Abnormal cortical thickness connectivity persists in childhood absence epilepsy

Abstract

ObjectiveChildhood absence epilepsy (CAE) is a childhood-onset generalized epilepsy. Recent fMRI studies have suggested that frontal cortex activity occurs before thalamic involvement in epileptic discharges suggesting that frontal cortex may play an important role in childhood absence seizures. Neurocognitive deficits can persist after resolution of the epilepsy. We investigate whether structural connectivity changes are present in the brains of CAE patients in young adulthood.MethodsCortical thickness measurements were obtained for 30 subjects with CAE (mean age 21 ± 2 years) and 56 healthy controls (mean age 24 ± 4) and regressed for age, sex, and total intracranial volume (TIV). Structural connectivity was evaluated by measuring the correlation between average cortical thicknesses in 915 regions over the brain. Maps of connectivity strength were then obtained for both groups.ResultsWhen compared to controls, the CAE group shows overall increased “connectivity” with focal increased connection strength in anterior regions including; the anterior cingulate and the insula and superior temporal gyrus bilaterally; the right orbito-frontal and supramarginal regions; and the left entorhinal cortex. Decreased connection strength in the CAE group was found in the left occipital lobe, with a similar trend in right occipital lobe.InterpretationBrains in young adults whose CAE was resolved had abnormal structural connectivity. Our findings suggest that frontal regions correlate most with cortical thickness throughout the brain in CAE patients, whereas occipital regions correlate most in well matched normal controls. We interpret this as evidence of a developmental difference in CAE that emphasizes these frontal lobe regions, perhaps driven by frontal lobe epileptiform activity.

Structural covariance networks relate to the severity of epilepsy with focal-onset seizures

“…The lack of differences between the two groups implies that the global characteristics of the SCN of patients with epilepsy is not significantly different from the healthy control group, which might be due to variations in the SCN between patients. This is in contrast to previous SCN studies in epilepsy ( Bernhardt et al 2013 ; Curwood et al 2015 ; Yasuda et al 2015 ), which might be explained by differences in patient populations, analysis method and sample size between our study and those studies. The current study shows that these variations in SCN between epilepsy patients reflect to some extent the epilepsy characteristics.…”

“…Furthermore, whether the SCN resemble patterns of white matter connections or are more related to functional connectivity still needs to be resolved. However, in the current and previous studies it has been shown that the SCNs can be a valuable metric in epilepsy research ( Bernhardt et al 2013 ; Curwood et al 2015 ; Yasuda et al 2015 ). The location of the epileptic focus seems not of influence in the current study, however, larger study samples for the different foci are prompted for to be more definite on this matter.…”

Altered Structural Network in Newly Onset Childhood Absence Epilepsy

“…5,6,[8][9][10] Subsequent studies that applied advanced imaging and analytical techniques to the regional Eun-Hee Kim a,b Woo-Hyun Shim c Jin-Seong Lee c Hee-Mang Yoon c Tae-Sung Ko d Mi-Sun Yum d JCN gray-matter (GM) and white-matter (WM) volumes and cortical thickness have revealed focal alterations of the volume and cortical thickness mainly in frontotemporal and parietal regions. 7,11,12 Although the results have not been consistent across studies, they support the cortical focus theory stating that absence seizures are initiated by a cortical focus with the secondary involvement of the thalamocortical network. 13 In particular, the frontal and parietal cortices are the main structures involved in absence seizures typified by the generation of diffuse slow-wave complexes.…”

Aberrant basal ganglia-thalamo-cortical network topology in juvenile absence epilepsy: A resting-state EEG-fMRI study

“…The significantly increased Lambda and Cp in our JAE patients suggests disrupted integration and enhanced segregation, reflecting a suboptimal topology of the functional network. Similar changes have been found in other epilepsy subtypes, such as the functional networks in temporal lobe epilepsy [27] and structural networks of young adults with childhood absence epilepsy [28] or children with recent-onset seizures [29]. Such topology tends to be a more regular network, which minimizes global cost at the expense of integration and is vulnerable to targeted attacks [27,29].…”