Outcomes after endovascular mechanical thrombectomy for low compared to high National Institutes of Health Stroke Scale (NIHSS): A multicenter study

Objective: The role of endovascular mechanical thrombectomy (MT) in patients presenting with “minor” stroke is uncertain. We aimed to compare outcomes after MT for ischemic stroke patients presenting with National Institutes of Health Stroke Scale (NIHSS) 5 and – within the low NIHSS cohort – identify predictors of a favorable outcome, mortality, and symptomatic intracranial hemorrhage (ICH). Methods: We retrospectively analyzed a prospectively maintained, international, multicenter database. Results: The study cohort comprised a total of 7568 patients from 29 centers. NIHSS was low (<5) in 604 patients (8%), and > 5 in 6964 (92%). Patients with low NIHSS were younger (67 + 14.8 versus 69.6 + 14.7 years, p < 0.001), more likely to have diabetes (31.5% versus 26.9%, p = 0.016), and less likely to have atrial fibrillation (26.6% versus 37.6%, p < 0.001) compared to those with higher NIHSS. Radiographic outcomes (TICI > 2B 84.6% and 84.3%, p = 0.412) and complication rates (8.1% and 7.2%, p = 0.463) were similar between the low and high NIHSS groups, respectively. Clinical outcomes at every follow up interval, including NIHSS at 24 h and discharge, and mRS at discharge and 90 days, were better in the low NIHSS group, however patients in the low NIHSS group experienced a relative decline in NIHSS from admit to discharge. Mortality was lower in the low NIHSS group (10.4% versus 24.5%, p < 0.001). Conclusions: Relative to patients with high NIHSS, MT is safe and effective for stroke patients with low NIHSS, and it is reasonable to offer it to appropriately selected patients presenting with minor stroke symptoms. Our findings justify efforts towards a randomized trial comparing MT versus medical management for patients with low NIHSS.