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WHAT HAPPENED TO KELLY?

"A seizure is abnormal electrical activity in the brain, where nerve cells start firing at the same time," says Dr. Privitera. Though they're still not sure of the cause, Osbourne's doctors gave her medication to prevent a recurrence.

March 7 began like any other day on the set of the E! talk show Fashion Police, with Joan Rivers, her daughter Melissa and Kelly Osbourne preparing to banter about Hollywood fashion victors and victims. But as time wore on, Osbourne grew pale. "We said, 'Let's get her a sip of water,' " Melissa Rivers told Entertainment Tonight. "My mom made a joke: 'Maybe you're pregnant!'"

Soon nobody was laughing, as Osbourne, 28, fell to the floor in the throes of a seizure. Days later the cause of the episode still had not been identified, and the reality star, who had finally seemed to be in a stable place in her life after battling drug addiction and struggling with her weight for years, remained hospitalized at Cedars-Sinai in L.A. to undergo tests. "My life is now like an episode of House," she tweeted March 11. "[There's a] look of fear in everyone's eyes."

Ultimately doctors concluded that the incident was likely a onetime freak episode, and Osbourne was discharged after five days with a clean bill of health. "A substantial number of people have a single seizure and never have one again," says Dr. Michael Privitera, director of the Epilepsy Center at the University of Cincinnati, adding that sleep deprivation and other factors can be triggers. The cause of her seizure may still be unknown, but Osbourne, for one, is ready to move on. Says her rep: "She is looking forward to getting back to business–and life –as usual."