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Alex Trebek Had Brain Surgery to Treat a Subdural Hematoma. Here’s What That Is

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Longtime Jeopardy! host Alex Trebek told fans on Thursday he’s recovering from brain surgery to correct a “slight medical problem” he suffered during the show’s holiday break: a subdural hematoma, or blood clots on the brain.

The 77-year-old host, who had a mild heart attack in 2012 and a knee replacement in 2015, thanked and reassured the show’s fanbase in a video posted to its YouTube page. “The prognosis is excellent, and I expect to be back in the studio taping more Jeopardy! programs very, very soon,” he said. “And I want to thank all of you for your concern.”

Here’s what you should know about Trebek’s diagnosis.

What is a subdural hematoma?

A subdural hematoma is a pooling of blood between the dura — the sturdy, protective layer of tissue encasing the brain — and the surface of the brain itself, according to the U.S. National Library of Medicine. Subdural hematomas happen when blood vessels, often veins, burst in this area, forming a collection of blood that presses on the brain, according to the Mayo Clinic.

What causes a subdural hematoma?

While this type of brain bleed is occasionally random, a subdural hematoma most often follows a traumatic head injury, such as a fall, collision or accident, according to the U.S. National Library of Medicine. Trebek told fans that his was the result of a fall that occurred a couple months ago.

What are the symptoms of a subdural hematoma?

Subdural hematoma symptoms typically include headache, vomiting, drowsiness and eventual loss of consciousness, dizziness, confusion, differing pupil size and slurred speech, according to the Mayo Clinic. Symptoms may appear immediately, but in some cases, they can take weeks or even months to manifest.

How serious is a subdural hematoma?

They can be fatal, but a person’s prognosis depends on multiple factors, from the size and severity of the bleed to how quickly treatment is sought, the U.S. National Library of Medicine says. Some subdural hematomas are reversed by drilling a hole in the skull to drain blood and relieve pressure on the brain, while others require more invasive brain surgery. Trebek did not comment on the severity of his case or his treatment plan.

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Write to Jamie Ducharme at jamie.ducharme@time.com