PROTON MR SPECTROSCOPY AND MR-IMAGING IN ACUTE AND CHRONIC MULTIPLE-SCLEROSIS - RING-LIKE APPEARANCES IN ACUTE PLAQUES

Purpose: We wanted to compare the metabolite status of brain lesions i n different clinical subtypes of multiple sclerosis (MS). Two acute MS lesions with ringlike appearances were also investigated. Material an d Methods: Twenty-three clinically stable MS patients, 2 patients with acute relapses, and 15 healthy individuals were examined by MR imagin g and localized proton MRS. Results: No metabolite differences were se en in plaques of different subtypes. Decreased NAA/Cr and NAA/choline ratios as well as increased inositol/Cr ratios were observed in the pl aques of the clinically stable or chronic active MS patients as compar ed with controls. The ring plaques had hyperintense cores with surroun ding halos, separated from the cores by rings with low signal intensit y in T2-weighted images. The core exhibited a prolonged T2 relaxation time. Proton spectra initially contained lactate. Conclusion: No diffe rences between the metabolite status of nonacute plaques in different clinical subtypes could be detected. The ring plaques contained lactat e signals indicating oedema, inflammation, and macrophage invasion, an d may be transition forms between acute oedematous lesions and chronic demyelinated plaques.