Quantitative proton magnetic resonance spectroscopy of the subcortical white matter in motor neuron disease

Abstract

Using proton magnetic resonance spectroscopy, the authors have previously demonstrated a reduction in the N-acetyl aspartate/(creatine and phosphocreatine) (NAA/(Cr + PCr)) ratio in the motor region in bulbar-onset MND patients, attributed to neuronal loss or dysfunction leading to a reduction in NAA. We have expanded this analysis to evaluate absolute concentrations of NAA, (Cr + PCr) and choline-containing compounds (Cho) in the subcortical white matter in the motor region in 16 MND patients (8 with bulbar onset and 8 with limb onset) and 8 healthy, age-matched controls. Single voxel 1H-MRS was performed using a PRESS localization sequence. Metabolite concentrations were determined using the water signal as an internal standard. We found no differences in the concentrations of NAA ([NAA]), (Cr + PCr) ([Cr + PCr]) or Cho ([Cho]) in the motor region on comparing the total MND group and controls (P > 0.3). No difference was found in [NAA] in the bulbar-onset group compared with the limb-onset group (P = 0.70), but [Cr + PCr] was significantly higher in the bulbar-onset group (P = 0.04). Our results suggest that [Cr + PCr] may be affected by the pathological process in MND, and this should be considered in the interpretation of metabolite peak area ratios. The elevated (Cr + PCr) may represent gliosis in the subcortical white matter in the motor cortex region.