The death of a California woman after riding a roller coast over the weekend has cast a spotlight on the safety and risks of thrill rides.
"This was a totally unforeseen, unforeseeable tragedy," says Dr. Lisa Scheinin, a Los Angeles pathologist who is also a thrill-ride enthusiast. "In general, coasters are safe rides."
Pearl Santos, 28, died after riding the Goliath roller coaster at Six Flags Magic Mountain in Valencia, Calif. An autopsy showed evidence of a ruptured aneurysm of the cerebral artery and bleeding near her brain stem.
Backing off from an early report that blamed the woman's death on the roller coaster ride, the Los Angeles County Coroner's Office is planning further tests before it rules on a cause of death.
Andy Gallardo, a spokesman for Magic Mountain, called the coroner's early report "unfortunate," but said there was no malfunction of the roller coaster, which has been temporarily shut down.
"Any medical doctor will tell you roller coasters do not cause aneurysms," he said. "They are pre-existing conditions. This was a very unfortunate occurrence that could have happened anywhere."
Even if thrill rides rarely cause weakened blood vessels to pop, they aren't without risks, said Scheinin, who has ridden more than 700 roller coasters around the world.
Abrupt changes in positive and negative gravitational, or G, forces akin to what aerobatic pilots experience can cause blood to slosh back and forth between the brain and body.
Positive Gs work against the heart's ability to pump blood into the upper extremities, including the brain. The condition first brings loss of visual acuity from lack of oxygen-bearing blood reaching the optic nerves. Then comes gray-out, a fading field of view in which details and colors wash out. Gray-out is followed by blackout, in which vision is lost completely. If high Gs persist, unconsciousness follows.
Goliath, for example, hits 4.5 positive Gs, about the limit most people can tolerate before they begin to black out.
Most riders have some difficulty repositioning their limbs at 2 Gs and their movements are a bit clumsier. At 3 Gs and 4 Gs, movements become difficult.
Negative Gs have the opposite effect. Blood pools in the head, causing the face to feel flushed. Most thrill rides don't push much past that point to avoid causing a reddening of vision that pilots know as "red out" and an uncomfortable eye-popping sensation.
"Goliath is an intense but nice ride," Scheinin said. "But there are others out there that are more extreme. And I'm not just talking coasters, but things like space shots and turbo drops, which can create extreme Gs."
Hard-core coaster fans gripe that some of the new extreme machines no longer are fun to ride. The most infamous reach speeds up to 100 mph, plunge 300-400 feet nearly straight down and twirl riders inverted eight times in 40 seconds.
Others feature sudden jolts and violent jerking - especially bumpy wooden coasters - that can throw out a weak back or even bash ears repeatedly against a ride's horse-collar restraints.
"This is becoming a disturbing trend," Scheinin said.
Even so, instances of people dying during or shortly after a roller coaster ride are extremely rare, Scheinin said.
"When you consider the many millions who ride them each year, serious injuries or deaths represent a small fraction of 1 percent," she said.
One injury case involved a 64-year-old Canadian man who took 11 coaster rides in one day. He had to stop because of a bad headache. The pain persisted, and medical tests several days later showed he had a pool of blood trapped between the brain and skull.
In another well-known case, a healthy 24-year-old woman who had ridden several coasters at a Japanese amusement park began to suffer headaches. After two months a scan showed the woman had a brain hemorrhage.
"There may be an association, but after two months it's too iffy to prove it," Scheinin said. "We don't know if she had pre-existing risk factors."
Some researchers have expressed concern that G-forces - or up-and-down and back-and-forth motions of faster, steeper new coasters - may be strong enough to cause many more brain injuries in the future.
Given the potential risks, however slight, Scheinin said, anyone considering taking a thrill ride should think twice and heed warnings each attraction posts prominently:
No one with a significant known heart disease, a neck or back problem, or who is pregnant should ride, Scheinin says.
"If you have a bad heart and get on a coaster, how is an attendant going to know?" she asked. "It's bad to hold a park responsible for a patron's poor judgment."