ACR Codes: 1.1
There are four major types of vascular malformation: » arteriovenous malformation
» cavernous malformation (cavernous hemangioma)
» capillary telangectasia
» developmental venous anomaly (venous angioma)
They are composed of radially arranged, dilated anomalous veins that converge into a "collector vein" - an enlarged transcortical or subependymal draining vein.
Microscopically they consist of dilated, thin walled venous channels separated by normal brain tissue. The precise etiology is unknown but they likely represent extreme anatomic variants and not true vascular malformations.
They are located in the deep cerebral or cerebellar white matter, most often near the margin of an adjacent ventricle. The most common site is adjacent to the frontal horn of the lateral ventricle.
They can occur at any age and often are asymptomatic and therefore may be incidental findings on imaging studies.
They are the most common vascular “malformation” found at autopsy. Most are solitary, but multiple lesions can occur in the rubber bleb nevus syndrome.
Imaging:
CT- Non enhanced CT scans are typically normal or show an ill-defined slightly hyperdense area. Following contrast administration, an enhancing tuft of rounded or linear vessels near the angle of a ventricle is identified. These enlarged medullary veins become continuous, with a dilated transcortical draining vein that in turn empties into an adjacent dural sinus, cortical or subependymal vein. Edema and mass effect are typically absent.
MR- On magnetic resonance scans a stellate tangle of venous tributaries drains into a larger, sharply delineated vein that often shows high-velocity signal void. Flow-related enhancement can occasionally be seen. After contrast administration, the enlarged medullary tributaries and the transcerebral or subependymal draining veins are typically well seen. Evidence of gliosis or hemorrhage is present in 10-15% of cases.
Reference(s): Osborn, Anne G. Diagnostic Neuroradiology. 1994. Mosby. Pgs 314-19.
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Disease Topic 6443 
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