Abstracts

RATIONALE: Ipsilateral "paradoxical" lateralization of ictal EEG pattern have been rarely reported to occur in patients with epileptogenic foci near the midline. We report on three patients, in whom ipsilateral EEG seizure patterns have been recorded. METHODS: We report on 3 patients (10-69 years old), in whom non-invasive 32-48 channel EEG recordings demonstrated seizure patterns ipsilateral to the ictal seizure semiology. Invasive EEG recordings were performed in one patient. RESULTS: During the ipsilateral seizure pattern somatosensory auras (n=1), unspecific auras (n=1) and clonic jerking of the leg (n=1) were present. Two patients had MRI lesions in the mesial frontal or parietal region. A 10-year-old girl had somatosensory auras of the right leg, which evolved into asymmetric tonic and right arm clonic seizures. Non-invasive EEG recordings revealed a right parasagittal seizure pattern. Subdural grid recordings covering the frontal parasagittal cystic lesion and surrounding cortex showed a left mesial frontal seizure pattern. CONCLUSIONS: Epileptic seizure foci in the mesial frontal or parietal region may lead to ipsilateral "paradoxically" lateralized seizure pattern on the scalp although the seizure focus is contralateral to the ictal semiology as evidenced by invasive recordings.