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.
Simister
Robert J
RJ
MRI Unit, The National Society for Epilepsy and Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, UK.
McLean
Mary A
MA
Salmenpera
Tuuli M
TM
Barker
Gareth J
GJ
Duncan
John S
JS
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