A number of studies over the past 30 years suggest that SCS has preferential success for common pain characteristics. In 1998, Kumar et al. reported that the five most common etiologies for treatment with SCS were Failed Back Surgery Syndrome (FBSS), peripheral vascular disease, peripheral neuropathy, multiple sclerosis (MS), and CRPS. The largest percentage of successful response to SCS was noted in peripheral neuropathy (73 %) and reflex sympathetic dystrophy (100 %). FBSS had a success rate of 52 %, likely secondary to its mixed neuropathic and nociceptive nature. Kumar went on to say that patients without surgical procedures prior to implant typically responded better, and if a surgical history was present, having a shorter transition time to implant improved the outcome. In summary, he found SCS most successful in intractable angina and ischemic pain, as well as CRPS and neuropathic pain after spinal surgery. North et al. reported that SCS was successful in producing pain relief in up to 60 % of patients with arachnoiditis secondary to failed back surgery. Additional work showed that SCS could be superior to reoperation in patients randomized to one of these treatment arms.

In the past two decades, significant advances in both hardware and software for these devices appear to have significantly improved the outcome for FBSS (Table 2.2). Specifically, data for new, advanced multicolumn paddle leads, percutaneous paddle lead arrays, high-frequency 10,000 kHz stimulation, and burst stimulation offer new promise to these patients that may reduce the burden of failed treatment and, if successful, may offer alternatives to additional back surgery or increasing opioids.

It has been suggested that SCS is most effective in the setting of sympathetically mediated pain states, with success rates approaching 70 %. Kemler and colleagues produced peer-reviewed, high-level evidence that SCS was superior to conservative treatment for CRPS. In addition to sympathetic pain, evidence of effectiveness for pain of vasculopathic origin is also mounting. Many studies have shown improved pain, better function, and, perhaps most importantly, improved limb salvage in settings where the distal extremity ischemic lesion measures less than 3 cm.

The development of novel systems to perform dorsal root ganglion (DRG) stimulation within the neuroaxis may result in improved outcomes in neuropathic groin and extremity pain owing to the ability to target specific abnormal pain fibers that were traditionally very challenging with SCS.