title: Silent arteriovenous malformation hemorrhage and the recognition of "unruptured" arteriovenous malformation patients who benefit from surgical intervention.
abstract: BACKGROUND
  Arteriovenous malformation (AVM) patients present in 4 ways relative to hemorrhage: (1) unruptured, without a history or radiographic evidence of old hemorrhage (EOOH); (2) silent hemorrhage, without a bleeding history but with EOOH; (3) ruptured, with acute bleeding but without EOOH; and (4) reruptured, with acute bleeding and EOOH.
  
  
  OBJECTIVE
  We hypothesized that characteristics and outcomes in the unrecognized group of silent hemorrhage patients may differ from those of unruptured patients.
  
  
  METHODS
  Two hundred forty-two patients operated-on since 1997 were categorized by hemorrhage status and hemosiderin positivity in this cohort study: unruptured (group 1), silent hemorrhage (group 2), and ruptured/reruptured (group 3/4). Group 3/4 was combined because hemosiderin cannot distinguish acute hemorrhage from older silent hemorrhage.
  
  
  RESULTS
  Hemosiderin was found in 45% of specimens. Seventy-five patients (31.0%) had unruptured AVMs, 30 (12.4%) had silent hemorrhage, and 137 (56.6%) had ruptured/reruptured AVMs. Deep drainage, posterior fossa location, preoperative modified Rankin Scale (mRS) score, outcome, and macrophage score were different across groups. Only the macrophage score was different between the groups without clinical hemorrhage. Outcomes were better in silent hemorrhage patients than in those with frank rupture (mean mRS scores of 1.2 and 1.7, respectively).
  
  
  CONCLUSIONS
  One-third of patients present with silent AVM hemorrhage. No clinical or anatomic features differentiate these patients from unruptured patients, except the presence of hemosiderin and macrophages. Silent hemorrhage can be diagnosed using magnetic resonance imaging with iron-sensitive imaging. Silent hemorrhage portends an aggressive natural history, and surgery halts progression to rerupture. Good final mRS outcomes and better outcomes than in those with frank rupture support surgery for silent hemorrhage patients, despite the findings of ARUBA.
authors.affiliation: *Departments of Neurological Surgery, ‡Anesthesia and Perioperative Care, Center for Cerebrovascular Research, §Radiology, and ¶Pathology, University of California, San Francisco, San Francisco, California.
authors.forename: Adib A
authors.initials: AA
authors.lastname: Abla
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Nelson
authors.forename: Helen
authors.initials: H
authors.lastname: Kim
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Hess
authors.forename: Tarik
authors.initials: T
authors.lastname: Tihan
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lawton
mesh_terms: D000328:Adult; D002543:Cerebral Hemorrhage / Q000175:diagnosis* / Q000209:etiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications* / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged