Benign partial epilepsy in childhood: selective cognitive deficits are related to the location of focal spikes determined by combined EEG/MEG.

Purpose: Benign partial epilepsy (BPE) in childhood is characterized by the occurrence of interictal stereotyped focal spikes with variable localization in the EEG. Children with BPE often exhibit neuropsychological deficits. It is unclear whether a correlation exists between these deficits and the localization of spikes, several EEG studies giving inconsistent results. Magnetoencephalography (MEG) improves the accuracy of spike localization. Therefore by using combined MEG/EEG, we investigated the topographic relation between focal spikes and neuropsychological findings in children with BPE.

Methods: Twenty-seven children diagnosed consecutively with BPE were enrolled in the study. All were examined by combined MEG/EEG and magnetic resonance imaging (MRI). Location of spikes was determined by dipole source estimation. A standardized neuropsychological assessment was conducted, including Kaufman ABC battery, language tests, and motor performance series. All children with sufficient MEG data were included in the correlation analysis (N = 20).

Results: Focal spikes were located in the perisylvian region in 13 children, in the occipital region in seven, and in the frontal region in one. Five children had bilateral or multiple foci. Children with left perisylvian spikes did not differ from the others in global IQ, but performed significantly lower in language tests (p = 0.01). Children with occipital spikes performed significantly lower in simultaneous information processing (p = 0.01), especially in visual transformation tasks.

Conclusions: Combined MEG/EEG investigation is a useful tool to examine interictal focal spikes. Our results show a correlation between the location of spikes and selective cognitive deficits in children with BPE. These findings indicate that focal interictal spikes may interfere with complex cognitive functions.