The mother of dragons recently opened up about brain aneurysms. Actress Emilia Clarke says she had life-threatening cerebral aneurysms in 2011 and 2013, while playing Daenerys Targaryen on HBO’s Game of Thrones.

Now, she says, scans show that “quite a bit” of her brain is “missing.”

Her statement caught a lot of attention, and headlines. But is it accurate? A neurosurgeon explains four facts about brain aneurysms.

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1. A burst aneurysm can permanently damage the brain.

“When an aneurysm ruptures and bleeds into the brain, or into the space around the brain, it is not uncommon to have permanent injury to a part of the brain,” explains Hartford Hospital neurosurgeon Eric Sussman, MD, who specializes in cerebral aneurysm treatment. “Over time, this injured part of the brain can atrophy, or shrink.”

Or, in Clarke’s words, go “missing.”

Recovery depends on which part of the brain is injured.

“In some cases, the brain can rewire its neural circuitry to ‘bypass’ the injured area,” says Dr. Sussman. “That’s why some patients, like Emilia Clarke, can make a remarkable recovery.”

For other patients, the damage occurs in a part of the brain that’s essential to neurological function. When that happens, it can lead to permanent disability or death.

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2. You can live your entire life with a brain aneurysm and not know it.

Still, for every patient like Emilia Clarke who needs surgery for a brain aneurysm, there are others who are simply monitored by their doctor, or who live with an aneurysm without ever realizing it.

That’s because not every aneurysm causes a brain bleed. A brain aneurysm is a weak or thin spot on an artery that balloons out and fills with blood. Some are so small, they don’t produce any symptoms at all.

Patients who are diagnosed with an unruptured brain aneurysm can go a long time without treatment. But at minimum, they need regular imaging to make sure the aneurysm isn’t growing or changing.

The problem is that some aneurysms will bleed. Although this only occurs in a minority of patients, the effects can be devastating,” says Dr. Sussman. “It’s essential that these patients be under the watchful care of a physician who specializes in brain aneurysm treatment.”

3. When a brain aneurysm ruptures, it often causes a severe, sudden headache.

When Clarke’s aneurysm ruptured in 2011 during a workout session, “I immediately felt as though an elastic band were squeezing my brain,” she later wrote in the New Yorker. She ran to the bathroom and vomited, as “the pain — shooting, stabbing, constricting pain — was getting worse.”

“This isn’t just your run of the mill headache,” says Dr. Sussman. “Patients almost uniformly describe it as the worst headache they have ever had.”

Ruptured aneurysms can cause a range of additional symptoms too, including:

  • Weakness
  • Numbness
  • Facial droop
  • Seizure
  • Loss of consciousness
  • Coma

4. With care and luck, some patients fully recover.

Clarke ultimately had two surgeries to treat her brain aneurysms.

Immediately after the first, she said she couldn’t remember her own name. For months after both, she dealt with pain, vision problems and difficulty speaking and writing.

Now, she’s fully recovered. “In the years since my second surgery I have healed beyond my most unreasonable hopes,” she wrote. “I am now at a hundred per cent.”

“Emilia is very lucky,” says Dr. Sussman. “Her recovery shows how important immediate intervention is for aneurysms, and what’s possible when a patient has the right medical team around them.”