Local cortical network stimulation as a concept for focal epilepsy treatment

BackgroundElectrical stimulation therapy for epilepsy patients is applied either to the epileptogenic region or to a larger network (e.g. with deep brain stimulation). Objective/hypothesisResponses to single pulse electrical stimuli (SPES) reveal potential stimulation sites that target the epileptogenic region for cortical network stimulation therapy. MethodsWe applied SPES to ten epilepsy patients who underwent intracranial electrocorticography recordings for pre-surgical evaluation. We detected cortico-cortical evoked potentials (CCEPs) in response electrodes after stimulating other pairs of electrodes, revealing effective connections. We calculated event-related spectral perturbation (ERSP) plots in all response electrodes after stimulating other electrode pairs. We detected interictal epileptic discharges (IEDs) before and after each single pulse and calculated the logarithmic IED ratio. We analyzed whether power suppression in the ERSP occurred in a response electrode when connected with the stimulus pair. We analyzed whether a larger change in IED ratio was accompanied by power suppression in the response electrode or when this electrode was connected with the stimulus pair. ResultsWe found that SPES has a neuromodulatory effect measured as: 1) the relationship of a CCEP and power suppression, 2) a larger change in IED rate when a CCEP was present, 3) a decrease in IED rate when power suppression was observed. Conclusion(s)Results suggest that stimulation in an area connected to the epileptogenic region can modulate IEDs in this region. SPES might provide a template for localizing a stimulation site outside the epileptogenic region for electrical stimulation treatment of epilepsy. HighlightsO_LIStimulation of an electrode pair can suppress power in an electrode on connected tissue. C_LIO_LIStimulation of an electrode pair changes IED rate in an electrode on connected tissue. C_LIO_LIA decrease in IED rate was accompanied by power suppression. C_LIO_LISPES indicates potential stimulation sites for neurostimulation therapy in epilepsy. C_LI