Magnetoencephalography Reveals a Widespread Increase in Network Connectivity in Idiopathic/Genetic Generalized Epilepsy

Abstract

Idiopathic/genetic generalized epilepsy (IGE/GGE) is characterized by seizures, which start and rapidly engage widely distributed networks, and result in symptoms such as absences, generalized myoclonic and primary generalized tonic-clonic seizures. Although routine magnetic resonance imaging is apparently normal, many studies have reported structural alterations in IGE/GGE patients using diffusion tensor imaging and voxel-based morphometry. Changes have also been reported in functional networks during generalized spike wave discharges. However, network function in the resting-state without epileptiforme discharges has been less well studied. We hypothesize that resting-state networks are more representative of the underlying pathophysiology and abnormal network synchrony. We studied functional network connectivity derived from whole-brain magnetoencephalography recordings in thirteen IGE/GGE and nineteen healthy controls. Using graph theoretical network analysis, we found a widespread increase in connectivity in patients compared to controls. These changes were most pronounced in the motor network, the mesio-frontal and temporal cortex. We did not, however, find any significant difference between the normalized clustering coefficients, indicating preserved gross network architecture. Our findings suggest that increased resting state connectivity could be an important factor for seizure spread and/or generation in IGE/GGE, and could serve as a biomarker for the disease.

Neuronal network models of epileptogenesis

“…In contrast to focal epilepsies, the gross network topology is preserved. 45 These findings appear similar to the increased connectivity in the sensory-motor and supplementary motor cortex reported among JME patient. 46 , 47 …”

Automatic Lateralization of Temporal Lobe Epilepsy Based on MEG Network Features Using Support Vector Machines

“…However, IC is still a widely used technique for revealing altered FC and has been applied in cases of brain tumors [56], brain lesions [57], and other disorders. In addition, in source-level network analyses, the IC has been suggested to effectively represent the true coupling of two brain regions with a nonzero time delay using MEG data [31,58]. Thus, we used the IC method to calculate the FC matrix for each subject in the source space.…”

Abnormal Brain Network in Epilepsy and Associated Comorbidites

“…Results showed some differences between connectivity patterns of single spikes related to focal epilepsy and connectivity patterns of repetitive spikes related to generalized epilepsy, which support the theory that higher global connections are seen in generalized epilepsy rather than the more local connections observed in the case of focal epilepsy. Magnetoencephalography (MEG) study [37] revealed a widespread increase in functional network connectivity in the resting state in IGE, with a particular focus on the motor network but clearly extending beyond this, which could be related to an increased likelihood to generate spontaneous, generalized seizures in patients. The fMRI functional connectivity method provided a map of the neural networks needed for seizure generation, and demonstrated ictal and interictal disturbances in normal physiological networks [38].…”