The effect of epileptic seizures on proton MRS visible neurochemical concentrations.
OBJECTIVE
To investigate post-ictal changes in cerebral metabolites.


METHODS
We 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 7h 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=30ms), and NAAt, Cr and lactate using a second sequence with longer echo time (TE=144ms). The control group was studied on two occasions using the same sequences.


RESULTS
No 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 144ms to TE 30ms (Cr(144)/Cr(30)) and GLX/Cr were higher and Cho lower in the post-ictal scan compared to the inter-ictal study. Change in Cr(144)/Cr(30) and NAAt(144)/Cr(144) correlated with the post-ictal interval. Lactate measurement at longer TE was not informative.


CONCLUSIONS
Proton MRS is sensitive to metabolite changes following epileptic seizures within the immediate post-ictal period. The ratio Cr(144)/Cr(30) is the most sensitive measure of metabolic disturbance and is highest in the post-ictal period but appears to normalise within 2h of the most recent seizure.
MRI Unit, The National Society for Epilepsy and Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK.
Robert J
RJ
Simister
Mary A
MA
McLean
Tuuli M
TM
Salmenpera
Gareth J
GJ
Barker
John S
JS
Duncan
D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001923:Brain Chemistry / Q000502:physiology*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004151:Dipeptides / Q000378:metabolism; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D010725:Phosphocreatine / Q000378:metabolism; D011522:Protons; D012640:Seizures / Q000378:metabolism*
D004151:Dipeptides; D011522:Protons; D010725:Phosphocreatine; C027172:isospaglumic acid; D001224:Aspartic Acid; D019344:Lactic Acid; D018698:Glutamic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline