WEDNESDAY, July 21 (HealthDayNews) -- Five and a half years ago, Japanese parents became alarmed when some children started having seizures while watching the popular television cartoon show Pokémon.
Although a strobe light effect in the program was implicated as a source of the seizures, which also affected some adults, doctors didn't know whether those who had the seizures would continue to have them, which would indicate undiagnosed epilepsy, or whether it was simply a one-time phenomenon.
A study in the July 22 issue of the New England Journal of Medicine seeks to answer that question by following up on most of the people who had seizures as a result of the program.
Many who had subsequent seizures had previously been diagnosed with epilepsy, researchers found, and others would later develop it -- and probably would have even if they hadn't seen the program.
The series, known as Pocket Monster in Japan, was very popular in that country at the time. In December 1997, one episode of the show triggered seizures in more than 100 children and adults.
"The seizures were considered to be induced by a four-second scene, in which red and blue light alternated at 12 hertz," said one of the study's authors, Dr. Akihisha Okumura. One hertz is a frequency equal to a cycle per second.
As a result of the incident, new production guidelines, including color restrictions, were implemented in Japan, according to Okumura, a pediatrician at Nagoya University Graduate School of Medicine in Aichi.
While the mechanism that causes such seizures to occur isn't clear, photo-stimulation, such as with strobe lights, can elicit seizures, explained Dr. Howard Weiner, a pediatric neurosurgeon at New York University Medical Center. Other factors that can trigger seizures include sleep deprivation, head trauma, significant stress, and hormonal influences, he added.
For this study, the Japanese researchers sent questionnaires to the doctors who treated 103 people for Pokémon seizures. Detailed medical information was available for 91.
Twenty-four from this group had been diagnosed with epilepsy before having the seizure. Twelve of them hadn't had a seizure since that time, while the other twelve did have at least one more seizure after the television program-induced fit.
Sixty-seven had no history of seizures. Of this group, only 13 went on to have repeated seizures. The average time between the seizures was 37 months. Ten of the children who had repeated seizures were diagnosed with either juvenile myoclonic epilepsy or with generalized epilepsy.
Children who had a history of seizures from high fevers, and children who were under the age of 12 at the time of the Pokémon seizure, were more likely to have a repeated seizure.
"In our study, only 25 percent of the patients had recurrent unevoked seizures. When limited to the patients in the no-epilepsy group, the rate of recurrence was 19 percent," said Okumura.
"Children with epilepsy are infrequent, even if they had a seizure induced by Pokémon. The scene responsible for the Pokémon seizures was extremely provocative, and such scenes are rare in the usual environment," Okumura added.
Weiner said this was an interesting study that identified different risk profiles for epilepsy from a photo-stimulating trigger. But he added that he didn't think parents needed to be concerned about kids watching the TV show or playing the video games.
"Video games don't equal seizures. If your child has a history of seizures, consult your physician to see if it's a risk, but I wouldn't shy away from playing Pokémon, and I don't think most neurologists are limiting video games, either," said Weiner.
To learn more about epilepsy, visit the National Institute of Neurological Disorders and Stroke.