Even doctors can struggle to diagnose concussions

On June 23rd a court case brought by more than 200 rugby-union players kicked off in London. The players claim the sport’s administrators failed in the past to protect them from repeated concussions and blows to the head that, they say, have left them with lifelong brain injuries and early-onset dementia.

Concussions and other forms of brain injury have become one of the biggest worries in sports from soccer to ice hockey. In America the National Football League, which governs American football, has had to pay out hundreds of millions of dollars to brain-damaged players.