The predictive value of sympathetic block for the success of spinal cord stimulation

Evaluation of thoracic sympathetic ganglion block as a predictor for response to ketamine infusion therapy and spinal cord stimulation in patients with chronic upper extremity pain

OBJECTIVE

To investigate the predictive value of thoracic sympathetic ganglion block (TSGB) in response to ketamine infusion therapy (KIT) and spinal-cord stimulation (SCS) in patients with chronic upper-extremity pain including complex regional pain syndrome (CRPS).

DESIGN

Retrospective.

SETTING

Tertiary hospital single-center.

SUBJECTS

Patients who underwent TSGB receiving KIT or SCS within a 3-year window.

METHODS

Positive TSGB outcomes were defined as ≥2 0-10 Numerical Rating Scale (NRS) score reduction at 2 weeks post-procedure. Positive KIT and SCS outcomes were determined by ≥2 NRS score reduction at 2-4 weeks post-KIT and ≥4 NRS score reduction at 2-4 weeks post-SCS implantation, respectively.

RESULTS

Among 207 patients who underwent TSGB, 38 received KIT and 34 underwent SCS implantation within 3 years post-TSGB; 33 patients receiving KIT and 32 patients receiving SCS were included. Among 33 patients who received KIT, 60.6% (n = 20) reported a ≥ 2 0-10 NRS pain-score reduction. Positive response to TSGB occurred in 70.0% (n = 14) KIT responders, significantly higher than that in 30.8% (n = 4) KIT non-responders. Multivariable analysis revealed a positive association between positive responses to TSGB and KIT (OR 7.004, 95% CI 1.26-39.02). Among 32 patients who underwent SCS implantation, 68.8% (n = 22) experienced short-term effectiveness. Positive response to TSGB was significantly higher in SCS responders (45.5%, n = 10) than in non-responders (0.0%). However, there were no associations between pain reduction post-TSGB and that post-KIT or post-SCS.

CONCLUSIONS

A positive response to TSGB is a potential predictor for positive KIT and SCS outcomes among patients with chronic upper-extremity pain, including CRPS.

Spinal Cord Stimulation for Intractable Visceral Pain Originating from the Pelvic and Abdominal Region: A Narrative Review on a Possible New Indication for Patients with Therapy-Resistant Pain

Aim

Visceral pain, characterized by pain that is diffuse and challenging to localize, occurs frequently and is difficult to treat. In cases where the pain becomes intractable despite optimal medical management, it can affect patients' Quality of Life (QoL). Spinal Cord Stimulation (SCS) has emerged as a potential solution for intractable visceral pain.

Purpose

In this narrative review, we collected all evidence regarding the efficacy of SCS for visceral pain across various underlying conditions.

Methods

A comprehensive literature search was conducted in PubMed, Embase, and Web of Science in which articles published from October 1st, 1963 up to March 7th, 2023 were identified.

Results

Seventy articles were included in this review of which most were retrospective cohort studies, case series and case reports. The studies, often with a small number of participants, reported on SCS for chronic pancreatitis, anorectal pain and bowel disorders, gynaecological diagnoses, visceral pelvic pain, urological disorders and finally general visceral pain. They found positive effects on pain and/or symptom relief, opioid consumption, anxiety and depression and QoL. Complications occurred frequently but were often minor and reversible.

Conclusion

Better screening and selection criteria need to be established to optimally evaluate eligible patients who might benefit from SCS. A positive outcome of a sympathetic nerve block appears to be a potential indicator of SCS effectiveness. Additionally, women receiving SCS for endometriosis had a better outcome compared to other indications. Finally, SCS could also relief functional symptoms such as voiding problems and gastroparesis. Complications could often be resolved with revision surgery. Since SCS is expensive and not always covered by standard health insurance, the incorporation of cost-analyses is recommended. In order to establish a comprehensive treatment plan, including selection criteria for SCS, rigorous prospective, possibly randomized and controlled studies that are diagnosis-oriented, with substantial follow-up and adequate sample sizes, are needed.

Sympathetic Blocks as a Predictor for Response to Ketamine Infusion in Patients with Complex Regional Pain Syndrome: A Multicenter Study

BACKGROUND

Ketamine infusions are frequently employed for refractory complex regional pain syndrome (CRPS), but there are limited data on factors associated with treatment response. Sympathetic blocks are also commonly employed in CRPS for diagnostic and therapeutic purposes and generally precede ketamine infusions.

OBJECTIVES

We sought to determine whether demographic and clinical factors, and technical and psychophysical characteristics of sympathetic blocks are associated with response to ketamine infusion.

