Impaired vigilance networks in temporal lobe epilepsy: Mechanisms and clinical implications

Abstract

Mesial temporal lobe epilepsy (mTLE) is a neurological disorder in which patients suffer from frequent consciousness‐impairing seizures, broad neurocognitive deficits, and diminished quality of life. Although seizures in mTLE originate focally in the hippocampus or amygdala, mTLE patients demonstrate cognitive deficits that extend beyond temporal lobe function—such as decline in executive function, cognitive processing speed, and attention—as well as diffuse decreases in neocortical metabolism and functional connectivity. Given prior observations that mTLE patients exhibit impairments in vigilance, and that seizures may disrupt the activity and long‐range connectivity of subcortical brain structures involved in vigilance regulation, we propose that subcortical activating networks underlying vigilance play a critical role in mediating the widespread neural and cognitive effects of focal mTLE. Here, we review evidence for impaired vigilance in mTLE, examine clinical implications and potential network underpinnings, and suggest neuroimaging strategies for determining the relationship between vigilance, brain connectivity, and neurocognition in patients and healthy controls.

Enhanced synaptic transmission in the extended amygdala and altered excitability in an extended amygdala to brainstem circuit in a Dravet syndrome mouse model

“…This highlights the general need to explore subcortical structures in epilepsy models, in part to shed light on comorbidities of epilepsy states. The few studies that have been performed evaluating these regions in human epilepsy patients show widespread alterations in subcortical network activity including the brainstem that correlates with impairments in vigilance and arousal (Englot et al, 2020). This current study emphasizes the need to evaluate these structures in DS and other epilepsy models, particularly moving to link circuit dysfunction to other behavioral and physiologic comorbidities seen in epilepsy.…”

Interictal Epileptiform Discharges are Task Dependent and are Associated with Lasting Electrocorticographic Changes

“…This may present a mechanism through which attention decreases the rate of IED occurrence during word presentation. Increased attention, and the corresponding increase in the activity of the ascending reticular activating system, may lead to a shift toward higher frequency cortical activity, that is, a decreased spectral tilt ( Moruzzi and Magoun 1949 ; Englot et al. 2020 ).…”

Enhanced Synaptic Transmission in the Extended Amygdala and Altered Excitability in an Extended Amygdala to Brainstem Circuit in a Dravet Syndrome Mouse Model

“…This highlights the general need to explore subcortical structures in epilepsy models, in part to shed light on the comorbidities of epilepsy states. The few studies that have been performed evaluating these regions in human epilepsy patients show widespread alterations in subcortical network activity, including the brainstem, that correlate with impairments in vigilance and arousal ( Englot et al, 2020 ). This current study emphasizes the need to evaluate these structures in DS and other epilepsy models, particularly in linking circuit dysfunction to other behavioral and physiologic comorbidities seen in epilepsy.…”