Summary of Evidence

Neurostimulation is an established interventional treatment for chronic pain of the trunk or limbs characterized by neuropathic pain that is refractory to standard therapy. To ensure effective suppression of pain, a trial period using temporary electrical stimulation must demonstrate adequate pain relief before permanent implantation of the stimulation device. Spinal cord and dorsal root ganglion (DRG) stimulation have resulted in improved health outcomes for a variety of chronic refractory neuropathic pain conditions of the trunk or limbs, such as failed back surgery syndrome (FBSS), complex regional pain syndrome (CRPS), and painful diabetic neuropathy, when conservative treatments have failed and no contraindications to implantation are present. Due to this, medical necessity criteria have been developed for temporarily implanted and permanently implanted spinal cord and DRG stimulation that closely align with professional society guideline recommendations and clinical literature. Spinal cord and DRG stimulation have also been proposed for other vascular indications and pain syndromes. The available published clinical evidence is insufficient to determine the impact of spinal cord and DRG stimulation on health outcomes for these indications. Therefore, the use of this treatment for all other indications, including but not limited to critical limb ischemia, refractory angina pectoris, heart failure, and cancer-related pain, is considered experimental/investigative.

Rationale

The Visual Analogue Scale (VAS) and Numerical Rating Scale (NRS) are common pain assessments used for measuring pain intensity. The scales range from 0-10 and the patient selects the number that fits best to their pain intensity, where a higher score indicates greater pain intensity:

• Score of 0: no pain,
• Score of 1-3: mild pain,
• Score of 4-6: moderate pain,
• Score of 7-9: severe pain,
• Score of 10: worst pain imaginable.

A large number of spinal cord and dorsal root ganglion neurostimulator devices have been approved by the FDA through the premarket approval process. In September 2020, the FDA released a letter to healthcare providers reminding them to conduct a trial stimulation period before implanting a spinal cord stimulator as the agency continues to receive reports of serious adverse effects associated with these devices. The FDA made the following recommendations for healthcare providers:

• Conduct a trial stimulation as described in the device labeling to identify and confirm satisfactory pain relief before permanent implantation.
• Permanent spinal cord stimulation should only be implanted in patients who have undergone and passed a stimulation trial.
• A stimulation trial is typically performed on a patient for 3-7 days, and success is usually defined by a 50% reduction in pain symptoms. Inform patients about the risks of serious side effects and what to expect during the trial stimulation.
• Before implantation of any spinal cord stimulation, discuss the benefits and risks of the different types of implants and other treatment options, including magnetic resonance imaging compatibility of the devices.
• Before implantation, provide patients with the manufacturer's patient labeling and any other education materials for the device that will be implanted.
• Develop an individualized programming, treatment, and follow-up plan for spinal cord stimulation therapy delivery with each patient.
• Provide each patient with the name of the device manufacturer, model, and the unique device identifier of the implant received.

In 2017, the North American Spine Society (NASS) published coverage recommendations for spinal cord stimulation (SCS) for pain related to an insult to the peripheral nervous system or axial back, neck, leg, and arm pain (radicular). The NASS Coverage Committee states that SCS has shown to be a safe, reversible therapy in difficult-to-treat medically intractable or refractory neuropathic pain in chronic pain patients. It has been documented to treat pain of varying topography and causes, including low back pain or radicular pain, failed back/neck surgery syndrome, complex regional pain syndrome (CRPS), and pain from peripheral neuropathy. SCS requires placement of the leads during trial so they cover the area of the patient’s typical pain. The NASS Coverage Committee’s recommendations for trial, implantation, and contraindications are outlined below.

A SCS trial is indicated when the following criteria are met:

• Moderate to severe pain causing some degree of functional deficit.
• Pain has been present for at least 6 months, with prior failure of multiple more conservative/ nonsurgical therapies such as medications, physical therapy, psychological therapy, and other modalities have been exhausted without definitive surgical pathology.
• No active substance abuse issues.
• Psychological evaluation has ruled out known risk factors such as significant cognitive dysfunction and untreated/poorly controlled addiction, psychological disorders, or social dysfunction.
• No identifiable cause for the pain that can be reasonably addressed with surgery or the risks of surgical treatment are too high.

SCS implantation is indicated when the following criteria are met:

• Successful completion of a spinal cord stimulation trial.
• At least a 50% reduction in pain and some improvement in functional status for at least 48 hours during the spinal cord stimulation trial.

SCS implantation is contraindicated with any of the following:

• Existing, untreated drug addiction or poorly controlled psychiatric/psychological disorders or social dysfunction.
• Presence of active systemic infection.
• Inability to operate the spinal cord stimulation device (e.g., an individual with cognitive dysfunction).
• Unable to be off anticoagulation or adequately bridged.
• Cancer pain.

In 2013, the American Society of Interventional Pain Physicians (ASIPP) updated their guideline on interventional techniques for chronic spinal pain. The guideline notes that SCS is primarily implanted for failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS). According to their recommendations, SCS is indicated in chronic low back pain with lower extremity pain secondary to FBSS, after exhausting multiple conservative and interventional modalities. SCS is recommended to the patient population for whom all other appropriate medical options have been tried without sufficient improvement in pain control. The guideline also states that the most commonly reported complication of SCS is lead migration followed by lead fracture and infections at the incision site of an implantable pulse generator or in the surgical pocket.

