Distribution and prognosis of acute ischaemic stroke with negative diffusion-weighted imaging

BACKGROUND AND PURPOSE: To examine the distribution and prognosis among patients with diffusion-weighted imaging (DWI)-negative acute ischaemic stroke (AIS) and explore the differences between mild (National Institute of Health Stroke Scale (NIHSS) score ≤5) and major (NIHSS score >5) ischaemic stroke in DWI-negative patients. METHODS: Patients with AIS with baseline DWI from the Third China National Stroke Registry (CNSR-III), based on a prospective, observational, multicentre cohort study, between August 2015 and March 2018, were included. Patients were classified into negative and positive DWI groups depending on the existence of acute lesions on DWI. RESULTS: Among 12 026 patients who had an ischaemic stroke, 932 (7.7%) had negative DWI. As the NIHSS score increased, the proportion of patients with DWI-negative AIS gradually decreased. Negative DWI was associated with a decreased risk of stroke recurrence (HR 0.63, 95% CI 0.49 to 0.82), combined vascular events (HR 0.72, 95% CI 0.56 to 0.92), mortality (HR 0.60, 95% CI 0.36 to 0.995) and poor functional outcomes (OR 0.57, 95% CI 0.43 to 0.76) within 1 year in all patients. Similar associations were observed in patients with mild AIS (p<0.05 for all) but not in patients with major AIS, excluding poor functional outcomes (OR 0.47, 95% CI 0.28 to 0.81). CONCLUSIONS: The proportion of patients with DWI-negative AIS gradually decreased as the NIHSS score increased, and negative DWI was mainly observed in patients with mild AIS. Negative DWI was associated with a better prognosis for all patients with AIS. However, these associations were significant for mild AIS but not for those with major AIS.