title: Intracranial thrombus extent predicts clinical outcome, final infarct size and hemorrhagic transformation in ischemic stroke: the clot burden score.
abstract: BACKGROUND
  In ischemic stroke, functional outcomes vary depending on site of intracranial occlusion. We tested the prognostic value of a semiquantitative computed tomography angiography-based clot burden score.
  
  
  METHODS
  Clot burden score allots major anterior circulation arteries 10 points for presence of contrast opacification on computed tomography angiography. Two points each are subtracted for thrombus preventing contrast opacification in the proximal M1, distal M1 or supraclinoid internal carotid artery and one point each for M2 branches, A1 and infraclinoid internal carotid artery. We retrospectively studied patients with disabling neurological deficits (National Institute of Health Stroke Scale score >or=5) and computed tomography angiography within 24-hours from symptom onset. We analyzed percentages independent functional outcome (modified Rankin Scale score <or=2), final infarct Alberta Stroke Program Early Computed Tomography Score and parenchymal hematoma rates across categorized clot burden score groups and performed multivariable analysis.
  
  
  RESULTS
  We identified 263 patients (median age 73-years, National Institute of Health Stroke Scale score 10, onset-to-computed tomography angiography time 165 min). Clot burden score<10 was associated with reduced odds of independent functional outcome (odds ratio 0.09 for clot burden score<or=5; odds ratio 0.22 for clot burden score 6-7; odds ratio 0.48 for clot burden score 8-9; all versus clot burden score 10; P<0.02 for all). Lower clot burden scores were associated with lower follow-up Alberta Stroke Program Early Computed Tomography Scores (P<0.02 for all). Lower clot burden scores were associated with lower follow-up Alberta Stroke Program Early CT Scores (P<0.001) and higher parenchymal hematoma rates (P=0.008). Inter-rater reliability for clot burden score was 0.87 (lower 95% confidence interval 0.71) and intra-rater reliability 0.96 (lower 95% confidence interval 0.92).
  
  
  CONCLUSIONS
  The quantification of intracranial thrombus extent with the clot burden score predicts functional outcome, final infarct size and parenchymal hematoma risk acutely. The score needs external validation and could be useful for patient stratification in stroke trials.
authors.affiliation: University of Calgary, Department of Clinical Neurosciences, Calgary Stroke Program, Canada. volker.puetz@calgaryhealthregion.ca
authors.forename: Volker
authors.initials: V
authors.lastname: Puetz
authors.forename: Imanuel
authors.initials: I
authors.lastname: Dzialowski
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hill
authors.forename: Suresh
authors.initials: S
authors.lastname: Subramaniam
authors.forename: P N
authors.initials: PN
authors.lastname: Sylaja
authors.forename: Andrea
authors.initials: A
authors.lastname: Krol
authors.forename: Christine
authors.initials: C
authors.lastname: O'Reilly
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hudon
authors.forename: William Y
authors.initials: WY
authors.lastname: Hu
authors.forename: Shelagh B
authors.initials: SB
authors.lastname: Coutts
authors.forename: Philip A
authors.initials: PA
authors.lastname: Barber
authors.forename: Timothy
authors.initials: T
authors.lastname: Watson
authors.forename: Jayanta
authors.initials: J
authors.lastname: Roy
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Demchuk
mesh_terms: D000368:Aged; D020520:Brain Infarction / Q000000981:diagnostic imaging* / Q000209:etiology; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D020767:Intracranial Thrombosis / Q000150:complications / Q000000981:diagnostic imaging*; D008297:Male; D020127:Recovery of Function; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed