Simultaneous multi-channel spikes and inverted spikes in focal epileptic ECoG are more after offset than during the seizure

•A novel spike and inverted spike detection algorithm.•Generalization to detect multi-channel simultaneous spikes.•Simultaneous occurrence of spikes and inverted spikes across focal channels are more after the seizure than during it.

A simple, real time, differential operator based spike detection algorithm has been described, which can efficiently detect seizure spikes in noisy ECoG signals. Simultaneous spikes and inverted spikes have been detected across all focal ECoG channels during preictal, ictal and postictal periods. Out of 79 seizures recorded from 21 patients, about 80% showed more occurrence of simultaneous spikes and inverted spikes across focal channels after the seizure offset than during the seizure in 0–40 Hz range, where the duration studied after the offset is equal to the duration of the seizure. This is an important finding because this goes contrary to the prevailing wisdom that epileptic seizure is a hyper-synchronous phenomenon.