Variability of presentation in medial temporal lobe epilepsy: a study of 30 operated cases

INTRODUCTION: To evaluate the homogeneity of patients operated on for MTLE. MATERIAL AND METHODS: 30 consecutive patients prospectively investigated with clinical, EEG, neuropsychology, MRI, FDG-PET criteria and eventually intracranial EEG, who underwent antero-medial temporal resection (follow-up: 24 months). RESULTS: Clear and well-lateralised MTLE was non-invasively ascertained in 22 patients (73%). Eight patients (27%) had a less pure presentation due to divergent scalp EEG features (bitemporal, widespread or extratemporal), unusual auras or absence of MRI-based hippocampal sclerosis or FDG-PET hypometabolism. They were explored by invasive monitoring which confirmed medial temporal origin of seizures. Outcome was excellent in 95% of the pure cases (Engel's class I) and less favorable in the more difficult ones (65% of class I). CONCLUSIONS: MTLE criteria, including the strong contribution of brain imaging, permit to select accurately a large percentage of patients. However a consistant number of patients present a less pure presentation suggesting more complex epileptogenic networks.