Megalencephaly due to impaired cerebral venous return in a Sturge-Weber variant syndrome.

An infant with a Sturge-Weber variant syndrome developed progressive megalencephaly and eventual hydrocephalus, which required shunting. Cerebral angiography revealed absence of the deep cerebral venous system and the development of abnormal drainage channels via the periorbital veins. It is postulated that the abnormal enlargement of the brain was due to the impaired venous return. Resistance of the brain to continued expansion may have caused an increase in hydrostatic pressure and the development of hydrocephalus.