Long-term Spinal Cord Stimulation Research Articles

Long-term efficacy and safety of spinal cord stimulation in patients with refractory angina pectoris.

The number of patients with refractory angina pectoris (RAP), associated with poor quality of life, has been steadily increasing. Spinal cord stimulation (SCS) is a last resort treatment option leading to significant improvement in quality of life over a one year follow-up. The aim of this prospective, single-centre, observational cohort study is to determine the long-term efficacy and safety of SCS in patients with RAP. All patients with RAP who received a spinal cord stimulator from the period July 2010 up to November 2019 were included. In May 2022 all patients were screened for long-term follow-up. If the patient was alive the Seattle Angina (SAQ) and RAND-36 questionnaire were completed and if the patient had passed away cause of death was determined. The primary endpoint is the change in SAQ summary score at long-term follow-up compared to baseline. From July 2010 up to November 2019 132 patients received a spinal cord stimulator due to RAP. The mean follow-up period was 65.2±32.8months. Seventy-one patients completed the SAQ at baseline and long-term follow-up. The SAQ SS showed an improvement of 24.32U (95% confidence interval [CI]: 18.71 - 29.93; p<0.001). The main findings of the study show that long-term SCS in patients with RAP leads to significant improvement in quality of life, significant reduction in angina frequency, significantly less use of short-acting nitrates and a low risk of spinal cord stimulator related complications over a mean follow-up period of 65.2±32.8months.

Neuromodulation and quality of life for patient with spasticity after spinal cord injury.

Spasticity develops in 80% of spinal cord injury cases and negatively affects the patents' quality of life. The most common method of surgical treatment for severe spasticity is a long-term intrathecal baclofen therapy (ITB). Long-term spinal cord stimulation is another possible treatment technique. This paper aims to evaluate the changes in quality of life for patients with spasticity who have been treated with neuromodulation (SCS or ITB) in 12 months after the surgery, as well to compare the changes in quality of life for patients who have been treated with spinal cord stimulation and those who received long-term intrathecal baclofen therapy. The influence of spasticity, experienced by the patients with a spinal cord injury, on their quality of life was analyzed before the surgery and 12 months after it. The severity of the spinal cord damage was determined with the scale of the American Spinal Injury Association (ASIA); spasticity was evaluated with the modified Ashworth scale, Penn Spasm Frequency Scale; pain levels were determined with visual analogue scale (VAS), anxiety and depression levels - with HADS. Functional activity of the patients was evaluated with the help of the Functional Independence Measure (FIM). The treatment results for 33 patients (25 men and 8 women), aged from 18 to 62, are presented. After the trial stimulation, the patients were randomly assigned to either SCS or ITB group (18 and 15 people respectively). The decrease of spasticity in both experimental groups caused lower levels of pain, less functional dependency on other people, lower stress and depression rates and, as a consequence, better quality of life and social adaptation. The obtained results for SCS and ITB groups are statistically similar.

O080 / #1053 MACHINE LEARNING ALGORITHMS PROVIDE GREATER PREDICTION OF RESPONSE TO SCS THAN LEAD SCREENING TRIAL: A PREDICTIVE AI-BASED MULTICENTER STUDY.: TRACK 1: SPINAL CORD STIMULATION, BEST PRACTICES, AND STUDIES

Persistent pain after spinal surgery can be successfully addressed by spinal cord stimulation (SCS) [1–6]. International guidelines strongly recommend that a lead trial be performed before any permanent implantation [7–10]. Recent clinical data highlight some major limitations of this approach [11], showing that patient outcomes, with or without lead trial, are similar. In contrast, during trialing, infection rate drops drastically within time and can compromise the therapy [6]. Using composite pain assessment experience and previous research, we hypothesized that machine learning models could be robust screening tools and reliable predictors of long-term SCS efficacy.

Is spinal cord stimulation useful in the long term? A commentary on Brill et al.

