Advice
Clinical and technical evidence
Clinical and technical evidence
A literature search was carried out for this briefing in accordance with the interim process and methods statement. This briefing includes the most relevant or best available published evidence relating to the clinical effectiveness of the technology. Further information about how the evidence for this briefing was selected is available on request by contacting mibs@nice.org.uk.
Published evidence
Five studies are summarised in this briefing. The evidence comes from descriptive feasibility studies, including 2 case studies and 3 case series involving a total of 11 adults. Two case series (Weisdorf et al. 2018, Gangstad et al. 2019) reported on are early subpopulations of Weisdorf 2019.
The clinical evidence and its strengths and limitations is summarised in the overall assessment of the evidence.
Overall assessment of the evidence
The published evidence suggests that the 24/7 EEG SubQ can identify additional seizure counts and seizure pattern information compared with standard care, to inform individual management plans. The evidence base is very limited, of low methodological quality, with a high risk of selection bias and small sample sizes.
Viana et al. (2020)
Study size, design and location
Case report of a 35-year-old woman with refractory epilepsy (n=1).
Key outcomes
The study found that there was substantial agreement between days of reported and recorded seizures, although multiple clustered seizures remained undocumented. Circular statistics identified significant subcutaneous electroencephalogram (EEG) seizure cycles at circadian (24‐hour) and multidien (5‐day) timescales. No adverse events were reported.
Weisdorf et al. (2020)
Study size, design and location
Case report of a 42-year-old woman with temporal lobe epilepsy (n=1).
Weisdorf et al. (2019)
Key outcomes
Case series of 9 people who had the subcutaneous EEG monitor implanted. Recording of 490 days of EEG was collected across 8 people completing at least 9 weeks of home monitoring. One person did not continue. The study found that the device revealed unrecognised seizures and informed treatment adjustment. Five participants appeared to have circadian rhythms and 2 individuals had too few seizures to establish a trustworthy pattern. No serious adverse events were reported. Most participants experienced soreness on the implantation site after the surgery, this passed within a week for 6 people and 2 people had longer lasting soreness for 2 and 4 weeks, respectively. Two individuals reported occasional headaches during the study. For one this was mild and for the other this was moderate and needed over-the-counter pharmacological treatment (this person had similar occasional headaches before to the study). One unclassified event was described as a tingling sensation in the implant, only while in specific locations at home. Technical examination of the implant after explanation revealed no malfunction. User experience information was collected anecdotally with people taking part in the study, who reported that the device was easy to use. Some minor annoyances were reported, but people reported that they did not feel constrained in their ability to do jobs or leisure activities.
Weisdorf et al. (2018)
Key outcomes
All recorded seizures were classified as temporal lobe seizures and there was 100% lateralisation match. One person reported slight soreness around the site, that receded gradually during the admission. For 1-person large parts of the subcutaneous EEG recorded during wakefulness was contaminated by high-frequency muscle artefacts, which almost completely disappeared during sleep. The study reported high similarity between subcutaneous EEG channels and nearby temporal scalp channels for most EEG events. The study concluded that subcutaneous EEG recordings are very similar to scalp recordings in both time and time-frequency domains, if the distance between them is small.
Strengths and limitations
The authors acknowledge the limitations of the data and present it as preliminary results contributing to a growing mass of evidence. The authors suggest that as many electroencephalographic events are local or regional, the positioning of the subcutaneous electrodes should be considered carefully to reflect the relevant clinical question. The effect of implantation depth of the subcutaneous electrode on recording quality should be further investigated. Two authors are full-time employees of UNEEG Medical and one further author has consulted for the company.
Gangstad et al. (2019)
Study size, design and location
Case series of 4 adults at Zealand University Hospital, Denmark.
Key outcomes
Shows effective automatic sleep score for people with 2 channel subcutaneous EEG, which are comparable to in-clinic recordings. An average Cohens kappa of k=0.78 (plus or minus 0.02) was achieved using patient-specific leave-one-night-out cross validation. When merging all sleep stages into a single class they reported to have 94.8% sensitivity and 96.6% specificity. Compared with manually labelled video-EEG, the model underestimated total sleep time and sleep efficiency by 8.6 minutes and 1.8 minutes, respectively. It overestimated wakefulness after sleep onset by 13.6 minutes. No adverse events were reported.
Strengths and limitations
Recordings were done in hospital with healthcare professional monitoring. The patient cohort is the same population reported in Weisdorf et al. 2018 and the subpopulation of Weisdorf et al. 2019. Three authors are UNEEG medical employees and a further 2 authors are partially funded by UNEEG medical.
Recent and ongoing studies
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Ultra-long-term sleep monitoring using UNEEG medical 24/7 EEG SubQ. ClinicalTrials.gov identifier: NCT04513743. Status: active. Indication: epilepsy. Devices: 24/7 EEGSubQ system. Date: April 2021. Country: Denmark.
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Evaluation of the 24/7 EEG SubQ system for ultra-long-term recording of patients with temporal lobe epilepsy an open-label, prospective, paired, comparative study. ClinicalTrials.gov identifier: NCT04526418. Status: recruiting. Indication: epilepsy. Devices: 24/7 EEG SubQ system. Date: August 2023. Country: the US and Germany.
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Subcutaneous EEG: forecasting of epileptic seizures (SUBER) an observational, non-randomised, non-interventional study. ClinicalTrials.gov Identifier: NCT04061707. Status: recruiting. Indication: epilepsy. Devices: 24/7 EEG SubQ. Date: May 2022. Country: UK.