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Diffusion-Weighted Imaging Patterns According to the Right-to-Left Shunt Amount in Cryptogenic Stroke

Background: Although patent foramen ovale (PFO) is considered to be the main cause of cryptogenic stroke, it is difficult to define “true” PFO-related stroke. Objective: In this study, we evaluated comprehensive diffusion-weighted imaging (DWI) findings in patients with cryptogenic stroke according to the right-to-left shunt (RLS) amounts on transcranial Doppler (TCD) sonography. Methods: We assessed consecutive patients with cryptogenic stroke between October 2010 and 2018. The RLS amount on TCD was assessed according to the International Consensus Criteria (ICC). Massive RLS was defined as the highest category of ICC (Curtain pattern). We assessed DWI findings, including the location of lesions, involved vascular territory, and DWI lesion patterns. Results: A total of 100 consecutive patients with cryptogenic stroke were assessed, and PFO was found in 59 patients. In multivariable analyses, massive RLS was noted to be positively associated with the presence of cortical lesion (adjusted OR [aOR] 15.75, 95% CI 1.94–127.71, p = 0.010), multiple territory involvement (aOR 5.24, 95% CI 1.57–17.53, p = 0.007), and number of DWI lesions (beta 0.713, 95% CI 0.245 to 1.181, p = 0.003) after adjusting for confounders. Conversely, massive RLS showed inverse correlations with posterior circulation involvement (aOR 0.22, 95% CI 0.06–0.87, p= 0.031) and number of large DWI lesions (beta –0.328, 95% CI –0.629 to –0.026, p = 0.034). Conclusions: We demonstrated that massive RLS on TCD was associated with multiple, small-scattered cortical lesion in patients with cryptogenic stroke. These DWI pattern is highly suggestive of PFO-related stroke.