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 presentations, radiological features, principles of surgical resection, and factors 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 period was 35 months (range, 2-76 mo). Outcomes, as assessed in follow-up visits and telephone interviews (using a questionnaire), were classified according to the Glasgow Outcome Scale. RESULTS: All 12 patients presented with intracranial hemorrhage, which was intraparenchymal and superficially situated in 10 patients (83%) and intraventricular in 2 patients (17%). Hemorrhages were large (mean volume, 23 ml3; range, 1-58 ml3) and were associated with neurological deficits for 10 of 12 patients (83%). The identification of an arterialized draining vein during surgery and stereotactic angiography greatly facilitated surgical localization of the lesions. One patient (8%) developed a mild permanent deficit as a result of surgery. Although Glasgow Outcome Scale scores were excellent for all except one patient, nine patients (75%) experienced long-term neurological problems. CONCLUSION: Micro-AVMs typically present with large hemorrhages and are associated with significant neurological deficits. If a superficial clot is present, surgical resection of the lesion is strongly advocated. The ultimate clinical outcomes are determined primarily by deficits present after the initial hemorrhaging episodes.