"Game of Thrones" star Emilia Clarke revealed that she had suffered two life-threatening brain aneurysms in the early years of filming the blockbuster series.

An aneurysm occurs when part of an artery wall weakens, allowing it to balloon out or widen abnormally. The bulge that forms in the blood vessel of the brain could lead to severe health issues.

In an essay entitled "A Battle For My Life" published in The New Yorker, Clarke recounted the first time the aneurysm rupture occurred just after filming the first season.

"On the morning of February 11, 2011, I was getting dressed in the locker room of a gym in Crouch End, North London, when I started to feel a bad headache coming on. I was so fatigued that I could barely put on my sneakers. When I started my workout, I had to force myself through the first few exercises," wrote, adding that she couldn't finish her workout and "crawled" her way to the locker room where the pain felt like"an elastic band were squeezing my brain" at first before it intensified to "shooting, stabbing, constricting pain."
"At some level, I knew what was happening: my brain was damaged."

"For a few moments, I tried to will away the pain and the nausea," she continued. "To keep my memory alive, I tried to recall, among other things, some lines from 'Game of Thrones.'"

Clarke, who was aged 24 at the time, was admitted to the hospital where she was diagnosed with a subarachnoid hemorrhage (a stroke caused by bleeding into areas that surround the brain).

After undergoing a one-month treatment, Clarke left the hospital, but received a warning that she had another aneurysm that could rupture at any moment.

During a routine brain scan in 2013, doctors found that the growth on the other side of her brain had doubled in size, and advised an immediate surgery that led to major complications which forced her to stay at the hospital for a month.

"The procedure had failed. I had a massive bleed and the doctors made it plain that my chances of surviving were precarious if they didn’t operate again. This time they needed to access my brain in the old-fashioned way—through my skull. And the operation had to happen immediately."

Clarke wrote that she has survived and healed beyond her "most unreasonable hopes", revealing that she has launched a charity "to help young adults become themselves again after brain injury and stroke."

"There is something gratifying, and beyond lucky, about coming to the end of 'Thrones'," Clarke wrote. "I'm so happy to be here to see the end of this story and the beginning of whatever comes next."