This journal recently published a paper by Brill et al., entitled ‘Short and long term effects of conventional spinal cord stimulation on chronic pain and health perceptions: a longitudinal controlled trial’. In fact, spinal cord stimulation (SCS) is considered a last-option technique to manage chronic refractory neuropathic pain, initially based on the gate control theory with subsequent other documented mechanisms of action. Even though pain relief assessment is highly subjective, objective SCS effects on clinical pain were well-documented years ago using nociceptive flexion reflexes-RIII (Garcia-Larrea et al., 1989), ruling out a possible paresthesia-based placebo effect of the procedure. While short-term pain relief following SCS is well documented, the long-term clinical SCS benefits remain questionable. Moreover, patients may develop tolerance to SCS, with loss of the therapeutic effect over time (Taccola et al., 2020). These issues can be tackled using a control group as a comparison, which is somewhat unethical, and/or a sham group which is unrealistic since conventional SCS induces paresthesiae. Very few studies considered the long-term effects of SCS on a large sample of patients. While the beneficial effect of SCS at 1 year on a large sample was clearly documented (EMP3OWER study, 401 patients; Rosenberg et al., 2016), longer beneficial effects have only been reported in very small series (Kumar et al., 2008). The recently published article in the European Journal of Pain concerns a study on 167 patients candidates for SCS followed for 28 weeks post-implantation (Brill et al., 2022). The authors used the patients whose SCS initial trial failed as a comparison group for the patients permanently implanted with SCS. They found no beneficial effects for the SCS group at the last follow-up compared to either the pre-operative status or the failed trial group. The results of this study are in contrast with those of most published data about the efficacy of SCS, and the strength of this series includes the absence of sponsorship by the devices' manufacturers, the number of patients (n = 167) and the test–retest study for the outcome measures—with clear cut-off values for a clinically significant difference. Notwithstanding these merits, the findings and conclusions of the study are to be interpreted with caution, since the study, although well conducted and interesting, carries limitations the reader must take into consideration. The comparison group used in this study is not typical and can induce bias in the comparison. Patients disappointed by the failure of the “last chance therapy” can either work psychologically on themselves and develop useful coping strategies, can successfully modify their other therapeutic approaches, or use illicit drugs and/or medications to overcome their suffering. Thus, they cannot be considered as a robust comparison group like a placebo/sham group. Of note, outcome measures did not include medication intake in the two groups; reporting this parameter is extremely important since a significant difference between the two groups would be in itself an objective marker of SCS efficacy. A third and important limitation is the absence of multivariate analysis, most probably because of the sample size, in order to investigate the influence of several factors like the device's manufacturer, the aetiology of the chronic pain and also the pain duration. The question that remains unanswered is why the findings of this study are in contradiction with most previously published data in the literature. One explanation might be that some studies exclude analysis of drop-out patients, but the probability that this alone explains the results appears very low. Given the generally good methodology followed in this paper, only the possible biases mentioned above, the patient population/selection process and/or the technique itself appear as potential explanations of the observed divergences with previous literature. In any case, the results are of potential importance and should prompt the development of other studies with a high level of evidence, which take into consideration the challenges of placebo/sham in this context, in order to document the real long-term effectiveness of SCS on pain relief in chronic refractory neuropathic pain.

Comparison of Spinal Cord Stimulation Trial Reporting Protocols and Long-Term Pain Relief Outcomes Following Implantation

