Angiographically occult angiomas: a report of thirteen cases with analysis of the cases documented in the literature.

Thirteen cases of angiographically occult angioma (AOA) are reported. Nine of these presented with intraparenchymatous hemorrhage, and the other 4 patients had epilepsy. The pathological diagnosis was arteriovenous malformation in 12 cases and cavernous angioma in 1. All surgical specimens but 2 contained hemosiderin pigment. In addition to these 13 cases, we reviewed 159 cases of AOA reported in the literature and analyzed them in terms of age, sex, symptoms and signs at admission, computed tomographic findings, location and size of angioma, history of previous and recurrent hemorrhage, type of hemorrhage, and outcome of operation to determine the characteristics of AOAs. The results of these analyses are described in detail, and the indications for surgical treatment of suspected AOAs are discussed. Our microsurgical technique for detecting the angioma within or adjacent to the hematoma is also presented.