---
title: "Moyamoya"
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pageDescription: "Moyamoya"
pageKeywords: "Pediatrics, Diagnosis, Pediatric Neuroradiology, Brain, Pathology-Based Diagnoses, Stroke, Moyamoya"
pageTitle: "Moyamoya | STATdx"
enhancedTitle: "Moyamoya"
type: "DX"
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breadcrumbs:
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- "Brain"
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- "Moyamoya"
---
# KEY FACTS
- ## Terminology
- Progressive narrowing of distal internal carotid artery (ICA) & proximal circle of Willis (COW) vessels → characteristic adjacent clusters of collateral flow appearing as "puff of smoke" on real-time angiography
- Moyamoya disease = primary (idiopathic) moyamoya
- More common in Japan, Korea
- Moyamoya arteriopathy (a.k.a. moyamoya syndrome or secondary moyamoya) due to other disorders
- ## Imaging
- Absent or narrowed distal ICA & abnormal COW
- Excessive tiny collaterals in basal ganglia & cisterns
- "Puff of smoke" (moyamoya in Japanese) of lenticulostriate & thalamoperforator collaterals
- Prominent collaterals in sulci
- Ivy sign on FLAIR & T1 C+ MR
- Acute & chronic infarcts
- CT/CTA: Acute use for ischemia or hemorrhage
- MR C+/MRA: Vascular protocol with DWI & perfusion
- DWI: Helpful to identify "acute on chronic" injury
- ## Pathology
- Moyamoya disease: Inherited idiopathic disorder
- Moyamoya arteriopathy: Secondary process
- Sickle cell disease, trisomy 21, neurofibromatosis type 1, radiation therapy, Alagille syndrome, morning glory syndrome, TB meningitis, among others
- ## Clinical Issues
- Bimodal age peaks: 6 & 35 years
- Most frequent cause of stroke in Asian children
- Presentation (children): Transient ischemic attacks (TIAs), alternating hemiplegia (exacerbated by crying), headache
- Presentation (adults): TIAs, hemorrhage (~ 30%), & cerebral infarct
- Prognosis depends on etiology, ability to form collaterals, age/stage at diagnosis
- Treatment: Indirect (more common in children) or direct (more common in adults) vascular bypass
- ## Diagnostic Checklist
- Seek underlying causes of secondary moyamoya
# TERMINOLOGY
- ## Synonyms
- Progressive stenoocclusive arteriopathy; spontaneous occlusion of circle of Willis (COW)
- ## Definitions
- Progressive narrowing of distal internal carotid artery (ICA) & proximal COW vessels → characteristic adjacent clusters of collateral flow appearing as "puff of smoke" on real-time angiography
- Moyamoya disease: Primary (idiopathic) moyamoya
- More common in Japan, Korea
- Moyamoya arteriopathy (a.k.a. moyamoya syndrome or secondary moyamoya) occurs in association with other disorders or after radiation treatment
# IMAGING
- ## General Features
- Best diagnostic clue: Multiple enhancing punctate dots (CECT) & flow voids (MR) in basal ganglia & cisterns
- Arterial occlusions: Distal ICA, COW, branches
- Anterior > posterior circulation
- Posterior circulation affected in ~ 25%
- Leads to prominent clusters of nearby collaterals
- "Cloud-like" lenticulostriate & thalamoperforator collaterals on angiography: "Puff of smoke" (moyamoya in Japanese)
- Also leads to prominent sulcal collaterals distally
- ## CT Findings
- ### NECT
- Children: Acute ischemia ± old infarcts
- Older children/adults: Usually ischemia but may present with intracranial hemorrhage
- CTA: Abnormal COW + basilar net-like collaterals
- Xe-133 CT: ↓ cerebral reserve with acetazolamide challenge
- ## MR Findings
- ### T2WI
- ↑ signal in gliotic areas from prior infarcts
- Collateral vessels: Net-like cisternal flow voids
- ### FLAIR
- Bright sulci = leptomeningeal ivy sign
- Slow-flowing engorged pial collateral vessels, thickened arachnoid membranes
- Correlates with ↓ cerebral vascular reserve