ObjectivesAppropriate spinal cord stimulation (SCS) candidates are required to undergo an SCS trial before implant, typically with ≥50% pain relief deemed “successful.” However, SCS trialing protocols can vary substantially. The primary aim of this retrospective study is to investigate the associations between SCS trial results and long-term SCS pain outcomes. Materials and MethodsThis study was a retrospective single-center review of successful SCS trials from January 1, 2017, to July 1, 2019. A total of 115 patients were included. Group differences in continuous variables were evaluated using t-tests, and group differences in categorical variables were evaluated using the χ2 test. The percentage improvement in long-term pain intensity was analyzed as a binary variable, where long-term success was defined as ≥50% improvement in numeric rating scale pain scores. The level of significance for all tests was set at p < 0.05. ResultsThe mean age was 64.9 years, and 52% of patients were men. The mean pain score at long-term follow-up was 4.7 ± 2.6, and the median time from implantation to follow-up was 13 months (25th–75th interquartile range; 4–22). In the logistic regression analysis adjusted for age, sex, and follow-up time, greater patient-reported percentage improvement in pain scale during the trial was significantly associated with greater odds of experiencing ≥50% improvement in pain scores (p = 0.048; 95% CI 1.00–1.70). All other assessed trial metrics were not significantly associated with greater odds of experiencing >50% improvement in pain scores at last follow-up. ConclusionsGiven the variability in current assessment techniques, we recommend the patient-reported percentage improvement in pain scale as the posttrial assessment method of choice instead of a calculated percentage improvement. However, our results indicate that current trial assessment methods are generally poor, and improved trial reporting protocols must be sought.

Development of Machine Learning-Based Models to Predict Treatment Response to Spinal Cord Stimulation.

Despite spinal cord stimulation's (SCS) proven efficacy, failure rates are high with no clear understanding of which patients benefit long term. Currently, patient selection for SCS is based on the subjective experience of the implanting physician. To develop machine learning (ML)-based predictive models of long-term SCS response. A combined unsupervised (clustering) and supervised (classification) ML technique was applied on a prospectively collected cohort of 151 patients, which included 31 features. Clusters identified using unsupervised K-means clustering were fitted with individualized predictive models of logistic regression, random forest, and XGBoost. Two distinct clusters were found, and patients in the cohorts significantly differed in age, duration of chronic pain, preoperative numeric rating scale, and preoperative pain catastrophizing scale scores. Using the 10 most influential features, logistic regression predictive models with a nested cross-validation demonstrated the highest overall performance with the area under the curve of 0.757 and 0.708 for each respective cluster. This combined unsupervised-supervised learning approach yielded high predictive performance, suggesting that advanced ML-derived approaches have potential to be used as a functional clinical tool to improve long-term SCS outcomes. Further studies are needed for optimization and external validation of these models.

Machine Learning Algorithms Provide Greater Prediction of Response to SCS Than Lead Screening Trial: A Predictive AI-Based Multicenter Study.

Persistent pain after spinal surgery can be successfully addressed by spinal cord stimulation (SCS). International guidelines strongly recommend that a lead trial be performed before any permanent implantation. Recent clinical data highlight some major limitations of this approach. First, it appears that patient outco mes, with or without lead trial, are similar. In contrast, during trialing, infection rate drops drastically within time and can compromise the therapy. Using composite pain assessment experience and previous research, we hypothesized that machine learning models could be robust screening tools and reliable predictors of long-term SCS efficacy. We developed several algorithms including logistic regression, regularized logistic regression (RLR), naive Bayes classifier, artificial neural networks, random forest and gradient-boosted trees to test this hypothesis and to perform internal and external validations, the objective being to confront model predictions with lead trial results using a 1-year composite outcome from 103 patients. While almost all models have demonstrated superiority on lead trialing, the RLR model appears to represent the best compromise between complexity and interpretability in the prediction of SCS efficacy. These results underscore the need to use AI-based predictive medicine, as a synergistic mathematical approach, aimed at helping implanters to optimize their clinical choices on daily practice.

Long-Term Spinal Cord Stimulation After Chronic Complete Spinal Cord Injury Enables Volitional Movement in the Absence of Stimulation.

