Irv Cross, NFL star of the 1960s and broadcasting pioneer, had most severe form of CTE when he died

    Irv Cross, center, talks with broadcast partners Dick Butkus, left, and Brent Musburger on the air prior to the start of an NFL game around 1989.

    (CNN)Irv Cross, a former NFL star and broadcasting pioneer who died two years ago at the age of 81, had stage 4 chronic traumatic encephalopathy, the Boston University CTE Center said Tuesday.

    "Mr. Cross was diagnosed during life with mild cognitive impairment and was found at autopsy to have stage 4 chronic traumatic encephalopathy (CTE), which is the most severe type of the disease," said Dr. Ann McKee, director of Boston University's CTE Center, in a statement. "He is one of the 345 former NFL players diagnosed with CTE by the BU CTE Center and UNITE brain bank team out of 376 former NFL players studied."
    Former players studied by the BU CTE Center have chosen to donate their brains to the center or have had their brains donated by their families after their deaths.
      CTE, a neurodegenerative brain disease, can be found in individuals who have been exposed to repeated head trauma. Studies have found that repetitive hits to the head -- even without concussion -- can result in CTE.
        The disease, which can only be formally diagnosed with an autopsy, is pathologically marked by a buildup of tau protein in the brain that can disable neuropathways and lead to a variety of symptoms including memory loss, confusion, impaired judgment, aggression, depression, anxiety, impulse control issues and sometimes suicidal behavior.
        Cross's widow described the struggle he faced.
        "For the last five years of his life