Dorsal column stimulation: modulation of somatosensory and autonomic function Bengt Linderoth and Bj¨ orn A. Meyerson Electric stimulation of the posterior parts of the spinal cord (dorsal column stimulation), a direct clinical off-spring of the ‘gate-control theory’ presented 30 years ago, came into use as a means of relieving intractable pain only a few years later. The method was spread rapidly in the US and in Europe and is today an important adjunct in the therapy of selected pain syndromes resistant to other forms of treatment. Especially pain due to nerve injury, pain in peripheral vascular disease as well as angina pectoris are conditions which often respond to this treatment modality. Application of electric current to the dorsal columns evokes both ortho- and antidromic activity, the former being the base for the paraesthesiae experienced by the patient during stimulation. DCS seems to selectively suppress neurogenic types of pain, but the method also has a profound influence on pain in ischemia, probably via an entirely different mechanism. The somato-sensory and autonomic modulatory properties of DCS are the subject of this review, and in discussing this, we will also touch upon the question of the mechanisms underlying the beneficial effects. Furthermore, we will try to refl ect the problems of generalizing observations from the laboratory, when DCS procedures are applied to subhuman subjects without concurrant disease, to the clinical setting and the suffering patient. Key words: autonomic modulation / dorsal column stimulation / microcirculation / pain / sensory effects ©1995 Academic Press Ltd ELECTRIC STIMULATION of the spinal cord has during the last three decades developed into an indis- pensable therapeutic tool for certain chronic pain conditions. The method was a clinical spin-off from the well known gate-control theory for segmental pain suppression. 1 The idea was to apply electric stimula- tion to an easily accessible neural structure containing large diameter afferent fibres: the dorsal columns of the spinal cord. Thus, stimulating electrodes were applied to the dorsal aspect of the spinal cord and the method was termed dorsal column stimulation (DCS; or simply spinal cord stimulation, SCS/ see Figure 1). The objective of this review is to describe the somatosensory and autonomic effects of DCS observed in man and in experimental animals. These observations may contribute to the understanding of the mechanisms underlying the beneficial effects of this treatment method. We will conclude by indicating some principal weaknesses in the research to date, and discuss possible guidelines for future studies. From The Karolinska Institute Center for Pain Research and Department of Neurosurgery, Karolinska Hospital, S-17176 Stock- holm, Sweden Figure 1. The ‘classical DCS theory’. Current spread from the extradural electrode (here a multipolar device) activates fibres in the dorsal columns with ortodromic (1) as well as antidromic (2) transmission of impulses. The orthodromic activity forms the base of the paraesthesiae experienced by the patients (as well as for the recruitment of hypothetical supraspinal inhibitory mechanisms). The antidromic impulses are transmitted to the dorsal horns below the cathode(s) where they excite neurons in the outer layers activating the ‘gate mechanism’ (3) with an inhibitory effect on the activity in the small diameter fibre systems subserving pain. seminars in THE NEUROSCIENCES, Vol 7, 1995: pp 263–277 ©1995 Academic Press Ltd 1044-5765/95/040263 + 15$12.00/0 263