[A case of aneurysm at the junction of the vertebral artery and a spinal arterial branch].

A 68-year-old male suffered from severe occipitalgia, nausea, and vomiting was admitted to our hospital. On admission, he complained only of headache and displayed no evidence of disturbed consciousness or neurological deficits. A computed tomographic (CT) scan revealed a subarachnoid hemorrhage in the basal subarachnoid cisterns, with the thickest, densest area in the bilateral ambient cisterns. Four-vessel angiograms disclosed no pathological findings. The patient was treated with bed rest and his blood pressure was maintained below 120 mmHg. Fortunately, no untoward events occurred during the period of bed rest, and a second vertebral angiogram was obtained 4 weeks after admission. At that time a vertebral artery aneurysm was discovered. At surgery a 3 X 3 X 3 mm aneurysm was found at the junction of the vertebral artery and a branch of the spinal artery. Small clots surrounding the aneurysm were removed. The aneurysm itself was easily clipped without destruction of the caudal cranial nerves and the patient recovered fully. The incidence of vertebral artery aneurysms is very small--about 5%. Moreover, to our knowledge an aneurysm on the proximal portion of the intracranial vertebral artery at the junction of the posterior-inferior cerebellar artery has never before been reported. On the other hand, our case might have been included among cases of subarachnoid hemorrhage of unknown etiology. The first cerebral angiogram revealed no aneurysm; it was found on the second set of angiograms. This case illustrates the importance of repeat angiography when the CT scan clearly shows a subarachnoid hemorrhage.