Bilateral synchrony

The term “bilateral synchrony” was introduced by Wilder Penfield. According to Penfield and Jasper “An epileptogenic lesion of the mesial or inferior aspect of a frontal lobe, although it is one-sided, may produce bifrontal synchronous discharges”. The mechanisms by which seizures that become secondarily generalised are not yet known fully.

The wave and spike of petit mal is a primary bilateral synchronous discharge . . . ; it appears not to be related to a unilateral cortical focus, but may be of subcortical origin …. On the other hand, a bilateral synchronous discharge which can be shown to arise from a unilateral cortical focus we shall call secondary bilateral synchrony - Tükel and Jasper^[1]

• it is important to differentiate between primary and secondary bilateral synchrony when bilaterally synchronous spike and wave discharges are seen on EEG
• Estimation of interhemispheric small time differences (TDs) during spike-wave bursts in the EEG by coherence and phase analysis is useful for differentiation between primary bilateral synchrony (PBS) and secondary bilateral synchrony (SBS) in epilepsy^[2].