Scrambler therapy: what's new after 15 years? The results from 219 patients treated for chronic pain

The Use of Scrambler Therapy in Treating Chronic Pain Syndromes: A Systematic Review

BACKGROUND

Scrambler therapy (ST) is a noninvasive method of transcutaneous neuromodulation that has 510(K) clearance from the United States Food and Drug Administration for treating acute pain, postoperative pain, and intractable chronic pain. Since its inception, ST has been used to treat many chronic pain syndromes in a variety of patient populations. We synthesized the available literature for ST to delineate its overall evidence basis.

MATERIALS AND METHODS

We performed a systematic review based on conventional Preferred Reporting Items for Systematic Reviews and Meta-Analyses methods by surveying multiple data sources from January 1950 through October 2021. Two review authors, independently and in a standardized, unblinded fashion, conducted a systematic review to identify relevant studies and extract the necessary outcome measures. A conservative search strategy was implemented to identify all ST studies for the treatment of chronic pain syndromes. Primary outcome parameters collected were analgesic benefit, adverse effects, and other metrics such as sensorimotor testing.

RESULTS

A total of 21 studies met the final criteria for study inclusion and comprised randomized controlled trials (n = 8), prospective observational studies (n = 10), and retrospective cohort studies (n = 3). Nearly all the reported studies explored the use of ST for the treatment of neuropathic pain, with chemotherapy-induced peripheral neuropathy being the most studied condition. Most studies were limited by small cohorts but reported ST being safe, well tolerated, and providing clinically meaningful pain reduction. The duration of posttreatment follow-up ranged from ten to 14 days (concordant with completion of typical ST protocols) to three months. Secondary benefits such as medication reduction and improvement of sensory and motor symptoms were noted by some studies.

CONCLUSIONS

ST is regarded as a safe intervention with potential for significant analgesic benefit for neuropathic pain conditions. Although the available evidence is most robust for treating chemotherapy-induced peripheral neuropathy, ST has also been shown to be effective in treating other neuropathic pain syndromes. Evidence for ST use in nociceptive pain conditions is limited but appears promising. The favorable safety profile and increasing evidence basis for ST warrant more extensive recognition and consideration for use in clinical care.

Efficacy of scrambler therapy in patients with painful diabetic peripheral neuropathy: A single-arm, prospective, pilot study

BACKGROUND

A variety of medications are available to manage painful diabetic peripheral neuropathy (DPN), but the proper treatment remains challenging. Accordingly, various neuromodulation modalities have been used. However, no prospective clinical trials have evaluated the use of scrambler therapy (ST) in painful DPN. This study aimed to explore the long-term effects of ST in managing painful DPN.

METHODS

The patients received 10 consecutive STs of 45 minutes every 1 to 2 days. The primary outcome was pain score. We measured the visual analog scale (VAS) pain scores at baseline, during ST, immediately after ST, and at 1, 2, 3, and 6 months after ST. The secondary outcomes were Michigan Neuropathy Screening Instrument (MNSI), Semmes-Weinstein monofilament test, and Leeds Assessment of Neuropathic Symptoms and Signs pain scores, which were measured at baseline, immediately after ST, and at 1, 2, 3, and 6 months after ST.

RESULTS

VAS scores showed significant improvement at the 8th, 9th, and 10th sessions during ST and 1 month after ST. The MNSI self-report component score was decreased 1 month after the ST. However, all other outcomes did not show significant differences compared to the baseline.

CONCLUSION

ST may have short-term effects and limited long-term effects on painful DPN.

