Preliminary evidence for neuronal damage in cortical grey matter and normal appearing white matter in short duration relapsing-remitting multiple sclerosis: a quantitative MR spectroscopic imaging study

Neuronal damage and loss is likely to underlie irreversible disability in multiple sclerosis (MS). The time of onset, location and extent of neuronal damage in early disease are all uncertain. To explore this issue 16 patients with short duration, mild relapsing-remitting disease (mean disease duration 1.8 years, median EDSS 1) were studied using short echo time proton magnetic resonance spectroscopic imaging ((1)H-MRSI) to quantify the concentration of the neuronal marker N-acetyl-aspartate (NAA). The data were compared with those from 12 age-matched controls. (1)H-MRSI was obtained from a 1.5-cm-thick slice just above the lateral ventricles. The Linear Combination (LC) Model combined with locally developed software allowed automated measurement of absolute metabolite concentrations from lesions, normal-appearing white matter (NAWM) and cortical grey matter (CGM). MS CGM exhibited significantly lower NAA (P=0.01) and myo-inositol (P=0.04) than control CGM. MS NAWM exhibited a lower concentration of NAA (P=0.01) and increased myo-inositol (P=0.03) than control white matter. More marked reductions in NAA and increases in myo-inositol were seen in lesions. The reduced NAA in MS CGM and NAWM suggest that mild but widespread neuronal dysfunction or loss occurs early in the course of relapsing-remitting MS. This preliminary finding should be confirmed in a larger cohort, and follow-up studies are also needed to determine the prognostic and pathophysiological significance of these early changes.