Regional variation in bilateral synchrony of spike-wave discharge before and after corpus callosotomy

In patients undergoing corpus callosotomy (CC), we investigated whether regions with a high degree of bilateral synchrony of spike-wave discharge correspond to the regions with major epileptogenic abnormalities and whether these regions are included within the cortical distribution of callosal fibers bisectioned. We studied 16 patients who underwent anterior (ant 2/3-4/5) CC for intractable symptomatic generalized epilepsies (SGE) with preoperative interictal generalized synchronous spike-wave discharges (GSSW). The degree of bisynchrony and synmorphism (i.e., similarity of wave form) was measured using cross-correlation analysis and the measurement of amplitude differences between homologous regions. Preoperatively, frontocentral regions had higher values of correlation coefficient (R) and interhemispheric synchrony (IS) than temporal and occipital regions. Furthermore, the temporal region, as compared with the other regions, had higher value of interhemispheric time difference (ITD). Postoperatively, the GSSW were disrupted and there was a significant decrease in the levels of R and IS, and a significant increase in amplitude difference in all regions, especially in the frontocentral regions where many of the lateralized spike-wave discharges were observed in routine electroencephalograms (EEGs). In our patients with SGE, the regions with a high degree of bilateral synchrony correspond to the regions with major epileptogenic abnormalities. They are predominantly frontocentral regions, and are included in the extent of the cortical distribution affected by the bisection of callosal fibers. These analyses will provide additional information regarding patient selection, the extent of callosal bisection, and seizure outcome. (C) 1998 by Elsevier Science Inc. All rights reserved.