Diffusion-weighted imaging-negative patients with transient ischemic attack are at risk of recurrent transient events

Background and Purpose - Among patients presenting with a transient ischemic attack ( TIA), some clinical features predispose to recurrent TIA, whereas others predispose to subsequent strokes. We assessed the implication of negative diffusion-weighted imaging on a baseline MRI in predicting subsequent TIA. Methods - We prospectively studied patients presenting in the emergency department within 12 hours of a TIA ( motor or speech). All patients had a MRI within 24 hours of the index event. The primary outcome was TIA within 1 year of study entry. The 1-year risk of stroke was also evaluated. Results - A total of 85 patients had a MRI, among which 35 patients ( 41.2%) had a diffusion-weighted imaging lesion. The mean time from symptom onset to MRI was 12.1 hours. Patients without a diffusion-weighted imaging lesion on baseline MRI were 4.6 times ( 27.4% versus 5.9%; P < 0.05) more likely to have a subsequent TIA at 1 year than patients with a diffusion-weighted imaging lesion, but 4.3 times ( 2.1% versus 9.1%; P = 0.19) less likely to have a subsequent stroke. Conclusions - The absence of a diffusion-weighted imaging lesion on the baseline scan predicts recurrent transient events rather than stroke.