Moyamoya Disease

Moyamoya disease (MMD) is a progressive occlusive disease of the cerebral vasculature with particular involvement of the circle of Willis and the arteries that feed it. The image below contains a schematic representation of the circle of Willis, arteries of the brain, and brain stem.

Schematic representation of the circle of Willis, arteries of the brain, and brain stem.

Moyamoya i.e. Japanese word for "puff of smoke" characterizes the appearance on angiography of abnormal vascular collateral networks that develop adjacent to the stenotic vessels. The steno-occlusive areas are usually bilateral, but unilateral involvement does not exclude the diagnosis.

The diagnosis is initially suggested by CT, MRI, or angiogram. Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease. MRI and MRA should be performed for the diagnosis and follow-up of moyamoya disease. Diffusion-weighted imaging can also be used for following the clinical course of children with moyamoya disease, in whom new focal deficits are highly suspicious of new infarcts.

Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease. Conventional angiography provided the conclusive diagnosis of moyamoya disease in most cases and should be performed before any surgical considerations.