Vein of Galen aneurysm

Findings

There is a large vascular structure just posterior to the third ventricle and superior to the cerebellar vermis. There is some mass-effect on the third ventricle with dilatation of the third ventricle and frontal horns. No definite intracranial hemorrhage noted. MRI shows a large tubular structure with flow identified in the region of the vein of Galen extending into the straight sinus towards the torcula Herophili. There are numerous collateral vessels within the ambient and perimesencephalic cisterns as well as surrounding the brainstem.


Diagnosis: Vein of Galen aneurysm


Key points

Vein of Galen "aneurysm" is actually an AVM with an associated varix of the vein of Galen.

Two main types exist
- Vein of Galen AVM.
- Vein of Galen aneurysmal dilatation.

Vein of Galen AVM is the result of a developmental malformation that involves the vein of Galen. It is an A-V shunt in the wall of an embryologic venous precursor (Median Vein of the Prosencephalon [MVP]) and in this situation a normal vein of Galen does not exist and is replaced by a persistent MVP. The MVP does not drain normal brain tissue. In other words, a Vein of Galen AVM is not anatomically associated with a parenchymal AVM. The dilated MVP drains via the dural sinuses. Vein of Galen AVM presents in infancy with high output cardiac failure and macrocephaly. The A-V fistulas may be single or multiple. Intrauterine diagnosis is usually possible by doppler. Intracranial hemorrhage is rare.

Vein of Galen AVM should be differentiated from aneurysmal dilatation of the vein of Galen which occurs in association with a parenchymal AVM or the rare asymptomatic varicose vein of Galen.

Therapy: Endovascular embolization via an arterial or venous access.


Radiology

Transcranial doppler sonogram shows an anechoic structure in the superoposterior aspect of the third ventricle with flow.
CT, MRI and MRA show the vascular abnormality and assess the brain parenchyma for abnormalities.
Conventional angiography is essential to assess the malformation and to plan the therapy.