TOF-MRA is reliable to evaluate the degree of MCA obstruction in acute stroke: an inter- and intra- observer study

Abstract

Introduction: Artery recanalization is one of the best predictors of good clinical outcome after acute ischemic stroke thrombolysis and it could be used as a surrogate marker for outcome if it can be graded reliably. The purpose of this study was to analyze the inter- and intra-observer reliability of the degree of MCA obstruction on TOF-MRA. Methods: 91 patients with a MCA stroke were prospectively included in a multicenter study. They underwent MRI including a TOF-MRA within the first 12 hours after symptoms onset. Two blinded observers quantified the degree of MCA obstruction on TOF-MRA according to a modified TIMI grading system. To assess intra-observer reliability, evaluations by the same investigators were repeated 15 days apart. Dichotomized (TIMI 0-1 versus 2-3) and ordinal TIMI score analyses were performed. Inter- and intra-observer reliability was categorized from poor to excellent based on kappa values. Results: The mean delay between symptom onset and MRI was 6.3 ± 3.3 hours. Analysis of TOF-MRA was impossible in 2.6 % for M1 segment and 6.9% for M2 segment due to technical limitations. The inter- and intra-observer reliability was good to excellent for the dichotomized TIMI score (kappa ranging from 0.77 to 0.91) as well as for the ordinal TIMI score (kappa ranging from 0.82 to 0.96). Conclusion: The substantial reproducibility of the dichotomized and the ordinal TIMI grading system makes the TOF-MRA sequence a reliable tool to evaluate the degree of MCA obstruction and thus recanalization in clinical practice as well as in clinical research.