Also in 2013, the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain published recommendations on interventional management of neuropathic pain. The following recommendations on SCS were provided:

• Recommendations support the use of SCS for FBSS with radiculopathy and CRPS.
• Epidural steroid injections are a reasonable option prior to SCS for medically refractory patients with FBSS with radiculopathy.
• Reserve SCS for patients who fail less invasive treatment options, including consideration of a trial of epidural steroid injections and/or sympathetic nerve blocks.

In 2014, the International Neuromodulation Society (INS) convened a Neuromodulation Appropriateness Consensus Committee (NACC) to develop recommendations on appropriate use of neurostimulation of the spinal cord and peripheral nervous system for the treatment of chronic pain and ischemic diseases. The NACC was comprised of experts in anesthesiology, neurosurgery, and pain medicine. Their recommendations regarding SCS include:

• SCS in the cervical epidural space appears to be effective in relieving upper extremity pain of neuropathic etiology and is as safe as thoracolumbar SCS. Recommend the use of cervical SCS for neuropathic pain syndromes affecting the upper extremities.
• Recommend that SCS or dorsal root ganglion (DRG) stimulation be used for axial back pain after identifying a specific pain generator.
• The use of SCS should be either conventional SCS or DRG stimulation when the pain is dominantly radicular in nature.
• Cervical SCS is recommended for the treatment of upper extremity pain of neuropathic pain syndromes affecting the upper extremities, including, but not limited to radiculopathy.
• Use of SCS is recommended early in the treatment algorithm for FBSS in the absence of neurological progression requiring surgical intervention with persistent axial and radicular complaints.
• SCS is recommended for the treatment of CRPS-I and CRPS-II with pain of at least 3 months’ duration or severe, rapidly progressing disease that is not responding to more conservative measures such as rehabilitation, and a psychological evaluation and successful trial have been performed.
• Use of SCS to treat painful diabetic peripheral neuropathy is often helpful but should be approached with caution considering the increased risk of infection.
• The use of electrical neuromodulation for congestive heart failure has drawn interest from both cardiologists and neuromodulators. Further research has been initiated in human clinical studies in an open label manner in patients with heart failure to assess changes in left ventricular function and New York heart classification status among those who received implantable SCS devices in the upper thoracic or lower cervical spine.
• SCS should be considered earlier and trialed in the first two years of chronic pain if certain conservative measures, such as over-the-counter (OTC) analgesics, exercise, physical therapeutic modalities, cognitive behavioral therapies, injection therapies, and the like have failed to provide acceptable pain relief.
• Trial SCS is recommended by the NACC for the treatment of pain. Trialing affords the opportunity to assess the therapy before committing to permanent implantation of an expensive and potentially more invasive SCS device. Assessment of the trial outcome by the clinician includes evaluations of pain relief, improvement in patient function, associated treatment (in particular medication) utilization, and any complications of therapy.
• A successful trial is defined as the patient having had at least 50% pain relief; evidence of improved function is a goal and should also be measured in appropriate patients.
• Recommend a psychological evaluation within less than one year before implementing any neuromodulation therapies to address any concerning psychiatric comorbidities. Patients with inadequately controlled psychiatric/psychological problems should not be implanted. Pain is, by definition, a sensory and emotional experience associated with or described in terms of actual or perceived tissue damage. The provider/clinician may not recognize the impact of mood, depression, anxiety, or other negative affective states on the experience of pain. The experience of pain always involves emotional factors. The challenge for the pain practitioner is to differentiate between the component that is biologically driven and the component that is emotionally driven or magnified. All patients should be evaluated by a mental health professional prior to implant.
• Criteria for placement of an implantable neurostimulation device require failure or inadequate response to conservative medical management. Recommend that neuromodulation for the treatment of pain should be used in patients who fail to have acceptable relief with reasonable efforts and/or who have unmanageable side effects with their current conservative treatment regimen.
• Exclusion criteria for SCS include evidence of active, uncontrolled psychiatric disorder, inability to comply with therapy, local or systemic infection, immunosuppression, and anticoagulant or antiplatelet therapy that cannot be suspended temporarily for implantation.
• SCS has a low risk of major complications, as befits a neuromodulation procedure. Minor complications, on the other hand, are more common. The majority of complications associated with SCS implants involve electrode fracture or lead migration, which are correctable by replacing or repositioning the lead.

