Lateralization of interictal spikes after corpus callosotomy

Corpus callosotomy may limit secondary bilateral synchrony into the primary epileptogenic hemisphere. This study investigated whether pre-operative EEG can predict post-operative spike lateralization.

The subjects included 14 patients with medically intractable drop attacks who underwent total corpus callosotomy. Pre-operative patterns of inter-hemispheric propagation were quantified by peak-latency analysis with the template-based spike averaging technique.

Postoperative lateralization of interictal spikes was observed in 5 of the 14 patients. Inter-hemispheric latency was significantly longer in these 5 patients (mean 14.0 ms, range from 0 to 78 ms, versus mean 5.2 ms, range from 0 to 29 ms, p<0.01). The lateralization occurred in association with the presence of structural lesions (p<0.05). The post-operative spikes were lateralized to the lesion side in 3 of 4 patients with unilateral epileptogenic lesion. Three patients presented one-way inter-hemispheric propagation pattern pre-operatively. The post-operative spikes were lateralized to the hemisphere of the leading spikes in two.

Interictal spikes are lateralized to the epileptogenic hemisphere in some patients after callosotomy. Lateralization can be expected in the presence of structural lesions and/or longer inter-hemispheric latency.

Analysis of pre-operative EEG spikes may predict the primary epileptogenic hemisphere before corpus callosotomy.