Neurostimulation for the treatment of epilepsy

Responsive Neurostimulation for Seizure Control: Current Status and Future Directions

Electrocorticography (ECoG) data are commonly obtained during drug-resistant epilepsy (DRE) workup, in which subdural grids and stereotaxic depth electrodes are placed on the cortex for weeks at a time, with the goal of elucidating seizure origination. ECoG data can also be recorded from neuromodulatory devices, such as responsive neurostimulation (RNS), which involves the placement of electrodes deep in the brain. Of the neuromodulatory devices, RNS is the first to use recorded ECoG data to direct the delivery of electrical stimulation in order to control seizures. In this review, we first introduced the clinical management for epilepsy, and discussed the steps from seizure onset to surgical intervention. We then reviewed studies discussing the emergence and therapeutic mechanism behind RNS, and discussed why RNS may be underperforming despite an improved seizure detection mechanism. We discussed the potential utility of incorporating machine learning techniques to improve seizure detection in RNS, and the necessity to change RNS targets for stimulation, in order to account for the network theory of epilepsy. We concluded by commenting on the current and future status of neuromodulation in managing epilepsy, and the role of predictive algorithms to improve outcomes.

Responsive neurostimulation: Review of clinical trials and insights into focal epilepsy

The responsive neurostimulator (RNS ®, NeuroPace Inc.) has been available clinically since 2013 for the treatment of medically refractory partial epilepsy. Using intracranial electrodes and a cranially implanted device, RNS ® provides on-demand electrical cortical stimulation to reduce seizures. A randomized, multicenter, double-blind clinical trial demonstrated seizure reduction compared with sham stimulation. Seizure reduction was improved and sustained over years in a long-term treatment trial. The RNS ® provides chronic ambulatory electrographic monitoring over years giving unprecedented insight into epilepsy dynamics. Studies to date have looked at the length of time to detecting bilateral seizure onsets in mesial temporal lobe epilepsy (MTLE), demonstrated biorhythms in interictal epileptiform activity over varied time scales, and shown promise in early detection of benefits of adding a new antiepileptic drug. Questions remain as to the boundaries of patient selection and lead placement. "This article is part of the Supplement issue Neurostimulation for Epilepsy."