- ### T2* GRE
- Hemosiderin if prior hemorrhage
- ### DWI
- Very useful for "acute on chronic" infarcts
- ### PWI
- ↓ cerebral blood flow (CBF) (ASL) in affected territories
- ↑ MTT in affected territories
- Variable rCBV depending on degree of collateral formation
- May be used to measure response to revascularization
- ### T1WI C+
- Lenticulostriate collaterals → enhancing "dots" in basal ganglia & net-like thin vessels in cisterns
- Leptomeningeal enhancement (ivy sign)
- Vessel wall imaging
- Most consistent finding is negative remodeling (local shrinkage of vessel size) of affected vessels
- Variable enhancement of affected vessel segments
- ↑ wall thickening and ↑ stenosis correlates with ↑ wall enhancement
- May help distinguish from other vasculopathies
- ### MRA
- Narrowed/occluded distal ICA & COW vessels
- ### MRS
- Lactate in acutely infarcted tissue
- NAA:Cr & Cho:Cr ratios in frontal white matter improve ↑ after revascularization
- ## Ultrasonographic Findings
- Grayscale: Reduction of ICA lumen size
- Pulsed Doppler
- Spectral waveforms in ICA show no flow (occluded) or proximal high-resistance flow pattern
- ↑ end-diastolic flow velocity, ↓ vascular resistance in external carotid artery (ECA) collaterals
- Color Doppler: Aliasing suggests stenoses
- Power Doppler: Improves visualization of slow-flow stenotic vessels & collaterals
- Can be used for vessel mapping prior to revascularization surgery
- ## Angiographic Findings
- Predominantly (not exclusively) anterior circulation
- Narrow proximal COW & ICA (early phase)
- Lenticulostriate & thalamoperforator collaterals (intermediate phase)
- Transdural/transosseous ECA-ICA collaterals (late phase)
- Dilation & branch extension of anterior choroidal artery predict adult hemorrhagic events
- ## Nuclear Medicine Findings
- PET: ↓ hemodynamic reserve capacity
- SPECT I-123-iomazenil: Neuronal density preserved if asymptomatic, ↓ if symptomatic
- ## Imaging Recommendations
- Best imaging tool: MR C+/MRA
- Contrast improves detection: Collaterals, synangiosis
- Catheter angiography defines anatomy prior to bypass
- Protocol advice
- Acetazolamide challenge with ASL has been performed to measure cerebrovascular reserve, but Xe-133 CT is gold standard
# DIFFERENTIAL DIAGNOSIS
- ## Ivy Sign
- Leptomeningeal metastases, subarachnoid hemorrhage, meningitis, ↑ inspired oxygen, collateral veins of Sturge-Weber or other chronic venous occlusion
- [Large Vessel Inflammatory Vasculitis](/document/miscellaneous-vasculitis/5a4d4cbd-67e3-4722-8a44-8d411cbb98f0)
- Postvaricella vasculitis, lupus, & other CNS vasculitides
- May be reversible with treatment
- [Cerebral Arterial Atherosclerosis](/document/intracranial-atherosclerosis/8d21d962-9c43-47bd-b995-c73f20e46b47)
- Very rare in children & young adults
- ## Severely Attenuated Circle of Willis
- Subarachnoid hemorrhage (spasm), meningitis, tumor encasement
# PATHOLOGY
- ## General Features
- ### Etiology
- Moyamoya disease
- Inherited polygenic or autosomal dominant
- Low penetrance
- Gene loci: 3p26-p24.2, 17q25, 8q23
- ↑ in growth factors, cytokines, adhesion molecules in CSF implicates inflammation
- Moyamoya arteriopathy (a.k.a. moyamoya syndrome or secondary moyamoya)
- Sickle cell disease, neurofibromatosis type 1 (NF1), radiation therapy, trisomy 21, Alagille syndrome, morning glory syndrome, tuberculous meningitis, many others
- NF1 + suprasellar tumor + radiation can be disastrous
- Epidemiology: Moyamoya disease
- Incidence in Japan: 1:100,000
- Incidence in North America, Europe: 0.1:100,000
- 10-15% familial
- ## Staging, Grading, & Classification
- Staging criteria (Suzuki)
- Stage 1: Narrowing of ICA bifurcation
- Stage 2: Anterior, middle, and posterior cerebral arteries (ACA, MCA, PCA) dilated
