Etiology of perfusion-diffusion magnetic resonance imaging mismatch patterns

Background and Purpose. Diffusion- and perfusion-weighted magnetic resonance imaging (DWI and PWI) are useful tools for the assessment of brain ischemia. Discrepancies between the extent of DWI and PWI abnormalities are thought to depend predominantly on time from symptom onset to magnetic resonance imaging (MRI) examination. However, underlying ischemic stroke etiology can also be important. A mismatch may indicate the presence of tissue at risk for infarction, whereas the relevance of other DWI/PWI patterns is uncertain. The authors therefore investigated the etiology of brain ischemia in patients with different DWI/PWI patterns. Methods. Retrospective study of 130 patients with acute brain ischemia and detailed stroke workup, including MRI within a week after symptom onset (40 ± 39 hours). Patients were divided into the following groups: mismatch (PWI > DWI), reverse mismatch (DWI > PWI), and match (<25% difference between PWI and DWI). Results. Mismatch occurred in 49% of patients, whereas 22% had reverse mismatch and 29% matched lesions. Time from symptom onset to MRI examination was similar between the 3 groups. Large-artery atherosclerosis increased by almost 4-fold the odds of mismatch (odds ratio: 3.89, 95% confidence interval: 1.72-8.78; P < .001), whereas patients with reverse mismatch were likely to have cryptogenic stroke. Patients with matched lesions were similarly distributed among different stroke subtypes. Conclusions. Ischemic stroke etiology appears to influence the development of specific DWI/PWI patterns. Prospective studies are needed to confirm these observations.