A publicist says it was a rare form of migraines called vestibular migraines, or migraine associated with vertigo.
"It feels so good to be back after being down just a little bit," Jackson told the crowd at Verizon Center in Washington, D.C., Wednesday.
"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," said Jackson's manager, Kenneth Crear, in a statement Tuesday. Jackson's agents said she was not available for comment.
Most people know migraines come with pain and nausea, but migraine with vertigo?
Doctors say Jackson's type of migraine is well-documented, but it only affects 3 to 5 percent of the general population. Why it happens remains somewhat of mystery.
"It's a variant of migraine headaches, but the pain it not so severe," said Dr. Susan Broner, an attending physician, neurologist and headache specialist at the Headache Institute at Roosevelt Hospital in New York, N.Y.
"We don't have strict diagnosis criteria for it yet & and we don't have any hard evidence of why people experience the dizziness," she said. "But we are interested in studying this."
In the past, doctors thought dizziness was figuratively in the patient's head, usually a woman's head.
"Twenty to 30 years ago this used to be called floating women's syndrome; [doctors] used to consider it a psychiatric or neurotic syndrome," said Dr. Steven D. Rauch, a professor of otology and laryngology at Harvard Medical School and a doctor at Massachusetts Eye and Ear in Boston.
Rauch said the symptoms of vestibular migraines may mimic the spinning in classic vertigo, or patients might just constantly feel off balance.
"Patients feel like they have no balance, or they feel like they're rocking on a boat all the time, like you're lost in space," said Rauch.
Those symptoms might sound exactly like vertigo to a lay person, but Lisa Haven, executive director of the Vestibular Disorders Association, said there's a clear difference.
"First of all, vertigo is a symptom; it's not a disorder," said Haven. A common cause of vertigo is something called Benign Paroxysmal Positional Vertigo, or BPPV.
Haven said patients often get BPPV with age or a head injury such as whiplash. In BPPV, the tiny particles in the inner ear that tell nerve cells which way is down become dislodged. Like a maraca, the loose particles move with any motion of the body confusing the nerves in the ear and the brain.
But with migraine-associated vertigo, the tiny particles are not the problem. Instead, Rauch said, doctors are redefining what it is to have a migraine.
"Migraine was all about headache, and now we realize the headache is part of the greater spectrum," said Rauch. "The modern migraine is this global distortion, and usually it's an intensification of a sensation."
That sensation could be pain, but it also could be vision, sound, smell and motion. But, according to Rauch, painkillers for migraines won't help the symptom of vertigo. Patients who have vertigo with migraines can only prevent migraines through lifestyle changes and carefully adjusted medication.
Just as all the other sensitivity during a migraine can be severe, so too can the problems with motion.
"It can be very disabling until it's brought under control, I really can believe she's unable to meet her obligations," said Rauch.
Rauch guessed Jackson would have a particularly challenging time managing her symptoms on tour, since preventing migraines requires a regular sleep, eating and exercise schedules.
But Jackson's publicist implied that everything was under control.
"She's a world-class entertainer and needs to be at the top of her game to give her fans the show they expect," said Crear, Janet's publicist. "She's feeling much better and is ready to hit the road again to finish the tour."