Assessment of lesion pathology in multiple sclerosis using quantitative MRI morphometry and magnetic resonance spectroscopy

Abstract

Quantitative measurement of MRI-defined brain lesions can provide an index of the extent and activity of disease in multiple sclerosis patients. However, the relationships between these indices and clinical features are not well-understood. Heterogeneity of the pathological changes underlying MRI lesions may be an important factor determining the correlation between MRI lesion volumes and clinical measures. Recent studies have suggested that with magnetic resonance spectroscopy (MRS), it may be possible to define chemical changes that better reflect the pathological changes in multiple sclerosis. Here we report results of combined quantitative brain T2-weighted MRI lesion volume and proton MRS examinations that demonstrate heterogeneity of the chemical pathology underlying brain lesions in patients selected on the basis of similar clinical disability but differing with respect to the presence or absence of clinical relapses. We examined 29 patients with disease characterized by either clear relapses with at least partial remissions (RR) or secondary, chronic progression after an earlier history of a more relapsing and remitting course (SP). Total hemispheric lesion volume was greater (P 3) than in the SP (16.2±9.0 cm³) patients, despire the longer duration of disease in the latter group. Central brain N-acetyl aspartate: creatine (NAA: Cr) ratios were reduced relative to normal controls (4.0±0.3. n = 19) by similar amounts in the two patient groups (RR. 3.1±0.5: SP, 3.2±0.4; P 3) than for the SP group (5.4±3.3 cm³, P 2-weighted MRI lesion volume alone and suggest that combined analysis of MR-based chemical and imaging data might allow improved non-invasive assessment of lesion pathology in order to better understand its relationship to clinical features of multiple sclerosis.