Background: Chronic spinal cord injury (SCI) portends a low probability of recovery, especially in the most severe subset of motor-complete injuries. Active spinal cord stimulation with or without intensive locomotor training has been reported to restore movement after traumatic SCI. Only three cases have been reported where participants developed restored volitional movement with active stimulation turned off after a period of chronic stimulation and only after intensive rehabilitation with locomotor training. It is unknown whether restoration of movement without stimulation is possible after stimulation alone.Objective: We describe the development of spontaneous volitional movement (SVM) without active stimulation in a subset of participants in the Epidural Stimulation After Neurologic Damage (ESTAND) trial, in which locomotor training is not prescribed as part of the study protocol, and subject’s rehabilitation therapies are not modified.Methods: Volitional movement was evaluated with the Brain Motor Control Assessment using sEMG recordings and visual examination at baseline and at follow-up visits with and without stimulation. Additional functional assessment with a motor-assisted bicycle exercise at follow-up with and without stimulation identified generated work with and without effort.Results: The first seven participants had ASIA Impairment Scale (AIS) A or B thoracic SCI, a mean age of 42 years, and 7.7 years post-injury on average. Four patients developed evidence of sustained volitional movement, even in the absence of active stimulation after undergoing chronic epidural spinal cord stimulation (eSCS). Significant increases in volitional power were found between those observed to spontaneously move without stimulation and those unable (p < 0.0005). The likelihood of recovery of spontaneous volitional control was correlated with spasticity scores prior to the start of eSCS therapy (p = 0.048). Volitional power progressively improved over time (p = 0.016). Additionally, cycling was possible without stimulation (p < 0.005).Conclusion: While some SVM after eSCS has been reported in the literature, this study demonstrates sustained restoration without active stimulation after long-term eSCS stimulation in chronic and complete SCI in a subset of participants. This finding supports previous studies suggesting that “complete” SCI is likely not as common as previously believed, if it exists at all in the absence of transection and that preserved pathways are substrates for eSCS-mediated recovery in clinically motor-complete SCI.Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03026816.

FV 22 Adverse events requiring surgical intervention during long-term Spinal Cord Stimulation for chronic pain syndromes_a retrospective single-center analysis

FV 22 Adverse events requiring surgical intervention during long-term Spinal Cord Stimulation for chronic pain syndromes_a retrospective single-center analysis

Long-Term Spinal Cord Stimulation Alleviates Mechanical Hypersensitivity and Increases Peripheral Cutaneous Blood Perfusion in Experimental Painful Diabetic Polyneuropathy

ObjectivesThis study utilizes a model of long‐term spinal cord stimulation (SCS) in experimental painful diabetic polyneuropathy (PDPN) to investigate the behavioral response during and after four weeks of SCS (12 hours/day). Second, we investigated the effect of long‐term SCS on peripheral cutaneous blood perfusion in experimental PDPN.MethodsMechanical sensitivity was assessed in streptozotocin induced diabetic rats (n = 50) with von Frey analysis. Hypersensitive rats (n = 24) were implanted with an internal SCS battery, coupled to an SCS electrode covering spinal levels L2–L5. The effects of four weeks of daily conventional SCS for 12 hours (n = 12) or Sham SCS (n = 12) were evaluated with von Frey assessment, and laser Doppler imaging (LDI).ResultsAverage paw withdrawal thresholds (PWT) increased during long‐term SCS in the SCS group, in contrast to a decrease in the Sham group (Sham vs. SCS; p = 0.029). Twenty‐four hours after long‐term SCS average PWT remained higher in the SCS group. Furthermore, the SCS group showed a higher cutaneous blood perfusion during long‐term SCS compared to the Sham group (Sham vs. SCS; p = 0.048). Forty‐eight hours after long‐term SCS, no differences in skin perfusion were observed.DiscussionWe demonstrated that long‐term SCS results in decreased baseline mechanical hypersensitivity and results in increased peripheral blood perfusion during stimulation in a rat model of PDPN. Together, these findings indicate that long‐term SCS results in modulation of the physiological circuitry related to the nociceptive system in addition to symptomatic treatment of painful symptoms.

Are Multidimensional Pain Inventory Coping Strategy Profiles Associated with Long-Term Spinal Cord Stimulation Effectiveness?

