A 28-year-old snowboarder who fell "quite hard on her buttocks" during a beginner's run at Keystone Ski Resort died from irreversible brain damage, the Summit County Coroner concluded.Jennifer Ash, of Indianapolis, was snowboarding on the Ina's Way run when she fell March 16. The Ski Patrol was not notified because her fall was not deemed serious.After her fall she continued to snowboard and did not complain of any pain, nor any headaches, the coroner said.However, about three hours later her friends drove her to Summit Medical Center where she was evaluated. A CT scan was negative but doctors in Summit County suspected a stroke, considering how she fell, so she was airlifted to St. Anthony's Central Hospital in Denver. There, another CT scan was negative.However, about 11 hours after her fall the injury manifested itself and an MRI confirmed she had a stroke, Coroner Joanne L. Richardson said.She had suffered "vertebral artery dissection" or a tear in a vertebral artery, which resulted in a "basilar artery stroke and brain damage," Richardson said.Ash had irreversible brain damage from the stroke and was pronounced brain-dead four days later, on March 23. The manner of her death has been ruled accidental."The decedent was not wearing a helmet, although it would not have assisted in this case," Richardson said in her report."The mechanism of this injury is best described as a shock wave that went all the way up her spine and whipped her head either side to side or hyperextended it. What this does to the vertebral artery is stretch it and it becomes thinned. It is also seen in T-bone car accidents. It can take several hours or days to manifest. The vessels in this part of the brain are highly turbulant with blood flow so a narrowed artery caused by the stretching causes a clot to form and travel up to the basilar artery. This, in turn, causes a stroke," Richardson said. "Just how rare the injury is, I can't say. I've not ever seen one before but neurologists do see it quite often.""We are sorry to hear about her death. The resort extends our deepest sympathies to her friends and family," said Keystone spokeswoman Kate Lessman.Lessman said the resort wasn't told of the injury on the mountain and didn't know about Ash's injury until Friday, when the coroner released her report."Usually, when there's an incident on the mountain, the people in the party will call the ski patrol. The ski patrol was not contacted in this case," Lessman said.Ash had arrived in Colorado the day before with friends for vacation. She was a pharmacy professor at Butler University in Indianapolis.She received her doctorate in pharmacy from Butler in 2003, and was in her first academic year on faculty at Butler's College of Pharmacy and Health Sciences, according to Butler spokeswoman Courtney Tuell.