Is Mike Tyson showing PD signs?

[Primo Carnera]

I don't get the recent fascination with CTE
It seems to be a hot topic in contact sports.

Hearns shows signs of it whereas Leonard
Hagler and Duran appear to be just fine.

Toney shows signs of it whereas Hopkins
Jones and Tarver appear to be just fine.

Bowe shows signs of it whereas Lewis
Holyfield and Tyson appear to be just fine.

That's nine fighters who don't have it
And three that might. It's not a huge problem.

It is for the 3 that might have it. Bear in mind , these are the most successful fighters , who perceivably get hit less and it's a possible 25% rate.
What about the less skilled journeymen who get hit for fun?