MOYAMOYA

Terminology Progressive narrowing of distal ICA and proximal circle of willis vessels with secondary collateralization Moyamoya disease: primary (idiopathic )moyamoya more common in Japan ,korea Moyamoya syndrome: secondary moyamoya is associated with a number of different putative causes . cases have been associated with neonatal anoxia ,trauma, basilar meningitis,cranial radiation therapy for optic pathway gliomas ,NF1, TS, FMD, brain tumor ,cereberal dissecting and sacular aneurysm

Pathology Moyamoya is a chronic progressive nonatherosclerotic , non inflammatory , nonamyloid occlusive intracranial vasculopathy of unknown cause Pathologically , there is fibrocellular intimal thickening , smooth muscle cell proliferation and increased elastin accumulation , resulting in stenosis of the suprasellar intracranial internal carotid arteries. Thrombotic lesions may be seen in major cerebral arteries .There are also numerous perforating and anastomotic branches around the circle of willis .

Imaging Best diagnostic clue: multiple punctate dots (CECT) and flow voids(MR) in basal ganglia Location : circle of willis ; anterior>>> posterior circulation Morphology: “puff of smoke” cloud like lenticulostriate and thalamosrtiate collaterals on angiography

Imaging MRI finding T1WI: Multiple dot like flow voids in BG T2WI: Increased signal of small vessel and cortical and white matter infarct FLAIR: Bright sulci=leptomeningeal “ivy” sign (slow flowing engorged pial vessels ,thickened arachnoid membrane T1WI C+: Enhancing dots in BG correlates with lenticulostriate and thalamostriate collaterals

Imaging Angiographic finding Suzuki’s 6 angiographic stages (1) stenosis of the carotid fork (2) initial appearance of moyamoya vessels at the base of the brain (3) intensification of moyamoya vessels (4) minimization of moyamoya vessels (5) reduction of moyamoya vessels (6) disappearance of moyamoya vessels (collaterals only from external carotid arteries)

Epidemiology Moyamoya disease has a bimodal age distribution with peaks in the first and fourth decades of life. Moyamoya affects children, adolescents, and young adults most frequently

And symptom Clinical sign Childhood moyamoya is characterized by ischemic manifestations, whereas adult moyamoya disease presents with hemorrhagic manifestations Moyamoya disease may cause TIAs, including hemodynamic paraparetic TIAs secondary to watershed paracentral lobule ischemia. TIAs are often precipitated by crying, blowing, or hyperventilation. Other sign and symptos are headaches, seizures , movement disorders (chorea, hemidystonia, hemichoreoathetosis), mental deterioration, cerebral infarction, or intracranial hemorrhage

Treatment The optimal treatment of ischemic moyamoya has not been determined. Platelet antiaggregants, vasodilators, calciumchannel blockers, and corticosteroids have been used with variable results. Anticoagulants are not useful. Good results have been reported with superficial temporal artery to MCA anastomosis and other indirect or combined surgical revascularization procedures. No clear superior therapy to prevent rebleeding has been shown in the hemorrhagic type of moyamoya disease.  

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