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

Jonas Duun-Henriksen,Mary Doreen Atkins,Jens Ahm Sørensen,Claus Bogh Juhl,Martin Rose,Rasmus Elsborg Madsen,David Looney,Troels Wesenberg Kjaer,Danilo P Mandic

doi:10.1155/2015/341208

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.

Highlights

Electroencephalography (EEG) is a standard procedure to obtain information about the metabolic and electric status of the brain
Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated with both quantitative and qualitative analysis
The power spectral density and coherence analysis were very similar during measurements of resting EEG

Summary

Introduction

Electroencephalography (EEG) is a standard procedure to obtain information about the metabolic and electric status of the brain. The clinical application of EEG is well described; the quality of long-term ambulatory monitoring of EEG is still compromised by inconvenient equipment and unstable electrodes, requiring continuous supervision. The positions of the electrodes on the scalp are given according to international conventions, such as the 10/20 system [1]. Standard scalp EEG-recordings are suitable for many applications in neurology; for long-term continuous monitoring it is desirable to perform recordings without causing discomfort to the patient, and outside clinical facilities [2]. EEG recorded over a prolonged period of time may provide deeper insight and open completely new avenues of research and applications compared to conventional EEG. Examples include the diagnosis of infrequent seizures and characterization of more frequent

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