Pediatric Epilepsy Fellow Columbia University Irving Medical Center Forest Hills, New York
Rationale: Intermittent photic stimulation (IPS) is a routine activation procedure used during electroencephalography (EEG) monitoring in attempt to provoke an abnormal electrographic pattern or seizure. A normal physiologic response to IPS is an occipital photic “driving” response, which represents repetitive visual evoked potentials (VEPs) produced in response to the photic flash. Photic driving is a common phenomenon captured on surface electrode EEG recordings; however, based our review of the literature, is not commonly observed during stereotactic-EEG (sEEG) monitoring. Methods: We discuss the case of a nine-year-old female with medically refractory focal epilepsy and left occipital horn heterotopia. On surface EEG, we captured both left and right posterior onset seizures. We implanted her with bilateral sEEG/depth electrodes in attempts to localize her seizure onset zone. Twelve depth electrodes were placed over the left hemisphere and five depth electrodes were placed over the right hemisphere. When activation procedures were performed, a photic “driving” response was recorded on sEEG during photic stimulation. Results: A photic “driving” response was the most robust at the right temporoparietooccipital junction (RTPOJ) lead, contacts 1-3. A sustained photic “driving” response was seen at all frequencies 3-30 Hz. It was also observed at the left temporoparietooccipital junction (LTPOJ) lead, contacts 1-3 at frequencies 6-8, 11-13, 16, 17, 21, 26, 29, and 30 Hz. The third depth electrode that showed a photic “driving” response was the left superior occipital to the isthmus of the cingulate gyrus (LISTH) lead, contacts 1-2 at frequencies 7, 11, 15-17, and 26 Hz. See attached images for a visual of the photic “driving” response, as well as the location of the depth electrodes. Conclusions: Photic “driving” is a common normal finding seen on surface EEG, however it is not reported in the literature to have been seen on sEEG recordings. In our patient, a photic “driving” response was seen in the most mesial leads in three depth electrodes. All three areas were deep in the occipitoparietal region (RTPOJ and LTPOJ- occipital; LISTH- occipitoparietal junction). To our knowledge, this is the first description of a photic “driving” response seen in a pediatric sEEG recording. Funding: Please list any funding that was received in support of this abstract.: NA Click here to view image/table
