Stability of large diffusion/perfusion mismatch in anterior circulation strokes for 4 or more hours

BACKGROUND: The stability of hypoperfused brain tissue in stroke patients with major artery occlusions is unknown. The purpose of this study was to determine the persistence of a diffusion/perfusion mismatch in patients with ICA or proximal MCA occlusions. METHODS: Fourteen patients with ICA and/or proximal MCA occlusion and a diffusion/perfusion mismatch at presentation were studied. All were enrolled in a pilot randomized study of normobaric oxygen therapy. None received thrombolytic therapy; 8 received normobaric oxygen and 6 room air. Diffusion/perfusion MRI was performed at baseline, 4 hours, 24 hours, and 1 week. Abnormal DWI, ADC, and MTT volumes were determined using standard image analysis methods. RESULTS: The mean time from symptom onset to baseline MRI was 7.5 ± 1 hours. Across all 4 time points there was a significant difference in DWI lesion (ANOVA, P < 0.0001) and abnormal MTT volumes (ANOVA, P < 0.01) with the 24 hour and 1 week abnormal volumes different from the earlier studies. However, comparing baseline and 4 hour scans, there was no significant interval change in the mean abnormal DWI volume (29.4 ± 8.2 ml vs. 28.1 ± 7.4 ml) or abnormal MTT volumes (137 ± 17.7 ml vs. 130.9 ± 13.8). By 24 hours, only 2 patients did not maintain a mismatch of 20% or greater. CONCLUSIONS: Patients who present outside the time window for thrombolytic therapy, and who have a large diffusion/perfusion mismatch on MRI may have a stable mismatch for 4 or more hours.