Muhammad Ali, who turned 70 on Tuesday, was celebrated as a newsmaker, a singular personality, the greatest boxer of all time, a man who stood up for his religious beliefs.
But really, he's most poignantly known these days as the poster boy of the effects of head injuries in athletes, more so now than ever as it's becoming clear that the effects are life-altering.
Ali used to boast in his entertaining and bombastic fashion, that his face was still pretty and unmarred by blows from Joe Frazier, George Foreman, Leon Spinks, Larry Holmes and all of the rest.
But he was unaware of the changes going on in his brain while he allowed repeated blows to his head from 61 bouts over 22 years. By 1983, CAT scans were already showing an atrophy in his brain more characteristic of older people. A scan showed a condition common in 50 per cent of boxers with more than 20 bouts, a condition also found four times more frequently in boxers than non-boxer. Even back then, doctors knew.
Ali was diagnosed with Parkinson's syndrome, (rather than disease) the following year. He was diagnosed by his own doctor as suffering from "dementia pugilistica" or to put it less delicately, "punch drunk."
Parkinson's syndrome has some of the same characteristics of Parkinson's disease, but they are not as severe and are caused by the gradual deterioration of certain nerve centres in the brain that control movements.
These days, Ali no longer can speak in public, although his friends say if you catch him in the morning before he becomes fatigued, conversation is possible.
The cause of Parkinson's is unknown, but doctors say that severe blows to the head can be one cause.
The damage comes from the rupture of small blood vessels in the brain – basically bruising of the brain. These heal, but lead to scarring.
For a very long time, Ali has not been able to float like a butterfly or sting like a bee. He is a living reminder of the danger of hits to the head.