The topographical distribution of epileptic spikes in juvenile myoclonic epilepsy with and without photosensitivity

Objective Up to 30% of people with juvenile myoclonic epilepsy (JME) have photoparoxysmal responses (PPR). Recent studies report on structural and pathophysiological differences between people with JME with (JME+PPR) and without PPR (JME−PPR). We investigated whether electrophysiological features outside photic stimulation differ between these subtypes. Methods We analysed EEG recordings of people with JME at a tertiary epilepsy centre and an academic hospital. Photosensitivity was assessed in a drug-naïve condition. We compared the occurrence and involvement of posterior electrodes for focal abnormalities and generalised spike-wave activity in the EEG outside photic stimulation between JME+PPR and JME−PPR. Results We included EEG recordings of 18 people with JME+PPR and 21 with JME−PPR. People with JME−PPR had less focal abnormalities in the posterior brain regions than people with JME+PPR (19% vs 55%, p <0.05). There was no difference in the distribution of generalised spike-wave activity between people with JME+PPR and JME−PPR. Conclusion This study demonstrates electrophysiological correlates of the previously described structural and physiological differences between JME+PPR and JME−PPR. Significance Findings support the hypothesis that posterior interictal EEG abnormalities reflect localised cortical hyperexcitability, which makes patients with JME more sensitive to photic stimuli.