In vivo measurements of glutamine plus glutamate (Glx) and N-acetyl aspartate (NAA) levels in human partial epilepsy

Objective - To investigate whether cerebral levels of N- acetyl aspartate (NAA), and glutamine + glutamate (Glx), are interictally altered in the epileptogenic regions of patients with partial seizures. Material and Methods - NAA, Glx, creatine (Cr), choline (Cho) and myo-inositol (mI) was measured in 28 patients with partial epilepsy and 10 healthy controls using localized H-1 magnetic resonance spectroscopy. According to the multimethodological consensus, the epileptogenic region was mesial temporal in 18 and neocortical in 10 patients. Results - The Glx/NAA and Glx/Cr ratios in epileptogenic regions were higher, and the NAA/Cr ratios lower than in the homologous regions (P=0.013, P=0.002 and P<0.0001). Applying the 95% confidence interval of controls, 17 of the 20 mesial temporal epileptogenic regions were correctly identified by an increased Glx/NAA and 15 of 20 by a decreased NAA/Cr ratio. Among patients with neocortical epilepsy the Glx/NAA ratio was increased in 8 of the 10 epileptogenic regions, whereas the NAA/Cr ratio was decreased in three. Conclusion - Both Glx and NRA are useful to identify the epileptogenic zone. The Glx/NAA ratios may be particularly useful to indentify neocortical epileptogenic regions.