Monday 22 August 2011

Vein of Galen Ectasia / Varix

A 30 y o male brought by relatives for his Psychiatric problems. 
Here is his Non contrast CT Brain and MRI Axial T2w images. 
Findings are prominence of right side internal cerebral vein with dilatation of Vein of Galen - vein of Galen ectasia.
Clinical significance of dilatation of vein of Galen is doubtful in this case.
Literatures mentions about variety in the clinical presentations of patients with vein of Galen dilatation. In milder forms even psychiatric complaints are known.

Vein of Galen Malformation

Three anatomic types of VG malformation have been individualized.
1. Vein of Galen arterio-venous malformation (AVM),
2. Cerebral AVM with vein of Galen ectasia,
3. Varix of the vein of Galen without AV shunt.

Ectasia / varix of the vein of Galen, are milder forms appear to present later in life with bleeding episodes and do not present in the neonate with cardiac failure, do not require any type of morphological correction. Ectasia or varix of the vein of Galen is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that Ectasia or varix of the vein of Galen, or a subtype of Ectasia or varix of the vein of Galen, affects less than 200,000 people in the US population.

Vein of Galen is short venous structure located centrally in pineal region, formed by confluence of internal cerebral veins and basal vein of Rosenthal, extend beneath splenium of corpus callosum, joins inferior sagittal sinus and continues as straight sinus. It drain thalami, medial temporal lobes, superior cerebellar vermis and part of occipital lobes.

Pathogenesis of VG Malformation is aneurysmal dilation with arteriovenous fistula, results from immaturity of the cerebral vascular system with persistence of fetal vessel, involves median prosencephalic vein of Markowski.
The median prosencephalic vein of is thought to be the embryonic precursor of vein of Galen. By 3rd month of development its posterior portion join internal cerebral vein and basal vein to form vein of Galen. Persistence of these primitive arterio venous connections may explains malformations of Vein of galen.

Lasjaunias has proposed a very functional and simple angiographic classification of vein of Galen malformation and divides these into true and secondary vein of Galen aneurysms. The true malformations have direct shunts in the wall of vein or in the cistern proximal to it. These shunts are all extra cerebral and are typically fed bilaterally by choroidal arteries, pericallosal arteries and thalamo striate perforators. The secondary vein of Galen malformation consist of a dilated vein of Galen secondary to an adjacent dural or parenchymal AV malformation.
Yasargil subdivided true vein of Galen malformation into types I through IV depending up on location of the fistula. The type I is simplest with pure cisternal component and a single or few multiple feeders from peri callosal and posterior cerebral arteries. Types II and III (most common varieties) are more complex lesions with higher flows and contributions from thalamic perforators and basilar arteries. Type IV is a true parenchymal AVM with secondary dilation of vein of Galen.

A grading system based of venous aspect of vein of Galen malformation has four grades.
Grade 1 the degree of ectasia of straight sinus is same as that of vein of Galen  both being minimally dilated. Grade 2 lesion occur when vein of Galen is more dilated than straight sinus both structures moderately increased in size. Grade 3 lesion demonstrates marked dilatation of both the structures and Grade 4 have Significant enlargement of vein of Galen with normal, stenotic or absent straight sinus.

Reference : Principles and Practice of Pediatric Neurosurgery by A. Leland Albright, Ian F. Pollack, P. David Adelson.

No comments: