Proton MR spectroscopy and MR imaging in acute and chronic multiple sclerosis - Ringlike appearances in acute plaques

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