- Stage 3: Maximal basal collaterals; small ACA/MCA
- Stage 4: Fewer collaterals (vessels); small PCA
- Stage 5: Further ↓ in collaterals; absent ACA/MCA/PCA
- Stage 6: Extensive ECA-pial collaterals
- ## Gross Pathologic & Surgical Features
- ↑ perforating (early) & ECA-ICA (late) collaterals in atrophic brain
- Hemorrhage (subarachnoid, intraventricular > parenchymal) in adults
- ↑ saccular aneurysms in adults (especially basilar)
- ## Microscopic Features
- Intimal thickening & hyperplasia
- Excessive infolding & thickening of internal elastic lamina
- Periventricular pseudoaneurysms (cause of hemorrhage)
# CLINICAL ISSUES
- ## Presentation
- ### Most common signs/symptoms
- Children: Transient ischemic attacks (TIAs), alternating hemiplegia (exacerbated by crying), headache
- Adults: TIAs, hemorrhage (~ 30%), cerebral infarct
- Hemorrhagic presentation more common in Asian adults
- ### Other signs/symptoms
- Children: Developmental delay, poor feeding, chorea
- ## Demographics
- ### Age
- Bimodal age peaks
- Japan, Korea: 6 years > 35 years
- North America, Europe: 35 years > 6 years
- ### Sex
- M:F = 1:1.8; in familial cases, M:F = 1:5
- ### Epidemiology
- Most frequent cause of stroke in Asian children
- ## Natural History & Prognosis
- Progressive narrowing, collateralization, & ischemia
- Prognosis depends on etiology, ability to form collaterals, age/stage at diagnosis
- Pediatric cases usually advance to stage 5 in < 10 years
- Infantile moyamoya progresses faster
- Hemorrhagic moyamoya more common in older patients
- May be due to large collateral vessels
- Has poorer outcome
- ## Treatment
- Aspirin therapy
- Direct bypass: Superficial temporal artery (STA)-MCA more common in adults
- Indirect bypass
- Pial synangiosis & encephaloduroarteriosynangiosis with STA more common in children
- 5-year risk of ipsilateral stroke post encephaloduroarteriosynangiosis = 15%
- Dural inversion with middle meningeal artery
- Correct/control prothrombotic states & inflammatory etiologies
- Transfusion therapy for sickle cell-related moyamoya
# DIAGNOSTIC CHECKLIST
- ## Consider
- Seek underlying causes of secondary moyamoya
- ## Image Interpretation Pearls
- Enhanced asymmetric atrophy found on childhood CT; look for abnormal vascular pattern
- Adult moyamoya can present with intracranial hemorrhage
- ## Reporting Tips
- Successful revascularization = ↓ basal collaterals, ↑ flow in MCA branches, ↑ caliber of STA (direct bypass)
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## References
# Selected References
1. [Larson AS et al: Vessel wall imaging features of moyamoya disease in a North American population: patterns of negative remodelling, contrast enhancement, wall thickening, and stenosis. BMC Med Imaging. 22(1):198, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36397005%5Bpmid%5D)
1. [Larson AS et al: Implementation and rationale for a unified clinical and imaging protocol for evaluation and treatment of moyamoya angiopathy: a single institutional experience. Front Neurol. 12:662393, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=34079514%5Bpmid%5D)
1. [Wang LX et al: Ivy sign in moyamoya disease: a comparative study of the FLAIR vascular hyperintensity sign against contrast-enhanced MRI. AJNR Am J Neuroradiol. 42(4):694-700, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33664105%5Bpmid%5D)
1. [Fan AP et al: Identifying hypoperfusion in moyamoya disease with arterial spin labeling and an [15O]-water positron emission tomography/magnetic resonance imaging normative database. Stroke. 50(2):373-80, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30636572%5Bpmid%5D)
1. [Lehman VT et al: Contemporary and emerging magnetic resonance imaging methods for evaluation of moyamoya disease. Neurosurg Focus. 47(6):E6, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31786551%5Bpmid%5D)
