Abstracts

Incorporating New Frequencies of Electrical Brain Stimulations, Tailored to Anatomical Location, Improves the Yield of Stereo-electroencephalography

Abstract number : 3.275
Submission category : 3. Neurophysiology / 3E. Brain Stimulation
Year : 2024
Submission ID : 541
Source : www.aesnet.org
Presentation date : 12/9/2024 12:00:00 AM
Published date :

Authors :
Presenting Author: Aube Darves-Bornoz, MSc – Brain and Cognition Research Center - CerCo, CNRS

Emmanuel Barbeau, PhD – Brain and Cognition Research Center - CerCo, CNRS
Anne Calvel, MSc – Laboratory for Analysis and Architecture of Systems - LAAS, CNRS
Marie Denuelle, MD – Departments of Neurology and Neurosurgery, Toulouse University Hospital
Kim Guines, MD – Departments of Neurology and Neurosurgery, Toulouse University Hospital
Benoît Marcy, MSc – Brain and Cognition Research Center - CerCo, CNRS
Amaury De Barros, MD – Departments of Neurology and Neurosurgery, Toulouse University Hospital
Jean Christophe Sol, MD – Departments of Neurology and Neurosurgery, Toulouse University Hospital
Luc Valton, MD – Departments of Neurology and Neurosurgery, Toulouse University Hospital
Jonathan Curot, MD, PhD – Departments of Neurology and Neurosurgery, Toulouse University Hospital

Rationale: Electrical brain stimulations (EBS) are critical for identifying epileptogenic networks and performing functional mapping during stereo-electroencephalography (SEEG). However, current EBS procedures are suboptimal, leading to false negatives and positives (Kahane P, et al. Clin Neurophysiol. 1993;23(4):305-326). This is due to empirical parameters and standardized frequencies (1 and 50 Hz) across all patients and brain regions, and limited understanding of EBS neuronal mechanisms (Borchers S, et al. Nat Rev Neurosci. 2012;13(1):63-70). Although SEEG is intended to be tailored to each patient, there is a need to develop stimulation protocols customized to individual patient needs. We propose an enriched EBS protocol based on prominent physiological frequency bands (Frauscher B, et al., Brain. 2018;141(4):1130-1144) specific to each brain lobe.


Methods: We analyzed over 3,500 EBS in 30 patients with drug-refractory epilepsy implanted with depth electrodes between 2018 and 2024. For each EBS, clinical effects (seizures, physiological effects) and intracranial EEG responses (afterdischarges) were compared to electrical parameters (charge density, frequency, duration, charge quantity) and their anatomical location within the epileptogenic network. We emphasized temporal structures, analyzing 1,609 EBS in 25 patients, focusing on the amygdala, hippocampus, temporal neocortex, parahippocampal gyrus, and white matter.


Results: When comparing EBS with similar intensity and duration, stimulation at 7 Hz induced more afterdischarges (e.g. hippocampal IZ: p< .001, rB=.869, or parahippocampal gyrus EZ: p=.002, rB=.970) and patients' typical seizures (seizures only at 7 Hz in the amygdala and the hippocampus) than 1 Hz EBS. They also induced more clinical signs in some conditions (e.g. sensory signs in the parahippocampal gyrus: p=.003, rB=1.00). Conversely, while 50 Hz EBS were more effective than 7 Hz EBS in certain areas (e.g. hippocampal IZ: p=.012, rB=.803), they also led to more false positives (afterdischarges in healthy tissue at 50 Hz only). When considering equivalent charge quantities, it was found that in structures such as the hippocampus and parahippocampal gyrus, 7 Hz EBS tended to trigger more afterdischarges and typical seizures than 50 Hz EBS (e.g. parahippocampal gyrus IZ: 75% at 7 Hz, 25% at 50 Hz for seizures), along with inducing more functional signs.


Conclusions: Our findings highlight the significant influence of frequency on EBS efficacy, which varies depending on the stimulated structure and its interactions with EBS intensity and duration. This suggests the potential for broadening the spectrum of EBS frequencies in SEEG, as significant effects are not confined to the standard frequencies. Specifically, stimulating at 7 Hz in the temporal lobe combines the beneficial properties of the standard frequencies (1 Hz and 50 Hz) while reducing the occurrence of false positives in epileptic seizures.


Funding: This research was funded by the French National Research Agency (DYNEUMICS project, ANR-21-CE17-0029).


Neurophysiology