title: National Institutes of Health Stroke Scale score is an unreliable predictor of perfusion deficits in acute stroke.
abstract: BACKGROUND
  Perfusion-weighted magnetic resonance imaging is not routinely used to investigate stroke/transient ischemic attack. Many clinicians use perfusion-weighted magnetic resonance imaging selectively in patients with more severe neurological deficits, but optimal selection criteria have never been identified.
  
  
  OBJECTIVE
  We tested the hypothesis that a National Institutes of Health Stroke Scale score threshold can be used to predict the presence of perfusion-weighted magnetic resonance imaging deficits in patients with acute ischemic stroke/transient ischemic attack.
  
  
  METHODS
  National Institutes of Health Stroke Scale scores were prospectively assessed in 131 acute stroke/transient ischemic attack patients followed by magnetic resonance imaging, including perfusion-weighted magnetic resonance imaging within 72 h of symptom onset. Patients were dichotomized based on the presence or absence of perfusion deficits using a threshold of Tmax (time to peak maps after the impulse response) delay ≥four-seconds and a hypoperfused tissue volume of ≥1 ml.
  
  
  RESULTS
  Patients with perfusion deficits (77/131, 59%) had higher median (interquartile range) National Institutes of Health Stroke Scale scores (8 [12]) than those without perfusion deficits (3 [4], P < 0.001). A receiver operator characteristic analysis indicated poor to moderate sensitivity of National Institutes of Health Stroke Scale scores for predicting perfusion deficits (area under the curve = 0.787). A National Institutes of Health Stroke Scale score of ≥6 was associated with specificity of 85%, but sensitivity of only 69%. No National Institutes of Health Stroke Scale score threshold identified all cases of perfusion-weighted magnetic resonance imaging deficits with sensitivity >94%.
  
  
  CONCLUSIONS
  Although higher National Institutes of Health Stroke Scale scores are predictive of perfusion deficits, many patients with no clinically detectable signs have persisting cerebral blood flow changes. A National Institutes of Health Stroke Scale score threshold should therefore not be used to select patients for perfusion-weighted magnetic resonance imaging. Perfusion-weighted magnetic resonance imaging should be considered in all patients presenting with acute focal neurological deficits, even if these deficits are transient.
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Victor
authors.initials: V
authors.lastname: Choi
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Kate
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jayme C
authors.initials: JC
authors.lastname: Kosior
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Brian
authors.initials: B
authors.lastname: Buck
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Trevor
authors.initials: T
authors.lastname: Steve
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Rebecca
authors.initials: R
authors.lastname: McCourt
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jeerakathil
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Ashfaq
authors.initials: A
authors.lastname: Shuaib
authors.affiliation: Department of Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Derek
authors.initials: D
authors.lastname: Emery
authors.affiliation: Division of Neurology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Ken
authors.initials: K
authors.lastname: Butcher
mesh_terms: D000368:Aged; D001921:Brain / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000175:diagnosis* / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D009316:National Institutes of Health (U.S.); D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors; D014481:United States
keywords: MRI; acute; acute stroke therapy; cerebral infarction; ischemic stroke; stroke