Aneurysmal Malformation of the Great Vein of Galen

Background Neuroimaging Gross Pathology

BACKGROUND AND CLINICAL INFORMATION: Head

Summary: This is not a true aneurysm but a consortium of congenital vascular malformations of the neonate that all share dilatation of the vein of Galen as a common feature. It is resulted from abnormal communication between one or several cerebral arteries and the vein of Galen. Such abnormal communication can be deep-seated arteriovenous malformation, an arteriovenous fistula, or a verix. The prognosis and the baby often die of cardiac failure. Embolization appear to show some promise. Rupture is an uncommon event.

Clinical features: The most common clinical symptom is high output cardiac failure.

Poor prognosis: Aneurysmal malformation of the vein of Galen is associated with very high mortality. Neonates turn symptomatic within the 1st month of age (mortality 95%)has 3 times higher mortality than those turn symptomatic between age 1-12 months (mortality 33%). Embolization seems to be much more effective in treating this disease. Infants with delayed presentation and treated with embolization may survival with limited neurologic deficits. Rupture, however, is uncommon.

Progressive hydrocephalus due to compress of the aqueduct.

Congestive heart failure: They usually cause massive shunting and are associated with high mortality. If the malformation is large, cardiomegaly and congestive cardiac failure within a few weeks after birth can be seen in the new born. The brain can be extensively damaged by the aneurysmal formation.

Differential diagnosis from congenital heart disease is very important. A continuous murmur can be heard at the base of the skull in about 80% of cases associated with arteriovenous fistula. Twitch or generalized tonic convulsions and hydrocephalus may occur as a result of compression of the adequate.

Secondary lesions: The aneurysmal dilation of the vein of Galen may be associated with distal venous drainage stenosis or occlusion. Collateral or accessory paths of venous drainage such as "accessory straight sinus", are not uncommon. Other lesions such as periventricular infarction, intraventricular hemorrhage, periventricular calcification, and thrombosis and calcification of the aneurysmal vein can also be seen.

NEUROIMAGING: Head

Feeding arteries: The dilated vein of Galen is generally fed by blood from one or both posterior cerebral artery or one of their branches, less frequently from small posterior branches of middle cerebral arteries and other arteries.

Angioarchitectural analyses classify these malformations into 5 different types: 44% parenchymatous AV-malformations, 20% mural AV-fistulas, 30% choroidal arteriovenous fistulas, 3% dural AV-fistulas, 7% vein of Galen varices. [Lasjaunias P, Acta Neurochir (Wien) 1989 99:26-37]
Choroidal form: Multiple arteriovenous shunts in the choroidal fissure draining into the vein of Galen or an abnormal embryonal vein that dilates as a result of increased flow. Most commonly seen in newborn.
Mural form: The arterial trunks open directly into the vein of Galen. They are smaller and has later onset, usually between 1-15 months of age.
Parenchymal form: Characterized by multiple arteriovenous shunt within the parenchyma. They are smaller and has later onset, usually between 1-15 months of age.

GROSS PATHOLOGY: Head

Abnormal blood vessel: The blood vessel may have a normal architecture, but more often a lace-like network of tortuous blood vessels empties into the saccular vein of Galen that may be up to several centimeters in diameter. The entire venous system, including the transverse and straight sinuses, is dilated.

Wispread damage of the brain including infarction and calcification of the brain may occur as a result of blood stealing by the malformation.

Hemorrhage: Occasional, the malformed vein may rupture and cause intracranial hemorrhage; this is quite uncommon.

Hydrocephalus may be present.

NeuroLearn NeuroHelp Vascular For Comment: KarMing-Fung@ouhsc.edu

Background Neuroimaging Gross Pathology