The Worst Case

The NFL has reduced some of the danger by outlawing head slaps and instituting rules to protect quarterbacks. But these measures are offset by increases in the size and speed of players, who in turn produce ever more violent collisions, and by heads bouncing off artificial turf. "That carpeted concrete is chaos," says Cantu.

After suffering concussions this season, the 49ers" Wallace and the Buffalo Bills' Beebe have turned to the ProCap, a polyurethane shell that attaches to the top part of the helmet. In laboratory tests the ProCap has reduced g-forces transmitted to the skull by an average of 30%, but a preliminary study by Torg and by Gary J. Stilwell at the University of Pennsylvania's Sports Medicine Center was inconclusive about ProCap's effectiveness in reducing the risk of concussion.

The virtual absence of brain testing is one of "the things that lead to the current problems," Kelly says. "I don't think most athletes want to know the effect an injury has had or the amount they've recovered, and I don't think most pro or college teams want their athletes scrutinized that way. They're not in the business of identifying worrisome neurological problems.

"I hope another player doesn't have to die before all this is taken seriously."