Arteriovenous malformations involving the vein of Galen.

The vein of Galen is the largest of the deep cerebral veins formed posterior to the pineal body by confluence of the two internal cerebral veins. It curves sharply upward around the splenium of the corpus collosum and drains the deep medially located veins of the diencephalon, basal ganglia, and mid brain. Dilatation of the vein of Galen results from the force of arterial blood either directly from an artery or by way of a tributary vein or veins which receive blood from an artery.2 The dilated vein of Galen is therefore a varix associated with an arteriovenous malformation. In most cases a venous (dural) anomaly can be demonstrated downstream from the draining vein,3 and this, together with the high blood flow into the vein of Galen causes its dilatation. Hoffman et a!4 have described four prominent angiographic patterns of Galenic arteriovenous malformations and related these to the clinical presentation treatment and outcome.