It is acknowledged that the way patients cope with pain may influence treatment outcome. In particular, psychological factors are deemed important when considering patients for suitability for spinal cord stimulation (SCS). The aim of the study is to observe how pre-implantation psychological characteristics impact the effectiveness of SCS for chronic pain. The analysis comprised data from 137 patients who underwent an SCS implant. Screening evaluation included a coping strategies profile (Multidimensional Pain Inventory) and psychiatric disorders (Mini-International Neuropsychiatric Interview). Based on SCS implant outcome collected during follow-up visits, patients were divided into three groups: subjects with long-term pain relief (long-term group), subjects who failed the SCS treatment and decided to explant trial device (trial explanter group [TE]), and those who chose a permanent device (permanent explanter group [PE]). Results showed that most of the patients who failed with the SCS (TE and PE groups) demonstrated a dysfunctional coping profile and showed a higher presence of psychiatric disorders, which significantly influenced the experience and perception of pain. The findings of this study support the value of a multidisciplinary screening. Addressing psychological issues before SCS implantation can reduce the failure rate of SCS.

Long-term spinal cord stimulation modifies canine intrinsic cardiac neuronal properties and ganglionic transmission during high-frequency repetitive activation.

Long‐term spinal cord stimulation (SCS) applied to cranial thoracic SC segments exerts antiarrhythmic and cardioprotective actions in the canine heart in situ. We hypothesized that remodeling of intrinsic cardiac neuronal and synaptic properties occur in canines subjected to long‐term SCS, specifically that synaptic efficacy may be preferentially facilitated at high presynaptic nerve stimulation frequencies. Animals subjected to continuous SCS for 5–8 weeks (long‐term SCS: n = 17) or for 1 h (acute SCS: n = 4) were compared with corresponding control animals (long‐term: n = 15, acute: n = 4). At termination, animals were anesthetized, the heart was excised and neurones from the right atrial ganglionated plexus were identified and studied in vitro using standard intracellular microelectrode technique. Main findings were as follows: (1) a significant reduction in whole cell membrane input resistance and acceleration of the course of AHP decay identified among phasic neurones from long‐term SCS compared with controls, (2) significantly more robust synaptic transmission to rundown in long‐term SCS during high‐frequency (10–40 Hz) presynaptic nerve stimulation while recording from either phasic or accommodating postsynaptic neurones; this was associated with significantly greater posttrain excitatory postsynaptic potential (EPSP) numbers in long‐term SCS than control, and (3) synaptic efficacy was significantly decreased by atropine in both groups. Such changes did not occur in acute SCS. In conclusion, modification of intrinsic cardiac neuronal properties and facilitation of synaptic transmission at high stimulation frequency in long‐term SCS could improve physiologically modulated vagal inputs to the heart.

Spinal cord stimulation improves forelimb use in an alpha-synuclein animal model of Parkinson's disease

Neuromodulation by spinal cord stimulation has been proposed as a symptomatic treatment for Parkinson's disease. We tested the chronic effects of spinal cord stimulation in a progressive model of Parkinson's based on overexpression of alpha-synuclein in the substantia nigra. Adult Sprague Dawley rats received unilateral injections of adeno-associated virus serotype 6 (AAV6) in the substantia nigra to express alpha-synuclein. Locomotion and forepaw use of the rats were evaluated during the next 10 weeks. Starting on week 6, a group of AAV6-injected rats received spinal cord stimulation once a week. At the end of the experiment, tyrosine hydroxylase and alpha-synuclein immunostaining were performed. Rats with unilateral alpha-synuclein expression showed a significant decrease in the use of the contralateral forepaw, which was mildly but significantly reverted by spinal cord stimulation applied once a week from the 6th to the 10th week after the AAV6 injection. Long-term spinal cord stimulation proved to be effective to suppress or delay motor symptoms in a sustained and progressive model of Parkinson's and might become an alternative, less invasive neuromodulation option to treat this disease.

Effect of spinal cord stimulation on sensory characteristics: a randomized, blinded crossover study.

