Localized proton magnetic resonance spectroscopy in relapsing remitting versus secondary progressive multiple sclerosis

Objective: To determine the efficacy of MRS in discriminating between relap sing remitting (RR) and secondary progressive (SP) MS. Methods: MRS at long and short echo times was carried out in 104 patients with MS stratified fo r clinical course (RR or SP), and the results were compared with those of 1 5 control subjects. Normal-appearing white matter (NAWM) was studied in 55 patients, and a high-T2-signal area on MRI in 49 others. Results: At long e cho times, there was a highly significant decrease in the ratios N-acetyl-a spartate/creatine (NAA/Cr) and NAA/choline (Cho) in high-T2-signal areas an d in the NAWM in patients with an SP course compared with control subjects and patients with an RR course. There was a significant negative correlatio n between these ratios and clinical disability measured by Expanded Disabil ity Status Scale score, which was independent of disease duration. Discrimi nant values between patients with RR and SP courses were found in the NAWM (NAA/Cr = 1.75 and NAA/Cho = 1.5), but not in high-T2-signal areas. At shor t echo times, there was a significant increase in the ratio myoinositol/Cr in high-signal areas of patients with an SP course compared with control su bjects, and the presence of abnormal resonances in the lesions and NAWM for free amino acids and lipids (in 30% and 8%, respectively) and GLX complex (glutamine, glutamate, gamma-aminobutyric acid; 16% and 20%, respectively). Conclusions: Studying normal-appearing white matter on MRI with MRS allows discrimination between relapsing remitting and secondary progressive patie nts. In the NAWM of patients with MS and an SP course, severe axonal loss/d ysfunction is negatively correlated to clinical disability and independent of the duration of the disease.