High similarity between EEG from subcutaneous and proximate scalp electrodes in patients with temporal lobe epilepsy

Abstract

Subcutaneous recording using electroencephalography (EEG) has the potential to enable ultra-long-term epilepsy monitoring in real-life conditions because it allows the patient increased mobility and discreteness. This study is the first to compare physiological and epileptiform EEG signals from subcutaneous and scalp EEG recordings in epilepsy patients. Four patients with probable or definite temporal lobe epilepsy were monitored with simultaneous scalp and subcutaneous EEG recordings. EEG recordings were compared by correlation and time-frequency analysis across an array of clinically relevant waveforms and patterns. We found high similarity between the subcutaneous EEG channels and nearby temporal scalp channels for most investigated electroencephalographic events. In particular, the temporal dynamics of one typical temporal lobe seizure in one patient were similar in scalp and subcutaneous recordings in regard to frequency distribution and morphology. Signal similarity is strongly related to the distance between the subcutaneous and scalp electrodes. On the basis of these limited data, we conclude that subcutaneous EEG recordings are very similar to scalp recordings in both time and time-frequency domains, if the distance between them is small. As many electroencephalographic events are local/regional, the positioning of the subcutaneous electrodes should be considered carefully to reflect the relevant clinical question. The impact of implantation depth of the subcutaneous electrode on recording quality should be investigated further. NEW & NOTEWORTHY This study is the first publication comparing the detection of clinically relevant, pathological EEG features from a subcutaneous recording system designed for out-patient ultra-long-term use to gold standard scalp EEG recordings. Our study shows that subcutaneous channels are very similar to comparable scalp channels, but also point out some issues yet to be resolved.

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

“…The system and surgical procedures have previously been described in greater detail in our proof-of-concept study. 16…”

“…4,5 Because the seizure count is a decisive factor in the choice of treatment, an imprecise seizure count could lead to suboptimal treatment with increased risk of complications. 16 In this study, we provide data on safety and compliance, and compare detection of seizures between seizure diaries and the new device using descriptive methods. 7 Objective and accurate seizure counting at home could be of great benefit in diagnosis, management, and research in epilepsy.…”

“…In our previous study, we found this device comparable to traditional scalp EEG in a controlled environment. 16 In this study, we provide data on safety and compliance, and compare detection of seizures between seizure diaries and the new device using descriptive methods. Finally, we discuss the clinical relevance of our data relating to other seizure-detection devices.…”

Subcutaneous EEG Monitoring Reveals AED Response and Breakthrough Seizures

“…A novel subcutaneous EEG device has been developed for EEG home monitoring. In a previously published proof-of-concept paper, we showed that the new device records clinically relevant potentials reliably compared to scalp EEG [2]. Here, we present a case in which EEG home monitoring reveals essential information on breakthrough seizures and AED response that would otherwise have remained unknown.…”

“…e study was approved by the regional ethical committee. e subcutaneous EEG device, described in more details here [2], consists of two main parts, the implanted electrode and an external logging device for battery and data logging. e electrode and external logging device communicate via a transceiver at either device.…”