title: MRI of the perihemorrhagic zone in a rat ICH model: effect of hematoma evacuation.
abstract: BACKGROUND
  Perihemorrhagic pathophysiology of spontaneous intracerebral hemorrhages (ICH) remains unclear. Recently, ischemic changes in the perihemorrhagic zone (PHZ) have been discussed as a potential source of secondary damage. In this study, we focussed on diffusion and perfusion characteristics of experimental ICH.
  
  
  METHODS
  Experimental ICH was induced with a double injection model in rats. In total, 49 animals were examined at three timepoints within 3.5 h after ICH with a 2.35T animal scanner. We investigated perihemorrhagic relative apparent diffusion coefficients (rADC) and relative mean transit time (rMTT). Animals were divided into 2 groups; controls (gr1, n = 27) and facilitated hematoma evacuation with recombinant tissue plasminogen activator (rt-PA) after the first of 3 imaging time points (gr2, n = 22). Diffusion (rADC) and perfusion (rMTT) characteristics were analyzed in 3 regions of interest surrounding the hematoma (ROI1-3).
  
  
  RESULTS
  Overall rADC and rMTT values in ROI3 (normal tissue) did not show any changes. There was mild edema--not ischemia--in ROIs1 and 2 at TP1 with rADC of 1.05-1.18 in both groups indicating vasogenic edema (not ischemia). This did not change with hematoma evacuation. There was mild (non-critical) perfusion reduction in ROIs1 and 2 at TP1, which disappeared after clot evacuation in group 2 (P < 0.05 for TP3). Multifactorial ANOVA showed a solid trend (0.06 < P < 0.1) for clot evacuation associated normalization of perfusion in ROIs 1 and 2 within and in between groups 1 and 2.
  
  
  CONCLUSIONS
  We demonstrated vasogenic edema and mild perfusion reduction in the PHZ above the ischemic threshold. The existence of a perihemorrhagic "penumbra" indicating critically ischemic tissue analogous to ischemic stroke is unlikely.
authors.affiliation: Department of Neurosurgery, University Hospital Heidelberg, Im Neuenheimer Feld 400, Heidelberg, Germany. berk.orakcioglu@med.uni-heidelberg.de
authors.forename: Berk
authors.initials: B
authors.lastname: Orakcioglu
authors.forename: Kristina
authors.initials: K
authors.lastname: Becker
authors.forename: Oliver W
authors.initials: OW
authors.lastname: Sakowitz
authors.forename: Christian
authors.initials: C
authors.lastname: Herweh
authors.forename: Martin
authors.initials: M
authors.lastname: Köhrmann
authors.forename: Hagen B
authors.initials: HB
authors.lastname: Huttner
authors.forename: Thorsten
authors.initials: T
authors.lastname: Steiner
authors.forename: Andreas
authors.initials: A
authors.lastname: Unterberg
authors.forename: Peter D
authors.initials: PD
authors.lastname: Schellinger
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D001929:Brain Edema / Q000473:pathology; D002545:Brain Ischemia / Q000473:pathology*; D002543:Cerebral Hemorrhage / Q000473:pathology* / Q000601:surgery*; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D006406:Hematoma / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D051381:Rats; D017208:Rats, Wistar