Magnetic resonance angiography in moyamoya disease.

Spontaneous occlusion of the circle of Willis, i.e., moyamoya disease (MMD), is a clinical disease entity angiographically characterized by progressive and bilateral stenosis of the carotid bifurcation, with a hazy collateral network at the base or convexity of the brain. Although the importance of computed tomography (CT) and conventional magnetic resonance (MR) imaging in diagnosing MMD has already been determined, conventional arteriography is still regarded as necessary for definitive diagnosis. Magnetic resonance angiography (MR-A) is a very recent vascular imaging technique which allows noninvasive and direct imaging of vessels without the use of contrast medium. We present four pediatric cases of MMD, evaluated by conventional angiography, CT, MR imaging, and MR-A. Our data demonstrate that MR-A is successful both in allowing detection of occlusive disease of the basal portion of the internal carotid artery and large branch basal cerebral vessels and demonstrating the collateral vessels at the base of the brain. As a noninvasive procedure, MR-A promises to become a valuable alternative to classical angiography in the diagnosis of MMD.