Objective: To improve epidemiological knowledge of neurological deterioration (ND) in patients with acute ischemic stroke (AIS).

Methods: In this prospective observational study, we captured ND prospectively in 29,446 AIS patients admitted to 15 hospitals in Korea within 7 days of stroke onset. ND was defined as an increase in National Institutes of Health Stroke Scale (NIHSS) score ≥2 (total), or ≥1 (motor or consciousness), or any new neurological symptoms. Change of incidence rate after stroke onset, causes, factors associated with ND, modified Rankin Scale (mRS) at 3 months and 1 year, and a composite of stroke, myocardial infarction and all-cause death at 1 year were assessed.

Results: ND occurred in 4299 (14.6%) patients. The highest rate, 6.95 per 1,000 person-hours incidence was within the first 6 hours which decreased to 2.09 within 24-48 hours, and 0.66 within 72-96 hours after stroke onset. Old age, women, diabetes, early arrival, large artery atherosclerosis as a stroke subtype, high NIHSS scores, glucose level, systolic blood pressure, leukocytosis at admission, recanalization therapy, transient ischemic attack without a relevant lesion, steno-occlusion of relevant arteries were associated with ND. The causes were stroke progression (71.8%), followed by recurrence (8.5%). Adjusted relative risks (95% confidence interval) for poor outcome (mRS 3-6) at 3 months and one year were 1.75 (1.70-1.80), and 1.70 (1.65-1.75), respectively. The adjusted hazard ratio (95% confidence interval) for the composite event was 1.59 (1.45-1.74).

Conclusions: ND should be taken into consideration as a factor that may influence the outcome in acute ischemic stroke.