Glutamine Metabolism and Metabolic Profiling Using 7 T CRT-FID MRSI in Focal Epilepsy.

BACKGROUND

Approximately one-third of people with epilepsy (PWE) remain drug-resistant. In these cases, surgical resection of the epileptogenic zone may significantly reduce or eliminate seizures. Surgery necessitates precise delineation of the epileptogenic zone (EZ) which proves especially challenging in the 20% of PWE that remain MRI-negative. The purpose of this study was to analyze the feasibility and robustness of ultra-high-field MRSI in identifying and characterizing pathologies in focal epilepsy. In addition, the relationship of glutamate and glutamine was evaluated in the EZ.

METHODS

Fifty-six people with focal epilepsy were prospectively measured using 7 T concentric ring trajectory direct acquisition of free-induction-decay MRSI, which generated whole-brain metabolic maps with an isotropic resolution of 3.4mm. After exclusion criteria were applied, we assessed metabolite ratios in 15 lesional and 14 MRI-negative PWE.

RESULTS

In the lesional group, metabolic alterations in the suspected EZ were present in 86.7% of maps normalized to N-acetyl-aspartate, whereas this was reduced to 80% in creatine ratios. Metabolites with the highest consistency in the lesional group included myo-inositol and choline, showing increases in 92.3% of PWE. In MRI-negative patients, changes were heterogeneous, with a detection rate of 57.1%. We also observed a tendency toward an inverse relationship of glutamate to glutamine in the EZ, with increases of glutamine in PWE with lower seizure frequencies, contrasting glutamate increases in higher seizure frequencies.

CONCLUSION

Our preliminary analysis suggests that 7 T CRT-FID MRSI shows promise not only in identifying metabolic alterations in focal epilepsy but may also provide insights into disease pathomechanisms.