Spinal cord stimulation: a 20-year retrospective analysis in 260 patients

Novel Pulsed Ultrahigh-frequency Spinal Cord Stimulation Inhibits Mechanical Hypersensitivity and Brain Neuronal Activity in Rats after Nerve Injury

BACKGROUND

Spinal cord stimulation (SCS) is an important pain treatment modality. This study hypothesized that a novel pulsed ultrahigh-frequency spinal cord stimulation (pUHF-SCS) could safely and effectively inhibit spared nerve injury-induced neuropathic pain in rats.

METHODS

Epidural pUHF-SCS (± 3V, 2-Hz pulses comprising 500-kHz biphasic sinewaves) was implanted at the thoracic vertebrae (T9 to T11). Local field brain potentials after hind paw stimulation were recorded. Analgesia was evaluated by von Frey-evoked allodynia and acetone-induced cold allodynia.

RESULTS

The mechanical withdrawal threshold of the injured paw was 0.91 ± 0.28 g lower than that of the sham surgery (24.9 ± 1.2 g). Applying 5-, 10-, or 20-min pUHF-SCS five times every 2 days significantly increased the paw withdrawal threshold to 13.3 ± 6.5, 18.5 ± 3.6, and 21.0 ± 2.8 g at 5 h post-SCS, respectively (P = 0.0002, < 0.0001, and < 0.0001; n = 6 per group) and to 6.1 ± 2.5, 8.2 ± 2.7, and 14.3 ± 5.9 g on the second day, respectively (P = 0.123, 0.013, and < 0.0001). Acetone-induced paw response numbers decreased from pre-SCS (41 ± 12) to 24 ± 12 and 28 ± 10 (P = 0.006 and 0.027; n = 9) at 1 and 5 h after three rounds of 20-min pUHF-SCS, respectively. The areas under the curve from the C component of the evoked potentials at the left primary somatosensory and anterior cingulate cortices were significantly decreased from pre-SCS (101.3 ± 58.3 and 86.9 ± 25.5, respectively) to 39.7 ± 40.3 and 36.3 ± 20.7 (P = 0.021, and 0.003; n = 5) at 60 min post-SCS, respectively. The intensity thresholds for pUHF-SCS to induce brain and sciatic nerve activations were much higher than the therapeutic intensities and thresholds of conventional low-frequency SCS.

CONCLUSIONS

Pulsed ultrahigh-frequency spinal cord stimulation inhibited neuropathic pain-related behavior and paw stimulation evoked brain activation through mechanisms distinct from low-frequency SCS.

EDITOR’S PERSPECTIVE

Is Thoracic Paddle Lead Spinal Cord Stimulator Implantation Safe in an Ambulatory Surgery Center?

OBJECTIVE

Spinal cord stimulation is an effective treatment modality for chronic pain. Although percutaneous leads are commonly placed in the outpatient setting, paddle leads are typically implanted in the inpatient setting. Given the substantial cost savings associated with the ambulatory setting, we aimed to demonstrate the feasibility and safety of thoracic paddle lead implantation in a freestanding ambulatory surgery center (ASC).

METHODS

Consecutive patients undergoing thoracic paddle lead implantation at a single freestanding ASC from January 2015 to December 2020 were queried. Demographic, perioperative, and outcome data were collected. Primary outcomes were incidence of intraoperative or immediate postoperative complications and need for inpatient transfer. Secondary outcomes included readmission at 30 and 90 days and reoperation at 30 days, 90 days, and 1 year.

RESULTS

A total of 46 patients underwent ambulatory thoracic paddle lead implantation over the study period. Two patients (4.3%) suffered an immediate postoperative complication requiring return to surgery at the ASC-one for an epidural hematoma, and one for a flank hematoma. All but one patient (97.8%) were discharged home on the day of surgery. The overall 30- and 90-day readmission rates were 4.3% and 6.5%, respectively. One patient (2.2%) required reoperation for a mechanical complication. No device-related infections were noted during the follow-up period.

