title: Chickenpox and stroke in childhood: a study of frequency and causation.
abstract: OBJECTIVE
  The purpose of this study was to determine whether infection with varicella is causal for arterial ischemic stroke (AIS) in children.
  
  
  METHODS
  First, a prospective cohort study was conducted in young children (aged 6 months to 10 years) with AIS at 2 institutions (cohort study). The presence of varicella infection <12 months before AIS was determined and compared with the published frequency of varicella infection in the healthy pediatric population. The clinical and radiographic features of AIS were compared between the varicella and nonvaricella study cohorts. Second, a literature search of varicella-associated AIS was conducted, and the clinical and radiographic features were compared with the study nonvaricella cohort.
  
  
  RESULTS
  In the cohort study, 22 (31%) of 70 consecutive children with AIS had a varicella infection in the preceding year compared with 9% in the healthy population. Children in the varicella cohort were more likely to have basal ganglia infarcts (P<0.001), abnormal cerebral vascular imaging (P<0.05), and recurrent AIS or transient ischemic attacks (P<0.05) than those in the nonvaricella cohort. The pooled literature analysis of 51 cases of varicella-associated AIS showed similar findings to the varicella cohort.
  
  
  CONCLUSIONS
  In young children with AIS, there is a 3-fold increase in preceding varicella infection compared with published population rates, and varicella-associated AIS accounts for nearly one third of childhood AIS. Varicella-associated AIS has characteristic features, including a 2-fold increase in recurrent AIS and transient ischemic attacks. Varicella is an important risk factor for childhood AIS.
authors.affiliation: Hospital for Sick Children and the University of Toronto, Toronto, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Askalan
authors.forename: S
authors.initials: S
authors.lastname: Laughlin
authors.forename: S
authors.initials: S
authors.lastname: Mayank
authors.forename: A
authors.initials: A
authors.lastname: Chan
authors.forename: D
authors.initials: D
authors.lastname: MacGregor
authors.forename: M
authors.initials: M
authors.lastname: Andrew
authors.forename: R
authors.initials: R
authors.lastname: Curtis
authors.forename: B
authors.initials: B
authors.lastname: Meaney
authors.forename: G
authors.initials: G
authors.lastname: deVeber
mesh_terms: D017677:Age Distribution; D001921:Brain / Q000098:blood supply / Q000473:pathology; D002170:Canada / Q000453:epidemiology; D015984:Causality; D002644:Chickenpox / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D007223:Infant; D002546:Ischemic Attack, Transient / Q000175:diagnosis / Q000453:epidemiology; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D008297:Male; D016017:Odds Ratio; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D020521:Stroke / Q000175:diagnosis / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed