venerdì 26 settembre 2008

Vein of Galen malformation










Findings

Figure 1 and Figure 2: Digital subtraction angiography. Left vertebral artery injection (lateral and frontal projections) demonstrating multiple dilated posterior thalamoperforating arteries filling a large sacular structure and early venous sinus enhancement.
Figure 4 and Figure 5: Fluoroscopic lateral and frontal images demonstrating a coil mass in the venous varix.
Figure 6: 3D TOF MRA demonstrating early filling of a dilated falcine vein and dural sinus via enlarged branches of the anterior and posterior cerebral arteries. The previously noted varix has been coiled and is no longer noted.
Figure 7: T1-weighted sagittal image demonstrating susceptibility artifact from coil material within the varix and a dilated falcine vein and dural sinus.

Differential Diagnosis:
- Vein of Galen malformation
- Childhood dural arteriovenous fistula
- Arteriovenous malformation
- Complex developmental venous anomaly


Diagnosis: Vein of Galen malformation


Vein of Galen malformation (VOGM) can result from
- a pial arteriovenous malformation with deep venous drainage (type 1, choroidal)
- a direct arteriovenous fistula (type 2, mural)
- a combination of both.

VOGM is often a misnomer because the median prosencephalic vein of Markowski is typically involved in the malformation. Arterial supply is usually from the thalamoperforating arteries, anterior cerebral branches, and branches from the posterior cerebral artery, including the posterior choroidal arteries.

The neonatal form of this malformation arises during weeks 6-11 of fetal development when an arteriovenous connection between primitive choroidal vessels and the median prosencephalic vein of Markowski (a temporary drain for the choroids plexus) occurs. The abnormal flow through this connection slows the regression of this embryonic vein, therefore preventing the formation of the vein of Galen. The persistant median vein usually drains into the sagittal sinus via a persistent falcine vein and the straight sinus fails to form.

Children and adults usually present with headaches, seizures, hemorrhage or focal neurologic symptoms. Neonates most commonly present with high output heart failure and seizures, and may have a striking cranial bruit. Mass effect, hydrocephalus, parenchymal loss, intracranial venous stenosis, and steal phenomena leading to ischemia are all sequelae of untreated VOGMs, all increasing morbidity and mortality despite early treatment.

MRA/MRV is as an invaluable imaging tool, helping both to preliminarily map for endovascular procedures and to subsequently monitor for successful therapy. After stabilizing the neonate with medical therapy, endovascular treatment is employed, with embolization options including coils and acrylics. A venous approach is more common due to complications with femoral artery catheterization in neonates; however, an arterial approach appears to be more successful. Multiple endovascular embolizations are often needed. Heart failure responds favorably to embolization. Refractory hydrocephalus may require shunt placement. Endovascular embolization has shown to decrease morbidity and mortality when compared to surgical repair in patients without evidence of cerebral parenchymal damage or multisystem failure.

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