Abstracts

Rationale:
This study aims to evaluate the effectiveness of a sub-scalp EEG monitoring device ('Minder') in capturing and lateralizing seizure activity in patients with unilateral structural pathology. Specifically, the objective is to understand how ultra-long-term EEG monitoring can improve patient care, particularly in surgical planning, by providing consistent and accurate seizure data over extended periods. Consistent long-term monitoring is crucial for accurate localization of seizure onset zones, understanding seizure patterns, and making informed decisions for surgical intervention. The primary outcome was the consistency of lateralisation over a prolonged period, as shown by the sub-scalp EEG device.




Methods:
The study involved four male patients aged between 24 and 64 years. Each participant had a unilateral structural pathology identified through MRI, and consistent lateralisation of ictal activity on scalp EEG recordings obtained in the Epilepsy Monitoring Unit (EMU). A sub-scalp EEG monitoring device with four contacts was employed. The contacts were positioned posterior to the vertex, with two contacts over each hemisphere. The device continuously captured EEG data, transmitting it via Bluetooth to a smartphone and subsequently to the cloud. The monitoring device was implanted in a minimally invasive procedure, performed under general anesthesia. 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 lateralisation of the scalp and sub-scalp signals for their interictal and ictal electrographic activity recorded during the co-monitoring period for comparison. Data analysis was conducted over a three-month period using both human review and a seizure detection algorithm, with the algorithm’s findings confirmed by human review. The study protocol was approved by the HREC at St Vincent’s Hospital Melbourne (HREC158/19) and registered under the CTN (ACTRN12619001587190).




Results:
In all four patients, the sub-scalp device demonstrated consistent lateralisation of seizure activity that correlated with the structural pathology identified on MRI. The prolonged recording period allowed for comprehensive data collection, reinforcing the reliability of the device in lateralising ictal activity.




Conclusions:

The sub-scalp EEG monitoring device proved to be a valuable tool in the lateralisation of seizure activity in patients with unilateral structural pathology. Its continuous data capture and reliable transmission, coupled with long-term consistency, make it a promising option for extended EEG monitoring outside of the traditional EMU setting. Capturing seizure data consistently over long periods can identify seizure patterns that can vary over time, and accurate lateralisation and understanding of seizure patterns directly impact the success rates of epilepsy surgery improving patient outcomes.




Funding: Funding for this study was provided by Epiminder.