Authors :
Presenting Author: Stefan Wolking, MD, MBA – RWTH Aachen University
Jan Heckelmann, MD – RWTH Aachen University Hospital
Anke Höllig, MD – RWTH Aachen University Hospital
Hussam Hamou, MD – RWTH Aachen University Hospital
Jonas Ort, MD – RWTH Aachen University Hospital
Rastislav Pjontek, MD – RWTH Aachen University Hospital
Karen van Loo, PhD – RWTH Aachen University Hospital
Daniel Delev, MD – University Hospital Erlangen
Yvonne Weber, MD – RWTH Aachen University
Henner Koch, MD, PhD – RWTH Aachen University
Rationale:
High-frequency oscillations (HFOs) have been extensively studied for over 25 years, primarily in invasive EEG recordings and later also in electrocorticography, surface EEG, and MEG. HFOs have emerged as a valuable clinical biomarker in the presurgical examination of epilepsy patients, being closely linked to the seizure onset zone. While HFOs do also occur physiologically, fast ripples (HFOs at >250Hz) are particularly linked to epileptic tissue. The underlying pathophysiologic mechanisms remain incompletely understood. Currently, HFOs in the human brain are predominantly investigated in patients during stereo-EEG (sEEG). However, such studies are constrained by number, limited sEEG coverage of the brain, and the limits to experimental interventions. Long-term human organotypic brain slices allow the study of brain physiology over an extended period of time, including electrophysiologic recordings using the multi-electrode array (MEA) technique to delineate neuronal activity and network properties.
Here, we present preliminary data demonstrating HFO detection in long-term organotypic brain slices, offering a potential
ex-vivo model to enhance our understanding of HFO pathophysiology.
Methods:
Brain tissue obtained from epilepsy or tumor surgeries is utilized to prepare brain slices. Human cerebrospinal fluid (hCSF) collected from patients with normal pressure hydrocephalus is used for long-term slice culture (up to three weeks) (1). We use a MEA system of 256 electrodes covering a 3.2x3.2mm
2 recording area to record whole-slice electrophysiology, enabling the measurement of local field potentials, action potentials, and propagation dynamics. Computational post-processing includes frequency filtering and automatic HFO detection using established tools such as RIPPLELAB (2), followed by visual validation based on in-vivo HFO classification principles. Recordings are conducted at varying temperatures and under the influence of excitatory or inhibitory agents to assess their impact on HFOs.
Results:
Our preliminary measurements demonstrate the consistent detection of HFOs in organotypic slices derived from hippocampal resections of temporal lobe epilepsy patients. HFOs spatially correspond with anatomical regions of increased spiking (Fig. 1). HFO frequency positively correlates with temperature. Treatment with norepinephrine and GABA
A-antagonists increases HFO frequency, while AMPA-antagonists reduce HFO occurrence.
Conclusions:
Our findings introduce a novel approach to study HFOs in human brain tissue, offering a platform for experimental interventions. We are expanding our dataset to include various types of epileptic and tumor tissues, as well as control samples from non-lesional access tissue. Our study opens new perspectives for investigation the pathophysiologic basis of HFOs and their role across different brain lesions.
Funding: This work was supported by the Chan Zuckerberg Initiative Collaborative Pairs Pilot Project Awards (Phase 1 and Phase 2) and by the German Research Foundation (DFG/FNR INTER research unit
FOR2715 WE4896/4-1 and
WE4896/4-2).