Introduction For large vessel occlusions, 24h NIHSS was described as most accurate early clinical predictor of functional outcome in acute stroke patients. M2 occlusions are characterized by more distal and smaller infarct cores, early clinical surrogates of functional outcome might differ.

Aim of Study To investigate early clinical surrogates for long-term independency of patients treated with mechanical thrombectomy for M2 occlusion stroke in comparison to patients with M1 occlusion stroke.

Methods All patients enrolled in the German Stroke Registry-Endovascular Treatment (05/2015–12/2021; N=13082) were screened for anterior circulation stroke. Receiver-operating-characteristics(ROC)-curve analyses and area-under-the-curve(AUC) were used to evaluate the performance of admission NIHSS, 24h NIHSS and NIHSS percentage and absolute change to predict functional outcome at 90d. Excellent and good outcome were defined as modified Rankin Scale(mRS) 0–1 and 0–2, respectively.

Results 1268 patients with M2 and 2749 patients with M1 occlusion were included. For both cohorts, 24h NIHSS had the highest discriminative ability to predict excellent functional outcome with AUC=0.86(95%CI=0.84–0.88) for M2 and AUC=0.86(0.84–0.88) for M1 occlusions. Optimal cutoffs were NIHSS≤7 and NIHSS≤8, respectively. Good long-term functional outcome was predicted with AUC=0.86(0.85–0.88) for M2 and AUC=0.86(0.85–0.88) for M1 occlusions with optimal cut-offs NIHSS≤8 and NIHSS≤9, respectively.

Conclusion 24h NIHSS was identified as best surrogate for long-term functional outcome after thrombectomy for patients with M1 and M2 occlusion, while optimal cut-offs to predict good and excellent outcome were 1 NIHSS-point higher in M2 occlusions compared to M1 occlusions.

Disclosure of Interest HK has financial interest in Eppdata GmbH.

GT received fees as consultant and lecturer from Acandis, Alexion, Amarin, Boehringer Ingelheim, Bayer, BMS/Pfizer, Daiichii Sankyo and Portola. He serves in the board of the TEA Stroke Study and of ESO.

JF is consultant for Cerenovus, Medtronic, Microvention, Penumbra, Phenox, Roche, Stryker and Tonbridge. He is stock holder of Tegus Medical, Eppdata and Vastrax. He serves as Associate Editor at JNIS.

All other authors have nothing to disclose.