16th International Epilepsy Colloqium

Associate Professor

Prof. Dr.

The role of glutamate homeostasis in glia cells of the epilepsy disease

Basic neuroscience

Abstract Background and study goal Glial glutamate transporter GLT1 plays a key role in the maintenance of extracellular glutamate homeostasis. Recent human genetic studies have suggested that de novo mutations in GLT1 (EAAT2) cause early-onset epilepsy with multiple seizure types. Consistent with these findings, global GLT1 null mice show lethal spontaneous seizures. The consequences of GLT1 dysfunction vary between different brain regions, suggesting that the role of GLT1 dysfunction in epilepsy may also vary with brain regions. In this study, we aim to investigate the correlation of astrocytic GLT1 expression with physiopathological phenomena, including neuronal morphology, and hyperexcitation/inflammation-related astrocytes and microglia activation in the epileptogenic zone via resected human specimen, which proved by MR images, PET, vEEG, or SEEG. Materials and methodsThe human specimen was collected from 30 patients with drug-resistant epilepsy (DRE), who underwent epilepsy surgeries for lesion resection. These patients underwent comprehensive presurgical evaluation, including each patient&quot;s clinical and noninvasive study such as semiology, scalp EEG, neuropychiatric test, PET, MEG, and SPECT. We will examine the human specimen using immunostaining analysis for GLT1, neuron marker NeuN, dendritic marker MAP2, reactive astrocyte marker GFAP, and microglia marker Iba1 to analyze the relationship between GLT1 expression and neuronal damage and gliosis. TUNEL and Fluoro-Jade C stain will be performed to determine the cell apoptosis and neuronal degeneration, respectively. The brain imaging, PET, EEG, neuropsychiatric test, and intraoperative ECoG will be interpreted and cross-correlated to the stain result. The brain connectivity study will also be discussed.Results By using AI to develop a module for automated counting, enabling the quantification of meaningful specific primary antibodies (neuronal markers: anti MAP-2, anti NeuN; astrocytic markers: anti GLT-1, anti GFAP; microglial marker: anti Iba-1, etc.). Since we have already recruited 30 patients, we are now able to make clinical correlations. This includes comparing glutamate buffering, neuro-astrocyte coupling, and hippocampal volume. We have observed significant trends in seizure onset time and frequency. In terms of cognitive function and staining of GLT-1, there is a positive trend in neuro-astrocyte coupling, and the study of functional connectivity also indicates a clear decline in patients with hippocampal atrophy.Discussion The results show that the smaller hippocampus volumes were tend to have poor glutamate buffering and neuro-astrocyte coupling, which also related to longer seizure onset period, duration and frequency. In neuro-cognitive study, some dominant side cognitive function (e.g. language function or naming function) were tend to have poor neuro-astrocyte coupling. Finally the functional connectivity of MR (+) and MR(-) patients were different, and this section are preparing to correlate with the sprouting of neuron or the function of glutamate buffering. However, we still need complete the patient collection and perform comprehensive statistics to prove the micro- and macro- relationship.

Poster

Prof. Dr. med.

Prof.

Interictal Epileptiform Discharges in the Hippocampus as Biomarkers of Memory Dysfunction in Epilepsy and Alzheimer's Disease

