NIHSS mismatch as a predictor of early neurological improvement after mechanical thrombectomy

The selection of acute ischemic stroke (AIS) patients for mechanical thrombectomy (MT) is based on the clinical-radiological mismatch, where the NIHSS is higher than expected based on the ASPECT score. Our objective was to estimate the mismatch (NIHSSmismatch%) between the expected NIHSS (NIHSSexpected) and the actual NIHSS (NIHSSactual) on admission, and to study its prognostic value for early neurological improvement (ENI, defined as a reduction of NIHSS of ≥ 8 points or reaching 0/1 at 24 h) in AIS patients with large vessel occlusion (LVO) of the anterior circulation treated with MT. A cross-sectional study was conducted on AIS related to anterior territory LVO (2017–2022) at a Stroke Center. Using multivariate linear regression models in the derivation cohort, a formula for calculating the NIHSSexpected on admission was developed, and the NIHSSmismatch% between NIHSSactual and NIHSSexpected was measured. Multivariate analyses were performed to identify if NIHSSmismatch% levels predicted ENI. In the derivation cohort (n = 123), the following formula was developed: NIHSSexpected = 10.8 + 0.05 x Age + 2.5 x DM + 2.6 x Hemisphere – 1.5 x ASPECTSadmission. In the validation cohort (n = 185), 64 (34.6%) patients experienced ENI. The ROC curve identified 75% of NIHSSmismatch% as the optimal cutoff for predicting ENI (80% sensitivity and 58% specificity). Multivariate analyses showed that both NIHSSmismatch% and NIHSSmismatch% >75 were predictors of ENI (OR 1.062; 95% CI 1.033–1.092 and OR 5.687; 95% CI 2.562–12.623, respectively), adjusted for potential confounders. NIHSSmismatch% could be a predictor of ENI in AIS patients treated with MT.