Synonyms:
Moyamoya disease a.k.a. idiopathic progressive arteriopathy of childhood a.k.a. spontaneous occlusion of circle of Willis:
Diagnosis:
Moyamoya syndrome is an angipathic pattern, not a specific disease. It has primary & secondary causes
Moyamoya disease referes to the idiopathic condition that represents primary moyamoya syndrome
Clinical features:
- Bimodal age of onset: children ~5 years old & adults ~40 years old.
- TIA, Ischemic stroke, intraparenchymal hemorrhage (basal ganglia), Subarachnoid hemorrhage, seizures, migraine-like headaches.
- Ophthalmoscopy: “morning glory disk,” an enlargement of the optic disk with concomitant retinovascular anomalies
Findings on Investigations:
CT:
- With contrast shows punctate dots in the basal ganglia & net like vessels in cisterns
- Intraventricular hemorrhage may occur
- Atrophy anterior> posterior in children
- Features of Complications (stroke, intraparenchymal hemorrhage, subarachnoid hemorrhage)
MRI:
- T1: Basal ganglia flow voids
- T2: white matter disease
- Reduced flow voids in the internal, middle, and anterior cerebral arteries
- Prominent flow voids through the basal ganglia and thalamus (from collateral vessels)
- FLAIR: Cortical flow= high signal in sulci = “ivy sign”
- T2 Gradient echo: prior hemorrhage
- DWI: acute stroke if acute on chronic disease
- T1+C: shows punctate dots in the basal ganglia & net like vessels in cisterns. Enhanced “Ivy sign”
CTA:
- Narrowed intracranial internal carotid arties & proximal ACA & MCA.
- Collaterals from internal carotid artery (basal ganglia) and external carotid artery.
- Aneurysms (circle of Willis, basal ganglia, collateral vessels)
Catheter Angiography:
- Gold standard test
- Stenosis of distal ICA bilaterally or proximal circle of Willis arteries
- Enlargement of lenticulostriate/thalamostriate arteries “puff of smoke” appearance.
- Dilated anterior choroidal artery
- Transdural & transosseous ICA ECA collaterals
- See Suzuki grade. Also do ECA angiograms to evaluate collaterals.
- Aneurysms may occur (circle of Willis, basal ganglia, collateral vessels).
EEG, in children:
- Posterior or centrotemporal slowing
- Hyperventilation: build up (monophasic slow waves during hyperventilation), re-build up (monophosic slow waves after hyperventilation) indicates diminished cerebral reserve.
Pathology:
- It affects Large vessels: Narrowed vessels
- Hyperplasia of smooth-muscle cells and luminal thrombosis
- Tunica Media: attenuated, with irregular elastic lamina
- Collaterals: fragmented elastic lamina, thinned tunica media, microaneurysms
Suzuki Grade:
- I: Narrowing of ICA apex
- II: Initiation of “puff of smoke” moyamoya collaterals
- III: Narrowing of internal carotids with prominent moyamoya collaterals (puff of smoke). Diminished cortical perfusion.
- IV: Development of ECA collaterals
- V: prominent ECA collaterals & reduction of moyamoya collaterals
- VI: Occlusion of ICAs & disappearance of internal carotid artery collaterals (persistence of ECA collaterals)
Treatment:
Atherosclerotic moyamoya syndrome should be treated like high grade intracranial atherosclerotic disease ICAD. The rest of the discussion refers to non-atherosclerotic moyamoya syndrome:
- Aspirin in adults presenting with ischemic stroke unless intraparenchymal hemorrhage is present
- Revascularisation in non-atherosclerotic moyamoya syndrome
- Indirect methods ECA branch to brain:
- ECA (dura, temporalis muscle, or superficial temporal artery)
- Examples:
- Encephalo-dural-arterio-synangiosis EDAS
- Encephalomyoarteriosynangiosis
- Pial synangiosis
- Direct methods ECA branch to ICA branch:
- Superficial temporal artery- Middle cerebral artery anastomosis, STA-MCA anastomosis
References:
- Kawaguchi, S., et al., Characteristics of intracranial aneurysms associated with moyamoya disease. A review of 111 cases. Acta Neurochir (Wien), 1996. 138(11): p. 1287-94.
- Fung, L.W., D. Thompson, and V. Ganesan, Revascularisation surgery for Pediatric moyamoya: a review of the literature. Childs Nerv Syst, 2005. 21(5): p. 358-64.