Spontaneous regression of giant arteriovenous fistulae during the perinatal period. Case report. A unique case of spontaneous regression of giant arteriovenous fistulae during infancy is described in this report. A female infant, the product of normal labor and delivery, demonstrated severe ventriculomegaly and an intracranial hemorrhage at birth. Cerebral angiography at 5 days of age revealed several large fistulae fed by the anterior and middle cerebral arteries draining into the deep venous system through a dilated internal cerebral vein and ectatic vein of Galen. Two days following the angiogram, a second intracranial hemorrhage occurred. Active hydrocephalus developed over the next 6 months and was treated with ventriculoperitoneal shunting. When the child was 8 months of age, angiography failed to demonstrate the fistulae. It was postulated that pressure effects from the intracranial hematoma and long-standing intracranial hypertension as well as stenosis in the anomalous venous outflow resulted in vascular stasis, venous thrombosis, and selective arterial occlusion. Hydrocephalus was a result of the compression of the intraventricular foramina by dilated embryonic vessels. This anomaly, predominantly involving the anterior circulation, may be homologous to the vein of Galen aneurysm in the posterior circulation. 