A STUDY OF METABOLITE CONCENTRATIONS IN IDIOPATHIC GENERALISED EPILEPSY USING PROTON MAGNETIC RESONANCE SPECTROSCOPY
Abstract number :
3.172
Submission category :
Year :
2002
Submission ID :
3445
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Robert J. Simister, Mary A. McLean, Gareth J. Barker, John S. Duncan. Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom; NMR Research Unit, Department of Neuroinflammation, Institut
RATIONALE: Cortical hyper-excitability may be important in the patho-physiology of idiopathic generalised epilepsy (IGE). Gamma amino butyric acid (GABA) and glutamate are respectively the principal inhibitory and excitatory neurochemicals in the brain. We have implemented methods for reliably measuring gamma-amino butyric acid plus homocarnosine (GABA+) and the glutamate plus glutamine signal complex (GLX) in vivo using proton magnetic resonance spectroscopy (MRS). We report on measurement of these metabolites in patients with IGE. The objective of this study was to determine whether IGE is associated with observable abnormalities in inhibitory (GABA+) or excitatory (GLX) neurochemical concentrations.
METHODS: Twenty-six patients with IGE and normal MR imaging and 20 normal control subjects were studied on a 1.5T 5x GE Signa scanner. One voxel was prescribed (approx 35cc) in each frontal lobe for each subject. N-acetyl aspartate plus N-acetyl aspartyl glutamate (NAA) and GLX were measured by performing short echo time PRESS localised MRS (TE/TR = 30 /3000 ms) whilst GABA+ measurement was via our double quantum GABA filter.
RESULTS: Comparison was made between IGE and control groups. The right (R) and left (L) voxels were considered separately. The main findings were low NAA (R: p[lt]0.05, L:p=0.08) and high GLX (R:p[lt]0.05,L:p[lt]0.05) in the IGE group. No group differences were observed for GABA+.
CONCLUSIONS: IGE is associated with frontal lobe metabolite changes that infer increased excitability or proportion of glutamatergic neurons (elevated GLX) and reduced NAA inferring reduced neuronal numbers or neuronal dysfunction. Normal GABA+ measures infer that GABA+ concentrations may not be abnormal in patients with IGE who are taking anti-epileptic drugs.[figure1]
[Supported by: Medical Research Council
Brain Research Trust
The National Society for Epilepsy]
