When someone gets a stroke caused by bleeding in the brain, an aneurysm is often the culprit.

Aneurysms are balloon-like swellings of the walls of blood vessels. They can rupture and release blood into the surrounding area.

When this happens in the brain, it triggers what is known as a haemorrhagic stroke. Such strokes account for around two in 10 of all strokes in Singapore every year. The more common cause of stroke - a condition where brain tissues are damaged as a result of interrupted blood supply - is blood clots in the brain.

On Thursday evening, Finance Minister Heng Swee Keat collapsed during a Cabinet meeting after suffering a stroke. He underwent initial neurosurgery to relieve pressure in his brain due to the bleeding. The aneurysm was successfully closed.

He is now sedated and in a stable condition and in intensive care at Tan Tock Seng Hospital.

Doctors told The Straits Times that the most important thing to do when a brain aneurysm ruptures is to try and seal it off.

This includes putting a clip across the neck of the aneurysm, or inserting coils of fine wire to prevent blood from flowing into the area.

Alternatively, said Dr Ng Puay Yong, a neurosurgeon at Mount Elizabeth Hospital, doctors can insert a device to direct blood flow away from the aneurysm.

Dr David Choy, a neurosurgery specialist at Raffles Neuroscience Centre, added: "Sometimes, there is a need to drain excess fluid from the brain, especially if the drainage system within the brain is blocked."

While strokes triggered by aneurysms often come on suddenly, some people experience warning signs, although they may not recognise them for what they are.

"Some people may have headaches for a few hours or days beforehand, but they don't take note of it or put it down to stress," said Dr Lee Kim En, a neurologist at Mount Elizabeth Hospital.

The experts said the outlook of a patient depends on factors like where the aneurysm is located and how quickly he gets medical care.

If it is near a critical area like the brain stem, the person may end up in a vegetative state, said Dr Ng.

Others may have some form of paralysis on one side of their body, while yet others recover fully.

Those with poorly controlled high blood pressure or high cholesterol stand a higher risk of getting strokes, as do diabetics, smokers and those whose family members have had a stroke.

One survivor of an aneurysm is 37-year-old Carine, a former engineering assistant who declined to give her full name. Seven years ago, she felt a burning pain in the back of her neck while at work, vomited and collapsed.

Doctors thought it was a viral attack and sent her home with medication. But two weeks later, the problem recurred. This time, she was admitted to intensive care and underwent surgery the next day.

"After that, I couldn't move the left half of my body," she said. She underwent physiotherapy to help her regain her strength and was discharged after a month.

"At first, I was in a wheelchair, but now I can stand up and walk with a walking stick," said Carine, who took on an administrative job after the stroke but is now unemployed.

"I've been in their shoes, and I can understand," she said.