A proton magnetic resonance spectroscopy study of metabolites in the occipital lobes in epilepsy.
OBJECTIVE
gamma-Amino butyric acid (GABA) and glutamate, respectively the principal inhibitory and excitatory neurochemicals in the brain, are visible to proton magnetic resonance spectroscopy (MRS). We report a study of GABA+ (GABA plus homocarnosine) and GLX (glutamate plus glutamine) concentrations in the occipital lobes in patients with idiopathic generalised epilepsy (IGE) and in patients with occipital lobe epilepsy (OLE).


METHODS
Fifteen patients with IGE, 15 patients with OLE, and 15 healthy volunteers were studied. A single voxel was prescribed in the occipital lobes for each subject. PRESS localised short-echo-time MRS was performed to measure GLX by using LCModel. A double quantum GABA filter was used to measure GABA+. Segmented T1-weighted images gave the tissue composition of the prescribed voxel.


RESULTS
Grey-matter proportion, GLX, and GABA+ were all elevated in IGE. However, analysis using grey-matter proportion as a covariable showed no significant group differences. No correlation was observed between GABA+ concentration and either seizure frequency or time since last seizure.


CONCLUSIONS
GLX and GABA+ were elevated in IGE. Elevated grey-matter content in the IGE group despite normal MRI appearance can be expected to account for some or all of this observed elevation of GLX and GABA+. GABA+ concentration did not correlate with seizure control or duration since most recent seizure.
Simister
Robert J
RJ
MRI Unit, The National Society for Epilepsy, London, England.
McLean
Mary A
MA
Barker
Gareth J
GJ
Duncan
John S
JS
D000293:Adolescent; D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D002336:Carnosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology*; D004829:Epilepsy, Generalized / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D009778:Occipital Lobe / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005973:Glutamine; D001224:Aspartic Acid; C005038:homocarnosine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002336:Carnosine; C000179:N-acetylaspartate