Significant stenosis (>70%) of the draining sinus is a significant factor for Vein of Galen malformation aneurysmal enlargement and the occurrence of hydrocephalus. Probably, venous outflow impairment decreases the incidence of high-output heart failure and increases the incidence of hydrocephalus 1).
1)
Hassan T, Sultan A, Ibrahim T, El-Saadany WF. The Impact of Angiographic Geometry on the Clinical Presentation of True Vein of Galen Aneurysmal Malformations. Pediatr Neurosurg. 2021 Jan 13:1-7. doi: 10.1159/000512213. Epub ahead of print. PMID: 33440394.