Angiographically occult arteriovenous malformations causing intracerebral hemorrhage

We had experienced 5 cases of angiographically occult AVMs led to intracerebral hemorrhage and progressive neurologic deficit and seizure. Cerebral angiography in each case failed to demonstrate the vascular nature of the lesion and conventional skull radiography was no use. Computed tomography (CT), in 4 cases out of 5, showed well demarcated, slightly hyperdense and ovoid masses which turned out resolving hematomas. These lesions had also contained focal areas of high densities. In one case we observed definitively enhanced area in the resolving hematoma and it was corresponded to histopathologically proved AVM. CT appearance of acute hemorrhage at the subcortical region of cerebral hemisphere was showed in another case. We believe that CT can afford important supplementary information regarding an associated hematoma for angiographically occult AVM. Caution is advised in assuming that angiographically avascular lesion demonstrable by CT is not vascular malformation.