Irish jockey JT McNamara was airlifted to hospital after being seriously injured in a fall at the Cheltenham Festival on Thursday.
Dr Adrian McGoldrick, chief medical officer of the Irish Turf Club, said the 37-year-old amateur jockey was placed in a medically-induced coma and taken by helicopter to Frenchay Hospital in Bristol.
The rider came off Galaxy Rock following a fall at the first fence in the Fulke Walwyn Kim Muir Chase, the next-to-last race of the festival's third day.
The Frenchay Hospital has a specialist center for head injuries.
''He has been put in an induced coma and airlifted to the regional spine unit where he will be scanned,'' McGoldrick told the Racing Post.
Earlier Thursday, racehorse Matuhi was destroyed after suffering a serious spinal injury in a fall at the last fence in the Byrne Group Plate.
The events overshadowed a day on which Solwhit seized on the absence of four-time winner Big Buck's to roar to victory in the World Hurdle, capping a miserable day for the favorites.
Oscar Whisky and Reve de Sivola were expected to dominate the standout race of the festival's third day but Solwhit, a 17-2 shot, found a turn of pace to overtake long-time leader Celestial Halo and win by 2 1/2 lengths.
Big Buck's had won the World Hurdle for the past four years as part of his 18-race winning streak, but isn't competing this season because of a leg injury.
Carrickboy (50-1) and Holywell (25-1) were other outsiders to prosper in winning the Byrne Group Plate and Pertemps Final, respectively. Benefficient (20-1) won the Novices' Chase to start the day.
The 9-year-old Solwhit recently returned from two years out with leg injuries and was tackling three miles (4,800 meters) for the first time, with jockey Paul Carberry aboard only after his intended mount, Monksland, picked up an injury last week.
''We knew he was coming back, but I kind of felt in the last few weeks that it had come together and I was very happy coming here,'' owner Charles Byrnes said.
The win took Ireland's tally to nine for the week and was the first Irish-trained success in the race since Dorans Pride in 1995.