Magnetic Resonance Imaging Assists With Determining Etiology After Transient Ischemic Attack or Minor Stroke.

BACKGROUND:Magnetic resonance imaging infarct topography may assist with determining stroke etiology. The influence of diffusion-weighted imaging (DWI)-positive lesions on etiology determination in patients with transient ischemic attack or minor stroke is not well studied. METHODS AND RESULTS:We prospectively enrolled patients between 2010 and 2017 in 2 studies; participants with a final diagnosis of probable or definite transient ischemic attack or stroke were pooled for analysis. The primary outcome was the adjudicated ischemic etiology. We compared proportion of each etiology (cardioembolic, large-vessel, small-vessel disease, other) in patients who had DWI positivity compared with DWI negativity. We used logistic regression to determine the adjusted odds ratio (OR) for each etiology compared with undetermined by DWI positivity. The final analysis included 1498 patients: 832 (55.5%) were DWI-positive. DWI-positive patients were more likely to be diagnosed with small-vessel disease (19.1% versus 5.3%) and less likely with undetermined etiology (36.9% versus 53.0%; P<0.001). After adjustment, the presence of any DWI lesion was associated with increased odds of assigning any etiology (OR, 1.8 [95% CI, 1.3-2.5]). A single DWI lesion was associated with increased odds of small-vessel disease diagnosis (OR, 9.5 [95% CI, 6.4-14.0]), and multiple DWI lesions with reduced odds of small-vessel disease (OR, 0.2 [95% CI, 0.1-0.4]) but increased odds of all other etiologies compared with undetermined etiology. CONCLUSIONS:Any DWI-positive lesion after suspected transient ischemic attack or minor stroke was associated with increased odds of assigning a etiology. Presence and topography of DWI lesions on magnetic resonance imaging may assist with etiology determination and may impact stroke prevention therapies.