As New York City chief medical examiner, Dr. Helpern performed autopsies on boxers who suffered boxing related fatalities (death by knockout). After several examinations, in 1965, he found that unlike normal (dead) brains, which retain their shape, the boxer's brains were liquefied.
"Brain tissue oozed out like toothpaste from a tube" -Dr. Helpern
(describing what happened when he drilled into the heads of the corpses).
What brand of toothpaste was unspecified
This would, in part, explain Mike Tyson.
Dates and certain specifics provided by Almanac of the Gross, Disgusting and Totally Repulsive.