1. [Lee S et al: Monitoring cerebral perfusion changes after revascularization in patients with moyamoya disease by using arterial spin-labeling MR imaging. Radiology. 288(2):565-72, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29714677%5Bpmid%5D)
1. [Kim DY et al: Infarct pattern and collateral status in adult moyamoya disease: a multimodal magnetic resonance imaging study. Stroke. 48(1):111-6, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27909201%5Bpmid%5D)
1. [Qiao PG et al: Clinical assessment of cerebral hemodynamics in moyamoya disease via multiple inversion time arterial spin labeling and dynamic susceptibility contrast-magnetic resonance imaging: a comparative study. J Neuroradiol. 44(4):273-80, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28168990%5Bpmid%5D)
1. [Blauwblomme T et al: Cerebral blood flow improvement after indirect revascularization for pediatric moyamoya disease: a statistical analysis of arterial spin-labeling MRI. AJNR Am J Neuroradiol. 37(4):706-12, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26585258%5Bpmid%5D)
1. [Kim JS: Moyamoya disease: epidemiology, clinical features, and diagnosis. J Stroke. 18(1):2-11, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26846755%5Bpmid%5D)
1. [Mossa-Basha M et al: Added value of vessel wall magnetic resonance imaging in the differentiation of moyamoya vasculopathies in a non-Asian cohort. Stroke. 47(7):1782-8, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27272486%5Bpmid%5D)
1. [Takagi Y et al: Histopathological characteristics of distal middle cerebral artery in adult and pediatric patients with moyamoya disease. Neurol Med Chir (Tokyo). 56(6):345-9, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27087193%5Bpmid%5D)
1. [Titsworth WL et al: National analysis of 2454 pediatric moyamoya admissions and the effect of hospital volume on outcomes. Stroke. 47(5):1303-11, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27048697%5Bpmid%5D)
1. [Griessenauer CJ et al: Encephaloduroarteriosynangiosis and encephalomyoarteriosynangiosis for treatment of moyamoya syndrome in pediatric patients with sickle cell disease. J Neurosurg Pediatr. 16(1):64-73, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25837886%5Bpmid%5D)
1. [Derdeyn CP: Direct bypass reduces the risk of recurrent hemorrhage in moyamoya syndrome, but effect on functional outcome is less certain. Stroke. 45(5):1245-6, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24668205%5Bpmid%5D)
1. [Ryoo S et al: High-resolution magnetic resonance wall imaging findings of moyamoya disease. Stroke. 45(8):2457-60, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24947295%5Bpmid%5D)
1. [Hishikawa T et al: Assessment of the difference in posterior circulation involvement between pediatric and adult patients with moyamoya disease. J Neurosurg. 119(4):961-5, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=23909250%5Bpmid%5D)
1. [Noguchi T et al: Arterial spin-labeling MR imaging in moyamoya disease compared with clinical assessments and other MR imaging findings. Eur J Radiol. 82(12):e840-7, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=24055185%5Bpmid%5D)
1. [Currie S et al: Childhood moyamoya disease and moyamoya syndrome: a pictorial review. Pediatr Neurol. 44(6):401-13, 2011](http://www.ncbi.nlm.nih.gov/pubmed/?term=21555050%5Bpmid%5D)
1. [Mugikura S et al: Posterior circulation and high prevalence of ischemic stroke among young pediatric patients with Moyamoya disease: evidence of angiography-based differences by age at diagnosis. AJNR Am J Neuroradiol. 32(1):192-8, 2011](http://www.ncbi.nlm.nih.gov/pubmed/?term=20801761%5Bpmid%5D)
