Quantitative MR spectroscopy reveals metabolic changes in the dorsolateral prefrontal cortex of patients with temporal lobe epilepsy.

OBJECTIVE: To characterize possible metabolic changes of the dorsolateral prefrontal cortex (DLPFC) in patients with temporal lobe epilepsy (TLE).

METHODS: Quantitative proton magnetic resonance spectroscopy (1H-MRS) studies were performed on 24 TLE patients and 22 healthy controls. Metabolite concentrations were calculated using a linear combination model (LCModel) and corrected for cerebrospinal fluid contamination. Comparisons were performed between the TLE patients and the controls and between the left DLPFC and right DLPFC in each group. Pearson correlation coefficients were calculated between the metabolite concentrations and epilepsy duration and between the metabolite concentrations and voxel tissue composition: [gray matter (GM)/(GM+white matter (WM))].

RESULTS: Metabolic asymmetry was found in controls between the left and right DLPFC, i.e., the NAA concentration of the left DLPFC was significantly higher than that of the right. However, such metabolic asymmetry was not observed in TLE patients. Compared with the controls, TLE patients showed significantly decreased NAA and Ins, and the reductions were greater in the left DLPFC. No significant correlation was found between the metabolite concentrations and epilepsy duration or between the metabolite concentrations and voxel tissue composition [GM/(GM+WM)].

CONCLUSIONS: This study suggests that TLE can produce metabolic changes to DLPFC that is remote from the seizure focus.

KEY POINTS: • Magnetic resonance spectroscopy probes the brain metabolism noninvasively. • Dorsolateral prefrontal reductions in NAA (a neuronal marker) and Ins are observed in TLE. • Temporal lobe epilepsy can result in metabolic changes remote from the seizure focus.