Arterial Spin Labelling Patterns in Acute Large Vessel Occlusion Stroke

Background: Arterial spin labelling (ASL) is a noncontrast, magnetic resonance perfusion technique which can provide information about the parenchymal perfusion status and collaterals in acute stroke. Its role in the setting of large vessel occlusion (LVO) is underutilized due to the limited availability of magnetic resonance imaging (MRI) in the emergency settings. However, it might serve as an useful adjunct to other perfusion modalities in future. Objective: To study ASL perfusion patterns in anterior circulation LVO stroke and evaluate the presence of arterial transit artefacts (ATA) as a surrogate marker of collaterals. Methods: We performed a retrospective analysis of our mechanical thrombectomy database over the last 2 years for acute stroke cases in which ASL perfusion as part of MRI was performed. ASL perfusion patterns in acute LVO stroke were reviewed, with respect to presence of ATA and diffusion-weighted imaging (DWI)-ASL mismatch. Inter-rater reliability was analyzed between 2 readers of varying experience. Baseline variables were analyzed between those with and without ATA. Results: Out of 95 patients, 78 had anterior circulation occlusions, among which 27 had ASL. Type I (with ATAs) was seen in 11 patients and all of these had DWI mismatch. Type II (without ATAs) was seen in 16 patients. Of these, 15 had mismatch with DWI and only 1 had no mismatch. Inter-rater reliability for the detection of ATA on ASL was substantial (Cohen’s k—0.64). No statistical significance was noted between ATA and clinical outcomes. Conclusion: ASL patterns vary amongst patients with LVO stroke and can be classified based on the presence of ATA since resulting DWI mismatch actually indicates a pseudo-perfusion deficit.