Abstracts

Rationale: In between seizures, the brain of an epileptic patient will also generate isolated sporadic discharges (Interictal Epileptiform Discharges, IEDs). Identification of IEDs allows clinicians to diagnose epilepsy and their waveforms may yield insights on basic epilepsy mechanisms. This study reveals that IEDs are initiated by a negative polarity, low-voltage pre-potential, a negative-preceding-wave (np-wave), describes its features and proposes hypotheses on its mechanism and role in epileptogenesis. Methods: In human neocortical intracranial EEGs, I measured np-waves occurrence, amplitude, kinetics and association to the subsequent positive pre-potential. I ran a computational model of IED onset to identify plausible mechanisms of np-waves' generation. Results: Np-waves manifested in zones with and without seizures, without a statistically significant prevalent anatomical location, in 40% of patients. They exhibited voltages of 140+42 V and durations of 39.9+12.2 milliseconds and were coupled with a positive pre-potential. In simulations of IEDs' onset, np-waves can be generated by the sequential recruitment of distinct microfoci over superficial cortical laminae. Conclusions: Np-waves are an overlooked component of IED waveforms. They prolong the duration of IEDs onset and can facilitate synaptic hypersynchrony. They may be associated with chronic epilepsy. Funding: No funding