What does this mean for the future of football, professional or otherwise? It can't be good. To begin with, some parents are bound to bar, or at least steer, their sons from the game. Even some NFL players share that impulse.
"I don't want my son to play football," New York Jets linebacker Bart Scott told the New York Daily News. Former Arizona Cardinals quarterback Kurt Warner said he wants his sons to avoid the game that made him rich and famous.
As the known casualties mount, fans may also recoil or drift away in search of less destructive forms of entertainment. It's not so much fun to savor a spectacular hit once you confront the insidious harm it can do to a player's most vital organ.
Players and fans have always accepted the risk of broken bones and torn ligaments. An epidemic of irreversible, devastating mental decline will be harder to discount.
Even if parents and fans don't care, there are people who will: trial lawyers and juries. More than 2,000 NFL alumni are already suing the league, accusing it of "actively concealing the risks players faced from repetitive impacts." Colleges and high schools will find legal bills raising the price of an expensive sport. A few big damage awards could upend the sport.
Walter Olson, a liability expert at the Cato Institute who founded the blog Overlawyered, told me, "My reading is that if the same legal principles that are applied to other industries are applied, football either goes away or gets transformed into a very different game."
For the moment, football will go on as always, beloved as always. But like a player who has just had his teeth rattled, it may be at the start of an inexorable journey to an unwanted destination.