• Spinal Cord Stimulation
• Pain Management
• Pain, Postoperative

The population health implications stemming from the global pain burden are sobering. However, there is tremendous potential and scope for developing and introducing new interventional therapies for patients in pain with the goal of improving the quality of their lives. Regional Anesthesia & Pain Medicine is committed to bringing its readers a diverse set of impactful scholastic products designed to inform and influence clinical practices. As such, we are excited to offer our readers a special edition on Neuromodulation for Pain Syndromes. Patients with persistent or chronic pain often have their lives impacted by pain in numerous ways including loss of employment, physical disability, depression, opioid dependency, and inability to play desired social roles. Mitigating pain by altering its processing in the central and peripheral nervous systems is one of the most intriguing and potentially impactful concepts in all of the medicine.

Neuromodulation is defined by the International Neuromodulation Society as ‘the alteration of nerve activity through targeted delivery of a stimulus, such as electrical stimulation or chemical agents, to specific neurological sites in the body’.1 Though electricity from eels was used centuries ago to treat pain, the modern era of neuromodulation began in the 1960s, with the use of spinal cord stimulation (SCS) for intractable pain.2 Intrathecal drug delivery (IDD) devices for infusing analgesics followed soon after with newer waveforms (burst, high frequency) and devices (dorsal root ganglion stimulation, lead-only peripheral nerve stimulation) introduced over the last decade.3 In modern day pain practice, implanted neuromodulation devices are used to treat refractory pain that can be neuropathic or ischemic, while nociceptive pain is also emerging as a type of pain that is potentially treatable with SCS.

As is true for any resource-intensive intervention with the potential for significant complications, there is debate regarding efficacy (outcomes in ideal conditions) and effectiveness (outcomes in real world conditions) of neuromodulation for pain. There are many unanswered questions about these therapies: What populations benefit the most and how do we identify them? What are the outcome metrics that matter? What is the cost-effectiveness? What are the perioperative considerations? Is there a role for neuromodulation for acute pain? This special edition is a cohesive attempt by clinicians and researchers in the fields of pain medicine and neuromodulation to address many of these questions. Two of the articles in this issue discuss the complex issues around trialing prior to implantation of neuromodulation systems. Shanthanna et al present the results of their review of over 200 publications on trialing practices for the use of SCS.4 They follow this up by presenting evidence-based guidelines that include 39 recommendations from a panel of experts on selection of patients likely to benefit from SCS and for trialing of SCS.5

In terms of ‘value’ (outcomes/costs) of SCS, Provenzano and Heller present a debate on the cost-effectiveness of SCS in treating common pain syndromes including persistent spinal and complex regional pain syndromes.6 Their work highlights the critical importance of appropriately selecting patients for optimizing outcomes. They also identify emerging technological factors that are likely to impact cost-effectiveness of SCS in the future such as including improvements in both hardware and software. The authors challenge us to consider if there are potential economic benefits of introducing SCS earlier on in patients with appropriate indications in whom conventional medical management is likely to be expensive and futile. Chow and Rosenquist supplement this perspective with their interpretation of data on the utilization of SCS.7 They identify trends in the delivery of SCS including an increase in the use of cylindrical SCS leads placed through smaller incisions (percutaneous approach vs laminotomy for the placement of paddle leads) and a rapid increase in the healthcare dollars spent on SCS over the last few years (from US$2.4 billion in 2020 to a predicted US$4.1 billion in 2027). The authors also caution about other headwinds facing the availability of SCS including its complications and doubts about its long-term efficacy.

Given the multidomain impacts of pain, neuromodulation should address more than just the intensity of pain. Elsaban et al address the impact of SCS on physical function in patients with low back pain through a systematic review that synthesizes evidence and identifies the potential for a positive impact of this therapy on physical function.8 The authors also identify the limitations of the current literature including the paucity of adequately powered trials that explore physical function as a defined outcome of SCS through the use of validated instruments.

Moving beyond SCS, we present articles on the use of peripheral nerve stimulation (PNS) and IDD. The findings of a survey of experts in the use of PNS suggest an emerging view around the use of PNS, a less invasive modality than SCS, prior to offering SCS in patients who have pain in a limited dermatomal distribution.9 Li et al also identify common barriers to the use of PNS in clinical practice including a lack of training. Unlike PNS, IDD is a neuromodulation therapy that has been in clinical use for several decades but there are some unresolved issues around its use. Brogan et al take on the controversies about IDD for treating cancer pain including dorsal versus ventral intrathecal positioning of the catheter and assessing the need to trial before committing to permanent placement.10

A unique feature of this issue is the inclusion of articles that explore neuromodulation within the perioperative and acute pain domains. Orhurhu et al present a narrative review that should be an excellent resource for anesthesiologists, surgeons, and other perioperative healthcare providers who encounter patients with implanted neuromodulation systems.11 This article is a timely contribution to the existing literature because neuromodulation therapies continue to evolve as do the indications for these therapies. A debate about the use of neuromodulation therapies for perioperative pain is also presented in this special edition.12 Tsui and Gupta present arguments for and against the application of PNS in this setting and they also identify questions around the cost and benefit balance of this therapy in the perioperative context.

A common theme that runs through this special edition is the need for continuing scientific enquiry on the role of neuromodulation therapies in relieving acute and chronic pain. After reading the content, we hope the readers appreciate the current state and the future directions for neuromodulation therapies for treating pain, both from a clinical and a research perspective. The mission remains (to paraphrase Captain James T. Kirk from Star Trek)—‘…to explore new indications. To seek out new research. To boldly go where no person has gone before!’