Subdural electrode recording of generalized photoepileptic responses.
We evaluated the spatiotemporal distribution of photic driving (PDR), photoparoxysmal (PPR), and photoconvulsive (PCR) responses recorded by intracranial electrodes (ic-EEG) in a patient with generalized photosensitivity and right frontal lobe cortical dysplasia. Intermittent light stimulation (ILS) was performed thirteen times in nine days. Cortical responses to ILS recorded by ic-EEG were reviewed and classified as PDRs, PPRs, and PCRs. Photic driving responses were restricted to the occipital lobe at ILS frequencies below 9 Hz, spreading to the parietal and central regions at > 9 Hz. Photoparoxysmal responses commonly presented as focal, medial occipital, and parietal interictal epileptic discharges (IEDs), the latter propagating to the sensorimotor cortices. Generalized IEDs were also generated in the setting of PPRs. Photoconvulsive responses, characterized by repetitive bilateral upper extremity myoclonus sustained until the end of the stimulus, were associated with propagation of the medial parieto-occipital discharge to the primary sensorimotor and supplementary area cortices, while generalized myoclonic seizures were associated with a generalized spike-and-wave discharge with an interhemispheric posterior cingulate onset sparing the sensorimotor cortices. Both types of PCR could occur during the same stimulus. Regardless of the pathway, PCRs only occurred when PDRs involved the parietal cortices. While there may be more than one pathway underlying PCRs, parietal lobe association cortices appear to be critical to their generation.
Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
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Mukundan
Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; South Texas Comprehensive Epilepsy Center, San Antonio, TX, USA.
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Lie
Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; Department of Pediatrics, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; South Texas Comprehensive Epilepsy Center, San Antonio, TX, USA.
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Leary
Department of Neurosurgery, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; South Texas Comprehensive Epilepsy Center, San Antonio, TX, USA.
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Papanastassiou
Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; South Texas Comprehensive Epilepsy Center, San Antonio, TX, USA.
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Morgan
Department of Neurology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; Department of Neurosurgery, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA ; South Texas Comprehensive Epilepsy Center, San Antonio, TX, USA.
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Szabó
Cortical dysplasia; Epilepsy surgery; Generalized photoconvulsive response; Intracranial EEG; Photosensitivity