Computed tomography-guided stereotactic aspiration has been carried out in 20 patients with hypertensive pontine hemorrhage. A Komai computed tomography-guided stereotactic apparatus and a suboccipital transcerebellar approach were used. The entire operative procedures were performed under local anesthesia or neuroleptanalgesia in the semilateral position. Of 20 patients, the outcome was assessed as good in 9, fair in 4, and poor in 7. No patient deteriorated after the operation. The relationship between the preoperative clinical features and the outcome in comparison with the conservative treatment is presented.

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To evaluate the effect of radiosurgery on angiographically occult vascular malformations (AOVMs), 9 patients treated with Gamma Knife surgery were followed up for 21–37 months. Eight patients had bleeding episodes, 1 had uncontrollable epilepsy. Rebleeding occurred in 3 AOVMs 5 or 6 months after treatment. One patient experienced transient radiation-induced edema. One patient underwent surgical extirpation due to uncontrollable epilepsy 21 months after Gamma Knife surgery. Histological findings revealed an arteriovenous malformation (AVM) and a cavernous angioma. There was hypertrophy of the internal membrane of the AVM, but no effect on the cavernous malformation. Radiosurgery should only be considered in cases of inoperable AOVM, because there is no definite proof that radiosurgery prevents AOVMs from rebleeding.

A case of multiple segmental agenesis of the cerebral arteries is presented. Cerebral angiography demonstrated bilateral so-called carotid rete mirabile, a similar "rete" of the right vertebral artery and intradural duplication of the left vertebral artery. These abnormalities are thought to be caused by multiple segmental agenesis of the cerebral arteries as they penetrate the dura mater. The embryological and anatomical significance of these findings is discussed.

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