title: Micro-arteriovenous malformations: significant hemorrhage from small arteriovenous shunts.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Neurosurgical Service, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
authors.forename: S I
authors.initials: SI
authors.lastname: Stiver
authors.forename: C S
authors.initials: CS
authors.lastname: Ogilvy
mesh_terms: D000328:Adult; D001166:Arteriovenous Shunt, Surgical / Q000009:adverse effects*; D002533:Cerebral Angiography; D002543:Cerebral Hemorrhage / Q000209:etiology*; D002648:Child; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications* / Q000175:diagnosis / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000209:etiology; D011183:Postoperative Complications; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome