BackgroundThe present study aimed to evaluate the prognostic value of the 24-h National Institute of Health Stroke Scale (NIHSS) for short- and long-term outcomes of patients with basilar artery occlusion (BAO) after endovascular treatment (EVT) in daily clinical routine. MethodsPatients with EVT for acute basilar artery occlusion study registry with the 24-h NIHSS, and clinical outcomes documented at 90 days and 1 year were included. The NIHSS admission, 24-h NIHSS, NIHSS delta, and NIHSS percentage change, binary definitions of early neurological improvement [ENI; improvement of 4/(common ENI)/8 (major ENI)/10 (dramatic ENI)] NIHSS points were compared to predict the favorable outcomes and mortality at 90 days and 1 year. The primary outcome was defined as favorable if the modified Rankin Scale (mRS) score was 0-3 at 90 days. ResultsOf the 644 patients treated with EVT, the 24-h NIHSS had the highest discriminative ability for favorable outcome prediction [receiver operator characteristic (ROC)(NIHSS 24 h) area under the curve (AUC): 0.92 (0.90-0.94)] at 90 days and 1 year [(ROCNIHSS 24 h AUC: 0.91 (0.89-0.94)] in comparison to the NIHSS score at admission [ROCNIHSS admission AUC at 90 days: 0.73 (0.69-0.77); 1 year: 0.74 (0.70-0.78)], NIHSS delta [ROC Delta NIHSS AUC at 90 days: 0.84 (0.81-0.87); 1 year: 0.81 (0.77-0.84)], and NIHSS percentage change [ROC%change AUC at 90 days: 0.85 (0.82-0.89); 1 year: 0.82 (0.78-0.86)]. ConclusionThe 24-h NIHSS with a threshold of <= 23 points was the best surrogate for short- and long-term outcomes after EVT for BAO in the clinical routine.