Three cases of occult micro-
arteriovenous malformations not identified by cerebral angiography or other imaging modalities were detected by superselective angiography. The first case had a small
intracerebral hemorrhage in the superior colliculus, the second had a perimesencephalic
subarachnoid hemorrhage, and the third presented with
intracerebral hemorrhage combined with massive intraventricular
hematoma. While repeated selective cerebral angiography (four-vessel study) was negative, superselective angiography clearly demonstrated each lesion with small early venous filling in accordance with the location of
hematoma. Successful superselective embolization with
polyvinyl alcohol particles was performed in each micro-
arteriovenous malformation by flow-guided microcatheter without postoperative complications. Our experience suggests that superselective angiography is necessary to visualize micro-
arteriovenous malformations in patients with
cerebral hemorrhage and negative four-vessel angiography. Furthermore, the superselective endovascular approach has the advantage of offering immediate obliteration of the micro-shunt, thereby reducing or eliminating the risk of further
hemorrhage.