EEG Signal Quality of a Subcutaneous Recording System Compared to Standard Surface Electrodes

Abstract

Purpose. We provide a comprehensive verification of a new subcutaneous EEG recording device which promises robust and unobtrusive measurements over ultra-long time periods. The approach is evaluated against a state-of-the-art surface EEG electrode technology.Materials and Methods. An electrode powered by an inductive link was subcutaneously implanted on five subjects. Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated with both quantitative (power spectral density and coherence analysis) and qualitative (blinded subjective scoring by neurophysiologists) analysis.Results. The power spectral density and coherence analysis were very similar during measurements of resting EEG. The scoring by neurophysiologists showed a higher EEG quality for the implanted system for different subject states (eyes open and eyes closed). This was most likely due to higher amplitude of the subcutaneous signals. During periods with artifacts, such as chewing, blinking, and eye movement, the two systems performed equally well.Conclusions. Subcutaneous measurements of EEG with the test device showed high quality as measured by both quantitative and more subjective qualitative methods. The signal might be superior to surface EEG in some aspects and provides a method of ultra-long term EEG recording in situations where this is required and where a small number of EEG electrodes are sufficient.

Ultra‐long‐term subcutaneous home monitoring of epilepsy—490 days of EEG from nine patients

“…[1][2][3] Many factors contribute to this problem, with unrecognized and undocumented seizures being the most important. 8,9 Recently, many new EEG devices have appeared, combining various electrode configurations and data processing methods, [10][11][12][13][14][15] but none of these have been tested in real-life. These clinical problems also concern the patients, 6 and in the context of epilepsy research the problem of wrongful reporting is also well known.…”

“…An EEG acquisition system usable during everyday life could be the tool currently lacking in the toolbox of epilepsy diagnostics and management. 8,9 Recently, many new EEG devices have appeared, combining various electrode configurations and data processing methods, [10][11][12][13][14][15] but none of these have been tested in real-life. In this study, we present the first real-life data on a subcutaneous EEG device for continuous home monitoring of epilepsy.…”

A new era in electroencephalographic monitoring? Subscalp devices for ultra–long‐term recordings

“…with closed and open eyes, and might be better during bodily movements. 29 Sleep recordings are also improved because subscalp electrodes are less obtrusive than scalp electrodes in the recumbent (sleeping) position. Many algorithms have been proposed to remove noise from EEG 30 ; however, especially for the modalities with only a few channels, this will be challenging although not entirely impossible.…”

“…24/7 EEG SubQ from UNEEG Medical (Lynge, Denmark) features two bipolar channels introduced under local anesthesia. The SubQ was used to record EEG in healthy subjects 29 as well as to detect clinically relevant electrographic seizures in epilepsy patients, showing high reliability and tolerance. 32,33 The device comes with dedicated software for automatic seizure detection and EEG visualization.…”

Automatic Computer-Based Detection of Epileptic Seizures

“…The most significant limitation remains the application of scalp-EEG based seizure detection systems in an outpatient setting because it is not acceptable for patients to wear EEG electrode arrays for prolonged time periods in everyday life ( 58 ). Recently developed subcutaneous EEG electrodes may offer a practical solution for this problem ( 63 ). Chronically implanted intracranial electrodes represent another option for long-term outpatient EEG recordings which have been successfully applied for seizure prediction ( 6 ) and seizure detection with responsive brain stimulation ( 17 – 21 ).…”