Electrical stimulation of neural or nervous tissue—neurostimulation—is a well established procedure for the treatment of various neurological disorders. Neurostimulation has been successfully applied to treat diseases, such as epilepsy, depression, Parkinson's disease, migraine, and for stroke rehabilitation. However, today's neurostimulation techniques have a lot of difficulties. In Vagus Nerve Stimulation (VNS) electrodes are implanted around the vagus nerve, which carries the signal rather systemically but not targeted into the brain. The VNS technique has a rather low efficacy in successfully treating epilepsy or depression. In Deep Brain Stimulation (DBS) and Responsive Neuro Stimulation (RNS), electrodes are implanted within the cranium having direct contact with the brain. The invasiveness of both techniques is a large barrier for using these techniques. In Transcranial Magnetic Stimulation (TMS), alternating magnetic fields are utilized to induce eddy currents in parts of the brain where they cause electrical stimulation. However, TMS requires rather large equipment and can not be built into a portable device that a patient can carry for the treatment of epilepsy or other chronic diseases. In Electroconvulsive Therapy (ECT), patients receive, under anesthesia, rather large electrical shocks. ECT can not be made as a portable technique to treat chronic diseases.
Intracranial stimulation in which the stimulating electrodes are located directly at the disease site appears to be the most promising stimulation treatment for chronic illnesses, such as epilepsy, Parkinson's, depression, and others. However, intracranial stimulation techniques are very invasive.
Concentric ring electrodes capable of delivering stimulation to defined brain areas have been disclosed in the art (e.g., WO/2006/04479), however, for diseases such as epilepsy, all current techniques can only be used if the foci of the seizure(s) are known and static, meaning the foci do not move away from the location of the electrodes or become larger beyond the region of the location of the electrodes. A partial epileptic seizure can transform into a generalized seizure when the focus is enlarged and spreads out to the size of the entire brain. Currently, there is no neurostimulation technique available that stimulates specific targeted brain tissue areas, is adaptable to moving or dynamically shape changing foci, and is less invasive.