title: Systematic review of methods for assessing leptomeningeal collateral flow.
abstract: OBJECTIVE
  The importance of LMF in the outcome after acute ischemic stroke is increasingly recognized, but imaging presents a wide range of options for identification of collaterals and there is no single system for grading collateral flow. The aim of this study was to systematically review the literature on the available methods for measuring LMF adequacy.
  
  
  METHODS
  We performed a systematic review of Ovid, MEDLINE, and Embase databases for studies in which flow in the leptomeningeal collateral vessels was evaluated. Imaging technique, grading scale, and reliability assessment for collateral flow measurement were recorded.
  
  
  RESULTS
  We found 81 publications describing 63 methods for grading collateral flow on the basis of conventional angiography (n = 41), CT (n = 7), MR imaging (n = 9), and transcranial Doppler (n = 6). Inter- and/or intraobserver agreement was assessed in only 8 publications.
  
  
  CONCLUSIONS
  There is inconsistency in how LMF is graded, with a variety of grading scales and imaging modalities being used. Consistency in evaluating collateral flow at baseline is required for the impact of collateral flow to be fully appreciated.
authors.affiliation: Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, UK.
authors.forename: F
authors.initials: F
authors.lastname: McVerry
authors.forename: D S
authors.initials: DS
authors.lastname: Liebeskind
authors.forename: K W
authors.initials: KW
authors.lastname: Muir
mesh_terms: D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D003097:Collateral Circulation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008578:Meninges / Q000098:blood supply / Q000503:physiopathology*; D055420:Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020521:Stroke / Q000503:physiopathology*