METHODS

In this multi-center retrospective study, 71 patients who underwent sympathetic blocks followed by ketamine infusions at 4 hospitals were evaluated. Sympathetically maintained pain (SMP) was defined as ≥ 50% immediate pain relief after sympathetic block and a positive response to ketamine was defined as ≥ 30% pain relief lasting over 3 weeks.

RESULTS

Factors associated with a positive response to ketamine in univariable analysis were the presence of SMP (61.0% success rate vs 26.7% in those with sympathetically independent pain; P = .009) and post-block temperature increase (5.66 ± 4.20 in ketamine responders vs 3.68 ± 3.85 in non-responders; P = .043). No psychiatric factor was associated with ketamine response. In multivariable analysis, SMP (OR 6.54 [95% CI 1.83, 23.44]) and obesity (OR 8.75 [95% 1.45, 52.73]) were associated with a positive ketamine infusion outcome.

CONCLUSIONS

The response to sympathetic blocks may predict response to ketamine infusion in CRPS patients, with alleviation of the affective component of pain and predilection to a positive placebo effect being possible explanations.

Outcomes of Sympathetic Blocks in the Management of Complex Regional Pain Syndrome

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Sympathetic dysfunction may be present in complex regional pain syndrome, and sympathetic blocks are routinely performed in practice. To investigate the therapeutic and predictive values of sympathetic blocks, the authors test the hypotheses that sympathetic blocks provide analgesic effects that may be associated with the temperature differences between the two extremities before and after the blocks and that the effects of sympathetic blocks may predict the success (defined as achieving more than 50% pain reduction) of spinal cord stimulation trials.

Methods

The authors performed a retrospective study of 318 patients who underwent sympathetic blocks in a major academic center (2009 to 2016) to assess the association between pain reduction and preprocedure temperature difference between the involved and contralateral limbs. The primary outcome was pain improvement by more than 50%, and the secondary outcome was duration of more than 50% pain reduction per patient report. The authors assessed the association between pain reduction and the success rate of spinal cord stimulation trials.

Results

Among the 318 patients, 255 were diagnosed with complex regional pain syndrome and others with various sympathetically related disorders. Successful pain reduction (more than 50%) was observed in 155 patients with complex regional pain syndrome (155 of 255, 61%). The majority of patients (132 of 155, 85%) experienced more than 50% pain relief for 1 to 4 weeks or longer. The degree and duration of pain relief were not associated with preprocedure temperature parameters with estimated odds ratio of 1.03 (97.5% CI, 0.95–1.11) or 1.01 (97.5% CI, 0.96–1.06) for one degree decrease (P = 0.459 or 0.809). There was no difference in the success rate of spinal cord stimulation trials between patients with or without more than 50% pain relief after sympathetic blocks (35 of 40, 88% vs. 26 of 29, 90%, P > 0.990).

Conclusions

The authors conclude that sympathetic blocks may be therapeutic in patients with complex regional pain syndrome regardless of preprocedure limb temperatures. The effects of sympathetic blocks do not predict the success of spinal cord stimulation.

Association Between Pain Scores and Successful Spinal Cord Stimulator Implantation

INTRODUCTION

Determining reduction in pain score during spinal cord stimulation (SCS) trial is important prior to permanent SCS implantation. However, this association remains elusive. We investigate the association between post-SCS pain scores and successful permanent SCS implants.

MATERIALS AND METHODS

This IRB-approved, retrospective study identified patients who underwent SCS trials and implantation. Predictive modeling with nonparametric regression and margins plot analysis was used to determine the threshold for post-SCS trial pain scores associated with successful permanent SCS implant (defined as >50% pain relief). Nonparametric sensitivity and specificity analysis was performed. p < 0.05 was considered significant.

RESULTS

Eighty-eight patients with SCS trials were retrospectively identified (57.95% female, median age 52.5 ± 15.5 years). Of the total cohort, 79% had successful permanent SCS implantation. Post-SCS trial pain scores less than or equal to 4.9 had greater than 50% probability of a successful permanent SCS implant (97.14% sensitivity, 44.44% specificity, ROC = 0.71). Post-SCS trial pain scores between 4 and 7 were associated with a significantly higher probability of a successful SCS implant among patients without spine surgery compared with those with a history of spine surgery. Compared with males, females with pain scores between 5 and 7 had a higher probability of a successful SCS implant.

CONCLUSION

Low pain scores after SCS trial are predictive of successful SCS implants with high sensitivity. Males and surgical patients with higher pain scores had a lower probability of successful SCS implant than their counterparts. Larger studies are needed to further elucidate this relationship.

