Relationship between magnetic resonance arterial patency and perfusion-diffusion mismatch in acute ischemic stroke and its potential clinical use

Background: In patients with acute ischemic stroke the magnetic resonance ( MR) perfusion-diffusion mismatch pattern (perfusion lesion at least 20% lar ger than the lesion on diffusion-weighted imaging) may indicate ischemicall y threatened but viable tissue. To our knowledge, the relationship of this MR pattern to serial changes in MR angiography (MRA) has not been reported. Objectives: To investigate the relationship between MRA changes and pattern s of diffusion-weighted imaging and perfusion abnormalities and to determin e if the information obtained could be used in clinical management. Methods: The MR studies of 35 patients who had undergone sequential multimo dality MR imaging studies within the first 4 days of stroke were reviewed. All lesions were in the internal carotid artery territory distribution. Mag netic resonance angiographies were read by 2 observers blinded to the clini cal data. Results: During the first 24 hours a perfusion-diffusion mismatch was prese nt in 22 (92%) of the 24 patients with an MRA arterial occlusive lesion. (A t this time 5 [46%] of the 11 patients with a normal MRA [P=.006] also had a mismatch.) Two to 4 days after stroke, of these 22 patients resolution of the mismatch occurred in 8 (87%) of 9 patients with recanalization on MRA compared with 5 (39%) of 13 patients without arterial recanalization (P=.03 ). Resolution of mismatch occurred in 3 (60%) of 5 patients with a normal M RA and a mismatch at the first time point. Conclusions: Concordance between MRA and the MR perfusion-diffusion mismatc h pattern provides supportive evidence for an arterial vascular basis for t his MR signature in acute stroke. Discordance between MRA lesions and misma tch may result from arterial branch occlusions undetected by MRA or from an alternate mechanism for the mismatch. The MR imaging patterns identified e xtend our understanding of the pathophysiology of stroke and may contribute to the improvement of stroke management in the future.