Reports of the 'Breaking Dawn' birth scene spurring seizures in Twilight fans have landed photosensitive epilepsy in the spotlight.
Not since the Pokemon incident of 1997, in which more than 700 Japanese cartoon viewers were hospitalized, have strobe-light-induced seizures garnered so much attention.
"There are many, many things that can induce seizures," said Dr. Dan Lowenstein, director of the University of California, San Francisco Epilepsy Center. "Certainly flashing lights are one trigger."
Besides blood, the birth of Edward and Bella's baby boasts flashing white light. Those flashes, at just the right frequency, can cause neurons in the brain to start firing in synch -- a deviation from their usual chaos.
"When the brain is functioning normally, there are neurons firing all over the place," said Lowenstein. "During a seizure, there's an abnormal synchronization that we don't usually have."
That synchrony, which starts in the visual part of the brain, can quickly spread, causing a seizure.
"We routinely flash lights in front of patients' eyes during electroencephalogram or EEG testing because it's known that sometimes flashing lights can trigger seizures," said Dr. Robert Laureno, chair of neurology at Washington Hospital Center in Washington, D.C.
Laureno, who said he was dragged to "Breaking Dawn" by his wife, was surprised to hear the scene had caused seizures.
"Personally, I don't even remember the flashing lights," he said. He does, however, remember the blood. In fact, his wife's friend, a nurse, had to help a fellow Twilight fan who fainted during the gory scene.
"It appears there's been all kinds of loss of consciousness associated with this movie," said Laureno.
The blood may even be causing the apparent seizures, according to Dr. Orrin Devinsky, director of the NYU Langone Comprehensive Epilepsy Center.
"For some people, fainting mimics seizures," said Devinsky. "And for a very small minority of people, fainting can induce a full-blown seizure."
People with epilepsy are particularly prone to seizures. For them, many things can trigger the abnormal brain firing, including fatigue, alcohol, infections and certain medications. In extremely rare cases, activities like math and reading as well as certain songs or voices have triggered seizures.
"I once saw a patient who only had seizures when he heard a particular Rod Stewart song," said Devinsky, although he couldn't remember the name of the song.
There was also a famous case of a woman who had seizures in response to "Entertainment Tonight" host Mary Hart's voice.
Devinsky, who saw "Breaking Dawn" with his daughters, was surprised to hear it may be inducing seizures.
Although they can be scary, isolated seizures are not typically dangerous unless the person falls. Viewers who start to feel unwell during the birth scene should stay seated and cover their eyes with their hands or clothing.
"The retina is still sensitive to flashing light even with the eyelids closed," said Dr. Juliann Paolicchi, director of pediatric epilepsy at Vanderbilt University Medical Center.
Paolicchi said most movies steer clear of flashing frequencies known to spur seizures.
"The filmmakers may want to add a disclaimer or modify the flash frequency," she said.
But some flashing lights are hard to avoid.
"In spring and fall it's common for patients to have seizures while driving on the road because the sunlight flickers through the trees," said Paolicchi. Evenly-spaced reflective pylons can also trigger seizures, she said.
The odds of having photosensitive epilepsy is up to 40 percent higher in people who have siblings with the disorder -- a sign of its strong genetic roots.
"There's a large group of people working together to try to understand the genetic basis of epilepsy," said Lowenstein, who is part of the Epilepsy Phenone/Genome Project -- a study sponsored by the National Institute of Neurological Disorders and Stroke. Roughly 4,000 patients have joined the study, which aims to improve care through better understanding of the disorder. The researchers ultimately hope to get to 5,000 patients.