Comparison between Scalp EEG and Behind-the-Ear EEG for Development of a Wearable Seizure Detection System for Patients with Focal Epilepsy

Ying Gu, Evy Cleeren, Jonathan Dan, Kasper Claes, Wim Van Paesschen, Sabine Van Huffel, Borbála Hunyadi, Ying Gu, Evy Cleeren, Jonathan Dan, Kasper Claes, Wim Van Paesschen, Sabine Van Huffel, Borbála Hunyadi

Abstract

A wearable electroencephalogram (EEG) device for continuous monitoring of patients suffering from epilepsy would provide valuable information for the management of the disease. Currently no EEG setup is small and unobtrusive enough to be used in daily life. Recording behind the ear could prove to be a solution to a wearable EEG setup. This article examines the feasibility of recording epileptic EEG from behind the ear. It is achieved by comparison with scalp EEG recordings. Traditional scalp EEG and behind-the-ear EEG were simultaneously acquired from 12 patients with temporal, parietal, or occipital lobe epilepsy. Behind-the-ear EEG consisted of cross-head channels and unilateral channels. The analysis on Electrooculography (EOG) artifacts resulting from eye blinking showed that EOG artifacts were absent on cross-head channels and had significantly small amplitudes on unilateral channels. Temporal waveform and frequency content during seizures from behind-the-ear EEG visually resembled that from scalp EEG. Further, coherence analysis confirmed that behind-the-ear EEG acquired meaningful epileptic discharges similarly to scalp EEG. Moreover, automatic seizure detection based on support vector machine (SVM) showed that comparable seizure detection performance can be achieved using these two recordings. With scalp EEG, detection had a median sensitivity of 100% and a false detection rate of 1.14 per hour, while, with behind-the-ear EEG, it had a median sensitivity of 94.5% and a false detection rate of 0.52 per hour. These findings demonstrate the feasibility of detecting seizures from EEG recordings behind the ear for patients with focal epilepsy.

Keywords: EEG; EOG; SVM; epilepsy; seizure detection; wearable sensor.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Behind-the-ear EEG setup. In the right picture, each white circle represents an EEG electrode. A line between two electrodes represents an EEG channel whose signal is derived by taking the potential difference between those two electrodes. White lines represent channels derived between the left and right ear. Blue lines represent unilateral channels.
Figure 2
Figure 2
Block diagram of seizure detector training and testing (m: number of channels; n: number of features of each channel).
Figure 3
Figure 3
EEG segment with EOG artifacts.
Figure 4
Figure 4
Boxplots on the left represent the distribution of amplitudes of EOG from Fp2-F8, LC-RC, LT-RT, LT-LC, and RT-RC among the patients. The right plot is a zoomed-in version of the portion indicated inside the gray rectangle in the left plot.
Figure 5
Figure 5
Grand average EOGs among the patients in the left. The right plot is a zoomed-in version of the portion indicated inside the gray rectangle in the left plot.
Figure 6
Figure 6
Time series of representative scalp EEG and behind-the-ear EEG during seizure.
Figure 7
Figure 7
Averaged PSD of scalp EEG and behind-the-ear EEG during seizures.
Figure 8
Figure 8
False detection rates and sensitivities of seizure detection among the patients.
Figure 9
Figure 9
Example of repetitive EOG artifacts causing false detections from scalp EEG and no false detections from behind-the-ear EEG on patient 10.
Figure 10
Figure 10
Example of abnormal EEG causing false detections from patient 2.
Figure 11
Figure 11
Example of abnormal EEG causing false detections from patient 4.
Figure 12
Figure 12
False detection rates and sensitivities of seizure detection from cross-head channels and unilateral channels among the patients.
Figure 13
Figure 13
Boxplots representing distribution of false detection rates and sensitivities from cross-head channels and unilateral channels among the patients.

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