title: Perihematomal edema in primary intracerebral hemorrhage is plasma derived.
abstract: OBJECTIVE
  The mechanisms of perihematomal injury in primary intracerebral hemorrhage (ICH) are incompletely understood. An MRI study was designed to elucidate the nature of edema and blood flow changes after ICH.
  
  
  METHODS
  Perihematomal blood flow and edema were studied prospectively with perfusion-weighted MRI (PWI) and diffusion-weighted MRI in 21 ICH patients. MRI and computed tomography (CT) images were coregistered to ensure perfusion and diffusion changes were outside of the hematoma. Edema volumes were measured on T2-weighted images. Apparent diffusion coefficient (ADC) values of the edematous regions were calculated.
  
  
  RESULTS
  Mean patient age was 64.2 years (45 to 89), and median National Institutes of Health stroke scale score was 12 (3 to 24). Median time to MRI was 21 hours (4.5 to 110). Average hematoma volume on CT was 26.1 (4 to 84) mL. PWI demonstrated perihematomal relative mean transit time (rMTT) was significantly correlated with hematoma volume (r=0.60; P=0.004) but not edema volume. Perihematomal oligemia (rMTT >2 s) was present in patients with hematoma volumes of >15 mL (average rMTT 4.6+/-2.0 s). Perihematomal edema was present in all patients. ADC values within this region (1178+/-213x10(-6) mm2/s) were increased 29% relative to contralateral homologous regions. Increases in perihematomal ADC predicted edema volume (r=0.54; P=0.012) and this was confirmed with multivariate analysis.
  
  
  CONCLUSIONS
  Acute perihematomal oligemia occurs in acute ICH but is not associated with MRI markers of ischemia and is unrelated to edema formation. Increased rates of water diffusion in the perihematomal region independently predict edema volume, suggesting the latter is plasma derived.
authors.affiliation: Department of Neurology, Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia. Kenneth.butcher@mh.org.au
authors.forename: Ken S
authors.initials: KS
authors.lastname: Butcher
authors.forename: Tracey
authors.initials: T
authors.lastname: Baird
authors.forename: Lachlan
authors.initials: L
authors.lastname: MacGregor
authors.forename: Patricia
authors.initials: P
authors.lastname: Desmond
authors.forename: Brian
authors.initials: B
authors.lastname: Tress
authors.forename: Stephen
authors.initials: S
authors.lastname: Davis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001929:Brain Edema / Q000209:etiology* / Q000473:pathology; D002543:Cerebral Hemorrhage / Q000150:complications* / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D006406:Hematoma / Q000209:etiology / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010949:Plasma / Q000378:metabolism