The effect of epileptic seizures on proton MRS visible neurochemical concentrations

SummaryPurposeTo investigate post-ictal changes in cerebral metabolites.MethodsWe performed a longitudinal quantitative proton magnetic resonance spectroscopy (MRS) study in 10 patients with epilepsy and 10 control subjects. The patients were studied on two occasions: immediately following a seizure, and on a second occasion at least 7 h after the most recent seizure. Each study measured N-acetyl aspartate plus N-acetyl aspartyl glutamate (NAAt), Creatine plus phosphocreatine (Cr), Choline containing compounds (Cho) and glutamate plus glutamine (GLX) concentrations using a short-echo time sequence (TE = 30 ms), and NAAt, Cr and lactate using a second sequence with longer echo time (TE = 144 ms). The control group was studied on two occasions using the same sequences.ResultsNo inter-scan differences were observed for the control group. NAAt and NAAt/Cr levels were lower in the patient group at both measured TEs but did not change significantly between studies. The ratio of Cr at TE 144 ms to TE 30 ms (Cr144/Cr30) and GLX/Cr were higher and Cho lower in the post-ictal scan compared to the inter-ictal study. Change in Cr144/Cr30 and NAAt144/Cr144 correlated with the post-ictal interval. Lactate measurement at longer TE was not informative.DiscussionProton MRS is sensitive to metabolite changes following epileptic seizures within the immediate post-ictal period. The ratio Cr144/Cr30 is the most sensitive measure of metabolic disturbance and is highest in the post-ictal period but appears to normalise within 2 h of the most recent seizure.