Clinical History
3 month-old baby boy presented with enlarging head circumference, and an audible cranial bruit.
Imaging Findings
3 month-old baby boy presented with enlarging head circumference, and an audible cranial bruit. An MRI examination of the brain was performed with SE T1, FSE T2, FLAIR sequences in three planes. MRI scan revealed numerous arterio-venous fistulas of the posterior circulation, draining to the rounded, signal-void aneurysmatic dilatation of the vein of Galen. The vein of Galen was connected to a large confluence of the sinuses via a short stenotic straight sinus. The MRI findings in our patient were consistent with a mural-type vein of Galen malformation. Third and lateral ventricles were enlarged prominently, and high signal areas of periventricular white matter in T2-weighted images represented transependymal cerebrospinal fluid (CSF) resorption areas secondary to hydrocephalus.
Discussion
The vein of Galen malfomations (VGM) are rare congenital malformations occuring between intracranial vessels, usually subependymal arteries, anterior and posterior choroidal, and anterior cerebral arteries, and a vein in the region of the vein of Galen. VGM’s are believed to develop early in embryogenesis prior to involution of the medial vein of the prosencephalon. Thus the dilated midline draining vein is not the vein of Galen, but rather the medial prosencephalic vein. The dural outflow is through primitive falceal sinuses rather than the straight sinus. Clinical findings vary greatly depending on the type of connection. There are two types of VGM’s. The difference between choroidal and
mural types of VGM depends on the
type of shunts spread in the choroid fissure or directly into the wall of the VGM. The more common one is choroidal type, which usually presents with congestive heart failure and involves arteriovenous connections in the anterior wall of the prosencephalic vein supplied by numerous choroidal, pericallosal, and thalamoperforator vessels. The other type is mural type, where fewer but larger caliber connections exist between the posterior choroidal or collicular arteries and the medial prosencephalic vein, which is usually aneurysmal because of outlet stenosis. The patients with mural type usually present in infancy with loss of developmental milestones, increasing head circumference, focal nerological deficits. Sonography shows median tubular cystic space with high-velocity turbulent flow demonstrated color Doppler sonography, brain infarction or leukomalacia, cardiac enlargement due to high-output heart failure, dilated veins of head and neck, and hydrocephalus. Hydrocephalus is due to the impairment of cerebrospinal fluid absorption produced by elevated venous pressure in the draining sinuses. Computed tomography reveals round well-circumscribed homogeneous slightly hyperdense mass in region of third ventricular outlet, focal hypodense zones due to ischemic changes, and rarely rim calcification in 15 % of the cases. On MRI areas of signal void areas related to serpentine vascular structures, vein of Galen, straight sinus are obviously seen. Angiography could be performed on the same session of endovascular intervention to define precise vascular anatomy. During the therapy medical management of the cardiac failure is an essential adjunct to the interventional therapy. In the differential diagnosis, VGM should be distinguished from dilatation of vein of Galen, which is secondary to the deep distant cerebral arteriovenous malformations draining into the vein and causing its dilatation.
Differential Diagnosis List
Vein of Galen malformation
Final Diagnosis
Vein of Galen malformation
