A MULTIPARAMETRIC DATA-ANALYSIS SHOWING THE POTENTIAL OF LOCALIZED PROTON MR SPECTROSCOPY OF THE BRAIN IN THE METABOLIC CHARACTERIZATION OFNEUROLOGICAL DISEASES

We conducted an extended clinical evaluation of localized proton magne tic resonance spectroscopy (MRS) of the brain, performed on various br ain diseases using short stimulated echo times. Pathologies studied we re mainly multiple sclerosis, stroke, leukoaraiosis, AIDS-related leuk oencephalopathies and glial tumors. Other miscellaneous pathologies we re also studied. Magnetic resonance examination of the brain was condu cted on a Siemens Magnetom SP63 (equipped with a 1.5 T magnet). Locali zed proton MRS was performed on a routine basis immediately after imag ing, using the STEAM (stimulated echo acquisition mode) with a short e cho time (20 ms) combined with a CHESS (chemical shift selective excit ation) sequence. One or two VOI (8 ml) were examined. Data on 125 spec tra were processed by principal component analysis (PCA) and conventio nal variance analysis. The following metabolite resonances were studie d: inositol-glycine, taurine-scyllo-inositol, choline derivatives, pho sphocreatine-creatine, aspartate, glutamine glutamate, N-acetylasparta te, acetate and lactate. PCA demonstrates that the different metabolic variables are independent. The analysis of groups of spectra clearly demonstrates that the metabolic profiles detected by localized MRS in various pathologies (i) differ significantly from controls, and (ii) a llow a metabolic discrimination between groups of pathologies. Results of PCA are confirmed by variance analysis. Strokes are characterized by an increase in lactate concentration and leukoaraiosis by a decreas e in inositol-glycine resonance. AIDS-related leukodystrophies are cha racterized by increases in lactate and choline concentrations. Reducti on in N-acetylaspartate which is observed in most pathologies is not s ignificant in the small lesions of white matter. Lactate has often bee n found in MS plaques, but no variation in the choline/phosphocreatine ratio was observed. GABA was tentatively assigned in the spectrum of a patient with epilepsy under sodium valproate treatment. This study i llustrates the clinical feasibility of the technique, the value of a m ultiparametric data analysis in the definition of the pertinent variab les characterizing the metabolic impairment, and the impact of localiz ed proton MR spectroscopy of the brain in the assessment of cerebral s uffering.