[moyamoya, Japanese = puff of smoke]XS

= uncommon occlusive cerebral arteritis classically involving supraclinoid internal carotid arteries with relative sparing of the posterior fossa in early stages

Etiology: unknown; NO underlying cause identified

Age: bimodal distribution in 1^st decade + 4^th decade of life

Path: development of extensive tiny basal perforator and transdural collateral vessels (moyamoya vessels)

Histo: endothelial hyperplasia + fibrosis without associated inflammatory reaction

• headaches, behavioral disturbances
• bilateral stenosis / occlusion of supraclinoid portion of ICA extending to proximal portions of MCA + ACA
• large network of moyamoya vessels in basal ganglia + upper brainstem fed by basilar a. + ACA + MCA (dilatation of lenticulostriate + thalamoperforating arteries)
• anastomoses between dural meningeal + leptomeningeal aa.

MR:

• tiny flow voids commonly arising from basal cisterns extending into basal ganglia / thalamus
• microbleeds (in 15–44%)
• ischemia and infarction
• NO nidus / dilated vessels
• “ivy” sign = curvilinear high signal intensities along cortical sulci + brain surface = sulcal hyperintensity on FLAIR ← leptomeningeal collateral vessels
• marked leptomeningeal enhancement along cortical sulci

◊Angio needed for planning of revascularization procedure

Cx: in children: transient ischemic hemiparetic attacks, cerebral infarction

in ½ of adults: intracranial hemorrhage