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Background and Purpose-1 H MR spectroscopy can be used to study biochemical changes occurring in the brain in stroke. We used it to examine the relationship between metabolite concentration (N-acetyl aspartate [NAA], lactate, cholines and creatines), size of infarct, clinical deficit, and 3-month clinical outcome in patients with middle cerebral artery (MCA) territory infarction. Methods-Thirty-one patients with acute MCA territory infarction were recruited within 72 hours of the onset of symptoms. Single-voxel short echo time stimulated echo acquistion mode spectroscopy was used to obtain metabolite data from the infarct core. Metabolite concentrations were determined with use of variable projection time domain-fitting analysis. Infarct size was determined with T2-weighted images. Patient outcome groups at 3 months were "independent," "dependent," or "dead." Results-All patients (100%; 95% CI 75% to 100%) who had an infarct Ͼ70 mL did poorly. Eighteen of 20 patients (90%; 95% CI 68% to 99%) with a core NAA concentration Ͻ7 mmol/L did poorly at 3 months, whereas 7 of 11 patients (64%; 95% CI 31% to 89%) with an initial NAA concentration Ͼ7 mmol/L did well. Combining these results showed that all patients who had an initial infarct volume Ͼ70 mL did poorly, irrespective of the NAA concentration. Of those patients with infarcts Ͻ70 mL, those who had a core NAA concentration Ͼ7 mmol/L did well (88%; 95% CI 47% to 100%), whereas those with a lower NAA concentration did poorly (80%; 95% CI 44% to 97%). There was no association between other metabolite concentrations and outcome. Conclusions-Infarct volume and NAA concentration can together predict clinical outcome in MCA infarction in humans.

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