A subgaleal electrode array for neurostimulation allows the recording of relevant information in closed loop applications

Background: Neurostimulation is an emerging treatment option for patients resistant to pharmacotherapy and ineligible for neurosurgical intervention. Compared to intracranial stimulation placement of electrodes in the subgaleal space offers a minimally invasive option for long-term seizure monitoring for responsive systems. New method: It was investigated, whether electrode contacts of a device being developed as a stimulation system placed in the subgaleal space are suited for recording of EEG activity for seizure detection. EEG was recorded intraoperatively in four participants participating in a clinical trial during the insertion of the device. Quantitative parameters like electrode impedance, signal amplitude ranges and amplitude spectra were determined. Epileptiform patterns in the recordings were compared to patterns occurring in scalp EEG prior to device implantation. Results: Electrode impedances, amplitude ranges for artefact free intervals and intervals containing artefacts were determined. Spectral analysis showed typical properties of EEG recordings with high amplitude content at low frequencies and a peak in the alpha band. No major noise except at power line frequency disturbed the recordings. In two patients, typical epileptiform patterns could be identified having similar characteristics as their respective scalp EEG recordings prior to device implantation. Comparison with existing methods: New and less invasive electrode system compared to existing solutions for responsive neurostimulation. Conclusions: The subgaleal electrode system allows for high quality EEG recordings even in an hostile unfavorable environment like an operation theatre. For the design of a signal acquisition unit of a responsive system using subgaleal electrodes, specifications could be obtained.