Vein of Galen malformations (VOGMs) are rare blood vessel malformations in the brain. The malformation develops before birth and may be found during pregnancy or very soon after birth. This condition affects a large vein deep at the base of the brain. The malformation causes oxygen-rich blood to flow directly through this vein away from the brain instead of delivering blood to surrounding brain tissues. This rush of blood away from the brain puts pressure on the heart and lungs, often causing congestive heart failure or pulmonary hypertension.