Purpose: To prospectively investigate metabolic changes in the normal-appearing white matter (NAWM) of patients presenting with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) and to correlate these changes to conventional MR imaging findings in terms of MR imaging criteria.
Materials and methods: Multisequence MR imaging of the brain and (1)H-MR spectroscopy of the parietal NAWM were performed in 31 patients presenting with CIS and in 20 controls using a 3. 0 T MR system. MR imaging criteria and International Panel criteria were assessed based on imaging, clinical and paraclinical results. Metabolite ratios and absolute concentrations of N-acetyl-aspartate (tNAA), myoinositol (Ins), choline (Cho), and total creatine (tCr) were determined. The metabolite concentrations were correlated with the fulfilled MR imaging criteria.
Results: In comparison to the control group, the CIS group showed significantly decreased mean tNAA concentrations (-8. 1%, p = 0. 012). Significant changes could not be detected regarding Ins, tCr and Cho. No significant correlations between absolute metabolite concentrations and MR imaging criteria were observed. Patients with and without a lesion dissemination in space showed no significant differences of their metabolite concentrations.
Conclusion: As assessed by (1)H-MRS a significant axonal damage already occurs during the first demyelinating episode in patients with CIS. Conventional MR imaging in terms of diagnostic imaging criteria does not significantly reflect NAWM disease activity in terms of metabolic alterations detected by (1)H-MR spectroscopy.