Contribution of diffusion-weighted imaging in determination of stroke etiology.

INTRODUCTION Diffusion-weighted (DW) MR imaging enables early identification of ischemic lesions in stroke. Stroke subtype may be related to different lesion patterns. The aim of this study was to analyze the subtype of ischemic lesions as determined by the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria by using DW MR imaging. METHODS AND RESULTS In this study, 510 consecutive patients with ischemic stroke (95%) and transient ischemic attack (5%) aged 65 +/- 12 years were investigated by use of DW MR imaging within 48 hours of the clinical onset of symptoms. Lesions on DW imaging were classified as single, scattered, or multiple lesions in one vascular territory and multiple in more than one vascular territory. We found a significant overall association of DW imaging lesion patterns and classification with stroke subtype by using the TOAST criteria (P < .001). Single corticosubcortical lesions (P < .01) and multiple bilateral lesions in the anterior (AC) and posterior circulation (P < .001) on DW imaging were significantly associated with a cardiac embolic source. Multiple unilateral lesions in the AC were significantly associated with large-artery arteriosclerosis. Because of the 15-mm criterion for small-artery occlusion, cryptogenic stroke was significantly associated with subcortical lesions >/=15 mm. CONCLUSION We found a strong relationship between stroke subtype and DW imaging lesion pattern. The finding of multiple bilateral lesions was significantly associated with a cardiac embolic source, which may be caused by a specific thrombus texture with a tendency for embolus dissemination.