Vein of Galen Malformation

The vein of Galen is located under the cerebral hemispheres and drains the anterior and central regions of the brain into the sinuses of the posterior cerebral fossa. The vein of Galen aneurysmal malformation is a choroidal type of arteriovenous malformation involving the vein of Galen forerunner and is distinct from an arteriovenous malformation with venous drainage into a dilated, but already formed, vein of Galen.

Aneurysmal malformations of the vein of Galen (VGAM) typically result in high-output congestive heart failure or may present with developmental delay, hydrocephalus, and seizures.

 

Classification:-

Five patterns of Galenic arteriovenous malformations have been described:

Pattern 1: Many vessels, including anterior cerebral arteries, thalamic perforating arteries, and superior cerebellar arteries discharge into the vein of Galen.

Pattern 2: A single posterior choroidal artery drains into the vein of Galen.

Pattern 3: One or both posterior choroidal and one or both anterior cerebral arteries drain directly into the Galenic system.

Pattern 4: An angiomatous network of posterior choroidal and thalamic perforating arteries enter the Vein of Galen directly.

Pattern 5: A high flow arteriovenous malformation in the right inferior frontal lobe drains via the inferior sagittal sinus and pericallosal vein into the Vein of Galen.

These malformations develop in utero by the persistence of fistulae between primitive pia arachnoidal arteries and plial veins that cross each other at right angles. Because the primitive Galenic system and the primitive choroidal system lie close together, an arteriovenous malformation involving the primitive choroidal system will inevitably involve the Galenic vein. Larger arteriovenous shunts correlate with greater hemodynamic effects and earlier symptom onset; small arteriovenous shunts correlate with greater local mass effect causing progressive neurological impairment.