The NACC also published best practices for the use of dorsal root ganglion (DRG) stimulation for the treatment of chronic pain syndromes in 2019. Their recommendations regarding DRG stimulation include:

• DRG stimulation should be considered primarily for focal neuropathic pain syndromes with identified pathology.
• DRG stimulation is an effective therapy in CRPS type I or type II of the lower extremity.
• DRG stimulation is superior to standard tonic SCS for unilateral focal pain caused by CRPS type I or type II in the lower extremity.
• DRG stimulation is recommended for the treatment of neuropathic groin pain.
• DRG stimulation in diabetic peripheral neuropathy (DPN) may be effective.
• Patients with significant psychological issues should be excluded or treated prior to consideration of DRG stimulation. A history of significant psychologic comorbidity should be considered a relative contraindication until proper counseling can be established and the therapist feels that an implant is indicated.
• Recommend a trialing methodology that attempts to treat the painful areas.
• Recommend that patient selection for DRG stimulation be based on commonly practiced principles for other forms of neurostimulation. This should include: psychologically stable, have a defined pathology, have any issues with addiction under control, have optimal anticoagulant management that allows for the safe placement of an epidural lead, have no unaddressed or poorly controlled medical conditions that may impact the outcome of the procedure, such as those relating to infection risk, and be properly educated on the device and treatment.
• A revision procedure may be required for lead fracture, migration, or movement of the system.

Also in 2019, three major global vascular surgical societies (the European Society for Vascular Surgery (ESVS), the Society for Vascular Surgery (SVS), and the World Federation of Vascular Societies (WFVS)) joined efforts to publish global vascular guidelines for management of chronic limb-threatening ischemia. This guideline states that the effectiveness of non-revascularization therapies (e.g., spinal cord stimulation, pneumatic compression, and hyperbaric oxygen) has not been established for chronic limb ischemia. They further conclude that only low-level evidence is available and the benefit of SCS is unproven, with insufficient evidence to recommend its use in the treatment of chronic limb ischemia.

In 2021, the American Society of Pain and Neuroscience (ASPN) published best practices and guidelines for interventional management of cancer-associated pain. The authors state that SCS may be considered for treatment of refractory cancer pain or on a case-by-case basis for pain that is related to cancer treatment such as chemotherapy-induced peripheral neuropathy, however this treatment is neither recommendable nor inadvisable.

The ASPN also published a guideline in 2022 for interventional therapies for knee pain. This guideline recommends DRG stimulation as a safe, proven, and effective treatment option for chronic post-surgical and focal neuropathic pain of the knee (i.e., complex regional pain syndrome [CRPS]) that is refractory to acute treatment. Acute treatment should focus on pain control with local nerve blocks and rehabilitative modalities to alleviate pain, manage edema, and prevent contractures. Pain management includes systemic steroids, tramadol, gabapentin, antidepressants, calcium channel blockers, bisphosphonates, and baclofen. Therapeutic modalities include edema control, range of motion, mirror therapy, graded motor imagery, acupuncture, biofeedback, stress loading, and aerobic conditioning. Chronic pain that is refractory to acute treatment is managed by progressing to spinal cord stimulator or DRG stimulator.

In addition, the ASPN published a second guideline in 2022 for interventional treatments for low back pain. This guideline recommends SCS for back pain from lumbar spinal surgery, in the treatment of non-surgical low back pain, and in the treatment of patients with predominate lumbar spinal stenosis. Regarding safety of SCS, the authors state that the majority of device failures are related to the hardware and more specifically the leads. Lead fractures and disconnects have been reported to occur in 5.9-9.1% of cases and lead migration rates have been reported anywhere between 13.2 and 22.6%. Regarding lead migration, additional issues that may arise include potential loss of efficacy with need for revision and possible replacement.

Also in 2022, the American Academy of Pain Medicine (AAPM) published practical diagnostic and treatment guidelines for CRPS. This guideline states that SCS is proven to be safe and effective for the treatment of chronic pain from CRPS. Data demonstrates pain reduction, improved quality of life and function, as well as a reduction in opioid pharmaceuticals when SCS is employed in the setting of failed conservative therapy.

In addition, the American Association of Clinical Endocrinology (AACE) published a guideline update in 2022 addressing diabetes mellitus. This guideline states that neuromodulatory techniques such as SCS and combining pharmacological with nonpharmacological approaches should be considered in those with refractory painful diabetic peripheral neuropathy (PDPN).

In 2023, the American Heart Association (AHA) and the American College of Cardiology (ACC), in collaboration with and endorsed by the American College of Clinical Pharmacy, American Society for Preventive Cardiology, National Lipid Association, and Preventive Cardiovascular Nurses Association, developed a joint clinical practice guideline for the management of chronic coronary disease. In this guideline, the authors comment on SCS used for refractory angina, stating that further research is needed to assess the utility of neuromodulation and thoracic spinal cord stimulation in patients with this condition.

