Patterns of Functional Connectivity in the Brain in Temporal and Frontal Epilepsy
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Patterns of Functional Connectivity in the Brain in Temporal and Frontal Epilepsy I. S. Samotaeva,1,2 A. M. Teplyshova,2 F. K. Rider,2 Yu. V. Solomatin,2 R. V. Luzin,2 N. N. Lebedeva,1,2 and A. B. Guekht2,3
Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 119, No. 11, Iss. 2, pp. 11–15, November, 2019. Original article submitted September 26, 2019. Accepted October 16, 2019. Objectives. To identify the pattern of functional connectivity (FC) between areas and networks in the brain in patients with frontal and temporal foci of epileptic activity. Materials and methods. A total of 43 patients aged 18–50 years with focal epilepsy – 32 with temporal epilepsy (TE) and 11 with frontal epilepsy (FE) – were studied. The control group consisted of 32 healthy subjects. The main method used in the study was brain MRI scans run using the epilepsy protocol and additionally including high-resolution structural images of the brain, along with resting-state fMRI. Results and conclusions. The most marked fMRI feature in patients with TE as compared with healthy subjects was a decrease in the FC of the insular cortex and the temporal opercula (the part of the temporal gyrus of each hemisphere overhanging the insula). In left-sided FE, the decrease on the left was significant. Increased FC in the dorsal part of the attention network on the left with the temporal and parietal areas of the cerebral cortex was specific for right-sided TE. TE also produced a decrease in FC between the anterior part of the cingulate gyrus and the basal ganglia. All significant results were linked with increases in FC in patients with FE as compared with healthy subjects, maximally in areas of the temporal cortex. Thus, the localization and lateralization of the focus of epileptic activity determine the pattern of FC in these areas and neural networks of the brain in patients with focal epilepsy. Keywords: temporal epilepsy, frontal epilepsy, resting-state fMRI, functional connectivity.
Introduction. It is believed that focal epileptic seizures can arise in different areas of the cerebral cortex or in structures of the limbic system. Temporal epilepsy (TE) is the commonest of the focal epilepsies [1]. About 60–70% of all focal seizures begin in the temporal lobe [2]. Frontal epilepsy (FE) accounts for 20–30% of all focal epilepsies and has received significantly less study than temporal epilepsy. In addition, disease-associated structural changes in the brain are seen significantly more rarely in FE. However, neurophysiological and neuroimaging studies in recent years have
provided evidence that the generation and maintenance of epileptic discharges involve not only the so-called epileptiform zones (seizure foci), but whole neural networks including areas of the brain remote from the focus [3]. The concept of epileptogenic neural networks suggests that seizure generation results from pathological activation of neuronal connections within such a network. fMRI studies provide for assessment of epilepsy-induced changes to the fu
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