The role of dural anomalies in vein of Galen aneurysms: report of six cases and review of the literature.

It is proposed that the vein of Galen aneurysm represents a venous ectasia secondary to an increased flow (usually caused by a deep-seated arteriovenous shunt draining either directly into the vein of Galen aneurysm or into a tributary of the vein of Galen) associated with obstruction of a dural sinus distal to the aneurysm. The closer the venous obstruction is to the vein of Galen, the better the chances are of developing obstructive (noncommunicating) hydrocephalus and the more likely it is that the venous drainage from the rest of the brain will be unaffected. The farther the venous obstruction is from the vein of Galen aneurysm, the better the chances are of developing a communicating type of hydrocephalus. The development of cardiac failure is related to the magnitude of the arteriovenous shunt. Brain damage, seizures, and hemorrhage may be related to the retrograde venous engorgement, causing impaired drainage of the healthy brain. Careful attention should be paid to the venous drainage characteristics of the lesion because the types of dural venous obstructions and anomalies vary from case to case. The term "vein of Galen aneurysm" should be abandoned in favor of the term "vein of Galen ectasia."