NIHSS 24 h After Mechanical Thrombectomy Predicts 90-Day Functional Outcome

Background Mechanical thrombectomy (MT) for large vessel occlusion (LVO) ischemic stroke is a safe and effective treatment modality. The National Institute of Health Stroke Scale (NIHSS) 24 h after MT (24 h-NIHSS) was shown to serve as the strongest surrogate for 90-day functional outcome. Here, we seek to externally validate 24 h-NIHSS as predictor for 90-day functional outcome and explore additional variables in this context. Methods Patients treated for anterior LVO between February 2016 and August 2020 with premorbid mRS < 3 were included. Receiver operating characteristics were used to compare different NIHSS-related surrogates, such as baseline (B) NIHSS, 24 h-NIHSS, Delta-NIHSS and percent (%) change NIHSS to predict favorable function outcome (mRS 0-2). Additional analysis was performed to assess predictors associated with poor outcome despite reaching the best predictor threshold. Results A total of 337 eligible cases were identified. The 24 h-NIHSS outperformed B-NIHSS, Delta-NIHSS, and %-NIHSS in terms of 90-day mRS 0-2 prediction. A 24-NIHSS <= 8 was identified as the optimal binary threshold. Multivariable analysis demonstrated that 24-NIHSS <= 8 and younger patient age were independently associated with mRS 0-2. Despite achieving 24 h-NIHSS <= 8, 23/143 (16.1%) cases experienced poor outcome (mRS 4-6). Older age, higher baseline NIHSS, coexisting chronic kidney disease, and longer hospital stay were independent predictors for poor outcome despite achieving 24 h-NIHSS <= 8. Conclusion An NIHSS of 8 or less 24 h after MT was validated to serve as an independent, strong surrogate for favorable functional outcome; however, cofactors such as older age, higher baseline NIHSS and coexisting comorbidities appear to mitigate this clinical adjunct.

Automated summary

The 24-hour NIHSS is a strong predictor for 90-day functional outcome following mechanical thrombectomy, especially when the NIHSS score is ≤ 8. Younger age and lower NIHSS score are independently associated with favorable functional outcome. However, factors such as older age, higher baseline NIHSS, and coexisting comorbidities may negate this relationship despite achieving a low 24-hour NIHSS score.