High-Frequency Spinal Cord Stimulation at 10 kHz for the Treatment of Complex Regional Pain Syndrome: A Case Series of Patients With or Without Previous Spinal Cord Stimulator Implantation

BACKGROUND

High-frequency spinal cord stimulation at 10 kHz (HF10-SCS) has been demonstrated to provide enhanced and durable pain relief in patients with chronic back and radiating leg pain. Patients with pain related to complex regional pain syndrome (CRPS) in the chronic stages are commonly challenging to treat and often receive traditional spinal cord stimulation (SCS). Very little information is currently available about the therapeutic outcomes following application of high-frequency stimulation in this cohort of patients.

METHODS

The purpose of the retrospective case series was to report on the initial experience of HF10-SCS in 13 patients with CRPS, some of whom had been exposed to low-frequency SCS. A temporary trial of HF10-SCS was carried out for 1 week, and those achieving a minimum of 50% pain intensity reduction underwent implantation. Successful responders were those who achieved a 50% decrease in pain intensity on subsequent follow-up.

RESULTS

Thirteen patients were trialed, 12 of whom went on to receive a permanent implant. Of the patients receiving permanent implants, the responder rate (50% pain relief) was 67% (95% confidence interval [CI] 0.34 to 0.90), with an average follow-up period of 12.1 ± 4.6 months. Of the 5 patients who had sympathetically independent pain, 3 were responders, and of the 7 patients who had sympathetically mediated pain, 5 were responders. There were no adverse events.

CONCLUSION

This small case series suggests that HF10-SCS may be a viable option for patients with CRPS who have chronic intractable pain, including those who had suboptimal results from traditional SCS.

Principles of electrical stimulation and dorsal column mapping as it relates to spinal cord stimulation: an overview

The last 30 years have witnessed the growth of spinal cord stimulation as a treatment modality for an increasing number of chronic pain conditions. In spite of this growth, one of the greatest criticisms is the lack of concrete evidence for the mechanism of action. With the ever increasing enlightenment with regards to the neurophysiology of pain, and the development of more dynamic neuroimaging techniques, the opportunity to better define the mechanism of action of the spinal cord stimulator will continue to expand. In the interim, clinicians will benefit from the consolidation of the available knowledge that will enhance the effective use of the device. This review serves to provide an overview of the key principles of electrical stimulation and dorsal column mapping as it relates to spinal cord stimulation. We aim at enhancing the understanding regarding the basis for successful placement of leads and manipulation of electrical parameters.

Spinal cord stimulation in adolescents with complex regional pain syndrome type I (CRPS-I)

Complex regional pain syndrome type I (CRPS-I) is not uncommon in children, particularly in adolescent girls. Most often, the condition involves a foot and is characterized by spontaneous pain, tactile allodynia and dysautonomic signs. There is usually a history of a minor, local trauma but sometimes no reasonable cause can be identified, and there are no signs of persistent tissue injury giving rise to ongoing nociception. Common analgesics are generally of no benefit, and the standard treatment includes sociopsychological support, physiotherapy, tricyclic antidepressants and antiepileptic drugs, sympathetic blocks (SB), and cognitive-behavioural therapy. For a minority of patients who prove to be resistant to such therapies, spinal cord stimulation (SCS) may be tried. The present study comprises seven girls, 11-14 years of age, presenting with severe, incapacitating and therapy-resistant CRPS-I, who were subjected to SCS. In two of them, percutaneous electrode implantation had to be performed in general anaesthesia. Trial stimulation was performed in all, but one. In two cases, it was not possible to produce paraesthesias that entirely covered the pain area. A pain relieving effect of SCS was usually not reported until after 1-2 weeks of trial stimulation. After another 2-6 weeks, pain alleviation was complete in five of the seven patients, one to eight years after the intervention. In one case, a local infection necessitated the removal of the electrode; nevertheless a few days of trial stimulation produced substantial pain relief that still persists. In four patients, the SCS use was gradually diminished and eventually the device could be removed. The favourable outcome in all seven cases with no or minor remaining symptoms and without severe recurrences illustrates that SCS may also be an efficient treatment in paediatric cases with exceptionally therapy resistant forms of CRPS I.

A multi-center analysis evaluating factors associated with spinal cord stimulation outcome in chronic pain patients

BACKGROUND

In addition to its conventional use as a treatment for refractory neuropathic extremity pain, spinal cord stimulation (SCS) has recently emerged as a possible treatment for visceral and arthritic pain. But concurrent with the expansion of possible conditions amenable to SCS, other studies have questioned the long-term efficacy of SCS for traditional indications. These disparate findings argue strongly for the refinement of selection criteria. The purpose of this study is to identify correlates of outcome for SCS.

