28 - Neurosurgical treatment for pain: spinal cord stimulation

Summary

Introduction

The concept of electrically stimulating the spinal cord or peripheral nerve to treat chronic pain followed as a practical application of the gate control theory proposed by Melzack & Wall in 1965. They proposed that pain perception was determined by a balance of small-fibre and large-fibre input into a central ‘gating’ mechanism located in the dorsal horn of the spinal cord, and that chronic pain could be caused by conditions that skewed this balance toward small-fibre input (Melzack & Wall 1965).

In testing predictions of the gate control theory, Wall & Sweet stimulated their own infraorbital nerves with needle electrodes (Wall & Sweet 1967; Sweet & Wepsic 1968). This stimulation caused a non-painful buzzing in the distribution of the nerve as well as an elevation of the threshold for pinprick appreciation during stimulation and shortly after its discontinuation.

There was a succession of reports involving the use of peripheral nerve simulation, both transcutaneously (TENS) and directly for the treatment of chronic pain (Wall & Sweet 1967; Sweet & Wepsic 1968; Long 1974; Shealy 1973). Shealy et al. (1967a, b) suggested that stimulation of the dorsal columns of the spinal cord would affect a greater concentration of large-diameter fibres and might therefore inhibit pain more effectively. In 1967, they reported the first use of dorsal column stimulation for the treatment of chronic pain, and in 1970 they reported results in six patients with ‘excellent’ pain control in three and ‘good’ control in two patients.