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[Surgical indication of arteriovenous malformation at ventrolateral craniocervical junction (author's transl)].

We presented four cases of arteriovenous malformation in the vicinity of medulla oblongata, located ventrolaterally at the craniocervical junction. All cases developed subarachnoid hemorrhage and the initial symptoms were not specific except for the severe nuchal rigidity and headache. Three cases were surgically treated. Satisfactory results were obtained by clipping of the feeding arteries and coagulation of the abnormal vessels with bipolar coagulator. One case died of fourth attack on the second day after admission and was autopsied. Bilateral vertebral angiography is the best for diagnosis and the open mouth projection is essential because a shortened vascular figures of vertebral arteries can be corrected and because abnormal vessels can be found usually in the open mouth space. In our cases, C2 radiculomedullary artery, anterior spinal artery, posterior spinal artery and the abnormally dilated artery branching from posterior inferior cerebellar artery and vertebral artery to flow into the lateral-inferior portion of medulla oblongata participated as feeding arteries. As the lesion located at the lateral and ventral surface of medulla oblongata, the surgical procedures were difficult totally to remove. If the anterior spinal artery is not the main feeding artery, the operating purpose can be attained by clipping or ligaturing the other feeding arteries and then coagulating the abnormal vessels as much as possible. When the main feeding artery is the anterior spinal artery and the arteriovenous malformation locates in the medulla oblongata, it is impossible to treat this surgically by the dorsal approach. It may be necessary to carry out the other ways such as the transclival approach.