Abstracts

RATIONALE: Determining the borders of the epileptogenic region of cortex that must be resected to permanently eliminate epileptic seizures has been a matter of considerable debate, but we have found that the analysis of ECoG coherence patterns may be helpful in this regard, and we have investigated whether interictal EcoG coherence patterns may be used to predict the location of epileptic foci.
METHODS: Subdural ECoGs were recorded from 12 medically refractive pediatric epileptic patients as part of their routine surgical work-up. Recording arrays were implanted over the frontal, parietal, occipital or temporal lobes for 4-10 days, depending on the patient[ssquote]s seizure semiology and imaging studies. Two minute segments of the ECoG were analyzed for changes in power and lateral coherence during the interictal, pre-ictal, ictal, and post-ictal periods. Differences in coherence magnitude and phase were registered to intra-operative photographs or 3-D rendered MRIs.
RESULTS: Coherence patterns revealed a rich topography, with reduced coherence across sulci and major fissures. As has been reported by others, coherence increased during the ictal and post-ictal periods, especially within the epileptic regions. However, this was not the case when multiple independent epileptic discharges were present. The clearest differences were between areas that participated in the subsequent seizures and areas that remained seizure-free, according to conventional measures. Post-hoc analyses of interictal records revealed higher coherence in areas that were resected compared to areas of normal function.
CONCLUSIONS: Our findings suggest that analysis of coherence patterns can supplement visual inspection of conventional records to help identify the borders of properly functioning and pathological regions of cortex. With further study, analysis of coherence may allow us to identify epileptic foci from interictal recordings, possibly obviating the need for extended monitoring.
[Supported by: NIH NS40514-02]