Has Tom had more than one concussion? I don't remember him ever having that issue.
There are definitely QBs and other guys that have had their heads damaged, but there are other older QBs that seem to be doing fine, such as Terry Bradshaw and maybe Frank Gifford was fairly healthy till his 70s I think.
There are Qbs in their 50s that seem ok like Flutie, Aikman, Marino, Steve Young and Boomer. Montana is almost 60
Interestingly, Gifford's brain showed signs of CTE, although I'm not sure how that manifested itself when he was alive.
He was also in his mid 80s when he died. At that age, almost anything will kill you. Been reluctant to put him in the same realm at Duerson or Seau.