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]]
((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.)).