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

•Epileptic spikes in photosensitive juvenile myoclonic epilepsy are prevalent in occipital areas.•The location of the maximum of generalised abnormalities is not affected by photosensitivity.•There are likely different epileptic networks in photosensitive and non-photosensitive JME.

ObjectiveUp 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.MethodsWe 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.ResultsWe 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.ConclusionThis study demonstrates electrophysiological correlates of the previously described structural and physiological differences between JME+PPR and JME−PPR.SignificanceFindings support the hypothesis that posterior interictal EEG abnormalities reflect localised cortical hyperexcitability, which makes patients with JME more sensitive to photic stimuli.