Preliminary experience using a minimally invasive sub-scalp device for ultra-long term seizure monitoring.

Background and aims: Accurate identification of seizure activity has important clinical implications. Unrecognised seizure activity presents significant challenges to patient management. Implantable device studies have shown the potential of such systems but have been relatively invasive. We conducted a preliminary study of a minimally invasive sub-scalp device to continuously record EEG to detect seizures from a variety of anatomical locations. Method(s): Eight patients with refractory epilepsy with at least one seizure weekly have been implanted with sub scalp devices (Minder), with four electrode contacts deployed in a coronal plane posterior to vertex providing two channels of data. Data is continuously captured via a behind-ear unit and transferred wirelessly to a mobile phone, from where it is accessible remotely via the cloud. Recordings were compared to a one week inpatient video-EEG monitoring session for four of these subjects. EEG recordings from both systems were reviewed blindly by two neurologists. The study was conducted as part of a registered clinical trial. Result(s): The procedures were well tolerated, no significant complications occurred. The sub scalp recording captured all 31 events identified during the video-EEG period from the four subjects. Two events were initially identified on the sub scalp monitoring system alone. Of the 20 total patient reported events, 12 were not associated with clinical or EEG changes on either system. Conclusion(s): A sub-scalp system can capture continuous EEG data and accurately detect focal seizure activity. Significant disparities between reported and confirmed seizure activity were found. Sub-scalp systems could potentially provide considerable clinical utility.