Disrupted intrinsic and remote functional connectivity in heterotopia‐related epilepsy

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Excerpt

Periventricular nodular heterotopia (PNH) is characterized by clusters of neurons along the ventricular walls that fail to migrate away from the embryonic ventricular zone to the developing cerebral cortex.1 Although PNH is a rare disorder due to an arrest in migration, it is one of the most commonly encountered epileptic development malformations.2 Bilateral, symmetrical PNH nodules, particularly in female patients, commonly have a genetic basis related to mutations in the Filamin A (FLNA) gene.3
Previous studies have demonstrated that focal onset can be observed in patients with PNH‐related seizures5; heterotopic nodules are also commonly found to be involved in the epileptogenic areas and that surgical resections are not always curative.6 It has been shown epileptogenesis in PNH involves a complex and variable network; nodules in PNH were structurally and functionally connected to overlying cortex.7 However, the features of local and interregional functional neural network are still largely unknown.
Evaluation of functional connectivity (FC) using resting‐state functional MRI (rsfMRI) has been widely used to image the brain network in multiple diseases, including epilepsy.8 Additionally, rsfMRI is relatively easy to implement in a clinical setting. The functional networks in temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) have been well studied in a large body of literature.9 However, the regional cerebral function analysis in PNH‐related epilepsy has not been investigated. There is also a lack of evidence in this population regarding resting‐state neural activity between regions in the functional network. We considered not only intrinsic regional activity abnormalities, but also interregional FC deficits, and consequently took an approach to evaluate the pathophysiologic functional changes in PNH by assessing the whole set of brain, which may also improve capacity to detect epileptic foci in PNH‐related epilepsy.
The present investigation used rsfMRI to assess both regional‐ and network‐level brain function in patients with PNH and epilepsy compared with age‐ and sex‐matched healthy controls. Moreover, we examined the associations between regional activity values and clinical characteristics. The aim was to fully characterize whole‐brain connections in patients with PNH and provide novel evidence to further the understanding of connectivity‐based pathophysiological mechanisms in PNH.

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