Specific Imaging Findings

In the earliest stages the typical vascular imaging features of moyamoya are narrowing of the terminal internal carotid arteries (ICAs) and proximal anterior and middle cerebral arteries, followed by development of abnormal dilated lenticulostriate and thalamoperforator collaterals with appearance similar to a “puff of smoke” (Moyamoya in Japanese), and in the late stages transdural and transosseous external-to-internal carotid artery collaterals. Aneurysms of the basilar artery tip and posterior communicating artery may also be found. The flow-voids in the ICAs, middle, and anterior cerebral arteries appear decreased, with prominent flow-voids in the region of the basal ganglia and thalami from Moyamoya collateral vessels, best seen on T2WI. The “ivy sign”, consisting of hyperintensity on FLAIR images along the cerebral sulci and leptomeningeal enhancement on post-contrast T1WI appears characteristic for Moyamoya. Pial collateral vessel engorgement in the attempt to compensate for the decreased perfusion pressure is responsible for this appearance.

Pertinent Clinical Information

Moyamoya disease and syndrome generally manifests with symptoms of brain ischemia or hemorrhage, seizures, and headache from dilated transdural collaterals. Intracranial hemorrhage, due either to bleeding from fragile collaterals or aneurysms, is more common in adults. Major neurologic deficits, personality changes and cognitive impairments are frequent. The natural history of the disease is variable with progression, either slow or fulminant, observed in the majority of untreated cases. A six-vessel cerebral angiography, including evaluation of the external carotid arteries (ECAs), is necessary to accurately stage the disease.