Real‐time effects of interictal spikes on hippocampus and amygdala functional connectivity in unilateral temporal lobe epilepsy: An EEG‐fMRI study

Summary

Objective

To explore the real‐time effects of interictal epileptiform discharges (IEDs) on hippocampus and amygdala functional connectivity (FC) in unilateral temporal lobe epilepsy (TLE).

Methods

Patients with unilateral TLE were recruited and underwent simultaneous electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) scanning. Simultaneous EEG was used to define the prespike (10 s before spike) and postspike (10 s after spike) periods. Dynamic FC analysis was applied using the left/right hippocampus and amygdala separately as a seed region to map the network alterations after IED occurrence.

Results

A total of 261 IED events (133 left, 128 right) from 21 patients with unilateral TLE (10 left, 11 right) were analyzed. Left IEDs had a greater influence on the hippocampus‐seeded networks, whereas right IEDs affected the amygdala‐seeded networks more. Left IEDs disconnected the ipsilateral hippocampus and the default mode network, which might be related to cognitive impairment in TLE. The reward‐emotion network (more of the prefrontal‐limbic system) and visual network also showed FC changes after left IEDs. The reward‐emotion network (more of the reward system) was coactivated after right IEDs, indicating a possible mechanism of forced normalization.

Significance

This study directly linked the disrupted functional networks in TLE to epileptic activities and offered a unique tool for future research to investigate mechanisms of comorbidities in TLE.

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