Edward F. Chang, MD, Guest Editor

Nicholas M. Barbaro, MD, Guest Editor

Over the last 30 years, tremendous progress has been made in expanding non-resective approaches to epilepsy surgery. With new advances in seizure detection, signal processing, and electrical stimulation, there is significant interest in developing a new generation of implantable devices for patients with intractable seizure disorders.

In this issue, we focus on emerging device technology in the field of epilepsy surgery. The articles are a compilation of topics that are highly relevant to neural interface technology. We are pleased to have significant contributions from experts in engineering, neurology, basic neuroscience, and neurosurgery. Together, they address the theoretical background, recent advances in research, and clinical outcomes of current and future devices in epilepsy surgery.

To start, Rolston and colleagues provide a comprehensive in-depth review of progress and obstacles in recording and stimulation technology applied to epilepsy. Several structures of the nervous system have been proposed as potential targets of device-based neuromodulation. Currently, the only FDA-approved device for epilepsy is the Vagal Nerve Stimulation by Cyberonics, Inc. Englot and coworkers report the largest analysis of VNS outcomes and their predictors performed to date from thousands of patients in the Cyberonics registry.

As a promising alternative to the extracranial-based device, DeGiorgio and colleagues report the development of infraorbital or supraorbital trigeminal nerve stimulation. This new approach offers the possibility of testing efficacy percutaneously before implantation.

The majority of other devices involve direct intracranial stimulation. Ooi and coworkers review the available literature on the anterior thalamus as a target for deep brain stimulation, including technical nuances and clinical results for this target. Tellez-Zenteno and Wiebe present a critical review of the emerging evidence for hippocampal stimulation as well as outlining what outstanding questions remain for prospective trials of efficacy.

Closed-loop systems that detect seizures to then trigger electrical stimulation to abort them are making clinical progress. Gigante and Goodman provide a historical overview and report on recent clinical trials conducted for the Responsive Neurostimulation System (RNS) from Neuropace. How cortical stimulation reduces seizures is unclear. Sohal and Sun report novel mechanistic findings from patients implanted with the RNS system, suggesting that stimulation acutely desynchronizes long-range gamma frequency activity, thereby functionally “disconnecting” the epileptogenic network.

Unpredictability is a major factor contributing to the morbidity and mortality related to seizures. Recent advances in seizure prediction research are leading to wide-ranging potential applications including systems that can warn patients of impending seizures or triggering stimulation in closed loop devices. Iasemidis presents an excellent review of how a dynamical systems approach applied to epilepsy has led to a better understanding of seizure onsets, periods of susceptibility, and localization. Han and colleagues report on the powerful application of independent components analysis for improving the reliability and robustness of seizure detection and localization.

For intracranial devices, subdural or depth electrodes are the most common interface with the brain parenchyma. Fountas performed a systematic review of the literature to report the safety and complication avoidance associated with chronic indwelling electrodes.

Finally, Smyth and Rothman describe a completely alternative approach using focal cortical cooling. They present an overview of the rationale and preclinical data in animals and humans leading to the development of implantable cooling devices.

The field of neuromodulation for epilepsy is in its infancy, and significant knowledge gaps remain regarding how best to apply rapidly developing technology to achieve the best clinical outcomes. This issue is intended to stimulate further efforts in innovative uses of technology to suppress seizures without inducing unwanted side effects.