Dural-pial arteriovenous malformation with unusual venous drainage.

A 41-year-old female presented with an uncommon mixed dural-pial arteriovenous malformation (AVM) with unusual venous drainage. Angiography at the initial operation for massive intracerebral hematoma in the parietal lobe showed no vascular malformations. Follow-up angiography 3 years later revealed a mixed dural-pial AVM at the previous surgical site. Unexpectedly, the venous drainage from the AVM was not into the patent superior sagittal sinus, but was retrograde into the contralateral cortical veins in the occipital lobe. No skull fracture or sinus thrombosis was demonstrated. The AVM was resected successfully without neurological deterioration. The pial portion of the lesion may have been a congenital anomaly, and the dural portion acquired. The development of a dural AVM at an earlier surgical site is uncommon, and may indicate the possible pathogenesis of acquired dural AVMs unrelated to sinus occlusion or accidental trauma. Furthermore, there are various possible patterns of venous drainage in vascular malformations.