CONCLUSIONS

Thoracic laminotomy for paddle lead spinal cord stimulator implantation can be performed in a freestanding ASC with complication rates comparable to the hospital setting. Future comparative studies that assess clinical outcomes and cost are necessary to determine the cost-effectiveness of the ambulatory setting.

Long-Term Outcome of Spinal Cord Stimulation in Complex Regional Pain Syndrome

BACKGROUND

Spinal cord stimulation (SCS) is an effective treatment in chronic neuropathic pain, but its efficacy in complex regional pain syndrome (CRPS) needs to be proven.

OBJECTIVE

To study the outcome of SCS in CRPS as measured by trial success, explantation rate, complications, and changes in opioid and neuropathic pain medication use over a 4-yr follow-up.

METHODS

We retrospectively reviewed all medical records of 35 consecutive CRPS patients who underwent SCS trials at 2 hospitals during January 1998 to December 2016. The purchase data of opioids and neuropathic pain medication during January 1995 to March 2016 were retrieved from national registries.

RESULTS

Based on a 1-wk trial, permanent SCS was implanted in 27 (77%) patients. During the median follow-up of 8 yr, 8 (30%) SCS devices were explanted, of which 7 were because of inefficient pain relief. Complications leading to revision occurred in 17 (63%) patients: 8 electrode migrations or stimulation to the wrong area, 1 deep infection, 9 hardware malfunctions, 2 pulse generator discomforts, and 2 SCS replacements. None of the 6 patients using strong opioids discontinued their use during the 2-yr follow-up. The mean opioid dose increased nonsignificantly both in patients with SCS in permanent use (53 ± 150 morphine milligram equivalents morphine milligram equivalent (MME)/day to 120 ± 240 MME/day) and in patients who had SCS explanted (27 ± 72 MME/day to 57 ± 66 MME/day).

CONCLUSION

Despite the fact that CRPS patients were not able to discontinue or reduce their strong opioid or neuropathic pain medication use, 70% continued to use their SCS device during a median 8-yr follow-up.

Acute Pain Management of Chronic Pain Patients in Ambulatory Surgery Centers

PURPOSE OF REVIEW

With the widespread growth of ambulatory surgery centers (ASCs), the number and diversity of operations performed in the outpatient setting continue to increase. In parallel, there is an increase in the proportion of patients with a history of chronic opioid use and misuse undergoing elective surgery. Patients with such opioid tolerance present a unique challenge in the ambulatory setting, given their increased requirement for postoperative opioids. Guidelines for managing perioperative pain, anticipating postoperative opioid requirements and a discharge plan to wean off of opioids, are therefore needed.

RECENT FINDINGS

Expert guidelines suggest using multimodal analgesia including non-opioid analgesics and regional/neuraxial anesthesia whenever possible. However, there exists variability in care, resulting in challenges in perioperative pain management. In a recent study of same-day admission patients, anesthesiologists correctly identified most opioid-tolerant patients, but used non-opioid analgesics only half the time. The concept of a focused ambulatory pain specialist on site at each ASC has been suggested, who in addition to providing safe anesthesia, could intervene early once problematic pain issues are recognized. This review focuses on perioperative pain management in three subsets of patients who exhibit opioid tolerance: those on large doses of opioids (including abuse-deterrent formulations) for chronic non-malignant or malignant pain; those who have ongoing opioid misuse; and those who were prior addicts and are now on methadone/suboxone maintenance. We also discuss perioperative pain management for patients who have implanted devices such as spinal cord stimulators and intrathecal pain pumps.

Neuromodulation for Refractory Angina, Heart Failure and Peripheral Vascular Disease

Use of spinal cord stimulation (SCS) has expanded beyond pain control. There are increasing indications in which SCS is being used. The understanding of central and peripheral neural pathways and their controlling influences on peripheral organs is better understood now. The concept of stimulating the spinal cord and modulating central pathways with SCS is already established. Different studies have shown the benefit with SCS on visceral pain control, improving quality of live in severe peripheral vascular disease and even assist in controlling the vago-sympathetic balance. We will discuss the art of implantation. Patient selection and stimulation with respect to current clinical data.

