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Moyamoya

KEY FACTS

TERMINOLOGY

• Progressive narrowing of distal internal carotid

artery/proximal circle of Willis (COW) vessels with

secondary collateralization

○ Collateral vessels → cloud-like "puff of smoke"

(moyamoya) at angiography

• Moyamoya disease (MMD) = primary (idiopathic)

moyamoya

○ Marked East-West gradient (more common in Japan,

Korea)

• Moyamoya pattern of collaterals = secondary to many

etiologies

IMAGING

• Best diagnostic clue: Attenuated COW with multiple tiny

basal ganglia "flow voids" on MR

• Best imaging tool: T1 MR C+/MRA; DSA for delineating

vascular details

PATHOLOGY

• Moyamoya disease

○ RNF213 polymorphism (95% of familial, 79% of sporadic)

– Correlated with early onset, severe form of MMD

• Secondary "moyamoya"

○ Moyamoya pattern of collaterals in other conditions

– Syndromic (e.g., neurofibromatosis type 1)

– Sickle cell disease

– Inflammatory or prothrombotic states

– Suprasellar irradiation in childhood

CLINICAL ISSUES

• Bimodal age peaks (5-10 years and 2nd peak during 4th

decade)

• Most frequent cause of stroke in Asian children

• Presentation

○ Children: Recurrent TIAs; hemorrhage rare

○ Adults: TIAs, infarcts, hemorrhage (20%), migraines

(Left) Coronal graphic shows

severe tapering of both distal

internal carotid arteries ſt

and strikingly enlarged

lenticulostriate arteries ﬇

coursing through basal

ganglia. This is the "puff of

smoke" (moyamoya). (Right)

Coronal T2WI in a 3-year-old

girl with moyamoya disease

shows severely attenuated

supraclinoid internal carotid

arteries ſt. An acute cortical

infarct is present in the right

middle carotid artery (MCA)

distribution ﬇.

(Left) Axial T2WI in the same

patient shows tiny, almost

inapparent "flow voids" of the

right MCA branches in the

sylvian fissure ſt. The acute

cortical infarct has produced

marked gyral edema, swelling

﬇. Note the tiny "squiggly"

flow voids st from the basal

collateral vessels. (Right)

Coronal MIP of the time-offlight MRA in the same patient

shows the severely attenuated

supraclinoid internal carotid

arteries ſt and the puff of

smoke appearance of the

basal collateral vessels st.

Trauma, and Stroke

Brain: Pathology-Based Diagnoses: Malformations,

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