"Please pray," Julianne wrote on her Instagram Story the same day, "and send all your love, healing and light to Hayley and Derek."
The dancing pro also expressed her gratitude on behalf of the Houghs for all the support they've received, adding, "Thank you from the depths of our families hearts!"
Following Derek and Hayley's Dec. 6 Symphony of Dance tour performance in Washington, D.C., she became "disoriented" and was transported to a local hospital, he wrote on Instagram.
She was diagnosed with a cranial hematoma—collection of blood within the skull—from a burst blood vessel, which "required an emergency craniectomy," according to the DWTS judge. "She is in stable condition."
The operation typically involves removing part of the skull to alleviate pressure on the brain.
"Sending all my love and energy for a speedy recovery!!!" wrote DWTS alum Alyson Hannigan, while the show's cohost Alfonso Ribeiro noted, "Sending you all the love I have in my soul. Prayers for a speedy recovery."
Derek and Hayley—who met through Julianne's tour in 2014—tied the knot in August during a private ceremony held in a redwood forest in Monterey County, Calif.