Active Recharge Burst and Tonic Spinal Cord Stimulation Engage Different Supraspinal Mechanisms: A Functional Magnetic Resonance Imaging Study in Peripherally Injured Chronic Neuropathic Rats

OBJECTIVES

To assess the supraspinal working mechanisms of the burst spinal cord stimulation (SCS) mode, we used functional magnetic resonance imaging (fMRI) in chronic neuropathic rats. We hypothesized that active recharge burst SCS would induce a more profound blood oxygenation level-dependent (BOLD) signal increase in areas associated with cognitive-emotional aspects of pain, as compared to tonic SCS.

METHODS

Sprague Dawley rats (n = 17) underwent a unilateral partial sciatic nerve ligation, which resulted in chronic neuropathic pain. Quadripolar SCS electrodes were epidurally positioned on top of the dorsal columns at Th13. Isoflurane-anesthetized (1.5%) rats received either tonic SCS (n = 8) or burst SCS (n = 9) at 66% of motor threshold. BOLD fMRI was conducted before, during, and after SCS using a 9.4-T horizontal bore scanner.

RESULTS

Overall, both tonic and burst SCS induced a significant increase of BOLD signal levels in areas associated with the location and intensity of pain, and areas associated with cognitive-emotional aspects of pain. Additionally, burst SCS significantly increased BOLD signal levels in the raphe nuclei, nucleus accumbens, and caudate putamen. Tonic SCS did not induce a significant increase in BOLD signal levels in these areas.

CONCLUSIONS

In conclusion, active recharge burst and tonic SCS have different effects on the intensity and localization of SCS-induced activation responses in the brain. This work demonstrates that active recharge burst is another waveform that can engage brain areas associated with cognitive-emotional aspects of pain as well as areas associated with location and intensity of pain. Previous studies showing similar engagement used only passive recharge burst.

Burst and Tonic Spinal Cord Stimulation Both Activate Spinal GABAergic Mechanisms to Attenuate Pain in a Rat Model of Chronic Neuropathic Pain

BACKGROUND

Experimental and clinical studies have shown that tonic spinal cord stimulation (SCS) releases gamma-aminobutyric acid (GABA) in the spinal dorsal horn. Recently, it was suggested that burst SCS does not act via spinal GABAergic mechanisms. Therefore, we studied spinal GABA release during burst and tonic SCS, both anatomically and pharmacologically, in a well-established chronic neuropathic pain model.

METHODS

Animals underwent partial sciatic nerve ligation (PSNL). Quantitative immunohistochemical (IHC) analysis of intracellular GABA levels in the lumbar L4 to L6 dorsal spinal cord was performed after 60 minutes of burst, tonic, or sham SCS in rats that had undergone PSNL (n = 16). In a second pharmacological experiment, the effects of intrathecal administration of the GABA_A antagonist bicuculline (5 μg) and the GABA_B antagonist phaclofen (5 μg) were assessed. Paw withdrawal thresholds to von Frey filaments of rats that had undergone PSNL (n = 20) were tested during 60 minutes of burst and tonic SCS 30 minutes after intrathecal administration of the drugs.

RESULTS

Quantitative IHC analysis of GABA immunoreactivity in spinal dorsal horn sections of animals that had received burst SCS (n = 5) showed significantly lower intracellular GABA levels when compared to sham SCS sections (n = 4; P = 0.0201) and tonic SCS sections (n = 7; P = 0.0077). Intrathecal application of the GABA_A antagonist bicuculline (5 μg; n = 10) or the GABA_B antagonist phaclofen (5 μg; n = 10) resulted in ablation of the analgesic effect for both burst SCS and tonic SCS.

CONCLUSIONS

In conclusion, our anatomical and pharmacological data demonstrate that, in this well-established chronic neuropathic animal model, the analgesic effects of both burst SCS and tonic SCS are mediated via spinal GABAergic mechanisms.

