Abstracts

Rationale: To evaluate the sensitivity of the Minder sub-scalp EEG system in detecting interictal and ictal EEG signals arising from various regions of the brain by comparing interictal signals and seizure activity recorded from the Minder sub-scalp EEG system with EEG signals acquired using standard scalp electrodes.


Methods: Minder device and electrodes were implanted sub-scalp to enable chronic and continuous recordings. Minder recordings were evaluated through comparison of Minder electrographic information with data acquired through two 7-day co-monitoring periods using international gold standard 10-20 scalp electrodes, performed at 4 and 24 weeks after Minder implantation. Board-certified US electrophysiologists rated the scalp and sub-scalp signals for their interictal and ictal electrographic activity recorded during the co-monitoring period for comparison. Signal clarity was rated on a 5-point scale (1 = Confident seizure, 5 = very unclear) between scalp and Minder recordings. The study protocol was approved by the Human Research Ethics Committee at St Vincent’s Hospital Melbourne (HREC158/19) and registered under the CTN (ACTRN12619001587190).

Results: The Minder system was implanted in people with focal and generalized epilepsy. Focal epilepsies originated from distributed regions through the brain. These regions included parietal, temporal, and frontal lobes, with the epileptogenic zone located up to 10cm from the minder electrodes. The Minder system successfully recorded EEG signals from a variety of epilepsy pathologies including hypothalamic hamartoma, periventricular nodular heterotopia, and polymicrogyria. EEG signals were also successfully recorded in all lesion-negative focal epilepsy cases, post-stroke epilepsy, post-encephalitic epilepsy, and generalized epilepsies. During co-monitoring, all seizures that were found using the gold standard 10-20 scalp system were also identified in the Minder EEG recordings. There was no statistical difference between the signal clarity of the seizures on the scalp compared to the Minder system (3.4 +/- 1.3 vs 3.3 +/- 1.3 respectively (p< 0.05)). The Minder system was also able to record interictal epileptiform activity and physiological EEG signals such as sleep spindles, vertex waves, interictal epileptiform events (IEE), and muscle artifacts in all cases.


Conclusions: The Minder system recorded clinically relevant EEG signals from all subjects regardless of the origin of the signals or the epilepsy subtype. There was no difference in signal clarity between recordings that were observed on the standard 10-20 scalp electrodes, thus showing Minder’s sensitivity to EEG signals is equivalent to scalp recordings. Furthermore, the Minder system permits continuous EEG recording from several epilepsy pathologies located far from the recording electrodes, making it suitable for ultra-long term epilepsy monitoring in patients across the epilepsy spectrum.

Funding: Funding was provided by Epiminder Pty. Ltd.