1. [Ibrahimi DM et al: Moyamoya disease in children. Childs Nerv Syst. 26(10):1297-308, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=20607248%5Bpmid%5D)
1. [Kim SK et al: Pediatric moyamoya disease: an analysis of 410 consecutive cases. Ann Neurol. 68(1):92-101, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=20582955%5Bpmid%5D)
1. [Mori N et al: The leptomeningeal "ivy sign" on fluid-attenuated inversion recovery MR imaging in moyamoya disease: a sign of decreased cerebral vascular reserve? AJNR Am J Neuroradiol. 30(5):930-5, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19246527%5Bpmid%5D)
1. [Park TS: Moyamoya disease in children. Neurosurg Focus. 24(2):E16a; discussion E16a, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18275293%5Bpmid%5D)
## Images
### Selected Images
*Axial DWI MR in a 13-month-old with increasing seizures shows left MCA distribution ischemia as well as a remote infarct in the right MCA territory. This is a typical acute on chronic ischemic pattern of moyamoya.*
*Axial DWI MR in a 13-month-old with increasing seizures shows left MCA distribution ischemia as well as a remote infarct in the right MCA territory. This is a typical acute on chronic ischemic pattern of moyamoya.*
, absence of the MCAs, & numerous lenticulostriate collaterals 
forming a "puff of smoke." The PCAs are also occluded. Note the enlarged ECA collaterals 
status post synangiosis & dural inversion.](images/app.statdx.com_image_thumbnail_3c6e5eec-bea7-4ef0-a828-0ea47ff5986e_annotated_true_size_900_quality_90_a4ea0607e984c6ad81ea8f4c54c5a49231c9d9de.jpg)
*Anterior 3D TOF MRA in the same patient at 8 years of age shows occlusions of the terminal ICAs , absence of the MCAs, & numerous lenticulostriate collaterals forming a "puff of smoke." The PCAs are also occluded. Note the enlarged ECA collaterals status post synangiosis & dural inversion.*
vessels within the deep nuclear structures.](images/app.statdx.com_image_thumbnail_0e64957a-0ae8-4733-bd51-8ff8a4db4bb4_annotated_true_size_900_quality_90_c73b1afba6d065ed282f7875aeb942ea7679574b.jpg)
*Axial 3D TOF MRA in a 5-year-old with idiopathic moyamoya arteriopathy shows multiple small lenticulostriate and thalamostriate vessels within the deep nuclear structures.*
*Axial FLAIR MR in the same patient shows areas of gliosis from vascular insufficiency, linear hyperintensities representing deep medullary collateral vessels, and hyperintensities conforming to the surface of the sulci representing pial collaterals (the leptomeningeal ivy sign).*
*Axial TOF MRA in a 14-year-old with neurofibromatosis type 1 shows absence of the right internal carotid terminus & MCA. In the expected location of the carotid terminus & MCA, there are multiple small leptomeningeal collaterals .*
*Axial FLAIR MR in a 21-year-old with sickle cell disease shows high signal within the right MCA distribution sulci, the so-called ivy sign. This abnormal signal corresponds to engorged pial collateral vessels & is often seen in moyamoya.*
*Frontal 3D TOF MRA in a 10-year-old with history of nasal rhabdomyosarcoma at age 3 treated with XRT shows absence of flow in the left distal ICA , severe narrowing of the right MCA , & absent right ACA. Terminal ICA & proximal MCA are the most common locations for moyamoya arteriopathy.*
*Axial T1 C+ MR in the same patient shows extensive leptomeningeal enhancement in the bilateral ICA territories with prominent vessel enhancement in the basal ganglia.*
*3D TOF MRA in a 6-year-old with trisomy 21 and severe moyamoya arteriopathy shows marked narrowing of the left ICA terminus & complete occlusion of the right MCA origin . Deep moyamoya collaterals have formed in the left basal ganglia.*
*Axial ASL MR perfusion in the same patient shows near absence of signal in the right MCA territory, consistent with dramatically reduced blood flow, corroborating the findings on MRA.*
