Interhemispheric threshold differences in idiopathic generalized epilepsies with versive or circling seizures determined with focal magnetic transcranial stimulation.

The interhemispheric difference of the motor-cortical threshold (IDMT) was studied with focal magnetic transcranial stimulation (TCS) in ten patients with idiopathic generalized epilepsy (IGE) who also displayed versive or circling seizures (IGEvc). The data were compared with those obtained from two control groups; 13 patients with IGE without asymmetrical motor seizures, and 25 normal volunteer subjects. The IDMT, referred to as the percentage of maximum stimulator output, was assessed by focal TCS applied to the hand areas. Seven patients with IGEvc and only one patient with IGE had an interhemispheric motor threshold beyond the normal range. The IDMT in IGEvc patients was significantly higher compared to that of IGE patients and normal individuals. An interhemispheric imbalance of cortical excitability may explain lateralized ictal motor manifestations in patients with IGEvc.