Moyamoya

Background

Circle of Willis

• A cerebrovascular disease characterized by progressive stenosis/occlusion of the arteries around the Circle of Willis.
• The narrowing or blockage stimulates angiogenesis to provide collateral circulation to the brain.
• On angiography, these small blood vessels give off a "puff of smoke" appearance (also known as "MoyaMoya" in Japanese).
• The disease is found more commonly in Asian countries and was first descried in Japanese literature in 1957.
• There is mounting evidence there is a genetic cause of the disease.

Clinical Features

• The developed collateral circulation is prone to bleeding, aneurysm, thrombosis exhibiting: focal neurological deficits, TIA, epilepsy, and bowel/bladder incontinence.
• Children predominately exhibit ischemic stroke.
• Approximately 2/3rd of children exhibit Electroencephalography (EEG) abnormalities: high voltage slow waves that occur during hyperventilation.
• Can be associated with atherosclerosis, meningitis, vasculitis, autoimmune diseases, hematological conditions, brain tumors, and chromosomal abnormalities

Differential Diagnosis

• Hemorrhagic stroke/Ischemic stroke
• Giant cell arteritis, vasculitis
• Head trauma
• Basilar artery thrombosis
• Blood dyscrasias
• Cavernous sinus thrombosis
• Cerebral aneurysms
• Dissection syndromes (e.g. intracranial vertebral and carotid artery dissection)
• Carotid atherosclerosis
• Fibromuscular dysplasia
• Craniopharyngioma

Evaluation

T1-weighted MR image of moyamoya disease. Flow void in the basal ganglia is indicated by the arrow.

Left: MIP reconstructed MR angiography of a 11-year-old girl with moyamoya disease. Right: healthy patient, for comparison.

• Head CT and/or brain MRI are important studies to visualize infarctions and brain hemorrhages.
• CT can show dilation of the sulci accompanies by focal ventricular enlargement.
• MRI has higher sensitivity for detecting ischemic regions.
• Magnetic Resonance Angiographic studies can demonstrate occlusions within the circle of Willis and better visualize the collateral vasculature. It is preferred over CTA in most institutions.

Management

• Symptomatic treatment: decrease elevated ICP, improve cerebral blood flow, control active seizures, pain control , supplemental O2
• Avoid hypotension, hypervolemia, hypernatremia, hypocarbia
• Ventricular drainage if there is hemorrhage
• Minimize crying/hyperventilation a decreased PaCO2 can worsen ischemia by vasoconstriction
• Antithrombotic and thrombolytic surgery has not been systematically analyzed for Moyamoya disease

Disposition

• Admit