Abstracts

Rationale: Corpus callosotomy (CC) has been established as one surgical treatment for patients with intractable epilepsy. CC is considered a palliative treatment for drug-resistant generalized seizures, including epileptic spasms (ES). However, this procedure sometimes results in lateralization of bilateral epileptiform discharges and seizures, thus providing subsequent resective surgery. Residual seizures are occasionally observed as asymmetric features (i.e., asymmetric neck or limb movements) in patients with ES. This study evaluated the lateralizing value of asymmetric ES after CC for predicting the hemisphere of seizure onset.  Methods: This study included nine patients with drug-resistant ES who were initially diagnosed with West syndrome. All were treated with stepwise procedure with CC and subsequent resective surgery. All had residual ES after the CC that disappeared after the resective surgery. To investigate the correlation between clinical manifestations of ES and the responsible hemisphere, we retrospectively reviewed video-EEG monitoring. A reviewer blindly observed all ES before and after CC. In particular, asymmetric neck flexion and limb movements were described, focusing on laterality. Results: Neck flexion was clearly observed in ES, 114 times before CC and 65 times after CC. Among these, asymmetric neck flexion was observed 13 times (11%) before and 54 times (83%) after CC. Significantly larger number of asymmetric neck flexions were observed in ES after CC (p=0.014). In terms of laterality, six patients (67%) showed neck flexion deviating ipsilaterally toward the side of resection. Limb movements were clearly observed in ES, 166 times before CC and 129 times after CC. As for the upper limbs, asymmetrical movement was observed 55 times (33%) before and 85 times (66%) after CC. Significantly larger number of asymmetrical upper-limb movements were observed in ES after CC (p=0.014). In terms of laterality, 7 patients (87.5%) predominantly showed gross movements contralateral to the side of resection. The same tendency was observed for the lower limbs, but no significant difference was seen between before and after CC. Conclusions: Asymmetric neck flexion and limb movements can be observed in some patients after CC. Our findings suggest that the side of deviated neck flexion and predominant upper-limb movements tend to be ipsilateral and contralateral to the responsible hemisphere, respectively. More attention to laterality may be needed in ES after CC when considering additional resective surgery. In addition, taking into account that these clinical manifestations were clearer after callosotomy, ES seems closely associated with cortical epileptogenicity. Funding: None