Technical Description of Long-Term High-Density EEG Monitoring Using 128-Channel Cap Applied With a Conductive Paste

Purpose: EEG is a common diagnostic tool to localize epileptic activity with excellent temporal resolution and, however, with relatively low spatial resolution. High-density EEG recording is limited in clinical practice, mainly because of electrode placement difficulties, need of high technical skills, and advanced equipment requirement. Methods: We described the technique of long-term EEG recording using a 128-channel neoprene cap placed with a dielectric paste in 7 patients with refractory epilepsy. We captured electrographic seizures in six of seven patients. The 128-channel EEG cap was well tolerated except for a mild headache. Daily impedance checks and reapplication of the high impedance leads maintained the recording with impedances below 10 kΩ. Results: Successful long-term recording of high-density EEG was able to capture seizures in six of seven patients. The time needed to apply the electrodes was approximately 1 hour and approximately 30 minutes daily for maintenance. The EEG source localization was obtained in six of seven patients, concordant within the sublobar region for both standard and high-density EEG recordings. Three patients reported a mild headache not leading to discontinuation of the recording. Conclusions: In general, long-term high-density scalp EEG recording with a dielectric paste is well tolerated and allows capturing both interictal and ictal data for localization. This small sample does not show a significant advantage in terms of sublobar localization when high-density EEG source is compared with standard 10 to 20 placement as long as the subtemporal areas are recorded.