Incremental changes in interhemispheric functional connectivity after two-stage corpus callosotomy in a patient with subcortical band heterotopia.

Corpus callosotomy (CC) has been reported to be effective in reducing generalized seizures in patients with drug-resistant epilepsies. However, efficacy is measured only by seizure frequency, without any electrophysiological guidance. Herein, we conducted a quantitative analysis of interhemispheric functional connectivity using inter-electrode coherence of scalp electroencephalogram (EEG) in a clinical case of subcortical band heterotopia to evaluate its relationship with seizure frequency. In our case, seizure frequency decreased significantly after posterior CC but not after anterior CC. Inter-electrode coherence also decreased after posterior CC, suggesting it correlated with seizure frequency. This case study supports the use of inter-electrode coherence as an electrophysiological tool that is useful as predictive factor in evaluating the effectiveness of CC.