Moyamoya disease in the United States.

The epidemiology and radiological features of Moyamoya disease (MMD) in the US were investigated. This study encompassed 98 cases; 26 were newly collected from eight US institutions and 72 were previously reported in the US literature. The patients ranged in age from 6 months to 67 years with age peaks in the first, third and fourth decades. MMD was seen in various ethnic groups and females were more commonly involved (71%) than males. A specific etiology could not be determined in most cases but arteriosclerosis and use of oral contraceptives were occasional associations. On angiography and/or magnetic resonance angiography (MRA), carotid arterial stenosis or occlusion was seen bilaterally in 95 cases (97%) and unilaterally in three. On MR or MRA, internal carotid steno-occlusive lesions were well demonstrated in all cases but Moyamoya collateral vessels (MMVs) were visualized in only 65% of the patients. MMVs in the basal ganglia and thalami were best demonstrated on T1 weighted images. Parenchymal lesions were seen in all patients and were often bilateral. With advances in MR techniques and increasing awareness of diagnostic guidelines, MMD will be diagnosed more frequently than before in the US.