Proton MRS reveals frontal lobe metabolite abnormalities in idiopathic generalized epilepsy

To assess gamma-aminobutyric acid (GABA) plus homocarnosine (GABA+) and glutamate plus glutamine (GLX) concentrations in the frontal lobes of patients with idiopathic generalized epilepsy (IGE).

Twenty-one patients and 17 healthy volunteers were studied. A single voxel was prescribed in each frontal lobe for each subject. Point-resolved spectroscopy (PRESS)-localized short echo time MR spectroscopy (MRS) was performed to measure GLX and the metabolites N-acetylaspartate plus N-acetylaspartylglutamate (NAAt), creatine and phosphocreatine (Cr), choline-containing compounds (Cho), and myo-inositol (Ins). A double quantum GABA filter was used to measure GABA+. Segmented T1-weighted images gave the tissue composition of the prescribed voxel.

Group comparisons showed elevation of GLX and reduction of NAAt in the patient group (p < 0.05). The metabolite ratios GLX/NAAt and GLX/Ins also showed elevation in IGE (p = 0.01). No group effect was observed for GABA+, Cr, or Cho. Ins concentrations were not significantly reduced in the patient group but were less in the subgroup of patients who were taking sodium valproate.

IGE was associated with bilateral frontal lobe metabolite changes. Elevation in GLX was observed, which may imply increased neuronal excitability, whereas reduction in NAAt suggests reduced overall neuronal numbers or neuronal dysfunction.