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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
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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
- Postvaricella vasculitis, lupus, & other CNS vasculitides
- May be reversible with treatment
Cerebral Arterial Atherosclerosis
- 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

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.

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.

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

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 .

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.

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KEY FACTS

Terminology

Imaging

Pathology

Clinical Issues

Diagnostic Checklist

TERMINOLOGY

Synonyms

Definitions

IMAGING

General Features

CT Findings

NECT

MR Findings

T2WI

FLAIR

T2* GRE

DWI

PWI

T1WI C+

MRA

MRS

Ultrasonographic Findings

Angiographic Findings

Nuclear Medicine Findings

Imaging Recommendations

DIFFERENTIAL DIAGNOSIS

Ivy Sign

Severely Attenuated Circle of Willis

PATHOLOGY

General Features

Etiology

Staging, Grading, & Classification

Gross Pathologic & Surgical Features

Microscopic Features

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Other signs/symptoms

Demographics

Age

Sex

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

Image Interpretation Pearls

Reporting Tips

References

Selected References

Images

Selected Images

Additional Images

35 KiB

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