Bilateral synchrony

This article needs significant updating in light of recent advances in this field(LIST).

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].

1. a Tukel K, Jasper H. The electroencephalogram in parasagittal lesions. Electroencephalogr Clin Neurophysiol. 1952 Nov;4(4):481-94. doi: 10.1016/0013-4694(52)90079-5.
2. a Kobayashi K, Ohtsuka Y, Oka E, Ohtahara S. Primary and secondary bilateral synchrony in epilepsy: differentiation by estimation of interhemispheric small time differences during short spike-wave activity. Electroencephalogr Clin Neurophysiol. 1992 Aug;83(2):93-103. doi: 10.1016/0013-4694(92)90022-a.
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