Authors :
Presenting Author: Kiefer Forseth, MD, PhD – University of California San Diego
Keundong Lee, PhD – University of California San Diego
Jing Gu, PhD – University of California San Diego
Wonjae Jeon, PhD – University of California San Diego
Jihwan Lee, PhD – University of California San Diego
Hao Le, MS – University of California San Diego
Gal Mishne, PhD – University of California San Diego
Eric Halgren, PhD – University of California San Diego
Ahmed Raslan, MD – Oregon Health & Science University
Angelique Paulk, PhD – Massachusetts General Hospital
Sydney Cash, MD, PhD – Massachusetts General Hospital
Sharona Ben-Haim, MD – University of California San Diego
Alexander Khalessi, MD – University of California San Diego
Shadi Dayeh, PhD – University of California San Diego
Rationale:
Drug-resistant epilepsy severely interferes with patients’ quality of life and carries significant associated morbidity and mortality. Planning surgical interventions for drug-resistant epilepsy benefits from Phase 2 evaluation with intracranial electrodes to map the epileptic network. The primary aims are to localize the epileptogenic foci, to characterize interictal activity in the irritative zone, and to establish boundaries of eloquent cortex. The ideal Phase 2 system would enable robust recording of many distributed sources with fine spatial scale – all while also freeing patients from their wired tether to the hospital bed. Traditional stereotactic depth electrodes provide excellent grid-like distribution of recordings but are only able to resolve local field potentials from relatively large tissue volumes. More recent approaches including microwires and superficial high-density mapping systems succeed in sampling small neuronal populations but sacrifice scope – making them less useful for epilepsy applications. To achieve global microscale recordings of the brain, we have developed high-fidelity, low-impedance, micrometer-scale penetrating electrodes with wireless data transmission. Here we present the first implantation of this full recording & stimulation system in a large animal survival model.
Methods:
Pigs were selected given their relative homology to humans, large cerebral volume for a non-primate, and biologic tolerance of implanted hardware for semichronic experiments. The pig underwent a first stage anesthetic event for CT and MRI imaging to facilitate surgical planning before a second stage implantation of stereotactic leads with neuronavigation. Each of the implanted leads was 15 μm thick and 1.2mm wide with 128 microcontacts for recording and 16 macrocontacts for stimulation distributed over 3cm. Head-mounted amplifiers and serializer protected by a titanium cap enabled a single line connection for data and power to a secondary backworn unit. This secondary unit was positioned between the shoulders, anchored to a jacket worn by the pig. The backworn unit enabled wireless recordings at 30kHz and current injection of up to 96 channels by chronometric or closed-loop triggers.
Results:
The pig was neurologically intact after successful surgical implantation of 6 microelectrode leads (864 total contacts) to subcortical and cortical targets: hippocampus, thalamus, and somatosensory cortex. Normal ambulatory, feeding, and socializing behavior were observed. Wireless transmission of intracranial electrophysiology was successful and single-pulse stimulation induced evoked responses across distributed electrodes.
Conclusions:
We present our first successful survival implantation of a large-scale micro-electrophysiology system for wireless recording and stimulation in a grid-like distribution suitable for Phase 2 mapping in drug-resistant epilepsy.
Funding: UG3NS123723