Scrambler Therapy for Patients With Complex Regional Pain Syndrome: A Case Series

Complex regional pain syndrome is a chronic debilitating pain disorder that is difficult to manage, in part due to its heterogeneous clinical presentation and lack of clearly defined pathophysiology. Patients usually require a multidisciplinary approach to treatment, which can entail pharmacotherapy, physical therapy, behavioral therapy, and interventional pain procedures, such as sympathetic nerve blocks, spinal cord stimulation, and dorsal root ganglion stimulation. However, many patients continue to experience pain refractory to these multimodal strategies. Scrambler therapy (ST) is a noninvasive method of neuromodulation that is applied through cutaneous electrodes, and can alleviate chronic neuropathic pain by stimulating C-fibers and replacing endogenous pain signals with synthetic non-nociceptive signals. Although the use of ST has been reported for several types of refractory central and peripheral neuropathic pain, there is a paucity of data regarding the use of ST for complex regional pain syndrome. We present two patients with complex regional pain syndrome of the right lower extremity, who each underwent ST and experienced significant pain relief and improvement in function and quality of life.

Complex Regional Pain Syndrome: Evidence-Based Advances in Concepts and Treatments

PURPOSE OF REVIEW

This review presents the most current information about the epidemiology of complex regional pain syndrome (CRPS), classification and diagnostic criteria, childhood CRPS, subtypes, pathophysiology, conventional and less conventional treatments, and preventive strategies.

RECENT FINDINGS

CRPS is a painful disorder with multifactorial pathophysiology. The data describe sensitization of the central and peripheral nervous systems, inflammation, possible genetic factors, sympatho-afferent coupling, autoimmunity, and mental health factors as contributors to the syndrome. In addition to conventional subtypes (type I and type II), cluster analyses have uncovered other proposed subtypes. Prevalence of CRPS is approximately 1.2%, female gender is consistently associated with a higher risk of development, and substantial physical, emotional, and financial costs can result from the syndrome. Children with CRPS seem to benefit from multifaceted physical therapy leading to a high percentage of symptom-free patients. The best available evidence along with standard clinical practice supports pharmacological agents, physical and occupational therapy, sympathetic blocks for engaging physical restoration, steroids for acute CRPS, neuromodulation, ketamine, and intrathecal baclofen as therapeutic approaches. There are many emerging treatments that can be considered as a part of individualized, patient-centered care. Vitamin C may be preventive. CRPS can lead to progressively painful sensory and vascular changes, edema, limb weakness, and trophic disturbances, all of which substantially erode healthy living. Despite some progress in research, more comprehensive basic science investigation is needed to clarify the molecular mechanisms of the disease so that targeted treatments can be developed for better outcomes. Incorporating a variety of standard therapies with different modes of action may offer the most effective analgesia. Introducing less conventional approaches may also be helpful when traditional treatments fail to provide sufficient improvement.

Safety of Scrambler Therapy: A Systematic Review of Complications and Adverse Effects

OBJECTIVE

The objective was to qualitatively synthesize all reported cases of complications, adverse effects, side effects, or harms arising from the use of scrambler therapy (ST).

METHODS AND DESIGN

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The PubMed, Embase, Scopus, Web of Science, United States National Library of Medicine clinical trials registry, and Cochrane Central Register of Controlled Trials databases were searched from database inception to December 10, 2021. Case reports/series, abstracts, retrospective studies, and prospective studies (e.g., open-label trials, randomized controlled trials) pertaining to ST and any description of a complication, adverse effect, side effect, or harm were screened. The search protocol was developed a priori and registered via the International Prospective Register of Systematic Reviews (PROSPERO ID: CRD42021291838).

RESULTS

A total of six RCTs, 19 prospective open-label trials, and 11 case series / case reports met the inclusion criteria, comprising 1,152 total patients. Two patients experienced contact dermatitis, and one patient reported minor ecchymosis that resolved without intervention. This yielded a composite complication rate of 0.26% (3/1,152). There were zero reported serious adverse events.

CONCLUSIONS

When used in accordance with the treatment protocols described by the United States Food and Drug Administration and device manual, ST is associated with a reported composite complication rate that is orders of magnitude lower than those of invasive neuromodulation devices. ST neuromodulation is a safe alternative for patients who cannot undergo invasive neuromodulation device implantation because of either risk or preference.

