Spinal Nerve Root Stimulation for Chronic Pain: A Systematic Review

Objective: Spinal cord stimulation (SCS) has been used as a minimally invasive and effective treatment modality for various chronic pain disorders, with the main target being stimulation of the dorsal columns; however, certain neuropathic pain areas involve dermatomes that are suboptimally covered by SCS. Stimulation of the spinal nerve roots has the advantage of targeting one or several dermatomes at the same time. The aim of this systematic review is to investigate the efficacy of spinal nerve root stimulation (SNRS) for chronic pain disorders. Materials and Methods: A detailed literature review was performed through the Ovid Embase and MEDLINE data bases in addition to reference searching. Gray literature was included by searching through common search engines using a simplified search strategy. Studies included were focused on adult patients (aged >18 years), diagnosis of chronic pain syndrome (including but not limited to complex regional pain syndrome, persistent spinal pain syndrome, neuropathic pain secondary to trauma or infection, postherpetic pain, and cancer pain). Patients must have undergone SNRS insertion, with >= six months of documented pain intensity scores on follow-up. Results: A total of 40 studies underwent full text review, and 13 articles were included in final analysis. Mean preoperative pain intensity was 8.14 +/- 0.74 on the visual analog scale, whereas mean postoperative pain intensity at one year was 3.18 +/- 1.44. Of 119 patients, 83 (70%) achieved >= 50% reduction in pain intensity after SNRS, whereas 36 (30%) achieved <50% reduction in pain intensity. Only three studies assessed changes in analgesia medication dose and reported morphine equivalent doses varied by case series. Overall, there was a trend toward a reduction in analgesia medications in the postoperative period. Conclusions: SNRS led to a mean 44% reduction in pain intensity, with a low level of certainty. In addition, there is some evidence to suggest that using SNRS is associated with reduced use of analgesics, including morphine and gabapentin.