### Additional Images
coursing through the basal ganglia. This is the characteristic puff of smoke (moyamoya) pattern.](2bfd6af4-572e-4cf4-a75b-9de6f00847e8)
*Coronal graphic shows severe tapering of both distal ICAs & strikingly enlarged lenticulostriate arteries coursing through the basal ganglia. This is the characteristic puff of smoke (moyamoya) pattern.*
*Axial FLAIR MR in an 8-year-old boy with Alagille syndrome shows confluent gliosis in the right frontal region & more patchy gliosis in the left deep white matter. Also note the serpentine collateral vessels near the midline. Moyamoya arteriopathy can be seen with Alagille syndrome.*
*Axial TOF MRA in an 8-year-old boy with Alagille syndrome shows absent signal in the region of the carotid termini & major ICA branch vessels. There are, however, small leptomeningeal collateral vessels in the midline inferior frontal & right anterior temporal regions & basilar cisterns . The findings are compatible with moyamoya arteriopathy.*
*Anterior projection from a left ICA DSA injection shows no opacification of the expected ACA branches with multiple leptomeningeal collaterals seen in the midline subfrontal region . Also note the enlarged left middle meningeal artery , which supplies portions of the right ACA territory. This is an example of an ICA to ECA collateral pathway.*
*Axial T2 MR in a 21-year-old man with sickle cell disease shows absence of the carotid termini & major branches. Note the numerous small leptomeningeal collateral vessels within the basilar cisterns, typical of moyamoya arteriopathy.*
*Axial MRA in a 21-year-old man with sickle cell disease shows multiple punctate foci of flow-related signal within the basal ganglia & thalami, consistent with typical lenticulostriate & thalamoperforator collateral vessels of moyamoya arteriopathy.*
*Axial T1 C+ MR in a 21-year-old man with sickle cell disease shows abnormal leptomeningeal enhancement in the right MCA distribution. This is the equivalent of the ivy sign on FLAIR & represents slow-flowing leptomeningeal collaterals that develop in areas of decreased cerebrovascular reserve (secondary to moyamoya arteriopathy).*
*3D MRA in a 16-year-old boy with moyamoya arteriopathy demonstrates severe stenosis/occlusion of the right carotid terminus . The patient is status post revascularization using a direct bypass. Note the prominent right superficial temporal artery , which is anastomosed to a distal right MCA branch .*
with a "puff of smoke" 
from the collateral lenticulostriate vessels.](4b237b46-0087-43cd-929c-7984216d51db)
*Lateral view of a selective internal carotid DSA shows severe stenosis of the supraclinoid ICA with a "puff of smoke" from the collateral lenticulostriate vessels.*
*Axial TOF MRA shows occlusion of both distal ICAs , nonvisualization of the MCAs & ACAs, & stenosis of the PCAs in an 8-year-old with hemiparetic migraines. This patient had an idiopathic arteriopathy of childhood.*
*Axial TOF MRA in another patient with idiopathic progressive arteriopathy of childhood shows occluded supraclinoid ICAs . Note the bilateral synangiosis .*
*Axial T1 MR shows right frontal & left temporooccipital atrophy from remote ischemia. There are multiple small basal ganglia flow voids from lenticulostriate collaterals.*
*Axial T1 C+ MR in the same patient shows multifocal white "dots" due to slow flow in multiple enlarged lenticulostriate collaterals.*
*Axial TOF MRA in a 2-year-old boy with moyamoya and multiple infarcts shows proliferation of small vessels in the thalamus.*
*Axial FLAIR MR in the same patient shows multiple wedge-shaped areas of cortical signal abnormality , consistent with multifocal infarcts.*