Pediatric Moyamoya Disease: Advanced Surgical Approaches and Revascularization Techniques

Pediatric moyamoya disease is a rare cerebrovascular disorder characterized by progressive stenosis or occlusion of the internal carotid arteries and their major branches, leading to reduced cerebral blood flow and an increased risk of stroke in children. To restore adequate perfusion to ischemic brain regions, several surgical revascularization techniques have been developed. These procedures aim to redirect blood flow from external carotid artery systems—rich in vascular supply—to the compromised areas of the cerebral cortex supplied by the internal carotid and middle cerebral arteries.

Common Surgical Strategies for Pediatric Moyamoya

Surgical intervention remains the cornerstone of long-term management in pediatric moyamoya disease. The primary goal is to establish new collateral circulation through either direct, indirect, or combined bypass methods. These approaches utilize nearby vascularized tissues such as the superficial temporal artery, temporal muscle, galeal fascia, and dura mater to promote angiogenesis and improve cerebral perfusion over time.

1. Direct and Indirect Combined Procedure: Dural Flap Turnover with Temporal Muscle Apposition and STA-MCA Bypass

This hybrid technique combines both direct and indirect revascularization methods. In this procedure, the superficial temporal artery (STA) is directly anastomosed to a branch of the middle cerebral artery (MCA), providing immediate blood flow to the ischemic cortex—a method known as direct bypass. Simultaneously, the dura mater is opened in a radial fashion and flipped outward, then sutured to the underlying temporal muscle, which is also placed in close contact with the cortical surface. This promotes gradual development of collateral vessels over weeks to months, enhancing long-term perfusion through neovascularization.

2. Large Craniotomy with Extensive Vascular Reconstruction

Also referred to as "enlarged window" or large bone flap surgery, this approach involves removing a larger section of the skull to expose a broader area of the brain's surface. Within this expanded field, surgeons perform either direct or indirect bypass techniques:

• Direct Bypass: Involves microsurgical anastomosis between the superficial temporal artery and a cortical branch of the MCA, offering instant restoration of blood flow.
• Indirect Bypass: Utilizes vascular-rich tissues like the temporal muscle, dura, or galea, laid directly onto the brain surface to encourage natural vessel growth over time.

The large craniotomy allows for more comprehensive coverage and greater potential for collateral network formation, particularly beneficial in pediatric patients whose brains are still developing and highly adaptable.

3. EDMAS or EDMS: Indirect Revascularization with Multilayer Tissue Grafting

Encephalo-Duro-Myo-Arterio-Synangiosis (EDMAS) or Encephalo-Duro-Myo-Synangiosis (EDMS) are advanced forms of indirect bypass surgery. These techniques involve placing multiple layers of vascularized tissue—such as the parietal branch of the STA, the periosteum, dura, and temporal muscle—directly onto the pial surface of the brain. Over time, these tissues stimulate the formation of new microvasculature that integrates with the existing cerebral circulation, effectively bypassing blocked arteries. EDMAS/EDMS is especially valuable in young children where vessel size may be too small for direct anastomosis.

4. Combined Direct and Indirect Bypass: STA and Middle Meningeal Artery (MMA) Anastomosis

In select cases, a dual approach is employed to maximize revascularization. This combined strategy includes not only the standard STA-to-MCA direct bypass but also additional anastomoses between the STA and the middle meningeal artery (MMA). By engaging multiple donor vessels, this technique enhances both immediate and delayed blood supply to the affected hemisphere. It is particularly effective in patients with extensive ischemic territories or those who have shown limited response to indirect methods alone.

Each surgical option is carefully tailored based on the child's age, severity of stenosis, cognitive status, and imaging findings. Postoperative monitoring using MRI, MRA, and cerebral blood flow studies ensures optimal outcomes. With timely intervention and appropriate surgical planning, most children experience significant improvement in cerebral perfusion, reduced stroke risk, and enhanced neurocognitive development.