Fear of complications delays moyamoya surgery, but early intervention cuts risk

Moyamoya disease is a cerebrovascular condition in which brain imaging—such as CT, MRI, or angiography—reveals abnormal, hazy blood vessels resembling a puff of smoke. The disease can lead to blocked blood vessels or cerebral hemorrhage.

Surgical intervention to restore blood flow is often necessary, but many patients hesitate due to the potential complications of brain surgery.

“The biggest fear for moyamoya patients considering surgery is the risk of complications,” said Professor Choe Tae-won of the Department of Neurosurgery at Seoul National University Bundang Hospital on the hospital’s YouTube channel. “Complications occur in about 2–6 percent of cases and can include cerebral infarction or hemorrhage.”

Ironically, while cerebral infarction and hemorrhage are among the very risks patients wish to avoid, delaying surgery can increase the likelihood of these outcomes. “It’s better to operate early -- when the patient is younger and the disease is less advanced -- to reduce the risk of complications,” Professor Choe emphasized.

According to Choe, the annual incidence of cerebral infarction among patients who do not undergo surgery is about 3 percent. That rate rises to 13 percent at five years and 28 percent at ten years. For patients who receive surgery, however, the corresponding rates drop sharply to 0.2 percent annually, 2.7 percent at five years, and 3.9 percent at ten years.

A similar trend is seen with rebleeding. Among patients with bleeding-type moyamoya disease, the annual rebleeding rate without surgery is 8.2 percent, rising to 23 percent at five years and 34 percent at ten years. With surgery, the annual rebleeding rate drops to 3.2 percent.

Despite these benefits, there are still no standardized surgical criteria for moyamoya disease. “Each hospital or medical team uses different criteria,” Choe said. “Some studies support surgery in certain cases, while others argue it’s not always necessary.”

At SNUBH, the decision is based on the patient’s symptoms. “We consider signs such as limb weakness, speech or vision issues, or evidence of brain infarction,” Choe explained.

One of the most important factors is the presence of “bleeding vessels” -- twisted moyamoya vessels near the brain's ventricles, which are known to cause bleeding. “If these vessels are identified, we recommend surgery -- even if the patient hasn’t experienced bleeding yet,” he said.

So when is the right time for surgery after a stroke or hemorrhage?

“If a patient has had a cerebral infarction, we usually wait at least a month until the patient is stable,” Choe said. “For cerebral hemorrhage, surgery is generally performed one to three months after the event.”

Although surgery is often recommended after a hemorrhage, there are exceptions. “We recommend surgery in most cases of brain bleeding,” Choe noted, “but if the bleeding results in severe disability, we may decide against it.”