PAPER

Idiopathic generalised epilepsy: a pilot study of memory and neuronal dysfunction in the temporal lobes, assessed by magnetic resonance spectroscopy

J M Dickson¹, I D Wilkinson², S J L Howell³, P D Griffiths², R A Grünewald³

¹ Department of Biomedical Science, University of Sheffield, Sheffield, UK
² Academic Unit of Radiology, University of Sheffield
³ Academic Unit of Neurology, University of Sheffield

Correspondence to:
Jonathan Mark Dickson
Magdalen College, University of Oxford, Oxford OX1 4AU, UK; jon.dickson{at}magdalen.oxford.ac.uk

Background: The memory deficits in patients with temporal lobe epilepsy (TLE) are associated with epileptogenic lesions of the temporal lobes, especially hippocampal sclerosis. Memory deficits have been extensively studied in TLE, but the presence of pre-existing temporal lobe abnormality has confounded studies on the relationship between memory dysfunction and seizure activity. Idiopathic generalised epilepsy (IGE) is characterised by primary generalised seizures and is found to occur in the absence of any macroscopic brain abnormalities. IGE is therefore ideal for investigations on the effects of seizure activity on memory and cognition.

Aim and methods: Magnetic resonance spectroscopy (MRS) and neuropsychological testing were used to investigate the relationship between epileptic seizures, memory performance and neuronal dysfunction in the temporal lobes of a group of patients with IGE. 30 patients and 15 healthy controls participated in the study.

Results: Patients with IGE were found to perform worse than controls on tests of speed of information processing, general cognitive performance and a range of memory tests, including face recognition, word recognition, verbal recall and complex figure recall. The performance of the patient group on the visual recognition and verbal recall sections of the Doors and People Test was found to correlate with MRS ratios of N-acetyl aspartate:choline and N-acetyl aspartate:creatine in the temporal lobes.

Conclusion: This result supports the hypothesis that memory deficits in epilepsy may be due to neuronal dysfunction secondary to epileptic activity itself in the absence of any macroscopic lesions in the temporal lobes.

Abbreviations: Cho, choline; Cr, creatine; D&P Test, Doors and People Test; EEG, electroencephalogram; GTCS, generalised tonic–clonic seizure; IGE, idiopathic generalised epilepsy; MRS, magnetic resonance spectroscopy; NA, N-acetyl aspartate; NART, National Adult Reading Test; SCOLP, speed and capacity of language processing; TLE, temporal lobe epilepsy; WAIS—R, Wechsler Adult Intelligence Scale—Revised

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