Spinal cord stimulation for chronic pain. 
Spinal cord stimulation (SCS) is a form of therapy used to treat certain types of chronic pain.  It involves an electrical generator that delivers pulses to a targeted spinal cord area.  The leads can be implanted by laminectomy or percutaneously and the source of power is supplied by an implanted battery or by an external radio-frequency transmitter.  The exact mechanism of action of SCS is poorly understood.  To assess the efficacy and effectiveness of spinal cord stimulation in relieving certain kinds of pain, as well as the complications and adverse effects of this procedure.  We searched MEDLINE and EMBASE to September 2003; the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 3, 2003); textbooks and reference lists in retrieved articles.  We also contacted experts in the field of pain and the main manufacturer of the stimulators.  We included trials with a control group, either randomized controlled trials (RCTs) or non-randomized controlled clinical trials (CCTs), that assessed spinal cord stimulation for chronic pain.  Two independent reviewers selected the studies, assessed study quality and extracted the data.  One of the assessors of methodological quality was blinded to authors, dates and journals.  The data were analysed using qualitative methods (best evidence synthesis).  Two RCTs (81 patients in total) met our inclusion criteria.  One was judged as being of high quality (score of 3 on Jadad scale) and the other of low quality (score of 1 on Jadad scale).  One trial included patients with Complex Regional Pain Syndrome Type I (reflex sympathetic dystrophy) and the other patients with Failed Back Surgery Syndrome.  The follow-up periods varied from 6 to 12 months.  Both studies reported that SCS was effective, however, meta-analysis was not undertaken because of the small number of patients and the heterogeneity of the study population.  Although there is limited evidence in favour of SCS for Failed Back Surgery Syndrome and Complex Regional Pain Syndrome Type I, more trials are needed to confirm whether SCS is an effective treatment for certain types of chronic pain.  In addition, there needs to be a debate about trial designs that will provide the best evidence for assessing this type of intervention.