June 7, 2007 -- If the goal of an animated promo for the London 2012 Olympics logo was to elicit a strong response from audiences, it worked.
But it's hard to imagine that the creators had seizures -- and a subsequent public outcry -- in mind.
The vividly animated footage promoting the logo was removed from the organizers' Web site Tuesday amid concern that it could trigger epileptic fits, British press reported.
Even though all reported cases of seizures occurred in the U.K. and the clip has since been pulled from broadcast, the case has revived some neurologists' claims that not enough is being done to protect those with photosensitivity -- a vulnerability to light-induced seizures -- in the United States from similar threats.
"The issue is that in the U.S., television shows and video games are not screened for these factors," said Dr. Giuseppe Erba, professor of neurology at the University of Rochester. "There is a population at risk for this, so it is a public health problem of some extent."
"Although only a small percent of the general population has this problem, television is viewed by millions, and some might respond with a seizure," said Dr. Anthony Murro, neurology professor at the Medical College of Georgia.
To See Is to Seize
Denise Pease, 54, said she never knew about photosensitivity disorder until it became a very real part of her life.
After recovering from cognitive problems due to a traumatic brain injury she suffered in a car accident 12 years ago, she said that she began experiencing lost time and confusion at work.
"Sometimes I would be sending e-mails, and there would be spurts of time where I would just be out of it," she told ABC News.
She finally realized that her desk was situated directly below a ceiling fan that created a "strobe" effect from the fluorescent lights above. Pease's neurologist later confirmed that this flashing light was likely responsible for her nonviolent -- albeit debilitating -- seizures.
Pease, now on the board of directors of the Epilepsy Foundation in New York, said she now takes special care in choosing how she views movies and television shows, as her photosensitivity puts her at risk of seizures from some of the images and sequences that are shown.
And she said that, like her, many of those with photosensitivity may not even be aware that they are vulnerable to these seizures.
"I would question the statement that it affects only a very few," she said. "It may affect a larger section of the population who may not even be aware that they are photosensitive."
Indeed, Dr. Imad Najm and Dr. Andreas Alexopoulos of the Cleveland Clinic Epilepsy Center estimate that photosensitivity, an abnormal brain activity response to light or pattern stimulation, is only known to occur in 0.3 to 3 percent of the population.
But the risk of such seizures increases dramatically in those with epilepsy. Najm and Alexopoulos report people with known diagnosis of epilepsy have a 2 to 14 percent chance of having seizures precipitated by light or pattern.
And the effects of such a seizure can be traumatic -- especially since some, like Pease, may not even know they are at risk until it happens.
"Flashing lights are a frequent trigger of epileptic seizures in people who are known to be epileptic and in others who never had a seizure," said Najm, who is director of the Epilepsy Center.
An infamous example of this phenomenon was seen in Japan in 1997, when more than 600 school-aged children visited hospitals with nausea and seizures thought to be caused by exposure to colorful flashes of light shown in a televised episode of the cartoon "Pokémon."
In what has since been referred to among some neurologists as "the Pokémon incident," Najm and Alexopoulos note that only about 1 in 4 children who had a seizure during the cartoon had previously experienced a seizure.
And it's not just television. Some physicians also point toward video games as a possible trigger.
"Every year around the holidays, a small number of kids open their video games and have a seizure when they play," said Dr. Shlomo Shinnar, director of the Comprehensive Epilepsy Management Center at the Albert Einstein College of Medicine's Montefiore Medical Center.
Shinnar adds that the Nintendo systems now even carry a warning that indicates this potential hazard.
An 'Electrical Storm' in the Brain
Though the exact mechanism of a light-induced seizure is not yet completely understood, researchers say barrages of light stimuli could create a kind of overload in the brain.
"It seems that when a light stimulus is applied, it does lead to the activation of more neurons than should be in the brain at once, and therefore a large area of the brain is activated all at once," Najm said. "This 'electrical brain storm' is associated with the shaking and other manifestations that we typically see in seizures, or 'fits.'"
Certain color combinations, such as red and blue, seem to be more risky than others when it comes to causing seizures. The frequency of the "flicker" emitted by the images, as well as contrast, can also play a role.
Erba said that in fact much is known about photosensitivity, and professor Graham Harding, the scientist who helped raise the alarm about the 2012 Olympics logo promo, did so after using a test he developed to screen potentially risky images on TV.
But while this test is available, regulators in the United States have not yet implemented its use.
"The government here does not seem to be interested," Erba said. "What bothers me is that this sense of social responsibility is lacking in this country."
Avoiding Pattern-Related Seizures
Fortunately, there are steps that photosensitive individuals can take to lessen their chances of an episode. Below are a few of the guidelines suggested by the Epilepsy Foundation:
Only watch television in a well-lit room.
Sit as far back from the screen as possible.
Avoid watching TV for long periods of time.
Know the warning signs. Such signs before such seizures are not always consistent, but commonly photic-induced seizures can start with a myoclonic jerk -- a very brief, rapid jerk of the body that may occur in the arms, legs or face.
If strange or unusual feelings or body jerks develop, turn off your television or remove yourself from the source of the light patterns immediately.
If you cannot get away from the source of the disturbance immediately, cover one eye to reduce your exposure.
For more information, visit the Epilepsy Foundation Web site at www.epilepsyfoundation.org.