Stimulation of the dorsal root ganglion (DRG) in the treatment of chronic, refractory pain has shown positive clinical results in multiple published studies, including a large prospective, randomized, controlled trial. Both safety and efficacy have been demonstrated utilizing this therapeutic approach for many chronic complaints. In 2017, Deer et al published results for the pivotal ACCURATE trial, a prospective, multicenter, randomized comparative effectiveness study in patients with CRPS or causalgia in the lower extremities (NCT01923285). 152 patients were randomized to either DRG stimulation (DRG group; n=76) or traditional SCS (SCS group; n=76) and proceeded to a temporary trial stimulation phase. Successful trial stimulation was determined by achieving at least a 50% lower limb pain relief during the trial phase; these patients were implanted with a permanent device. The primary endpoint was a composite of safety and efficacy at 3 months, and subjects were assessed through 12 months for long-term outcomes. The percentage of subjects receiving ≥50% pain relief and treatment success was greater in the DRG arm (81.2%) than in the SCS arm (55.7%, p<0.001) at 3 months. Device-related and serious adverse events were not different between the two groups. DRG stimulation also demonstrated greater improvements in quality of life and psychological disposition. Finally, subjects using DRG stimulation reported less postural variation in paresthesia (p<0.001) and reduced extraneous stimulation in nonpainful areas (p=0.014), indicating DRG stimulation provided more targeted therapy to painful parts of the lower extremities. The researchers concluded that DRG stimulation provided a higher rate of treatment success with less postural variation in paresthesia intensity compared to SCS.

In 2018, Morgalla et al published results for a smaller prospective, single center trial that studied the long-term outcomes of DRG stimulation for the treatment of chronic neuropathic pain. After a successful test-trial (duration of 3-14 days, pain decrease >50%), a permanent stimulator was implanted in 51 patients and they were re-examined after 1 year, 2 years, and 3 years. Results at 3 years showed a significant decrease in all pain assessments (VAS: p=0.0001; PDI: p=0.003; PCS: p=0.001; BPI: p=0.003; BDI: p=0.010). The researchers concluded that DRG stimulation may be an effective long-term method of treating discrete, localized areas of chronic neuropathic pain and recommended this treatment for chronic neuropathic pain in such areas.

Deer et al published a post-market safety analysis in 2019 that assessed ongoing DRG device safety when used to treat chronic pain. Manufacturer records yielded data from >500 DRG and 2000 SCS implants from a 2-year time period. Overall, DRG stimulation reported safety event rates were 3.2%, compared to an event rate during the same timeframe of 3.1% in SCS. Comparatively, both the DRG and SCS systems demonstrated equivalent event rates from the manufacturer records with slight variations in individual categories. The authors concluded that DRG stimulation demonstrated an excellent safety profile and reported event rates were similar to previously reported adverse event and complaint rates in the literature for this therapy. Similarly, safety events rates were lower or similar to previously reported rates for SCS, further demonstrating the comparative safety of this neuromodulation technique for chronic pain treatment. In addition, several other retrospective reviews and studies have been published investigating DRG stimulation for the treatment of various etiologies of chronic pain, including neuropathic pain, CRPS, and refractory painful diabetic peripheral neuropathy (PDPN). Overall, results support the use of DRG stimulation as a safe and effective treatment for these chronic pain conditions and it is stated that this technique offers a useful alternative for pain conditions that do not always respond optimally to traditional SCS therapy.

Patients with neuropathic pain secondary to failed back surgery syndrome (FBSS) typically experience persistent pain, disability, and reduced quality of life. SCS has been found to be an effective therapy in this patient population where conservative management and further operations are often unsuccessful. In 2007 and 2008, Kumar et al published 12-month and 24-month results for a prospective randomized, controlled, multicenter trial that included 100 FBSS patients with a VAS pain score ≥5 for at least 6 months. Patients were randomized to either SCS plus conventional medical management (SCS group; n=52) or conventional medical management alone (CMM group; n=48) for at least 6 months. Crossover after 6 months was permitted, and all patients were followed up to 1 year. Conventional therapy included oral medications (i.e., opioid, non-steroidal anti-inflammatory drug, antidepressant, anticonvulsant/ antiepileptic, and other analgesic therapies), nerve blocks, epidural corticosteroids, physical and psychological rehabilitative therapy, and/or chiropractic care. The primary outcome was the proportion of patients achieving ≥50% pain relief. At 6 months, 48% of the SCS patients and 9% of the CMM patients (p<0.001) achieved the primary outcome. Compared with the CMM group, the SCS group experienced improved leg and back pain relief, quality of life, and functional capacity, as well as greater treatment satisfaction (p≤0.05 for all comparisons). At 12 months, 48% of the SCS patients and 18% of the CMM patients (p=0.03) achieved the primary outcome. In addition, 32% of SCS patients had experienced device-related complications and 24% required surgery to resolve. Principal complications were electrode migration (10%), infection or wound breakdown (8%), and loss of paresthesia (7%). Additional data analysis showed that 42 patients continuing SCS (of 52 randomized to SCS) reported significantly improved leg pain relief (p<0.0001), quality of life (p≤0.01), and functional capacity (p=0.0002). Furthermore, at 24 months, of 46/52 patients randomized to SCS and 41/48 randomized to CMM who were available, the primary outcome was achieved by 17 (37%) randomized to SCS vs 1 (2%) to CMM (p=0.003), and by 34/72 (47%) patients who received SCS as final treatment vs 1/15 (7%) for CMM (p=0.02). The researchers concluded that in patients with FBSS, SCS provides sustained pain relief, clinically important improvements in functional capacity and health-related quality of life, and satisfaction with treatment compared with CMM alone.

