Endovascular Electroencephalogram Records Simultaneous Subdural Electrode-Detectable, Scalp Electrode-Undetectable Interictal Epileptiform Discharges

Abstract

Introduction: We hypothesized that an endovascular electroencephalogram (eEEG) can detect subdural electrode (SDE)-detectable, scalp EEG-undetectable epileptiform discharges. The purpose of this study is, therefore, to measure SDE-detectable, scalp EEG-undetectable epileptiform discharges by an eEEG on a pig. Methods: A pig under general anesthesia was utilized to measure an artificially generated epileptic field by an eEEG that was able to be detected by an SDE, but not a scalp EEG as a primary outcome. We also compared the phase lag of each epileptiform discharge that was detected by the eEEG and SDE as a secondary outcome. Results: The eEEG electrode detected 113 (97%) epileptiform discharges (97% sensitivity). Epileptiform discharges that were localized within the three contacts (contacts two, three and four), but not spread to other parts, were detected by the eEEG with a 92% sensitivity. The latency between peaks of the eEEG and right SDE earliest epileptiform discharge ranged from 0 to 48 ms (mean, 13.3 ms; median, 11 ms; standard deviation, 9.0 ms). Conclusion: In a pig, an eEEG could detect epileptiform discharges that an SDE could detect, but that a scalp EEG could not.

Making a case for endovascular approaches for neural recording and stimulation

“…In many cases, a standard metal guidewire was advanced to the recording location and a standard catheter was used to insulate the entire length except for a few millimeters at the end, producing a single electrode at the tip [23,53]. In some cases, custom insulated guidewires with exposed metal electrodes [15,16,19,24,[46][47][48][49][50][51] or catheters with embedded electrodes [25,52] were built specifically for recording purposes (rather than using existing guidewires, which were not insulated, or existing catheters, which did not contain electrode sites). Guidewire-and catheterlike devices used for endovascular recording typically range from 0.2 to 0.6 mm in diameter with a 1.5-60 mm exposed tip (electrode) length [15,19,[22][23][24][25].…”

“…In some cases, custom insulated guidewires with exposed metal electrodes [15,16,19,24,[46][47][48][49][50][51] or catheters with embedded electrodes [25,52] were built specifically for recording purposes (rather than using existing guidewires, which were not insulated, or existing catheters, which did not contain electrode sites). Guidewire-and catheterlike devices used for endovascular recording typically range from 0.2 to 0.6 mm in diameter with a 1.5-60 mm exposed tip (electrode) length [15,19,[22][23][24][25]. Although there are some publications reporting stimulation, the primary focus in most research with guidewire or catheter electrodes was recording.…”

“…This trend is supported by several animal studies, including work by He et al [23] which showed larger amplitude, a wider frequency band, and 100 times better SNR in EV EEG versus scalp EEG in rabbit. Fujimoto et al [19] found that 97% of artificially generated epileptic discharges captured by subdural electrodes were also captured by endovascular electrodes in pig superior sagittal sinus (SSS).…”

“…A minimally invasive alternative is an endovascular electrode, which is delivered to the target region via a standard catheterization procedure and does not require an open brain surgery. This type of recording is known as endovascular EEG (EV EEG) and has a comparable recording and stimulation resolution to ECoG, providing detailed information on local brain areas and with the potential to treat neurologic disorders currently treated with small, implanted electrodes [7,9,10,[14][15][16][17][18][19][20].…”

Endovascular electroencephalography (eEEG) can detect the laterality of epileptogenic foci as accurately as subdural electrodes

“…We have reported that eEEG can detect the epileptic discharges detected by subdural electrodes in experiments using a pig animal model [ 23 ]. The previous experiment [ 23 ] placed the eEEG electrode in the superior sagittal sinus, not allowing clarification of whether lateralization can be judged.…”