Historical and present state of neuromodulation in chronic pain.

Neuromodulation is based on the revolutionary concept that paresthesia-inducing electrical stimulation could be analgesic. Its historical basis emanates from Melzack and Wall's gate control theory of pain proposed in 1965. Neuromodulation has given us ready access to the systems of pain modulation and helped mature the understanding of the pathophysiology of pain. Physiologic studies highlight the complex ascending influence of neurostimulation on sensory processing. However, the present understanding of pain is rudimentary and evidence that neuromodulation works is modest. This paper emphasizes the historical antecedents, present state, and emerging future of 3 commonly applied neuromodulatory techniques--spinal cord stimulation, peripheral nerve and field stimulation, and deep brain stimulation--for chronic pain. It is hoped this article will enhance the understanding of neuromodulation and its role in pain management.