Scrambler therapy for noncancer neuropathic pain: a focused review

PURPOSE OF REVIEW

Therapeutic methods for neuropathic are limited; available drugs can be inadequate or have adverse effects that compromise quality of life. Interest has grown in alternatives to pharmacologic therapy for neuropathic pain. We present a focused review of the literature about the relatively novel noninvasive, nonpharmacologic electrocutaneous nerve stimulation technique called scrambler therapy for treating noncancer neuropathic pain.

RECENT FINDINGS

Neuromodulation techniques targeting peripheral sites have changed rapidly in recent years. Several clinical studies have demonstrated the analgesic effect of scrambler therapy after 10 sessions of treatment for various types of pain. Although scrambler therapy was originally used for cancer pain, its indications have broadened to postoperative pain, chemotherapy-induced peripheral neuropathy, postherpetic neuralgia, low back pain, diabetic neuropathy, complex regional pain syndrome and central pain syndrome. That said, some of the studies are controversial owing to their small sample size, lack of appropriate scrambler therapy protocol and possible lack of experience of the operators.

SUMMARY

We present the historical perspective, mechanism of action and trial outcomes of scrambler therapy, representing an avenue for managing neuropathic pain without drugs. Well designed phase II/III clinical trials must be conducted to confirm the positive findings reported using scrambler therapy technology. If validated, scrambler therapy could be a game changer.

Differential response to scrambler therapy by neuropathic pain phenotypes

Scrambler therapy is a noninvasive electroanalgesia technique designed to remodulate the pain system. Despite growing evidence of its efficacy in patients with neuropathic pain, little is known about the clinical factors associated with treatment outcome. We conducted a prospective, open-label, single-arm trial to assess the efficacy and safety of scrambler therapy in patients with chronic neuropathic pain of various etiologies. A post-hoc analysis was performed to investigate whether cluster analysis of the Neuropathic Pain Symptom Inventory (NPSI) profiles could identify a subgroup of patients regarding neuropathic pain phenotype and treatment outcome. Scrambler therapy resulted in a significant decrease in the pain numerical rating scale (NRS) score over 2 weeks of treatment (least squares mean of percentage change from baseline, − 15%; 95% CI − 28% to − 2.4%; p < 0.001). The mean score of Brief Pain Inventory (BPI) interference subdimension was also significantly improved (p = 0.022), while the BPI pain composite score was not. Hierarchical clustering based on the NPSI profiles partitioned the patients into 3 clusters with distinct neuropathic pain phenotypes. Linear mixed-effects model analyses revealed differential response to scrambler therapy across clusters (p = 0.003, pain NRS; p = 0.072, BPI interference subdimension). Treatment response to scrambler therapy appears different depending on the neuropathic pain phenotypes, with more favorable outcomes in patients with preferentially paroxysmal pain rather than persistent pain. Further studies are warranted to confirm that capturing neuropathic pain phenotypes can optimize the use of scrambler therapy.

Scrambler therapy for incident pain in bone metastases

Incident pain, described as pain induced by bone metastasis and produced by movement, can be devastating. The high doses of opioids needed to control such pain may sedate the patient and cause additional complications. Treatment of incident pain with pharmaceuticals has rarely been studied; only eight patients have been reported in the literature who did not receive additional opioids. We present the case of a 69 year old man with shoulder destruction due to bone metastases who was able to use his arm for normal activities without pain after three sessions of scrambler therapy, a noninvasive form of electrical neuromodulation that requires further study.

NCCN Guidelines Insights: Survivorship, Version 2.2019

The NCCN Guidelines for Survivorship provide screening, evaluation, and treatment recommendations for consequences of cancer and cancer treatment to aid healthcare professionals who work with survivors of adult-onset cancer. Guidance is also provided to help promote physical activity, weight management, and proper immunizations in survivors and to facilitate care coordination to ensure that all needs are addressed. These NCCN Insights summarize some of the topics discussed by the NCCN Survivorship Panel during the 2019 update of the guidelines, including the survivorship population addressed, ways to improve care coordination, and pain management.