STIMULATION OF THE CENTRAL AND PERIPHERAL NERVOUS-SYSTEM FOR THE CONTROL OF PAIN

After suffering some setbacks since its introduction in 1967, stimulat ion of the spinal and peripheral nervous systems has undergone rapid d evelopment in the last ten years. Based on principles enunciated in th e Gate Control Hypothesis that was published in 1968, stimulation-prod uced analgesia [SPA] has been subjected to intensive laboratory and cl inical investigation. Historically, most new clinical ideas in medicin e have tended to follow a three-tiered course. Initial enthusiasm give s way to a reappraisal of the treatment or modality as side-effects or unanticipated problems arise. The last and third phase proceeds at a more measured pace as the treatment is refined by experience. This rev iew is divided into three parts as ii traces the progress of spinal co rd stimulation [SCS] and peripheral nerve stimulation [PNS]. The revie w commences with a discussion of the theory of SCS and PNS, and is fol lowed by early reports during which it became apparent that the modali ty is essentially only effective in the treatment of neuropathic pain. The last section describes the modern experience including efficacy i n specific types of pain and concludes with recent accomplishments tha t dramatize the relief of pain which can be achieved in nonoperable pe ripheral vascular disease or myocardial ischemia. Over the years, a se arch for those transmitters that might be influenced by spinal cord st imulation focused on somatostatin, cholecystokinin (CCK), vasoactive i ntestinal polypeptide (VIP), neurotensin and other amines, although on ly substance ''P'' was implicated. More recently, in animal studies, e vidence that GABA-ergic systems are affected may explain the frequent successful suppression of allodynia that follows spinal cord stimulati on. During the past eight years, much attention has been directed to s tudies that use a chronic neuropathic pain model. While PNS held signi ficant promise as a pain relieving modality, early electrode systems a nd their surgical implantation yielded variable results due to evolvin g technical and surgical skills. These results dramatically reduced th e continued development of PNS, which then gave way to a preoccupation with SCS. Modern development of SCS with outcome studies, particularl y in relation to failed back surgery syndrome [FBSS] and the outcome o f peripheral nerve surgery for chronic regional pain syndromes, has ea rned both modalities a place in the ongoing management of patients wit h intractable neuropathic pain. The last section, dealing with pain of peripheral vascular and myocardial ischemia, is perhaps one of the mo re exciting developments in stimulation produced analgesia and as the papers discussed demonstrate, fan provide a level of analgesia and eff icacy that is unattainable by other treatment modalities. SCS and PNS has an important role to play in the management of conditions that are otherwise refractory to conservative or other conventional management .