Clinical and translational research

<table><tr><td>Objective</td></tr><tr><td>Cognitive impairment is common in patients with epilepsy (PWE) and can severely affect the quality of life. Interictal epileptiform discharges (IEDs) are transient abnormal electrophysiological events happening between seizures, associated with transient cognitive impairment in PWE and observed in patients and rodents with Alzheimer&quot;s disease (AD). IEDs interfere with physiologic oscillations during sleep that are instrumental for memory consolidation, specifically hippocampal sharp-wave ripples (SWRs) and cortical spindles. Recently we demonstrated a negative effect of IEDs on memory consolidation and SWRs in the hippocampal CA1 region in an AD mouse model. Here we characterize the negative impact of IEDs in other hippocampal subfields and in human hippocampal recordings.</td></tr></table><table><tr><td>Methods</td></tr><tr><td>We analyzed the spread of IEDs and their impact on neuronal firing in the hippocampus in two distinct settings. First, we investigated IEDs on 312 hours of human microwire data (Behnke-Fried electrodes) from the hippocampus of surgical PWE with temporal (n=8) and extratemporal (n=7) epilepsy focus. The anatomical locations of the microwires and macroelectrodes were determined via CT-MRI co-registration and hippocampal subfield segmentation (ASHS software). Next, we obtained high-density recordings from the entire dorsal hippocampus (1024 Channel, SiNAPS, Neuronexus) from adult AD transgenic mice (APP/S1, n=5) and analysed the data by hippocampal subfields.</td></tr></table><table><tr><td>Results</td></tr><tr><td>We observed IEDs in the hippocampus of epilepsy patients with temporal and frontal lobe foci and in AD mice, independent of seizure generation or seizure onset zone. SWRs were only detected on electrodes in the CA1 and CA2 regions in all rodents and only in a subset of patients, possibly because of location of the recording electrode outside the CA1/CA2 region. By contrast IEDs were easily detected in human microwire recordings. IEDs showed similar local field potential features and waveforms in both subject groups, and quickly generalized across channels, leading to global suppression of neuronal firing, that could explain the previously observed interruption of physiologic signaling. The high-density rodent recordings demonstrated that the IED spread respected anatomical pathways.</td></tr></table><table><tr><td>Conclusion</td></tr><tr><td>IEDs may be a suitable biomarker for treatment of memory disorders in epilepsy and Alzheimer's Disease by targeted closed-loop stimulation, because of their impact on neuronal firing and feasible detection.</td></tr></table>

Bridging Pediatric Epilepsy Surgery with Basic Science: From sEEG to Intracellular Recordings

Pediatric epilepsy

ObjectivePre-surgical evaluation from refractory pediatric epileptic patients is crucial in order to identify epileptogenic zone (EZ) and increases the chances of post operative seizures free. However the complexity of an epileptic circuitry remains unclear. High frequency oscillations (HFOs) expressed during sEEG recordings are commonly used as biomarkers to identify EZ. In this study, we performed electrophysiological recordings on acute slices from pediatric patients to better understand the physiopathology of EZ.MethodsElectrophysiological recordings were performed in acute slices from surgical resections containing maximal HFOs recorded in sEEG evaluation from pediatric patients with refractory epilepsy. Spontaneous excitatory post-synaptic currents (sEPSCs) and spontaneous seizures like events (sSLEs) were analyzed. Immersion chamber bath application of in vitro pro-convulsivants (e.g. 4-aminopyridine (4AP) and bicuculline methobromide (BMO)) was performed to investigate pharmacological properties from induced interictal epileptiform discharges (IEDs).Results Abnormal trends of sEPSCs were recorded in 10 neurons and 10 sSLEs were identified in 9 other cells. Both sEPSCs and sSLEs were completely abolished by application of NBQX (5 µM). Application of 4AP (150 µM) and BMO (100 µM) induced transient recurrence of GABAB outward currents (GABOCs; n = 55) before neuronal network synchronization and the generation of IEDs. GABOCs were completely blocked by the GABAB receptors antagonist CGP-55845 (10-20 µM; n = 11). Levetiracetam (300-1200 µM) reduced amplitude and frequency (n = 14) but failed to block IEDs and Lacosamide (200-800 µM) strongly reduced (n = 4) and completely abolished (n = 16) IEDs.ConclusionUsing sEEG for exact localization of EZ and target resection increases identification of sEPSCs and sSLEs electrophysiological ex vivo recordings, thus providing unique scenario for better epileptogenesis comprehension in pediatric epilepsy. GABOCs play a major role in neuronal network synchronization and cadence of IEDs. Lacosamide shows better effect in blocking IEDs compared to Levetiracetam.

Lecture hall 1

Poster session

Short presentations – Basic science

Poster session
Short presentations – Basic science

Appointment

Chairs

Programme

Poster sessionShort presentations – Basic science

Appointment

Chairs

Programme

Poster session
Short presentations – Basic science