Perhaps "DUH!!!!" It shouldn't take a medical degree to figure this one out.
local6.com - News - Doctor Bans Boy From Playstation To Stop Head Twitching: "A 9-year-old boy in California who suffered from uncontrollable head jerking movements after long hours of video game playing stopped the twitching after his doctor banned him from playing PlayStation, according to a report. Nicholas Lavin said that he played PlayStation constantly over the holidays at his home in San Diego and began to notice that his head would jerk back and forth.'I would do funny things with my head,' Nicholas said.
Lavin's mother said her son began to twitch so badly that she took him to the family's pediatrician.The doctor told her he was not allowed to play PlayStation anymore. Once he stopped playing PlayStation, the twitching stopped, according to the report.
'All the head jerking is gone and his eyes are completely back to normal,' Barbara Lavin said. 'I think it's a direct connection to the PlayStation and the amount of time he spent on it.'"