What is glioma? Walking Dead star dies of rare cancer

Actress Kelley Mack, best known for her roles on “The Walking Dead” and “Chicago Med,” has died at age 33 after a seven-month battle with an aggressive form of cancer.

In January, the rising star was diagnosed with diffuse midline glioma, a fast-growing tumor that attacks the central nervous system. The illness surfaced just months after she began experiencing pain she believed was from a simple back injury.

Mack, born Kelley Klebenow, “passed peacefully” on August 2 in her hometown of Cincinnati, Ohio, with her mother and aunt by her side, her sister shared in an Instagram post on Tuesday.

Gliomas are considered rare, with just six cases diagnosed per 100,000 people each year in the US. 

Still, they are the most common type of tumor that begins in the brain or spinal cord, rather than spreading there from other parts of the body.

Here’s everything you need to know about the potentially life-threatening condition.

What is a glioma?

It’s a type of tumor that forms in the brain or spinal cord when glial cells — which normally support and protect neurons — begin to grow uncontrollably, according to the Cleveland Clinic.

There are different types of gliomas, classified by the specific kind of glial cell they originate from. Mack had an astrocytoma, a tumor that develops from astrocytes, the star-shaped glial cells in the brain and spinal cord, according to a blog on health platform Caringbridge about her health journey.

Gliomas are often cancerous, but not always. They can be life-threatening, especially when tumors grow near critical brain areas, making treatment more difficult and potentially affecting neurological functions.

What causes gliomas?

Doctors still aren’t sure, but they believe it begins when cells in the brain or spinal cord develop changes in their DNA that make them multiply out of control.

It’s possible to inherit these genetic mutations from your parents, but they can also happen spontaneously at any point in your life.

What are the symptoms?

Symptoms can vary widely depending on the tumor’s size and location, according to the Mayo Clinic.

Common signs include:

• Headaches, especially those that are worst in the morning
• Nausea and vomiting
• Confusion or trouble thinking clearly
• Memory loss
• Personality changes or irritability
• Vision problems like blurred vision, double vision, or loss of peripheral vision
• Speech difficulties
• Seizures, particularly in someone with no prior history
• Balance issues such as dizziness or trouble walking
• Muscle weakness or paralysis

For Mack, the first warning sign came in October 2024, when she developed persistent lower back pain.

Assuming it was a slipped disc, she brushed it off — until she started experiencing “neuropathic itching” in her right leg, a strange nerve-related sensation that’s not caused by a skin condition.

“Then, the shooting pains in my legs and back began, which resulted in me having to sleep in a recliner for a month because laying down was too painful,” she wrote in an Instagram post on January 3.

On the night before Thanksgiving, an emergency MRI revealed a mass in her spinal cord. A biopsy later confirmed it was glioma.

How do you treat gliomas?

Treatment varies depending on the tumor’s size, location and how quickly it’s growing, according to Johns Hopkins Medicine.

First, doctors usually perform a biopsy to remove a small tissue sample for testing before starting treatment.

Surgery typically comes next, with doctors aiming to remove as much of the tumor as possible without harming the surrounding healthy brain or spinal cord tissue.

Radiation and chemotherapy usually follow surgery. In some cases, when the tumor is located in areas too risky for surgery, these treatments may be the first option.

After her MRI, Mack had a biopsy on the mass in her spinal cord, which caused her to lose movement in her right leg and most of her left leg, requiring her to use a walker and wheelchair to get around.

“It has been a very emotional and challenging time, truly testing my mental fortitude, faith, and physical strength,” she wrote on social media.

Following surgery, Mack underwent radiation treatment in Cincinnati and shared regular updates about her progress online. In March, she posted a video of herself walking up stairs, calling it “a big deal for me.”

Who’s at risk for glioma?

While the exact cause of glioma remains unknown, researchers have identified certain groups who may be at higher risk.

Gliomas can develop at any age but are most common in adults between 45 and 65 years old.

People exposed to high doses of ionizing radiation — such as during certain cancer treatments — may also have an increased risk.

Though rare, gliomas can sometimes run in families. However, more research is needed to determine if and how this risk is passed from parents to children.

Currently, there are no known ways to prevent glioma.