Competitive leptomeningeal flow impact on thrombectomy reperfusion grade rating

Background Competitive leptomeningeal flow (CLF) can be observed immediately after mechanical thrombectomy (MT) reperfusion with retrograde contrast clearing of the distal leptomeningeal branches from non-contrast opacified flow through different vascular territories. We aim to evaluate the frequency of the CLF phenomenon, to determine if it has an association with the degree of leptomeningeal collateral status, and to understand the potentia impact it may have on the final expanded Treatment in Cerebral Ischemia (eTICI) score rating. Methods Retrospective analysis of a prospective MT database spanning November 2020 to December 2021. Consecutive cases of intracranial internal carotid (i-ICA) or middle cerebral artery (MCA) M1 occlusions were included. CLF was defined by the observation of retrograde clearing of distal MCA branches that were previously opacified by antegrade reperfusion. The clearance of the distal branches is presumed to occur due to CLF via non-contrast opacified posterior cerebral artery or anterior cerebral artery flow. The washout was considered CLF if it cleared abruptly with or without forward reconstitution of antegrade opacification. Results A total of 125 patients met the inclusion criteria. The median age was 64 years (IQR 52.5–75) and 64 (51%) were men. The baseline median National Institutes of Health Stroke Scale score was 17 (IQR 12–22) and the Alberta Stroke Program Early CT Score was 9 (IQR 8–10). Median last known well time to puncture was 7 hours (IQR 4–13.1) and 30.4% received tissue plasminogen activator. Final eTICI 2c–3 was achieved in 80%. CLF was present in 32 (25.6%) patients, who had comparable baseline characteristics to patients without CLF. Twelve (37.5%) patients had regional CLF and 20 (62.5%) had focal CLF. The CLF arm had better leptomeningeal single-phase CTA collaterals than the non-CLF arm (P=0.01). The inter-rater agreement for the eTICI score was moderate when CLF was present and strong in its absence (Krippendorf’s alpha=0.65 and 0.81, respectively). There was minimal agreement (Kappa=0.3) for the presence versus absence of CLF between the two operators, possibly related to reader experience. Conclusion CLF was observed in 32% of patients, was associated with better collateral flow, and impacted the reported procedural eTICI rating.