Diffusion weighted imaging, apparent diffusion coefficient maps and stroke etiology

In acute ischemic stroke, the number and distribution of lesions on diffusion weighted imaging (DWI) have been shown to give clues to the underlying pathogenetic mechanisms. The objective of this study was to determine whether lesion features on DWI differ between stroke due to large artery atherosclerosis (LAA) and cardioembolism (CE), and to assess the role of apparent diffusion coefficient maps (ADC).

We retrospectively studied 83 consecutive patients with stroke caused by either LAA (n=40) or cardioembolism (n=43). DWI lesions were characterized by number, size, distribution (i. e. lesion pattern) and signal intensity on ADC maps. In part A, all hyperintense DWI lesions regardless of their ADC were compared. In part B, only hyperintense DWI lesions with hypointense appearance on ADC maps (i. e. acute lesions) were assessed.

Part A: The frequency of multiple hyperintense DWI lesions (LAA: 28/40, CE: 21/43; p< 0.05) and the lesion number (LAA 4.7+/- 4.9; CE: 3.1+/- 4.7; p=0.01) were higher in LAA-patients. Involvement of >1 circulation (i. e. anterior plus posterior or bilateral anterior circulations) was present in 5 LAA-patients (13 %) and 4 CE-patients (9 %). Lesion size did not differ between LAA-stroke (35.1+/- 33.7 mm) and CE-stroke (35.4+/- 27.8 mm). Part B: Multiple hyperintense DWI lesions with low ADC occurred in 23/40 LAA-patients and in 15/43 CE-patients (p<0.05). Lesions in >1 circulation occurred only in CE-stroke (n=3; 7%) and never in LAA-stroke.

(1) Multiple ischemic lesions occur significantly more often in LAA-stroke than in CE-stroke. (2) ADC maps are important in the comparison of DWI lesion patterns; DWI lesions in >1 circulation can only be assigned to a cardioembolic etiology if they appear hypointense on ADC maps.