In 2019, Rigoard et al published results for the PROMISE study, a randomized, controlled, open label, multicenter trial in patients with FBSS and an average NRS pain score ≥5 for at least 6 months duration despite other conservative treatment modalities (pharmacological, surgical, physical, or psychological therapies). 218 patients were randomized to SCS plus optimal medical management (SCS group; n=110) or optimal medical management alone (OMM group; n=108) and followed for 24 months. Crossover after completion of the 6-month outcome assessment was permitted. Optimal medical management included non-investigational pharmacologic agents (e.g., tricyclic antidepressants, opioid analgesics or tramadol, antiepileptics, or lidocaine) and/or interventional therapies (e.g., therapeutic injections, radiofrequency, acupuncture, functional restoration, physical therapy, and psychological interventions, such as cognitive behavioral therapy) as appropriate. The primary outcome was the proportion of patients with ≥50% reduction in low back pain (responder) at 6 months. At 6 months, there were significantly more responders in the SCS group than in the OMM group (13.6%, 15/110 vs 4.6%, 5/108, difference 9% with 95% CI 0.6%-17.5%; p=0.036). In addition, the SCS group improved in all secondary outcomes compared with the OMM group (changes in low back and leg pain, functional disability, health-related quality of life [HRQoL], return to work, healthcare utilization including medication usage, and patient satisfaction). In the SCS group, 17.6% (18/102) experienced SCS-related adverse events through 6 months, with 11.8% (12/102) requiring surgical reintervention. Furthermore, at 24 months, of the 57.3% (63/110) continuing SCS (SCS-SCS) and reporting 24-month data, 20.6% (13/63) achieved ≥50% reduction in low back pain. The researchers concluded that SCS improved pain relief, HRQoL, and function in a traditionally difficult-to-treat population of FBSS patients with predominant low back pain. Improvements were sustained at 12 and 24 months.

Chronic regional pain syndrome (CRPS; also called chronic reflex sympathetic dystrophy [RSD]) is a painful, disabling disorder of unknown pathophysiology which usually commences after trauma or operation on a limb, results in pain, functional impairment, and trophic changes. SCS has been evaluated as one of very few possible treatments for this condition. In 2000 and 2004, Kemler et al published 6-month and 2-year results for a randomized, controlled trial in patients with CRPS for at least 6 months, a mean VAS pain score ≥5, and no sustained response to 6 months of standard therapy (i.e., physical therapy, sympathetic blockade, transcutaneous electrical nerve stimulation, and pain medication). 54 patients were randomized to either SCS plus physical therapy (SCS group; n=36) or physical therapy alone (control group; n=18). Test stimulation of the spinal cord was successful in 24 patients; the other 12 patients in the SCS group did not receive implanted stimulators. Assessed outcomes included pain intensity, global perceived effect, and HRQoL. At 6 months, in an intention-to-treat analysis, the SCS group had a mean reduction of 2.4 in pain intensity, compared with an increase of 0.2 in the PT group (p<0.001). In addition, the global perceived effect was much higher in the SCS group than in the control group (p=0.01) and HRQoL improved in all 24 patients that underwent SCS implantation. At 6 months, the researchers concluded that SCS can reduce pain and improve HRQoL for CRPS patients. At the 2-year follow up, the intention-to-treat analysis showed improvements in the SCS group concerning pain intensity (-2.1 vs 0.0 cm; p<0.001) and global perceived effect (43% vs 6% "much improved"; p=0.001). In addition, HRQoL improved only in the SCS group. At 2 years, the researchers concluded that SCS results in a long-term pain reduction and HRQoL improvement in CRPS.

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus. Unfortunately, pharmacological treatment is often partially effective or accompanied by unacceptable side effects. SCS has become an established treatment for PDN and has been shown to improve pain scores significantly and more effectively than pharmacotherapy. In 2014, Slangen et al published results for a prospective randomized, controlled, multicenter trial in patients with moderate to severe PDN in the lower limbs, a mean NRS pain score ≥5 for a duration >6 months, and insufficient response to conventional drug therapy (including antidepressants, antiepileptic drugs, opioids, or a combination of these therapies). A psychological assessment was also performed. 36 patients were randomized to either SCS plus best medical treatment (SCS group; n=22) or best medical treatment alone (BMT group; n=14). The SCS system was implanted only if trial stimulation was successful, which occurred in 77% of the SCS patients. Treatment success was defined as ≥50% pain relief at 6 months. Treatment success was observed in 59% of the SCS and 7% of the BMT patients (p<0.01). In addition, pain relief during daytime and during nighttime was reported by 41% and 36% in the SCS group and 0% and 7% in the BMT group, respectively (p<0.05). Pain and sleep were "(very) much improved" in 55% and 36% in the SCS group, whereas no changes were seen in the BMT group, respectively (p<0.001 and p<0.05). Serious adverse events were noted in 2 patients (post-dural puncture headache and infection of the SCS system). The researchers concluded that SCS effectively reduces pain in patients with PDN compared with BMT over a 6-month period. In 2023, Zuidema et al published results for an 8-10 year follow up of the previous RCT for PDN. The study population for this prospective cohort study consisted of a subgroup of patients who still used SCS treatment ≥8 years after implantation (n=19). Pain intensity scores (NRS) during the day and night and data on secondary outcomes (i.e., quality of life, depression, sleep quality) were reported during yearly follow-up. Results showed that pain intensity, day and night, was significantly (p<0.01) reduced by 2.3 (NRS 6.6-4.3) and 2.2 (NRS 6.8-4.6) points, respectively, when comparing the long-term data with baseline. Moreover, for >50% of patients, the pain reduction was >30%, which is considered clinically meaningful. No differences were found regarding the secondary outcomes. The researchers concluded that this 8-10 year follow-up study indicates that SCS can remain an effective treatment in the long term to reduce pain intensity in patients with PDN.

