Altered Network Characteristics of Spike-Wave Discharges in Juvenile Myoclonic Epilepsy

Epilepsy is a disease marked by hypersynchronous bursts of neuronal activity; therefore, identifying the network characteristics of the epileptic brain is important. Juvenile myoclonic epilepsy (JME) represents a common, idiopathic generalized epileptic syndrome, characterized by spike-and-wave discharge (SWD) electroencephalographic (EEG) waveforms. We compare herein the network properties of periods of SWD and baseline activity using graph theory. EEG data were obtained from 11 patients with JME. Functional cortical networks during SWD and baseline periods were estimated by calculating the coherence between all possible electrode pairs in the delta, theta, alpha, beta and gamma bands. Graph theoretical measures, including nodal degree, characteristic path length, clustering coefficient, and small-world index were then used to evaluate the characteristics of epileptic networks in JME. We also assessed short- and long-range connections between SWD and baseline networks. Compared to baseline, increased coherence was observed during SWD in all frequency bands. The nodal degree of the SWD network, particularly in the frontal region, was significantly higher compared to the baseline network. The clustering coefficient and small-world index were significantly lower in the theta and beta bands of the SWD versus baseline network, but the characteristic path length did not differ among networks. Long-range connections were increased during SWD, particularly between frontal and posterior brain regions. Our study suggests that SWD in JME is associated with increased local (particularly in frontal region) connectivity. Furthermore, the SWD network was associated with increased long-range connections, and reduced small-worldness, which may impair information processing during SWD.