Maksim Chmerkovskiy, Melissa Gilbert Maksim Chmerkovskiy, Melissa Gilbert

Just minutes after she danced an intense paso doble on Monday night's Dancing With the Stars, actress Melissa Gilbert was taken out of the ballroom on a stretcher. She was absent for the rest of the show. The 47-year-old star, who has been celebrating her recovery from major back surgery almost two years ago, hit the back of her head during a dramatic drop in the middle of the routine.

"One of the tricks she did, she hit her head," says pro Val Chmerkovskiy, brother of Gilbert's partner, pro Maksim Chmerkovskiy. "But there was adrenaline, so she recovered and everything was good. She came upstairs [to the Dancing skybox, where she did her post-dance interview], she sat down, and then she started getting really dizzy. When there are concussion symptoms, you want to check that out right away."

"We're worried because she's actually had back and neck injuries," says pro Derek Hough, moments after the show. Hough has had the experience of partnering another star recovering from major spine surgery: Season 11 winner Jennifer Grey. "For me, I know when I [danced with] Jennifer, I was terrified. If she ever even grabbed her neck, it was like, 'Oh, my gosh.' So for Melissa to be on a stretcher is pretty terrifying."

Gilbert, who is best known for playing Laura Ingalls Wilder on the long-running hit series, Little House On The Prairie, hurt her back when she fell during the national tour of the Little House musical in 2010. She says she didn't know she had been seriously hurt until the tour was over and she went in for treatment of a ruptured disk. During preparation for that outpatient surgery, doctors discovered that she had actually broken her back and had a cracked vertebrae that would require major surgery and the insertion of permanent titanium screws in her spine. The recovery took more than a year.

Just last week, Gilbert insisted that her back felt fine. "You don't have to worry about it," she said. "It's all metal and fused bone. The rest of [my body] is up for grabs. My back doesn't hurt at all, not as much as my feet hurt right now."

But the show isn't taking any chances. "We wanted her to get checked out," says an ABC rep. "We'll have a statement on her condition [Tuesday] on the show."

Maksim Chmerkovskiy accompanied Gilbert to the hospital. His brother tried to put a lighter spin on the moment. At the end of the paso doble, Gilbert had stood up, victorious, having "killed" her partner, Maks, in a dance that is supposed to represent a traditional Spanish bull fight. "That's what happens when you try to kill a Chmerkovskiy," says Val. "You go to the hospital."

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