In 2014 and 2016, de Vos et al and Duarte et al published results for a randomized, controlled, multicenter trial investigating the effectiveness of SCS in patients with refractory PDN in the lower extremities that existed for more than one year and an average VAS pain score ≥5. A psychological assessment was also performed. 60 patients were randomized 2:1 to either SCS plus best conventional medical practice (SCS group) or best conventional medical practice alone (control group) and followed for 6 months. The primary outcome parameters were the average pain reduction and the percentage of patients with >50% pain reduction at 6 months. The average VAS score was significantly reduced to 31 in the SCS group (p<0.001) and remained 67 (p=0.97) in the control group. In addition, results showed that patients in the SCS group, unlike those in the control group, experienced reduced pain and improved health and quality of life after 6 months of treatment. The researchers concluded that in patients with refractory PDN, SCS therapy significantly reduced pain and improved quality of life, offering further support for SCS as an effective treatment for this patient population. Most recently in 2024, Yeung et al published a clinical literature review evaluating SCS for PDN. Reviewers concluded that recent evidence indicates that SCS can provide safe and effective treatment for pain from PDN, especially when risk factor modification, nonpharmacological therapy, and pharmacotherapy have all failed.

SCS has been advocated for the management of ischemic pain and the prevention of amputations in patients with inoperable critical limb ischemia (CLI), however data on benefit are conflicting and clinical evidence is not sufficient to determine whether SCS would improve outcomes for patients with CLI. A published meta-analysis in 2009 identified 5 RCTs with a total of 332 patients that used SCS to treat patients with CLI. The reviewers did not observe significant interactions between any predefined risk factors and the effect of SCS and the analysis did not indicate a subgroup of patients who might specifically be helped by SCS. Meta-analysis including all randomized data showed insufficient evidence for higher efficacy of SCS treatment compared with best medical treatment alone. Although some factors provide prognostic information as to the risk of amputation in patients with CLI, there was no data supporting a more favorable treatment effect in any group. An updated Cochrane review in 2013 identified the same 5 RCTs as the 2009 meta-analysis, as well as one additional nonrandomized study, evaluating the efficacy of SCS in non-reconstructable, chronic CLI. In a pooled analysis of data from all 6 studies, there was a significantly higher rate of limb survival in the SCS group than in the conservative treatment group at 12 months (relative risk [RR], 0.75; 95% CI, 0.57-0.95; absolute risk difference, -0.11; 95% CI, -0.20 to -0.02). However, when the nonrandomized study was excluded, the difference in the rate of amputation no longer differed significantly between groups (RR, 0.78; 95% CI, 0.58-1.04; absolute risk difference, -0.09; 95% CI, -0.19-0.01). Overall, no significantly different effect on ulcer healing was observed between SCS and conservative treatment, the risk of complications with SCS was 17%, and average overall costs were significantly higher with SCS.

Several small RCTs and various reviews have evaluated SCS as a treatment for refractory angina. Overall, the evidence is mixed and insufficient to permit conclusions on whether health outcomes were improved for this population. In 2012, Zipes et al published results for a single blind, controlled trial that included 68 patients randomized to either high stimulation (treatment group; n=32) or low stimulation (control group; n=36). This trial was terminated early because interim analysis by the data and safety monitoring board found the treatment futile. The primary efficacy endpoint was the number of angina attacks recorded by patients at 6 months. The proportion of patients experiencing major adverse cardiac events at 6 months did not differ significantly between groups (12.6% in the treatment group vs. 14.6% in the control group; p=0.81). In 2011, Lanza et al published results for a small single blind study that included 25 refractory angina patients randomized to standard SCS (n=10), low-level SCS (75% to 80% of the sensory threshold; n=7), or very low-intensity SCS (sham group; n=8). Patients in the low-level SCS and sham groups were unable to feel sensation during stimulation. After a protocol adjustment at 1 month, patients in the sham group were re-randomized to one of the other groups, which resulted in 13 patients in the standard SCS group and 12 patients in the low-level SCS group. At the 3-month follow-up (2 months after re-randomization), there were statistically significant between-group differences in only 1 of 12 outcome variables (angina episodes). In a systematic review and meta-analysis published in 2017, 12 RCTs involving 479 patients were identified that evaluated SCS vs control in patients with refractory angina pectoris. Most studies had small sample sizes (i.e., n<50), follow-up ranged widely from 2 weeks to 12 months, and control interventions were not well described. Pooled analyses favored the SCS group for most outcomes (e.g., exercise time after intervention, pain level [VAS score], angina frequency) however there were no significant differences between SCS and control groups for physical limitation or angina stability. It was concluded that further investigation is required before SCS should be recommended and applied.

