Early Functional Recovery and the Fate of the Diffusion/Perfusion Mismatch in Patients with Proximal Middle Cerebral Artery Occlusion

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Abstract
Background: The relationship between early neurological recovery, time to recanalization and the salvage of hypoperfused, but not diffusion-restricted tissue was investigated. Methods: In 17 patients with acute middle cerebral artery occlusion, a multiparametric stroke MRI protocol was performed <6 h after symptom onset, as well as at day 2 and 7. Recanalization was monitored with transcranial Doppler or with conventional angiography (during local thrombolysis). Functional improvement was defined as a change of ≧4 points on the National Institutes of Health Stroke Scale score. Results: In patients with functional improvement, 78% (median, range 66–95%) of the acute mean transit time (MTT) lesion escaped infarction compared with 28% (median, range –13 to 78%) in patients without neurological improvement (p < 0.01). Similarly, the percentage of tissue with a time-to-peak (TTP) delay of ≧2 s not progressing to infarction was 80 and 4% in the groups with and without improvement, respectively (p < 0.01). Neurological improvement was more frequent in patients with early (≤3 h after presentation) recanalization, due to the salvage of larger areas of initially hypoperfused tissue. Conclusions: The salvage of hypoperfused tissue is a major factor influencing early neurological improvement.