» Articles » PMID: 38896508

Electrode Surface Area Impacts Measurement of High Frequency Oscillations in Human Intracranial EEG

Overview
Date 2024 Jun 19
PMID 38896508
Authors
Affiliations
Soon will be listed here.
Abstract

Objective: High-frequency oscillations (HFOs) are a promising prognostic biomarker of surgical outcome in patients with epilepsy. Their rates of occurrence and morphology have been studied extensively using recordings from electrodes of various geometries. While electrode size is a potential confounding factor in HFO studies, it has largely been disregarded due to a lack of consistent evidence. Therefore, we designed an experiment to directly test the impact of electrode size on HFO measurement.

Methods: We first simulated HFO measurement using a lumped model of the electrode-tissue interaction. Then eight human subjects were each implanted with a high-density 8x8 grid of subdural electrodes. After implantation, the electrode sizes were altered using a technique recently developed by our group, enabling intracranial EEG recordings for three different electrode surface areas from a static brain location. HFOs were automatically detected in the data and their characteristics were calculated.

Results: The human subject measurements were consistent with the model. Specifically, HFO rate measured per area of tissue decreased significantly as electrode surface area increased. The smallest electrodes recorded more fast ripples than ripples. Amplitude of detected HFOs also decreased as electrode surface area increased, while duration and peak frequency were unaffected.

Conclusion: These results suggest that HFO rates measured using electrodes of different surface areas cannot be compared directly.

Significance: This has significant implications for HFOs as a tool for surgical planning, particularly for individual patients implanted with electrodes of multiple sizes and comparisons of HFO rate made across patients and studies.

References
1.
Worrell G, Gardner A, Matt Stead S, Hu S, Goerss S, Cascino G . High-frequency oscillations in human temporal lobe: simultaneous microwire and clinical macroelectrode recordings. Brain. 2008; 131(Pt 4):928-37. PMC: 2760070. DOI: 10.1093/brain/awn006. View

2.
Wang A, Jung D, Park J, Junek G, Wang H . Electrode-Electrolyte Interface Impedance Characterization of Ultra-Miniaturized Microelectrode Arrays Over Materials and Geometries for Sub-Cellular and Cellular Sensing and Stimulation. IEEE Trans Nanobioscience. 2019; 18(2):248-252. DOI: 10.1109/TNB.2019.2905509. View

3.
Kondylis E, Wozny T, Lipski W, Popescu A, DeStefino V, Esmaeili B . Detection of high-frequency oscillations by hybrid depth electrodes in standard clinical intracranial EEG recordings. Front Neurol. 2014; 5:149. PMC: 4123606. DOI: 10.3389/fneur.2014.00149. View

4.
Wang S, Wang I, Bulacio J, Mosher J, Gonzalez-Martinez J, Alexopoulos A . Ripple classification helps to localize the seizure-onset zone in neocortical epilepsy. Epilepsia. 2012; 54(2):370-6. DOI: 10.1111/j.1528-1167.2012.03721.x. View

5.
von Ellenrieder N, Beltrachini L, Perucca P, Gotman J . Size of cortical generators of epileptic interictal events and visibility on scalp EEG. Neuroimage. 2014; 94:47-54. DOI: 10.1016/j.neuroimage.2014.02.032. View