The vein of Galen abnormality is the most frequent arteriovenous malformation in neonates.
It commonly presents in the neonatal period, although it may present later, in early childhood. Typically, in the neonatal period, VGAM presents with congestive heart failure, a cranial bruit, and marked carotid pulses.Hydrocephalus may be the presenting feature in older infants.
It is thought to result from the development of an arteriovenous connection between primitive choroidal vessels and the median prosencephalic vein of Markowski. The abnormal flow through the connectionretards the normal involution of this embryonic vein and thus prevents the development of the vein of Galen. The shunt is maintained through the remainder of brain development, with the persistent median vein draining into the sagittal sinus, often via a persistent falcine vein, with absence of the straight sinus.
There are two basic types of vein of galen malformation. :choroidal or mural subtypes.
Choroidal VGAMs usually emerge in the neonatal period with cardiac failure; with abundant, usually bilateral blood supply from choroidal arteries and pericallosal arteries. In contrast, the blood supply for mural VGAMs comes from collicular and posterior choroidal arteries, with fistulas on the wall of the malformation draining into the median vein of the prosencephalon and then to the dural sinuses .
Postulated causes of cerebral damage are reduced cerebral perfusion secondary to venous hypertension, abnormalities of CSF reabsorption leading to hydrocephalus and elevated intracranial pressure, and brain herniations with the fetal venous anatomy contributing to the development of venous watershed ischemia.
Criteria for endovascular treatment includes congestive heart failure that cannot be controlled with medical therapy.Various endovascular approaches used for embolisation include transarterial, transvenous or transtrocular approaches.
Transarterial approach: The arterial approach is more efficient in accomplishing a lasting reversal of the congestive high output failure as compared with the venous treatment. It is certainly not necessary to close the entire vein of Galen malformation to accomplish a reversal in the high output failure as reduction by about 30% to 40% of the arteriovenous shunt (two or three of the largest arterial feeders) will likely have this desired impact.The preferred agent is NBCA, used alone or with coils . Acrylics provide permanent occlusion, minimizing the risk of recanalization.
Transvenous or transtorcular approach: The indications for transfemoral venous treatment includes persistent symptoms despite transarterial and transtorcular embolisation or the inadvisability oftransarterial embolization because of an excessive number of feeding arteries .Transvenous approach is contraindicated when the vein of Galen enlargement is caused by an adjacent pial arteriovenous malformation draining into it.