Venous malformation serving as the draining vein of an adjoining arteriovenous malformation. Case report and review of the literature.

BACKGROUND: Widely accepted pathologic classification of venous malformations includes discrete venous, arteriovenous, capillary, and cavernous malformations, each with distinct pathological criteria for definition. Several authors have described mixed or transitional vascular malformations with pathological features of more than one type of malformation within the same lesion. We present a rare case of a venous malformation associated with an arteriovenous malformation (AVM). CASE DESCRIPTION: A 37-year-old woman presented with a loss of consciousness. Computed tomography showed an enlarged vein running along the lateral wall of the right lateral ventricle. A cerebral angiogram demonstrated an AVM and a venous malformation in the right hemisphere; the AVM and the venous malformation were located in proximity to each other with the AVM using the venous malformation as its draining vein. In this case, where an AVM used the venous malformation as the draining vein, only the AVM was treated by proton-beam radiosurgery. Follow-up magnetic resonance angiography demonstrated complete obliteration of the AVM with the venous malformation remaining unchanged.
CONCLUSION: Arteriovenous shunting would have disturbed venous drainage resulting in the development of the venous malformation. Thus, in addition to demonstrating a rare coexistence of AVM and venous malformation, this case also offers a new insight into the pathogenesis of these vascular malformations.