Drivers and Risk Factors of Unplanned 30-Day Readmission Following Spinal Cord Stimulator Implantation

OBJECTIVES

Unplanned 30-day readmission rates contribute significantly to growing national healthcare expenditures. Drivers of unplanned 30-day readmission after spinal cord stimulator (SCS) implantation are relatively unknown. The aim of this study was to determine drivers of 30-day unplanned readmission following SCS implantation.

METHODS

The National Readmission Database was queried to identify all patients who underwent SCS implantation for the 2013 calendar year. Patients were grouped by readmission status, "No Readmission" and "Unplanned 30-day Readmission." Patient demographics and comorbidities were collected for each patient. The primary outcome of interest was the rate of unplanned 30-day readmissions and associated driving factors. A multivariate analysis was used to determine independent predictors of unplanned 30-day readmission after SCS implantation.

RESULTS

We identified 1521 patients who underwent SCS implantation, with 113 (7.4%) experiencing an unplanned readmission within 30 days. Baseline patient demographics, comorbidities, and hospital characteristics were similar between both cohorts. The three main drivers for 30-day readmission after SCS implantation include: 1) infection (not related to SCS device), 2) infection due to device (limited to only hardware infection), and 3) mechanical complication of SCS device. Furthermore, obesity was found to be an independent predictor of 30-day readmission (OR: 1.86, p = 0.008).

CONCLUSION

Our study suggests that infectious and mechanical complications are the primary drivers of unplanned 30-day readmission after SCS implantation, with obesity as an independent predictor of unplanned readmission. Given the technological advancements in SCS, repeated studies are necessary to identify factors associated with unplanned 30-day readmission rates after SCS implantation to improve patient outcomes and reduce associated costs.

Prevalence and Cost Analysis of Complex Regional Pain Syndrome (CRPS): A Role for Neuromodulation

OBJECTIVE

The diagnosis and treatment of complex regional pain syndrome (CRPS) is challenging and there is a paucity of data describing its overall cost burden and quantifying its impact on the US healthcare system. The aim of this study was to assess the prevalence and healthcare utilization costs associated with CRPS.

MATERIALS AND METHODS

A retrospective longitudinal study was performed using the Truven MarketScan® database to identify patients with a new indexed diagnosis of CRPS (Type I, II, or both) from 2001 to 2012. We collected total, outpatient, and pain prescription costs three years prior to CRPS diagnosis (baseline), at year of CRPS diagnosis, and eight-year post-CRPS diagnosis. A longitudinal multivariate analysis was used to model the estimated total and pain prescription cost ratios comparing patients diagnosed before and after CRPS.

RESULTS

We included 35,316 patients with a newly indexed diagnosis of CRPS (Type I: n = 18,703, Type II: n = 14,599, Unspecified: n = 2014). Baseline characteristics were similar between the CRPS cohorts. Compared to two- and three-year baseline costs, one-year prior to diagnosis for all CRPS patients yielded the highest interquartile median [IQR] costs: total costs $7904[$3469, $16,084]; outpatient costs $6706[$3119, $12,715]; and pain prescription costs $1862[$147, $7649]. At the year of CRPS diagnosis, the median [IQR] costs were significantly higher than baseline costs: total costs $8508[$3943, $16,666]; outpatient costs $7251[$3527, $13,568]; and pain prescription costs $2077[$140, $8856]. Over the eight-year period after CRPS diagnosis, costs between all the years were similar, ranging from the highest (one-year) to lowest (seven-years), $4845 to $3888. The median total cumulative cost 8-years after CRPS diagnosis was $43,026 and $12,037 for pain prescription costs. [Correction added on 06 November 2017 after first online publication: the preceding sentence has been updated to demonstrate the median cumulative cost in replacement of the additive cumulative mean costs.]. During the CRPS diagnosis period, patients are expected to have a total cost 2.17-fold and prescription cost 2.56-fold of their baseline cost annually.

