Review Article
Michelangelo Buonocore
Abstract
Spinal cord stimulation (SCS) is a physical invasive therapy largely used to treat patients with neuropathic pain refractory to pharmacologic treatments. Its mechanisms of action are not completely understood and, so far, patients continue to be enrolled with a trial and error approach. SCS is based on the electrical stimulation of dorsal columns, which evokes a typical electrical paresthesia, similar to that experienced by any person when an electrical stimulation is applied over the skin. This electrical sensation is not physiological because it is the result of an ectopic, direct activation of nerve fibers with a by-pass of the receptor’s activation. The electrical stimulation of dorsal columns induces action potentials in the lemniscal pathway, a “system” made by fibers with large diameter and high conduction velocity. As any other electrical stimulation of nerve fibers, SCS creates potentials which travel in opposite direction: cranially and caudally. Afferent, orthodromic propagation of action potentials during SCS is mandatory for any supposed antalgic mechanism occurring in brainstem or brain, while antidromic propagation is considered the basis for the antalgic, segmental effect of SCS. Studies on neurophysiological effects of SCS are rare and further investigations are warranted in order to achieve a better understanding of the antalgic effects of SCS, and consequently improve therapeutic targeting and patient selection.