Abstract T P150: NIHSS Zero Strokes: Immeasurable but Not Innocent

Aims: Patients with acute ischemic stroke (AIS) lasting >24 hours may have an immeasurable deficit on the admission NIHSS score. We sought to better characterize factors that are associated with NIHSS zero strokes and evaluate their long term outcome. Methods: We used all AIS patients with a measurable admission NIHSS in the Acute STroke Registry and Analysis and of Lausanne (ASTRAL) from 2003 - 2012. We then retrospectively analyzed and compared patients with an admission NIHSS of zero with all other patients regarding demographics, clinical characteristics, radiological and laboratory findings in uni- and multivariate analyses. Patients with a pre-stroke NIHSS>0 were also considered “NIHSS zero strokes” if a clearly described preexisting deficit accounted for the current deficit and no new NIHSS points were found. Outcome was assessed at 3 months using the modified Rankins score corrected for pre-stroke disability (corrected mRS) and considered favorable if it was ≤ 1. Combined stroke & TIA recurrences and rehospitalisation rates over 12 months were compared. Results: Comparing 109 NIHSS zero with 2’189 other strokes in multivariate analysis, patients with NIHSS zero stroke had lower pre-stroke disability levels, longer onset-to-hospital delays, and more lacunar and infratentorial strokes. When comparing radiological and laboratory finding in the two groups, NIHSS zero patients were less likely to have acute ischemic changes on acute NCCT, less arterial pathology on acute cervical and intracranial imaging and lower creatinine levels. In unadjusted analysis, NIHSS zero patients were more likely to have favorable corrected mRS (zero vs. others: 83.2% vs. 44.6%) and less likely to die (3.9% vs. 13.3%) at 12 months. Recurrence rates were similar (9.2% vs. 12.9%). Conclusion: Patients with NIHSS zero strokes as compared with all other patients have more frequently lacunar and infrantentorial strokes, normal acute CT, and less arterial pathology. However a significant minority faces persisting handicap at 12 months and recurrent ischemic events. These findings suggest that NIHSS zero stroke patients have better outcomes but still require support and aggressive secondary prevention.