A new era in long-term brain monitoring

The recording capabilities of the electroencephalogram, better known as EEG, have steadily improved over the years. EEG has become the most advanced method for diagnosing transient neurological dysfunctions, such as those that occur in epilepsy. Today, EEG can not only pinpoint the exact location of seizures in the brain, but also detect the smallest changes in brain activity. These capabilities are crucial to understanding and diagnosing seizures and play a central role in planning effective treatments.

In order to provide optimal treatment for chronic brain diseases such as epilepsy in the future, methods must be found to monitor electrical brain activity in daily life. Over the past decade, medical research has been intensively searching for ways to enable unobtrusive and continuous monitoring of brain activity in epilepsy patients outside of the hospital. The previous solutions, especially the intracranial systems, which are mainly used for neurostimulation in difficult-to-treat epilepsy, could only record EEG data to a very limited extent and for a short period each day.

A newer, promising approach is the «subscalpale EEG», in which electrodes are implanted between the scalp and the skull for long-term monitoring. The first such systems can effectively detect seizures. However, due to the limited number of electrodes, they have limitations when it comes to the precise localization of brain activity. This is where a new brain monitoring method developed by the Wyss Center for Bio and Neuro Engineering and the Department of Neurology at Inselspital comes in. The system, called EpiosTM, uses a special electrode lead that can be implanted under the scalp and combines full coverage of the head with ultra-long recording of brain activity over many months.

Since 2018, Prof. Maxime Baud, senior physician at the University Department of Neurology, and Prof. Claudio Pollo, deputy head physician at the University Department of Neurosurgery, have been working closely with the Wyss Center at Inselspital to develop a minimally invasive electrode that can be inserted between the scalp and the skull. In an initial feasibility study, the researchers tested the applicability and safety of the EpiosTM system in eight patients with drug-resistant epilepsy who had to undergo brain surgery for clinical reasons. The study participants first underwent the clinically indicated procedure under general anesthesia and, during the same operation, received the so-called EpiosTM trident electrodes, which were placed between the scalp and skull using specially designed instruments through four small incisions of ≤ 1 cm. The patients were then monitored as inpatients for up to nine days.

The study results show that the EpiosTM system is safe and practical. In a procedure lasting about an hour, up to 28 electrodes could be placed securely throughout the head; there were no serious side effects caused by the EpiosTM system. In addition, the EpiosTM system provided results comparable to conventional EEG techniques, both in recording normal brain activity and in detecting pathological discharges. A key advantage of the EpiosTM system is its precise localization of these brain signals, which illustrates its effectiveness and added value compared to other implantable EEG devices.

However, the study also has limitations, including its short duration and small number of participants, which limits the generalizability of the results. Nevertheless, it provides convincing initial evidence that subscalpale EEG systems are safe and effective at capturing brain signals over extended periods of time. Prof. Baud, inventor of the device and head of the study, explains: «The EpiosTM system has the potential to revolutionize the treatment of epilepsy and other neurological disorders by enabling ultra-long-term monitoring of physiological and pathological brain activity. In the case of epilepsy, more data can be obtained on the localization of seizures, which helps to optimize medical treatment and plan epilepsy surgery. In the long term, this system could also help usher in a new era of brain monitoring with improved seizure prediction and disease management capabilities.»