METHODS

Data were retrospectively collected on 244 patients who underwent a SCS trial at two academic medical centers. Success was predefined as ≥50% pain relief sustained for ≥6 months. Variables analyzed for their association with outcome included demographics, location of pain, diagnosis, presence of coexisting diseases, pain descriptors, opioid and adjuvant medication use, duration and pain relief during trial, and complications.

RESULTS

The presence of allodynia and/or hyperalgesia correlated with both a positive SCS trial (P = 0.01) and long-term implantation outcome (P = 0.05). History of substance abuse was associated with a negative permanent SCS outcome (P = 0.05) but bore no relationship to trial results. The variable most strongly associated with an SCS outcome was experiencing <50% pain relief during the trial, which strongly presaged a negative result (P < 0.001).

CONCLUSIONS

Although weak associations with outcome were noted for several clinical variables, none was strongly associated with trial and permanent implantation results. The strongest predictor of a negative SCS outcome was obtaining <50% pain relief during the trial period.

Asians differ from non-Hispanic Whites in experimental pain sensitivity

This study examined differences between Asians and non-Hispanic Whites (Whites) in pain sensitivity, and its relationship to mean arterial pressure (MAP) and heart rate (HR). In 30 Whites (50% female) and 30 Asians (50% female), experimental pain sensitivity was assessed with a hand cold pressor task, yielding measures of pain threshold, tolerance, intensity, and unpleasantness. Mean arterial pressure and HR measurements taken at rest and in response to speech stress were assessed. Perceived stress, anxiety, perfectionism, parental criticism, parental expectations and depressive symptoms were also measured. The results indicated that for the cold pain test, Asians demonstrated significantly lower pain threshold and tolerance levels than Whites. Although no ethnic differences were seen for MAP or HR responses to stress, for Whites higher stress MAP levels were correlated with reduced pain sensitivity, while for Asians higher baseline and stress HR levels were correlated with reduced pain sensitivity. Asians reported higher parental expectations and greater parental criticism than Whites. For Asians only, higher levels of perfectionism were related to more depressive symptoms, anxiety and perceived stress. These results indicate that Asian Americans are more sensitive to experimental pain than Whites and suggest ethnic differences in endogenous pain regulatory mechanisms (e.g. MAP and HR). The results may also have implications for understanding ethnic differences in clinical pain.

Advances in treatment of complex regional pain syndrome: recent insights on a perplexing disease

PURPOSE OF REVIEW

The paper is a critical appraisal of recent advances in the treatment of complex regional pain syndrome. Rapidly changing concepts related to the pathophysiology of this disease has transformed its current management and necessitates an updated review of the literature.

RECENT FINDINGS

Chronic regional pain syndrome is a perplexing disease that continues to challenge researchers with respect to its cause and treatment. Recent modification to diagnostic criteria has enabled clinicians to diagnose this disease in a more consistent fashion. Emerging data indicate a possible role of inflammation in the overall pathophysiology and have led to treatment trials with newer anti-inflammatory medications. Certain 'conventional' interventional techniques have been recently scrutinized. A few novel therapeutic options like graded imagery are also outlined.

SUMMARY

Enhanced insight into the pathophysiology of chronic regional pain syndrome has modified current clinical practice and the focus of research. Certain 'standard' therapeutic options for chronic regional pain syndrome have failed the test of time while others have prevailed. New options have recently been evaluated and have shown promising early results. Knowledge of recent advances in chronic regional pain syndrome will help pain physicians provide optimal care to these patients.

Quantitative Sensory Testing for Spinal Cord Stimulation in Patients With Chronic Neuropathic Pain

OBJECTIVE

A prospective pilot study was conducted, attempting to identify objective tests that would help clinicians to assess the efficacy of spinal cord stimulation (SCS) trial preceding permanent device implantation.

SETTING

Four university hospitals in the United States and Israel.

PARTICIPANTS

Thirteen patients with radicular leg pain due to failed back surgery syndrome (FBSS) or leg pain due to complex regional pain syndrome (CRPS) who were candidates for SCS.

METHODS

PARTICIPANTS underwent a series of quantitative sensory tests prior to, and seven days after the initiation of SCS trial. These tests included: vibration threshold (conducted using the VSA 3000; Medoc Inc., Ramat Ishay, Israel), cold threshold, warm threshold, heat pain threshold, phasic heat pain threshold, tonic heat pain threshold (conducted using the TSA 2001; Medoc Inc.), and electrical pain tolerance at 5, 250 and 2000 Hz (administered using the NerveScan 2000; Neurotron, Inc., Baltimore, MD, USA).

