Neuromodulation: an overview

For over two centuries, electricity has been known to induce modification of neural and nerve fiber activity and has been proposed to be used to treat some neurological dysfunctions. The new era of the use of electrical current in the treatment of neurological symptoms began in 1967 with the use of totally implanted devices that deliver a controlled amount of electricity on a precise structure within the nervous systems and was first used to control pain. Extensive research has been carried out ever since to elucidate the mechanism of action of this treatment and extend its indication for the treatment of the other neurological symptoms. So far, there is evidence that the treatment is safe and efficient for long periods of time, as it does not induce permanent damage to the stimulated structure. Most likely, electrical current at the parameters used for therapeutic purpose induces an inhibition of the structure on which it is applied. However, this may be accompanied by either inhibition or excitation of anatomically related structures. For this reason, it seems more convenient to refer to this type of therapy as neuromodulation.A review of the historical development of this fascinating area is presented, with special attention to the evidence derived from experimental work on the parameters that electrical current must maintain to avoid damage to the underlying tissue.