Absolute quantification of brain metabolites by proton magnetic resonance spectroscopy in normal-appearing white matter of multiple sclerosis patients

The aim of this research was to obtain an absolute quantification of the N- acetyl-aspartate, choline, creatine and phosphocreatine levels in normal-ap pearing white matter by means of H-1 magnetic resonance spectroscopy in a g roup of multiple sclerosis patients (27 with the relapsing-remitting form a nd 13 with the secondary progressive form). These values were compared with those of a group of 12 age-matched healthy control subjects, A significant decrease in the N-acetyl-aspartate concentration was found in normal-appea ring white matter of frontal and parietal brain areas in multiple sclerosis patients compared with the same areas in control subjects. This reduction was more evident in progressive patients. The decrease in the N-acetyl-aspa rtate concentration in normal-appearing white matter significantly correlat ed with the Expanded Disability Status and the lesional load, No significan t change was found in the concentration of creatine or choline. This findin g concurs with previous evidence of heterogeneity in the multiple sclerosis pathological process which is not confined to the lesions and involves not only myelin, but also axons, even in white matter which appears normal on MRI.