Is Moyamoya Surgery Risky? Understanding the Benefits and Risks of Revascularization Procedures

When it comes to treating Moyamoya disease, surgical intervention is often recommended to restore proper blood flow to the brain and prevent strokes. While any brain surgery naturally raises concerns about safety, modern revascularization techniques have significantly improved outcomes. The two primary surgical approaches—direct and indirect bypass procedures—are generally considered safe when performed by experienced neurosurgical teams. Below, we explore each method in detail, highlighting their risks, benefits, and long-term impact on patient recovery.

Direct Revascularization: A Targeted Approach for Immediate Results

Direct vascular bypass surgery is a well-established procedure designed to immediately enhance cerebral blood circulation. In this operation, a section of bone is temporarily removed from the skull to allow access to the brain's surface. Surgeons then connect a healthy blood vessel—typically the superficial temporal artery—from outside the brain directly to the middle cerebral artery within the brain. This creates a new, reliable pathway for oxygen-rich blood to reach compromised areas.

Over the years, direct bypass techniques have evolved with high success rates and relatively low complication risks. When the graft remains patent (open), patients often experience rapid symptom relief, including reduced frequency of transient ischemic attacks (TIAs) and improved cognitive function. Potential risks include bleeding, infection, or stroke during the perioperative period, but these are uncommon in centers with specialized expertise.

Advantages of Direct Bypass Surgery

One of the main strengths of direct revascularization is its immediate effect. Blood flow increases right after surgery, offering fast protection against future ischemic events. Additionally, long-term studies show that properly executed direct bypasses maintain patency in over 90% of cases, leading to durable neurological improvement.

Indirect Revascularization: A Gradual but Effective Alternative

For patients who may not be ideal candidates for direct surgery—especially children or those with fragile vasculature—indirect bypass techniques offer a safer and effective alternative. This method does not involve connecting vessels directly. Instead, surgeons place vascularized tissues such as the temporalis muscle or dura mater in contact with the brain surface, encouraging the growth of new collateral blood vessels over time.

Common procedures under this category include encephaloduroarteriosynangiosis (EDAS) and encephalomyosynangiosis (EMS). Because no microsurgical anastomosis is required, the procedure is less invasive and carries fewer immediate surgical risks. However, the therapeutic benefits develop gradually, typically over several weeks to months, as the brain naturally forms new connections.

Why Choose Indirect Surgery?

Indirect methods are particularly favored in pediatric cases, where the developing brain responds well to angiogenic stimulation. These procedures avoid manipulation of delicate intracranial vessels, reducing the chance of intraoperative complications. Though results take longer to manifest, the long-term outcome is often comparable to direct bypass, especially when multiple indirect techniques are combined.

Comparing Risks and Making an Informed Decision

Both direct and indirect revascularization surgeries are considered low-risk relative to the potential consequences of untreated Moyamoya disease, which include recurrent strokes and progressive cognitive decline. The choice between them depends on factors like age, disease stage, overall health, and surgeon experience.

While direct bypass offers faster results, it requires advanced microsurgical skills. Indirect methods, though slower, are less technically demanding and highly effective in younger patients. Ultimately, a personalized treatment plan developed by a multidisciplinary team ensures optimal safety and long-term success.