Intracranial stimulation therapy for epilepsy

Epilepsy is a common chronic neurological disorder effecting 1 to 2% of the population. Despite advances in anti-epileptic drug therapy, epilepsy surgery, and vagus nerve stimulation, approximately 30% of patients continue to have seizures. Intracranial stimulation is currently under investigation as an adjunctive treatment to anti-epileptic medications in adults with medically intractable epilepsy. Several different approaches are now being investigated. Specifically, acute and long-term clinical studies have delivered stimulation either to inhibitory regions outside the seizure focus or directly to the seizure focus. These studies have demonstrated the safety of intracranial stimulation and proof of principle in epilepsy patients. In addition to the different locations tested, clinical studies have also used different temporal patterns of stimulation. The majority of studies have used open-loop or scheduled stimulation, in which, stimulation is delivered on a fixed schedule and is independent of electrographic activity. In contrast, a number of recent investigations have demonstrated the feasibility of closed-loop or responsive stimulation, which is stimulation that is contingent upon the detection of epileptiform activity. This chapter will review the acute and long-term clinical studies of intracranial stimulation, including focal, and nonfocal, and open-loop and responsive stimulation. We will also discuss the optimization and safety of therapeutic parameters used in neurostimulation for epilepsy.