Two RCTs have evaluated SCS as a treatment for heart failure (HF). In 2014, Torre-Amione et al published results for a small randomized, double blind, pilot crossover study. In this study, 9 patients underwent SCS implantation and received 3 months of active and 3 months of inactive (off position) treatment, in random order with a 1-month washout period between treatments. The primary outcome was a composite of death, hospitalization for worsening heart failure, and symptomatic bradyarrhythmia or tachyarrhythmia requiring high-voltage therapy. Four patients experienced at least 1 of the events in the composite endpoint. It was concluded that the SCS devices did not interfere with the functioning of implantable cardioverter defibrillators, however the ability to detect an objective signal of benefit was limited and the utility and efficacy of SCS for the treatment of HF require further investigation. In 2016, Zipes et al published results for a small randomized, single blind, controlled study. In this study, 66 patients were implanted with either active SCS (n=42) or sham SCS (n=24). The primary endpoint was change in left ventricular end-systolic volume index from baseline to 6 months. It was found that there was no significant difference between groups (p=0.30). Other endpoints related to HF hospitalization and HF-related quality of life scores and symptoms also did not differ significantly between groups. After completion of the 6-month randomization period, all patients received active SCS. From baseline to 12-month follow-up, there were no significant treatment effects for echocardiographic parameters (p=0.36). The trial was originally powered based on a planned enrollment of 195 implanted patients, however enrollment was stopped early due to futility. The absence of any treatment effects or between-group differences is further suggestive of a lack of efficacy of SCS for HF.

A Cochrane review by Peng et al in 2013 assessed SCS for the treatment of cancer-related pain in adults. Four case series that included a total of 92 patients were identified, however reviewers did not identify any RCTs evaluating the efficacy of spinal cord stimulation in this population. Peng et al updated this review in 2015, finding no new studies meeting inclusion criteria identified. The reviewers concluded that current evidence is insufficient to establish the role of spinal cord stimulation in treating refractory cancer-related pain.

Complications that follow SCS placement are common, and incidences have historically been reported in approximately 30-40% of these procedures. Hardware-related problems such as lead failure and migration are more common than biological complications (e.g., infection, wound breakdown). In a published retrospective review, it was concluded that hardware-related complications were a prominent issue, and revisions or replacements were required to correct these problems. Most common complications included lead migration (22.6%), lead connection failure (9.5%), and lead breakage (6%). A published systematic review and meta-analysis also concluded that hardware-related complications accounted for the majority of SCS complications, with lead migration, hardware malfunction, and inadequate stimulation the most common. In addition, a published retrospective review specific to DRG stimulators concluded that similar to traditional SCS, lead migration and lead damage for DRG stimulators were the most frequently reported complications at 28% and 10% respectively, and the majority of complications were managed surgically with revision rather than explant.

Centers for Medicare & Medicaid Services (CMS)

Medicare covers dorsal column neurostimulators for the relief of chronic intractable pain when other treatment modalities (pharmacological, surgical, physical, or psychological therapies) have been tried and failed and careful screening, evaluation, and diagnosis have been performed prior to implantation, including psychological evaluation. In addition, pain relief with a temporarily implanted electrode must be demonstrated prior to permanent implantation. The complete coverage policy is found in the Medicare National Coverage Determinations (NCD) Manual, Section 160.7.

Smoking Cessation

The findings that current smokers have a higher risk of wound infection and wound disruption can be explained by the pathophysiological mechanisms related to the toxic effects and oxidative destruction induced by smoking and nicotine. Smoking impedes the innate defense system of the lung, including damaging mucus transport, aggravating mucus production, and diminishing macrophage function, resulting in increased risk of pulmonary complications. While NRT contains nicotine, it contains lower amounts without other carcinogens, and the impact on the body is more gradual. Plasma nicotine levels provided by NRT vary according to dose and delivery method but in general are lower than those maintained during active smoking. The exclusion of NRT will remove barriers to accessing surgical care and promote overall smoking cessation, while promoting consistency with clinical guidelines. Based on consistent factors for decision making, smoking cessation criteria for spinal cord and dorsal root ganglion was found to be appropriate and was included in the policy.

Smoking can impact spinal cord stimulation (SCS) efficacy and also rates of common complications with SCS, such as lead migration, the need for revision, and delayed wound healing. Mekhail et al published retrospective cohort studies in 2018 and 2020 investigating the correlation of smoking and SCS effectiveness for pain relief. In a combined total of 633 patients, results showed that smoking was associated with reduced SCS effectiveness for pain relief at 12 months postimplant. Other published retrospective reviews also show correlation between tobacco use and less success with SCS, as well as smoking and failure, lead migration with revision, and revision due to new pain symptoms. More specifically, in 2016, Knezevic et al concluded that smokers were significantly likely to experience lead migration (p=0.006) and the need for revision (p=0.001).

