Micro-arteriovenous malformations: Significant hemorrhage from small arteriovenous shunts

OBJECTIVE: Micro-arteriovenous malformations (AVMs) represent approximately 8 to 10% of surgically treated brain AVMs. We examined the clinical presen tations, radiological features, principles of surgical resection, and facto rs affecting outcomes for micro-AVM lesions. METHODS: Twelve patients with micro-AVMs that had been treated by surgical resection were retrospectively analyzed. The mean follow-up monitoring peri od was 35 months (range, 2-76 mo). Outcomes, as assessed in follow-up visit s and telephone interviews (using a questionnaire), were classified accordi ng to the Glasgow Outcome Scale. RESULTS: All 12 patients presented with intracranial hemorrhage, which was intraparenchymal and superficially situated in 10 patients (83%) and intrav entricular in 2 patients (17%). Hemorrhages were large (mean volume, 23 ml( 3); range, 1-58 ml(3)) and were associated with neurological deficits for 1 0 of 12 patients (83%). The identification of an arterialized draining vein during surgery and stereotactic angiography greatly facilitated surgical l ocalization of the lesions. One patient (8%) developed a mild permanent def icit as a result of surgery. Although Glasgow Outcome Scale scores were exc ellent for all except one patient, nine patients (75%) experienced long-ter m neurological problems. CONCLUSION: Micro-AVMs typically present with large hemorrhages and are ass ociated with significant neurological deficits. If a superficial clot is pr esent, surgical resection of the lesion is strongly advocated. The ultimate clinical outcomes are determined primarily by deficits present after the i nitial hemorrhaging episodes.