CONCLUSIONS

Our study demonstrates that there is a significant increase in cost and healthcare resource utilization one-year prior to and around the time of CRPS diagnosis. Furthermore, there is an increased annual cost post-diagnosis compared to baseline costs prior to CRPS diagnosis.

A Comprehensive Outcome-Specific Review of the Use of Spinal Cord Stimulation for Complex Regional Pain Syndrome

BACKGROUND

Complex regional pain syndrome (CRPS) is a painful, debilitating affliction that is often difficult to treat. It has become common international practice to use spinal cord stimulation (SCS) for the treatment of CRPS as other therapies fail to provide adequate relief, quality of life, or improvement in function. This comprehensive outcome-specific systematic review of the use of SCS for CRPS was performed to elucidate the available evidence with focus on clinically relevant patient-specific outcomes.

METHODS

A systematic review of the literature was conducted to evaluate the effects of SCS on patients with CRPS for the following outcomes and provide summary levels of evidence in regard to each outcome: perceived pain relief, pain score, resolution of CRPS signs, functional status, quality of life, psychological impact, sleep hygiene, analgesic medication utilization, and patient satisfaction with SCS therapy. Search terms included "complex regional pain syndrome," "spinal cord stimulation," and "reflex sympathetic dystrophy," without restriction of language, date, or type of publication, albeit only original data were included in analyses. Of 30 studies selected, seven systematic reviews were excluded, as were four studies reporting combination therapy that included SCS and other therapies (ie, concurrent peripheral nerve stimulation, intrathecal therapy) without clear delineation to the effect of SCS alone on outcomes. A total of 19 manuscripts were evaluated.

RESULTS

Perceived pain relief, pain score improvement, quality of life, and satisfaction with SCS were all rated 1B+, reflecting positive high-level (randomized controlled trial) evidence favoring SCS use for the treatment of CRPS. Evidence for functional status improvements and psychological effects of SCS was inconclusive, albeit emanating from a randomized controlled trial (evidence level 2B±), and outcomes evidence for both sleep hygiene and resolution of CRPS signs was either nonexistent or of too low quality from which to draw conclusions (evidence level 0). An analgesic sparing effect was observed in nonrandomized reports, reflecting an evidence level of 2C+.

CONCLUSIONS

Spinal cord stimulation remains a favorable and effective modality for treating CRPS with high-level evidence (1B+) supporting its role in improving CRPS patients' perceived pain relief, pain score, and quality of life. A paucity of evidence for functional improvements, resolution of CRPS signs, sleep hygiene, psychological impact, and analgesic sparing effects mandate further investigation before conclusions can be drawn for these specific outcomes.

Basic science and clinical management of painful and non-painful chemotherapy-related neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting toxicity of several chemotherapeutics used in the treatment of all the most common malignancies. There are several defined mechanisms of nerve damage that take place along different areas of the peripheral and the central nervous system. Treatment is based on symptom management and there are several classes of medications found to be efficacious in the treatment of neuropathic pain. Neuropathic pain that persists despite appropriate pharmacotherapy may respond to interventional procedures that span a range of invasiveness. The purpose of this review article is to examine the basic science of neuropathy and currently available treatment options in the context of chemotherapy induced peripheral neuropathy.

Spinal cord stimulation for chronic limb ischemia

The treatment of chronic limb ischemia involves the restoration of pulsatile blood flow to the distal extremity. Some patients cannot be treated with endovascular means or with open surgery; some may have medical comorbidities that render them unfit for surgery, while others may have persistent ischemia or pain even in the face of previous attempts at reperfusion. In spinal cord stimulation (SCS), a device with electrodes is implanted in the epidural space to stimulate sensory fibers. This activates cell-signaling molecules that in turn cause the release of vasodilatory molecules, a decrease in vascular resistance, and relaxation of smooth muscle cells. SCS also suppresses sympathetic vasoconstriction and pain transmission. When patient selection is based on microcirculatory parameters, SCS therapy can significantly improve pain relief, halt the progression of ulcers, and potentially achieve limb salvage.