFL.

Seau shot himself in the heart on May 2. His death stunned not only the football world but also his hometown, San Diego, where he played the first 13 years of his 20-year career. Seau led the Chargers to their first and only Super Bowl appearance and became a beloved figure in the community.

Tyler and Gina Seau talked about the results of tests on Junior Seau's brain. ABC

Within hours of Seau's death, Tyler Seau said he received calls from researchers hoping to secure his father's brain for study. The family ultimately chose the National Institutes of Health in Washington to oversee the research.

Gina Seau said the family chose the NIH because it was a "complete, comprehensive, unbiased scientific institution of the highest level."

In a statement, the NFL said the NIH's finding "underscores the recognized need for additional research to accelerate a fuller understanding of CTE."

The statement also said: "The NFL, both directly and in partnership with the NIH, Centers for Disease Control and other leading organizations, is committed to supporting a wide range of independent medical and scientific research that will both address CTE and promote the long-term health and safety of athletes at all levels. The NFL clubs have already committed a $30 million research grant to the NIH, and we look forward to making decisions soon with the NFL Players Association on the investment of $100 million for medical research that is committed in the collective bargaining agreement. We have work to do, and we're doing it."

The NFLPA, meanwhile, called on Congress to look into player safety in the NFL and noted that it set aside $100 million for medical research when it negotiated the latest CBA.

"The only way we can improve the safety of players, restore the confidence of our fans and secure the future of our game is to insist on the same quality of medical care, informed consent and ethical standards that we expect for ourselves and for our family members. This is why the players have asked for things like independent sideline concussion experts, the certification and credentialing of all professional football medical staff and a fairer workers compensation system in professional football," the players' union said.

"Given their keen interest in Health and Safety issues in football, we call on Congressman Cummings, Congressman Issa and the Congressional Committee on Oversight and Government Reform to review this issue as well.

"Our players deserve the best care, and we will fight to hold the NFL and the Clubs accountable for providing it."

Dr. Russell Lonser, the former chief of surgical neurology at the NIH, helped coordinate the study. In an interview, Lonser, who was recently named chairman of the department of neurological surgery at Ohio State University, said that because of the publicity surrounding the case, the study of Seau's brain was "blinded" to ensure its independence.

Three independent neuropathologists from outside the NIH were given unidentified tissue from three different brains; one belonged to Seau, another to a person who had suffered from Alzheimer's disease, and a third to a person with no history of traumatic brain injury or neurodegenerative disease.