Elysa Widjaja
Epilepsy is considered a disorder of large neural networks. There is considerable interest in examining the neural networks in patients with epilepsy. Functional connectivity and structural connectivity can be assessed using fMRI and diffusion tensor imaging, respectively. Resting-state networks refer to spatially segregated brain regions that exhibit spontaneous low-frequency fluctuations and may represent intrinsic brain functional connectivity in discrete neuroanatomic systems. A variety of resting-state networks have been identified, including the default mode network (DMN), attention, sensorimotor, visual, and auditory networks. We postulated that in children with frontal lobe epilepsy, functional connectivity within the frontal network is abnormal. Because children with frontal lobe epilepsy frequently have secondary, generalized tonic-clonic seizures, the spread of seizure activity beyond the frontal lobe may lead to abnormal connectivity within and also across the resting-state networks. Our aim was to assess functional connectivity within resting-state networks and also functional network connectivity across resting-state networks in children with frontal lobe epilepsy.
We found that the frontal network showed reduced connectivity, while the other networks, including attention, DMN, sensorimotor, visual, and auditory networks, showed both reduced and increased functional connectivity within the resting-state networks in patients compared with controls. There was reduced functional network connectivity between the DMN-attention, frontal-sensorimotor, and frontal-visual networks, and increased functional network connectivity between frontal-attention, DMN-sensorimotor, and frontal-visual networks in patients relative to controls.
Subsequently, we also examined the structural connectivity in children with localization-related epilepsy, including those with frontal lobe epilepsy. When compared with controls, patients showed disrupted global network connectivity, including reduced network strength, increased characteristic path length and reduced global efficiency, and reduced nodal efficiency in frontal, temporal, and occipital lobes.