Spinal Cord Stimulation. Techniques, Indications and Outcome

Abstract

Spinal cord stimulation (SCS) as a direct clinical application of the gate-control theory is an exceptionally good example of translational pain research, i.e., when data derived from the laboratory bench are translated to bedside practice. In fact, in the classical publication in Science 1965, Melzack and Wall [1] explicitly stated that the theory could have therapeutic implications by means of selectively activating large diameter fiber systems for the control of pain. Later, Wall together with Sweet tested the possible applicability of the gate-control concept to pain in man by stimulating their own infra-orbital nerves by percutaneous needle electrodes and they observed that the pain sensitivity was decreased in the maxillar region after stimulation [2]. It should be noted, however, that the perception of pain being modified by an alteration of the interplay between large and fine fiber systems had been postulated and discussed by earlier researchers. Thus, already in 1906 Head and Thompson proposed that discriminative sensations, such as touch, normally exert an inhibitory influence on the impulses subserving pain. They further postulated that facilitation or inhibition of sensory impulses occur in the posterior horn before they are relayed to secondary neurons [3]. The notion that epicritic sensory system exerts an inhibitory influence over protopathic sensations was the base for trials with sensory thalamic stimulation already performed in 1962 in Paris by Mazars and colleagues [4]. They were thus the first to apply electric stimulation of the sensory nervous system as treatment of severe neuropathic pain conditions. There is reason in this context also to refer to Noordenbos [5] who described the inhibitory influence of the fast on slow fibers as “fast blocks slow,” and, actually, Zotterman [6] earlier postulated that hyperalgesia may be due to absence of impulses rapidly conducted to the brain.