Pediatric Cerebrovascular Disease

Moyamoya. Moyamoya is a progressive occlusive arteriopathy of the distal internal carotid arteries. The idiopathic form, also known as “primary moyamoya” or “moyamoya disease,” occurs more commonly in children of Japanese or Korean descent, although it has been observed in all ethnicities. Secondary moyamoya, or “moyamoya syndrome,” can develop after brain radiation for the treatment of childhood cancers, most commonly retinoblastoma, or can occur in genetic conditions, such as sickle cell disease, Down syndrome, neurofibromatosis type 1, and a rare form of primordial dwarfism. The name, Japanese for “haze” or “puff of smoke,” comes from small collateral blood vessels that form near the site of occlusion and give a hazy appearance on conventional angiography. Moyamoya typically manifests with ischemic strokes or transient ischemic attacks in early to mid childhood. However, if a child develops enough collateral blood flow to preclude ischemic events, he or she may not present until young adulthood with a hemorrhagic stroke, typically due to rupture of the abnormal moyamoya collaterals. Surgical treatment of moyamoya includes a variety of revascularization procedures intended to bypass the internal carotid circulation and improve cerebral perfusion.

PHACE Syndrome. PHACE is a recently recognized neurocutaneous syndrome that includes Posterior fossa abnormalities, such as cerebellar hypoplasia or Dandy-Walker malformation; large, segmental cervicofacial Hemangiomas; cervical and/or cerebral Arterial anomalies; Cardiac anomalies, such as coarctation of the aorta; and Eye abnormalities, such as optic nerve atrophy, congenital cataracts, and retinal vascular abnormalities. The skin hemangiomas seen in PHACE are considered infantile hemangiomas, defined as benign neoplasms of the vascular endothelium that display a characteristic natural history of being absent or minimally apparent at birth, growing rapidly during infancy, and then slowly regressing. The cerebrovascular anomalies vary widely from clinically insignificant “normal variants,” such as a duplicated vessel or persistent fetal vessel, to severe hypoplasia of the internal carotid artery that can lead to ischemic stroke.

Vein of Galen Malformations. Vein of Galen malformations (VOGM) are congenital arteriovenous fistulas, or direct connections between arteries and veins, that drain into the developmental precursor of the vein of Galen, a midline vein that is part of the deep venous drainage system of the brain. VOGMs are easily detected on head imaging, even prenatal ultrasounds, as a large midline vascular structure. VOGMs can present in the neonatal period with high-output congestive heart failure, often with pulmonary hypertension. If the flow is not sufficient to lead to heart failure, they will often present later in infane with symptoms of hydrocephalus. VOGMs can injure the brain by causing venous ischemia (poor perfusion due to local high venous pressures), or, rarely, intraventricular or intracerebral hemorrhage. Findings on exam will include a pulsatile cranial bruit, macrocephaly, and prominent scalp veins. These lesions are treated with embolization, that is, endovascular placement of embolic material to close off the abnormal artery to vein connections. Although presentation during the neonatal period with congestive heart failure portends a poor prognosis, children whose VOGMs can be cured before the brain is injured can have a normal outcome.

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