A STEREOELECTROENCEPHALOGRAPHIC (SEEG) STUDY OF LIGHT-INDUCED MESIOTEMPORAL EPILEPTIC SEIZURES

Purpose: This study explored the mechanism of light-induced complex pa rtial seizures by using ictal intracerebral recordings in a patient wi th refractory epilepsy of the right temporal lobe. Methods: Presurgica l evaluation of this patient was realized by means of video-EEG record ings, WADA test, magnetic resonance imaging (MRI), F-18-deoxyglucose a nd C-11-flumazenil positron emission tomography (PET) interictal neuro imaging data, and stereoelectroencephalographic (SEEG) ictal recording s. Results: SEEG investigations demonstrated the right mesiotemporal o rigin of all the patient's seizures. This result was confirmed by a su ccessful right temporal lobectomy. Moreover, SEEG recordings revealed a frequent interictal spiking activity in the right occipital visual c ortex that was undetectable on scalp recordings. However, the occipita l cortex was not involved at the onset of mesiotemporal ictal discharg es and was not hyperresponsive to focal electrical stimulation. Conclu sions: This study shows that, in spite of interictal occipital spiking , the photosensitivity of mesiotemporal seizures can be observed in bo th the absence of occipital cortex involvement during ictal discharges and demonstrable hyperexcitability of the occipital cortex to light o r direct electrical stimulation.