Cortical thickness analysis in operculo-insular epilepsy

Abstract

BackgroundIn temporal lobe epilepsy (TLE), advanced neuroimaging techniques reveal anomalies extending beyond the temporal lobe such as thinning of fronto-central cortices. Operculo-insular epilepsy (OIE) is an under-recognized and poorly characterized condition with the potential of mimicking TLE. In this work, we investigated insular and extra-insular cortical thickness (CT) changes in OIE.MethodsAll participants (14 patients with refractory OIE, 9 age- and sex-matched patients with refractory TLE and 26 healthy controls) underwent a T1-weighted acquisition on a 3 T MRI. Anatomical images were processed with Advanced Normalization Tools. Between-group analysis of CT was performed using a two-sided t-test (threshold of p < 0.05 after correction for multiple comparisons; cut-off threshold of 250 voxels) between (i) patients with OIE vs TLE, and (ii) patients with OIE vs healthy controls.ResultsSignificant widespread thinning was observed in OIE patients as compared with healthy controls mainly in the ipsilateral insula, peri-rolandic region, orbito-frontal area, mesiotemporal structures and lateral temporal neocortex. Contralateral cortical shrinkage followed a similar albeit milder and less diffuse pattern.The CT of OIE patients was equal or reduced relative to the TLE group for every cortical region analyzed. Thinning was observed diffusely in OIE patients, predominantly inboth insulae and the ipsilateral occipito-temporal area.ConclusionOur results reveal structural anomalies extending beyond the operculo-insular area in OIE.

Structural Connectivity Alterations in Operculo-Insular Epilepsy

“…Although the results varied between studies, a pattern of increased connectivity involving the ipsilateral mesiotemporal region and associated limbic structures was commonly observed [22,24,54]. The limited connections of the mesiotemporal structures mainly incorporating, but not restricted to, the frontocentral and temporolimbic areas [19,56,57] likely constrain a more confined epileptic network in patients with TLE [22,24,27,54,55]. It is therefore not surprising that we observed a more extensive pattern of increased CS in patients with OIE.…”

“…It is reasonable to believe that the observed connectivity changes in patients with OIE may result from similar pathological processes affecting a particularly vast insular network. Furthermore, we previously described the pattern of cortical thinning in patients with OIE [19]. Interestingly, the ample distribution of cortical thinning in OIE seems to mirror the extensive pattern of connectivity alterations [19].…”

“…Interestingly, the ample distribution of cortical thinning in OIE seems to mirror the extensive pattern of connectivity alterations [19]. Cortical atrophy in patients with OIE probably reflects a pathological process related to the operculo-insular epileptic network, resulting in glutamatergic excitotoxicity and concomitant neuronal death within a vastly hyperconnected network or, alternatively, deafferentation of connections constituting the more limited network of decreased connectivity [19].…”

“…It is likely that OIE remains an under-recognized condition, and additional non-invasive methods that would improve its recognition would be a welcome addition to the current diagnostic tools. In this regard, we previously showed that cortical thickness analysis may potentially help as patients with OIE exhibited widespread thinning of the ipsilateral insula and specific extra-insular areas connected to the insula [19].…”

Insulectomy for Refractory Epilepsy: Case Series and Literature Review

“…14,18,20,21 Because of this cluster of symptoms and signs, a thorough analysis and assessment is usually performed, especially regarding the history of the seizures and the auras, since insular and operculoinsular seizures with preserved consciousness are characteristically associated with asphyxia, painful sensations, and taste auras. 14,22 Finally, when insular epilepsy is drug resistant, the resection of the epileptogenic area usually correlates with good to excellent seizure control over time. Also important is the use of invasive electroencephalography (EEG) monitoring when needed to better understand the size and right topography of the epileptogenic area and the seizure dissipation pattern.…”