Janet Jackson Janet Jackson

No, it wasn't poor ticket sales that caused Janet Jackson to nix a string of tour dates. It was, in fact, an actual illness.

The singer was suffering from vestibular migraines described as "migraine-associated vertigo" for which she is receiving treatment, her manager revealed to E! Online, and is expected to finally get back on stage Wednesday night in Washington, D.C.

"Janet wanted very much to resume her tour so as not to disappoint her fans, but she continued to suffer from vertigo and could not perform," manager Kenneth Crear said. "She's a world-class entertainer and needs to be at the top of her game to give her fans the show they expect.She's feeling much better and is ready to hit the road again to finish the tour."

Jackson, 42, has postponed nine shows on her Rock Witchu tour since falling ill shortly before her Montreal show on Sept. 29. All dates are expected to be rescheduled.