Anterior Nucleus of Thalamus Gates Progression of Mesial Temporal Seizures by Modulating Thalamocortical Synchrony

The anterior nucleus of the thalamus (ANT) mediates cortical-subcortical interactions between the limbic system and is hypothesized to facilitate the early organization of temporal lobe seizures. We set out to investigate the dynamic changes in synchronization parameters between the seizure onset zone (SOZ) and ANT during seizure stages (pre-onset to post-termination) in seven patients (n=26 seizures) with drug-resistant nonlesional temporal lobe epilepsy. Using local field potentials recorded directly from the limbic system and the ANT during stereoelectroencephalography, we confirm that the onset of mesial temporal lobe seizure is associated with increased thalamocortical network excitability and phase-amplitude coupling. The increase in thalamocortical phase synchronization preceded seizure onset, thereby suggesting that the early organization of temporal lobe seizures involves the integration of the ANT within the epileptic network. Towards seizure termination, there is a significant decrease in thalamic excitability, thalamocortical synchronization, and decoupling, thereby suggesting a breakdown in thalamocortical connectivity. A higher disease burden is significantly correlated with increased synchronization between the ANT and epileptic networks. Collectively, the results elucidate mechanistic insights and provide the temporal architecture of thalamocortical interactions that can be targeted in the rational designing of closed-loop seizure abortive interventions.HighlightsAnterior nucleus of thalamus is coactivated at the onset of temporal lobe seizuresIncrease thalamocortical synchronization and excitability is observed at seizure onsetSeizure termination is characterized by a breakdown in thalamocortical connectivityIncreased seizure burden affects thalamocortical synchronization

Mesial Temporal Glioma

A patient with classic temporal lobe seizure semiology may present with aura, automatisms, and dystonic posturing. Video-electroencephalography (EEG) may identify the ictal onset and magnetoencephalography may further elucidate the anatomy of a temporal lobe abnormality, EEG dipoles, epileptogenic spike sources, and eloquent areas of language or motor function. Structural imaging of the temporal lobe with magnet resonance imaging (MRI) should also be obtained, as well as functional and metabolic imaging such as a subtraction single-photon emission computed tomography (SPECT) and interictal positron emission tomography (PET). Early surgery should be considered in pediatric patients for seizure control, to minimize the adverse effects of anti-epileptic drugs, maximize the child’s developmental potential, and reduce behavioral, cognitive and psychosocial problems. Intraoperative stereotactic navigation and electrocorticography (ECoG) can guide resection. Careful pre-operative planning for correct extent of surgery is key to the best possible seizure outcome.

Role of the temporal pole in temporal lobe epilepsy seizure networks: an intracranial electrode investigation

OBJECTIVEA convergence of clinical research suggests that the temporal pole (TP) plays an important and potentially underappreciated role in the genesis and propagation of seizures in temporal lobe epilepsy (TLE). Understanding its role is becoming increasingly important because selective resections for medically intractable TLE spare temporopolar cortex (TPC). The purpose of this study was to characterize the role of the TPC in TLE after using dense electrocorticography (ECoG) recordings in patients undergoing invasive monitoring for medically intractable TLE.METHODSChronic ECoG recordings were obtained in 10 consecutive patients by using an array customized to provide dense coverage of the TP as part of invasive monitoring to localize the epileptogenic zone. All patients would eventually undergo cortico-amygdalohippocampectomy. A retrospective review of the patient clinical records including ECoG recordings, neuroimaging studies, neuropathology reports, and clinical outcomes was performed.RESULTSIn 7 patients (70%), the TP was involved at seizure onset; in 7 patients (70%), there were interictal discharges from the TP; and in 1 case, there was early spread to the TP. Seizure onset in the TP did not necessarily correlate with preoperative neuroimaging abnormalities of the TP.CONCLUSIONSThese data demonstrate that TPC commonly plays a crucial role in temporal lobe seizure networks. Seizure onset from the TP would not have been predicted based on available neuroimaging data or interictal discharges. These findings illustrate the importance of thoroughly considering the role of the TP prior to resective surgery for TLE, particularly when selective mesial resection is being considered.