Successful epilepsy surgery with a resection contralateral to a suspected epileptogenic lesion

We report on a case of frontal lobe epilepsy in an eight-year-old girl. Seizure semiology and EEG indicated an epileptogenic zone localized in the mesial frontal structures, without clear-cut lateralization. MRI showed a lesion in the right cingulate gyrus, initially regarded as a hamartoma. Ictal SPECT did not have a localization value. MR spectroscopy revealed two metabolic abnormalities: one in the area of the MRI lesion and a second contra-laterally. Invasive monitoring using subdural electrodes covering the convexity and mesial part of the right frontal lobe including mesial strips with bilateral contacts was used. The invasive monitoring failed to localize ictal onset in the right hemisphere; however, electric stimulation induced seizures from electrodes facing the left supplementary sensorimotor area ("through" the falx cerebri). We re-implanted the electrodes over the left frontal lobe and the second invasive monitoring clearly localized the ictal onset zone in the left supplementary sensorimotor area, which was subsequently resected. Histopathology found MRI-negative focal cortical dysplasia. The contralateral lesion was reassessed as nonspecific enlargement of perivascular spaces. The patient has been seizure-free for more than two years.[Published with video sequences].