Spinal cord stimulation in chronic neuropathic pain: mechanisms of action, new locations, new paradigms.

Abstract

Neuropathic pain is a complex, heterogeneous disorder that affects approximately 8% of the total adult human population and comes with significant burden for both the patient and health care system.13 The international association for the study of pain defines neuropathic pain as “pain caused by a lesion or disease of the somatosensory nervous system” and classifies chronic neuropathic pain as a disease under International Classification of Diseases 11th Revision (ICD-11).89 Despite the development and use of many pharmacological drugs and guidelines for the treatment of chronic neuropathic pain over the years,8 a substantial amount of neuropathic pain patients remain undertreated or untreated, with less than 50% of patients responding to pharmacological treatment.30 The development of novel, last-resort interventional treatment therapies is crucial to also relief pain in these refractory patients. Over the years, spinal cord stimulation (SCS) has proven to be a valuable last-resort treatment option (approximately 50% pain reduction in 50%-70% of patients) for a wide variety of refractory pain disorders, such as painful diabetic peripheral neuropathy (PDPN),22,94 complex regional pain syndrome (CRPS),42,43 and failed back surgery syndrome (FBSS).53,77 The mechanism underlying Tonic SCS (see section 2) is partly understood, and evidence has been provided for a mechanism of action through both spinal (section 2.1) and supraspinal levels (section 2.2). Recently, new physiological targets for stimulation as well as novel SCS paradigms were introduced to bridge the gap between currently achieved pain relief (as obtained with Tonic SCS) and the desired pain relief. Literature on the effect of stimulation at new anatomical locations, such as dorsal root ganglion stimulation (DRGS) (see section 3), and the use of new subsensory SCS paradigms such as high-frequency (HF) SCS (see section 4.2) and Burst SCS (see section 4.3) are discussed. This review ends with concluding remarks and future directions for research.