In 2022, Fan Chiang et al published results on a retrospective, cohort study of 1,156,002 patients, utilizing files of the American College of Surgeons National Surgical Quality Improvement Program database. Multivariable logistic regression was used to calculate the odds ratios (ORs) with 95% confidence intervals (CIs) for postoperative wound complications, pulmonary complications, and in-hospital mortality associated with smokers. Smoking was associated with a significantly increased risk of postoperative wound disruption (OR 1.65, 95% CI 1.56-1.75), surgical site infection (OR 1.31, 95% CI 1.28-1.34), reintubation (OR 1.47, 95% CI 1.40-1.54), and in-hospital mortality (OR 1.13, 95% CI 1.07-1.19) compared with nonsmoking. The length of hospital stay was significantly increased in smokers compared with non-smokers. They found that current smokers who underwent surgery had approximately 30% increased odds of developing surgical site infection (SSI) and 65% increased odds of developing wound disruption. Study conclusions state smoking status is related to increased perioperative risk for wound complications following major surgical procedures. The current literature review has shown that smoking harms wound healing. The study adds to existing evidence and improves understanding of healing complications in smoking surgical cases. Wound complications are associated with other adverse outcomes and have a significant impact on patient quality of life and health care budgets. Therefore, patients who smoke should be informed about the potentially increased risks of complications before surgery. Concluding results encourage smoking cessation prior to surgery.

In 2022, Liu et al published a meta-analysis on the effect of preoperative smoking and smoking cessation on wound healing and infection in post-surgery subjects. This analysis incorporated 11 trials involving 218,567 patients following surgery; 176,670 were previous or non-smokers, and 41,897 were smokers. Never smokers or those who had ceased smoking had significantly lower postoperative wound healing problems (odds ratio 0.74; 95% CI 0.63-0.87, p<0.001) compared with smokers. Non-smokers had significantly lower postoperative wound healing problems and surgical site wound infection compared with smokers.

Sorensen et al (2012), reported on the results of a meta-analysis that sought to clarify the evidence on smoking and postoperative healing complications across surgical specialties and determine the impact of perioperative smoking cessation intervention. Smokers and non-smokers were compared in 140 cohort studies that included 479K patients. Pooled adjusted odds ratios (95% CI) were 3.60 (2.62-4.93) for necrosis, 2.07 (1.53-2.81) for healing delay and dehiscence, 1.79 (1.57-2.04) for surgical site infection, 2.27 (1.82-2.84) for wound complications, 2.07 (1.23-3.47) for hernia, and 2.44 (1.66-3.58) for lack of fistula or bone healing. Investigators concluded that postoperative healing complications occur significantly more often in smokers compared with non-smokers and in former smokers compared with those who never smoked.

Nolan and Warner (2015) authored a narrative review to discuss the current evidence for nicotine replacement therapy’s (NRT)efficacy and safety in patients scheduled for surgical treatment and other invasive procedures. Noting the lack of human trials, the authors stated that although available data are limited, there is no evidence from human studies that NRT increases the risk of healing-related or cardiovascular complications. Clinical trials of tobacco use interventions that include NRT have found either no effect or a reduction in complications. Authors concluded that given the benefits of smoking abstinence to both perioperative outcomes and long-term health and the efficacy of NRT in achieving and maintaining abstinence, any policies that prohibit the use of NRT in surgical patients should be reexamined.

In 2020, Stefan et al reported on a retrospective study (n=147,506). Researchers analyzed the association between nicotine replacement therapy (within 2 days of admission) and inpatient complications and outcomes. In the propensity-matched analysis, there was no association between receipt of NRT and in-hospital complications (OR, 0.99; 95% CI, 0.93-1.05), mortality (OR, 0.84; 95% CI, 0.68-1.04), all-cause 30-day readmissions (OR, 1.02; 95% CI, 0.97-1.07), or 30-day readmission for wound complications (OR, 0.96; 95% CI, 0.86-1.07). Authors concluded that this demonstrates that perioperative NRT is not associated with adverse outcomes after surgery. These results strengthen the evidence that NRT should be prescribed routinely in the perioperative period.

The Society for Perioperative Assessment and Quality Improvement (SPAQI) convened a multidisciplinary panel of 17 experts in perioperative smoking cessation. In 2020, members of the Task Force (from the fields of anesthesiology, internal medicine, surgery, public health, and pharmacy from both academic and nonacademic settings in Canada, United States, Australia, New Zealand, Asia, and Europe) published the following consensus statement:

Interventions should occur as soon as practicable in relation to surgical scheduling. Evidence from observational studies of spontaneous quitting suggests that longer durations of preoperative abstinence are associated with lower rates of respiratory and wound healing complications. Evidence from RCTs supports an effect of preoperative smoking cessation interventions that are 4-8 weeks long.

In 2024, The National Comprehensive Cancer Network (NCCN) published guidelines on smoking cessation. The guideline states the following: Nicotine replacement therapy (NRT) is not a contraindication to surgery. There is no evidence that NRT degrades the wound-healing benefits of abstinence from smoking in humans. NRT offers benefits over continued smoking. NRT typically provides less nicotine than cigarettes, and nearly doubles the chance of smoking abstinence.

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