Moyamoya Disease

Moyamoya disease is a chronic, progressive steno-occlusive disorder of the distal internal carotid arteries and their proximal branches, accompanied by a fragile network of collateral vessels at the base of the brain. On angiography this network resembles a 'puff of smoke' — moyamoya in Japanese. It can cause ischemic events, especially in children, and hemorrhage, more often in adults.

Definition

Moyamoya disease is a progressive intracranial arteriopathy characterized by bilateral stenosis or occlusion of the terminal internal carotid arteries and the proximal anterior and middle cerebral arteries, with development of an abnormal collateral vascular network at the base of the brain.

Scope

This entry defines moyamoya disease, describes the characteristic arterial narrowing and collateral network, distinguishes disease from syndrome, and introduces the rationale for revascularization surgery. It is a reference and educational overview and does not provide individualized treatment guidance.

Core questions

• What arterial territories does moyamoya disease characteristically affect?
• Why does the collateral network produce the 'puff of smoke' angiographic appearance?
• How does moyamoya disease differ from moyamoya syndrome?
• What is the rationale for surgical revascularization?

Key concepts

• Steno-occlusive arteriopathy of the distal internal carotid artery
• Moyamoya collateral network ('puff of smoke')
• Ischemic presentation in children
• Hemorrhagic presentation in adults
• Moyamoya disease versus moyamoya syndrome
• Direct bypass (STA-MCA) revascularization
• Indirect revascularization

Mechanisms

In moyamoya disease, progressive narrowing of the distal internal carotid arteries and their proximal branches reduces forward flow to the brain. In response, a fragile network of dilated perforating and collateral vessels develops at the base of the brain to maintain perfusion; these vessels produce the hazy 'puff of smoke' appearance on angiography and are themselves prone to rupture. The reduced perfusion predisposes to ischemic events, which tend to predominate in children, while the fragile collaterals contribute to hemorrhage, which is relatively more common in adults. When the same angiographic pattern occurs in association with another condition it is termed moyamoya syndrome rather than disease. Surgical revascularization aims to deliver new blood supply to the hypoperfused brain, either by directly connecting a scalp artery to a cortical artery (direct bypass) or by laying vascularized tissue on the brain surface to encourage new vessel growth (indirect revascularization).

Clinical relevance

Understanding the arterial pattern, collateral physiology, and revascularization rationale of moyamoya disease supports critical reading of the cerebrovascular literature. This entry describes those concepts; it does not direct whether or how a specific patient should undergo revascularization, which depends on presentation, perfusion status, and current evidence and rests with the treating team.

Epidemiology

Moyamoya disease is rare and is reported most frequently in East Asian populations, with a recognized bimodal age distribution: a childhood peak, typically with ischemic presentations, and an adult peak, with a relatively greater proportion of hemorrhagic events. It occurs worldwide, and a familial component is recognized in a subset of cases.

Evidence & guidelines

The condition was delineated by Suzuki and Takaku (1969), who described the characteristic net-like vessels and staged the angiographic progression. A widely cited clinical overview distinguishing moyamoya disease from moyamoya syndrome and summarizing presentation and surgical approaches is provided by Scott and Smith (2009). Management is individualized and informed by such sources.

History

Moyamoya disease was characterized by Suzuki and Takaku (1969), who named the disorder for the smoky angiographic appearance of its collateral network and described its angiographic stages. Subsequent decades clarified the distinction between idiopathic moyamoya disease and moyamoya syndrome associated with other conditions, and the development of direct and indirect surgical revascularization, summarized in clinical reviews such as Scott and Smith (2009).

Debates

Direct versus indirect revascularization

Both directly connecting a scalp artery to a cortical artery and indirectly inducing new vessel growth can augment cerebral blood supply, and the relative merits of each, including by patient age, remain a topic of discussion in the literature.

Key figures

• Jiro Suzuki
• Akira Takaku
• R. Michael Scott
• Edward R. Smith

Seminal works

• suzuki-takaku-1969
• scott-smith-2009

Frequently asked questions

Why is it called moyamoya?

Moyamoya means 'puff of smoke' in Japanese, describing the hazy appearance on angiography of the abnormal network of small collateral vessels that develops at the base of the brain.

What is the difference between moyamoya disease and moyamoya syndrome?

Moyamoya disease refers to the idiopathic disorder with the characteristic bilateral arterial narrowing and collateral network, whereas moyamoya syndrome describes the same angiographic pattern occurring in association with another underlying condition.