Idiopathic generalised epilepsies (IGE) have a complex inheritance pattern. Previous studies support the genetic basis of EEG traits, with an increased prevalence of epileptiform and non-epileptiform abnormalities in unaffected relatives of patients with epilepsy compared to controls. These abnormalities or ‘endophenotypes’ in clinically unaffected relatives, may represent a genetic liability to develop symptoms. Characterising such traits could be of use, both for understanding seizure pathology, and for identifying individuals at increased risk. Given that epilepsy is characterised by abnormalities in the synchronisation of neuronal activity, we investigated altered synchronisation properties and network properties in a group of patients with IGE and their first degree relatives using quantitative EEG methods. We recorded resting, eyes-closed EEG data from 15 patients with IGE, 19 unaffected relatives, and 24 controls. The phase locking factor which is a measure of synchronisation was calculated for each pair of channels. We also assessed network properties including clustering coefficient and path length. Both IGE patients and clinically unaffected relatives differed significantly from controls with increased mean phase locking factor, reduced mean clustering coefficient and increased mean path length. Our data suggests that IGE is associated with significant changes to phase synchronisation properties and network topology of resting electrical activity. They also provide evidence that such changes are found in clinically unaffected relatives of patients with IGE, suggesting that such abnormalities may by characteristic of those with a high liability to develop IGE.
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