A CT-based perfusion mismatch ratio may help predict how much brain tissue is ultimately lost in medium vessel occlusion strokes, according to a small multinational study presented at the American Society of Functional Neuroradiology meeting. Among 94 patients with isolated M2-segment occlusion, each higher mismatch ratio was tied to significantly smaller follow-up infarct volume (beta -0.26, 95% CI -0.37 to -0.14, P<0.001), and the association held on multivariate analysis (beta -0.14, P=0.026).
The mismatch ratio compares the volume of potentially salvageable hypoperfused tissue to the volume of the irrecoverable ischemic core. It has been studied mainly in large vessel occlusion strokes, where higher mismatch has predicted benefit from thrombolytics and thrombectomy. The new findings suggest the measure behaves similarly in medium vessel occlusions, although absolute mismatch volume was not predictive (P=0.84).
Study author Hamza Adel Salim of MD Anderson Cancer Center said the results should pave the way for trials testing whether mismatch ratio can identify which distal medium vessel occlusion patients might benefit from thrombectomy. He stressed that the study does not establish treatment selection based on mismatch ratio, and that its current use should be limited to prognosis.
Limitations include the retrospective observational design, possible selection bias, a cohort treated predominantly with thrombectomy, and variability in perfusion processing and infarct measurement across centers. The researchers called for prospective external validation before mismatch ratio is used as a biomarker to triage patients for mechanical thrombectomy.