Between October 2002 and September 2003, we treated 5 cases of basal ganglia AVMs manifested by putaminal hemorrhage. The patients were 3 males and 2 females 32 to 65 years of age (mean 52.1). We performed craniotomy and removed hematomas in all cases. AVMs were successfully removed from 4 cases, but only coagulated in the remaining 1 case. Preoperative angiography was performed on 3 cases. AVMs were angiographically occult in 2 cases, while a tiny malformation was revealed in 1 case. The

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... ing 2 patients were in critical and rapidly deteriorating conditions, so that we had no time to perform preoperative angiography. Thus there was little preoperative information about AVM in our patients, but we did not encounter uncontrollable bleeding during surgery in any of them. We have concluded that basal ganglia AVMs may be a more common cause of putaminal hemorrhage than we previously suspected. It appears that in patients requiring removal of hematomas, preoperative cerebral angiography should be performed as far as possible. Even if angiography gives no evidence of AVMs, the presence of an occult AVM should be suspected. Nevertheless, because such an occult AVM does not seem to involve a high risk of intraoperative uncontrollable bleeding, its removal at the first surgery may be recommended.