RESULTS

Useful data were obtained from 12 patients. The results of the vibration threshold and the tolerance to electrical stimulation at 5 and 250 Hz changed with an SCS trial. These results also correlated with the decision regarding the permanent implantation, which was made independently of them. In contrast, the results of thermal thresholds and tolerance to electrical stimulation at 2000 Hz tests did not change with the SCS trial.

CONCLUSIONS

Our findings, which agree with those of a few other studies, suggest that the vibration threshold and the tolerance to electrical stimulation at 5 and 250 Hz tests can assist the clinician to select the right patients for permanent stimulation.

Neurostimulation for chronic noncancer pain: an evaluation of the clinical evidence and recommendations for future trial designs

Object

Neurostimulation to treat chronic pain includes approved and investigational therapies directed at the spinal cord, thalamus, periaqueductal or periventricular gray matter, motor cortex, and peripheral nerves. Persistent pain after surgery and work-related or neural injuries are common indications for such treatments. In light of the risks, efforts, costs, and expectations associated with neurostimulation therapies, a careful reexamination of the methods used to gather evidence for this treatment’s long-term efficacy is in order.

Methods

The authors combed English-language publications to determine the nature of the evidence supporting the efficacy of neurostimulation therapies for chronic noncancer pain. To formulate recommendations for the design of future studies, the results of their analysis were compared with established guidelines for the evaluation of medical evidence.

Evidence supporting the efficacy of neurostimulation has been collected predominantly from retrospective series or from prospective studies whose design or methods of analysis make them subject to limited interpretation. To date, there has been no successful clinical study focused on establishing the efficacy of neurostimulation for pain and incorporating sufficient numbers of participants, matched control groups, sham stimulation, randomization, prospectively defined end points, and methods for controlling experimental bias. Currently available data provide little support for the common practices of psychological or pharmacological screening or trial stimulation to predict and/or improve long-term results.

Conclusions

These findings do not diminish the value of previous investigations or positive patient experiences and do not mean that the treatments are ineffective; rather, they reveal that new data are required to answer the questions raised in and by previous study data. Future analyses of emerging neurostimulation modalities for pain should, whenever feasible, require unambiguous diagnoses as an entry criterion and should involve the use of randomization, parallel control groups that receive sham stimulation, and blinding of patients, investigators, and device programmers. Given the chronicity of patient symptoms and stimulation therapies, efficacy should be studied for 1 year or longer after device implantation. Meticulous study methods are especially important to evaluate new therapies like motor cortex and occipital nerve stimulation.

Interventional Therapies in the Management of Complex Regional Pain Syndrome

Invasive procedures have long held a place in the therapeutic armamentarium for the management of complex regional pain syndrome (CRPS). However, this has evolved considerably, particularly as research into the mechanisms of CRPS has called into question long-held presumptions about the key role of sympathetic dysfunction in the syndrome. This review summarizes some of the key information currently available about interventional treatments, including nerve blocks, spinal cord and peripheral nerve stimulation, chemical and surgical sympathectomies, and deep brain stimulation. The potential roles for these procedures in facilitating functional rehabilitation goals that are primary to the treatment of CRPS are emphasized.

Spinal cord stimulation in chronic pain management

As a general rule, even though it is always difficult to predict the efficacy of a method ina single patient, we consider SCS in every non-malignant chronic pain patient when other conservative treatments have failed. After three decades of clinical experience with SCS, we have learned a lot about its efficacy indifferent pain conditions and have made great technical progress with the materials and surgical procedures. Acceptance of the technique was slow at the beginning; however, we must be aware of the problems related to the application of a therapy that cannot be shamed, and thus the necessity of performing studies that include large numbers of patients. This is even more complicated when dealing with pain patients because of the well-known multifactoriality of pain. Nowadays, every algorithm for the treatment of different pain conditions includes SCS; consequently, every pain center should be able to offer this therapy in its treatment program. This article discusses what has been learned so far with regard to SCS, but there is a lot more to learn about this technique as well as about other types of neuromodulation procedures. As mentioned in the introduction of this article and discussed in the section on the effects of SCS, particularly in clinical applications like peripheral vascular disease and angina, the results of the interaction with the function of the nervous system can be observed in other systems in the body affecting pathologic conditions that are of interest to different specialists. Only the strict cooperation of different medical disciplines can provide substantial help in acquiring knowledge about the mechanisms put into play by SCS and the possible extension of its clinical applications. The complexity of the procedures of neuromodulation and the theoretic background needed for safe and proficient clinical use and for progress raise the issue for medical schools of offering courses in this new discipline.