Glutamate metabolism in temporal lobe epilepsy as revealed by dynamic proton MRS following the infusion of [U13-C] glucose

- Interictal Glu levels were lower in bilateral temporal regions in persons with epilepsy focus compared with controls.
- The rate of metabolic turnover of glutamate did not differ between those with epilepsy and controls.
- Decreased Glu levels are not due to reduced oxidative metabolism, but other processes such as neuronal loss or simplification.

Focal metabolic dysfunction commonly observed in temporal lobe epilepsy (TLE), and is associated with the development of medical intractability and neurocognitive deficits. It has not been established if this dysfunction is due to cell loss or biochemical dysfunction in metabolic pathways. To explore this question, dynamic 1H MRS following an infusion of [U13- C] glucose was performed to measure glutamate (Glu) metabolism. Subjects (n = 6) showed reduced Glu levels (p < 0.01) in the ipsilateral mesial temporal lobe (MTL) compared with controls (n = 4). However, the rate of 13C incorporation into Glu did not differ between those with epilepsy and controls (p = 0.77). This suggests that reduced Glu concentrations in the region of the seizure focus are not due to disruptions in metabolic pathways, but may instead be due to neuronal loss or simplification.