On Thursday, December 7, Derek Hough shared a scary health update that his wife, Hayley Erbert, had just undergone emergency brain surgery.

“At the end of last night’s tour performance in Washington, D.C., my wife Hayley became disoriented and was taken to the hospital,” he wrote in an Instagram post. Derek said that Hayley needed to have an “emergency craniectomy,” but is now in stable condition.

He also thanked the first responders and medical personnel who helped Hayley and asked for “prayers and positivity” from fans. Of course, the couple’s friends were quick to show support. “Prayers and love for you both !!!” Jenna Dewan commented, while Derek’s sister Julianne Hough reposted his announcement on her own Instagram Story saying, “Please pray and send all your love, healing and light to Hayley and Derek.” She continued, “Thank you from the depths of our families hearts!”

Hayley’s health emergency has raised a lot of questions. Specifically, what is a craniectomy and how serious is this surgery for Hayley? Here’s what you need to know.

Why did Hayley have emergency craniectomy?

In his post, Derek explained that Hayley was diagnosed with something called a cranial hematoma that resulted from a burst blood vessel, which usually occurs in the skull or brain.

This diagnosis prompted an emergency craniectomy at a hospital. However, aside from saying she was doing okay now, Derek did not share any other details about Hayley’s surgery or health condition.

What is a cranial hematoma and how is it caused?

An intracranial hematoma is a collection of blood in the skull, and it’s usually caused by a blood vessel that bursts in the brain, according to the Mayo Clinic. With a cranial hematoma, blood may collect in the brain tissue or underneath the skull and press on the brain.

This is a potentially life-threatening medical emergency and usually requires immediate treatment, per the Mayo Clinic.

Usually, intracranial hematomas are caused by head injuries or major traumas, like a car accident or a hard fall.

What is a craniectomy?

A craniectomy is a type of brain surgery that relieves pressure on your brain, the Cleveland Clinic says. During the procedure, a portion of the skull is removed. Patients usually need to wear a helmet to protect their skull after surgery. (A follow-up procedure called a cranioplasty replaces the removed section of skull.)

How serious is a craniectomy?

This is major brain surgery, per the Cleveland Clinic, so it’s very serious. Pressure in the skull from swelling or extra fluid is life-threatening or can cause brain damage because there isn’t a lot of room between the brain and skull, the Cleveland Clinic explains, noting that any internal pressure can impact how your brain functions.

This explains why Hayley started feeling “disoriented” at the end of the performance.

What happens during a craniectomy?

During the procedure—which is usually an emergency surgery—the following will happen, per the Cleveland Clinic:

• Medical staff shave your hair and clean the area of your head near the incision site.
• An incision is cut into your skin.
• Muscles or tissues will be moved away to expose the scalp.
• A drill is then used to make holes in the skull.
• Doctors cut between each hole to remove a piece of the skull.
• From there, doctors treat the thing causing brain pressure.
• The open part of the skull is then covered with mesh material.
• The skin tissue and muscles are moved back into place.
• The incision is closed with staples or sutures.

Derek hasn’t shared any updates on Hayley’s condition or what will happen with his tour from here. But everyone is hoping she has a speedy recovery. Sending good thoughts your way, Hayley!

Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.