Responsive brain stimulation in epilepsy.

Stimulation devices are considered in patients with drug-resistant epilepsy and who are not surgical candidates. Responsive neurostimulation (RNS) is a cortically based stimulator activated by electrocorticography (ECoG) patterns. Stimulation is applied directly to the seizure focus. The vagal nerve stimulator AspireSR 106 is also a responsive device which, in addition to basal stimulation, is activated by tachycardia. Deep brain stimulation of the anterior nucleus of the thalamus is used in Europe for intractable epilepsy and yields similar response rates to RNS using duty cycle stimulation. Chronic subthreshold cortical stimulation is an experimental form of constant, low-level stimulation applied to a seizure focus. These modalities are discussed and compared in this review.