title: Admission insular infarction >25% is the strongest predictor of large mismatch loss in proximal middle cerebral artery stroke.
abstract: OBJECTIVE
  Previous univariate analyses have suggested that proximal middle cerebral artery infarcts with insular involvement have greater severity and are more likely to progress into surrounding penumbral tissue at risk. We hypothesized that a practical, simple scoring method to assess percent insular ribbon infarction (PIRI score) would improve prediction of penumbral loss over other common imaging biomarkers.
  
  
  METHODS
  Of consecutive acute stroke patients from 2003 to 2008, 45 with proximal middle cerebral artery-only occlusion met inclusion criteria, including available penumbral imaging. Infarct (diffusion-weighted imaging), tissue at risk (magnetic resonance mean transit time), and final infarct volume (magnetic resonance/computed tomography) were manually segmented. Diffusion-weighted imaging images were rated according to the 5-point PIRI score (0, normal; 1, <25%; 2, 25%-49%; 3, 50%-74%; 4, ≥75% insula involvement). Percent mismatch loss was calculated as an outcome measure of infarct progression. Receiver operating characteristic curve and multivariate analyses were performed.
  
  
  RESULTS
  Mean admission diffusion-weighted imaging infarct volume was 30.9 (±38.8) mL and median (interquartile range) PIRI score was 3 (0.75-4). PIRI score was significantly correlated with percent mismatch loss (P<0.0001). When percent mismatch loss was dichotomized based on its median value (30.0%), receiver operating characteristic curve area under curve was 0.89 (P=0.0001) with a 25% insula infarction optimal threshold. After adjusting for time to imaging and treatment, binary logistic regression, including dichotomized PIRI (25% threshold), age, National Institutes of Health Stroke Scale score, diffusion-weighted imaging infarct volume, and computed tomography angiography collateral score as covariates, revealed that only dichotomized insula score (P=0.03) and age (P=0.02) were independent predictors of large (68.2%) versus small (8.1%) mismatch loss. There was excellent interobserver agreement for dichotomized PIRI scoring (κ=0.91).
  
  
  CONCLUSIONS
  Admission insular infarction >25% is the strongest predictor of large mismatch loss in this cohort of proximal middle cerebral artery occlusive stroke. This outcome marker may help to identify treatment-eligible patients who are in greatest need of rapid reperfusion therapy.
authors.affiliation: From the Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: Shervin
authors.initials: S
authors.lastname: Kamalian
authors.forename: Andre
authors.initials: A
authors.lastname: Kemmling
authors.forename: Roderick C
authors.initials: RC
authors.lastname: Borgie
authors.forename: Livia T
authors.initials: LT
authors.lastname: Morais
authors.forename: Seyedmehdi
authors.initials: S
authors.lastname: Payabvash
authors.forename: Ana M
authors.initials: AM
authors.lastname: Franceschi
authors.forename: Shahmir
authors.initials: S
authors.lastname: Kamalian
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Yoo
authors.forename: Karen L
authors.initials: KL
authors.lastname: Furie
authors.forename: Michael H
authors.initials: MH
authors.lastname: Lev
mesh_terms: D000368:Aged; D000465:Algorithms; D015331:Cohort Studies; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000473:pathology; D015999:Multivariate Analysis; D010343:Patient Admission; D012372:ROC Curve; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed
keywords: MCA; imaging-predictor; insula; penumbra; stroke