title: New grading system based on magnetic resonance imaging in a mouse model of subarachnoid hemorrhage.
abstract: OBJECTIVE
  A grading system for experimental subarachnoid hemorrhage (SAH) that does not require animal euthanasia is currently unavailable. We proposed a new grading system based on MRI and evaluated the feasibility of this method in a mouse model of SAH.
  
  
  METHODS
  SAH was induced by endovascular perforation in adult male C57BL/6 mice. Mice underwent MRI 24 hours after SAH and were categorized into the following 5 grades based on T2*-weighted imaging: Grade 0, no visible SAH or intraventricular hemorrhage (IVH); Grade 1, minimal/localized SAH without IVH; Grade 2, minimal/localized SAH with IVH; Grade 3, thick/diffuse SAH without IVH; and Grade 4, thick/diffuse SAH with IVH. Neurological deficits were then assessed and the mice euthanized for conventional SAH grading.
  
  
  RESULTS
  Among a total of 47 mice, 4% were scored as grade 0, 30% as grade 1, 11% as grade 2, 30% as grade 3, and 26% as grade 4. This MRI grading had excellent interobserver reliability (weighted κ value =0.94), and there were strong correlations between the MRI grading and the conventional grading (r=0.85; P<0.001) or between MRI grade and neurological scores (r=-0.46; P<0.01).
  
  
  CONCLUSIONS
  The new MRI grading correlated well with conventional grading and enabled in vivo evaluation of SAH severity. This grading system may offer advantages in future studies of experimental SAH.
authors.affiliation: From the Department of Neurosurgery, University of Michigan, Ann Arbor, MI.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Egashira
authors.affiliation: From the Department of Neurosurgery, University of Michigan, Ann Arbor, MI.
authors.forename: Hajime
authors.initials: H
authors.lastname: Shishido
authors.affiliation: From the Department of Neurosurgery, University of Michigan, Ann Arbor, MI.
authors.forename: Ya
authors.initials: Y
authors.lastname: Hua
authors.affiliation: From the Department of Neurosurgery, University of Michigan, Ann Arbor, MI.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Keep
authors.affiliation: From the Department of Neurosurgery, University of Michigan, Ann Arbor, MI. guohuaxi@umich.edu.
authors.forename: Guohua
authors.initials: G
authors.lastname: Xi
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D013345:Subarachnoid Hemorrhage / Q000378:metabolism / Q000473:pathology*
keywords: MRI; grading system; mice; subarachnoid hemorrhage