Spinal cord stimulation (SCS) is increasingly used to treat various chronic pain conditions. One undetermined issue is to what extent SCS alters the processing of sensory information from the periphery, including those stimuli that are mediated by small-fiber populations. We aimed to investigate these possible changes using quantitative sensory testing (QST). Fourteen patients in long-term SCS treatment for complex regional pain syndrome (n=5) or pain following peripheral nerve injury (n=9) were examined with QST. All patients answered questions about their pain and underwent QST while the SCS treatment was activated and deactivated (12 h interval between the sessions) in a randomized, double-blinded crossover setting. Both the painful side and the corresponding contralateral side were examined. Thermal and mechanical thresholds were similar during SCS activation and deactivation. The same result was found for intensity of pain and areas with painful symptoms even though all patients had documented long-term benefit of the treatment. The results support existing evidence suggesting that SCS does not change sensory characteristics, which is important information for both patients and clinicians. Changes in pain intensity after deactivation of SCS may be different in short-term and long-term SCS treatment.

Event-Related Cortical Processing in Neuropathic Pain under Long-Term Spinal Cord Stimulation

Background: Several mechanisms were suggested in the past to explain the beneficial effect of spinal cord stimulation (SCS) in patients suffering from neuropathic pain. Little is known about potential supraspinal mechanisms. Objective: In this study cortical signaling of patients with neuropathic pain and successful longterm treatment with SCS was analyzed. Study Design: Observational study. Setting: University hospital, neurosurgical department, outpatient clinic for movement disorders and pain, institute for cognitive and clinical neuroscience. Methods: Nine patients with neuropathic pain of a lower extremity with a lasting response to chronic SCS were included. Cortical activity was analyzed using event-related potentials of the electroencephalogram after non-painful and painful stimulation. Each patient was tested under the effect of long-term SCS and 24 hours after cessation of SCS. Cortical areas involved in the peaks of evoked potentials were localized using a source localization method based on a fixed dipole model. Results: Detection threshold and intensity of non-painful stimulation did not differ significantly on both sides. Pain threshold was significantly lower on the neuropathic side under the effect of SCS (P = 0.03). Bilateral pain thresholds were significantly lower (P = 0.03 healthy side, P = 0.003 neuropathic side) in 5 patients with increased pain after cessation of SCS. Under the effect of SCS cortical negativities (N1, N2, N3) and positivities (P1) demonstrated bilaterally comparable amplitudes. After cessation of SCS, decreased threshold for peripheral stimulation resulted in lowered negativities on both sides. The positivity P1 was differentially regulated and was reduced more contralateral to the unaffected side. N2 was localized at the sensory representation of the leg within the homunculus. The main vector of P1 was localized within the cingular cortex (CC) and moved more anteriorly under the effect of SCS. Limitations: The exact time span that SCS continues to have an effect is not known. However, due to patient discomfort discontinuation of SCS therapy was not prolonged over a 24 hour period. Further limitations were the low number of patients who agreed to discontinue SCS therapy for research purposes. Conclusions: Long-term SCS for treatment of neuropathic pain influenced both pain thresholds and cortical signalling. Source localization of P1 suggests involvement of regions involved in cognitive/associative processing of pain. Key words: Event related cortical processing, neuropathic pain, spinal cord stimulation, SCS

Chronic spinal cord stimulation modifies intrinsic cardiac synaptic efficacy in the suppression of atrial fibrillation.

We sought to determine whether spinal cord stimulation (SCS) therapy, when applied chronically to canines, imparts long-lasting cardio-protective effects on neurogenic atrial tachyarrhythmia induction and, if so, whether its effects can be attributable to i) changes in intrinsic cardiac (IC) neuronal transmembrane properties vs ii) modification of their interneuronal stochastic interactivity that initiates such pathology. Data derived from canines subjected to long-term SCS [(group 1: studied after 3-4 weeks SCS; n = 5) (group 2: studied after 5 weeks SCS; n = 11)] were compared to data derived from 10 control animals (including 4 sham SCS electrode implantations). During terminal studies conducted under anesthesia, chronotropic and inotropic responses to vagal nerve or stellate ganglion stimulation were similar in all 3 groups. Chronic SCS suppressed atrial tachyarrhythmia induction evoked by mediastinal nerve stimulation. When induced, arrhythmia durations were shortened (controls: median of 27 s; SCS 3-4 weeks: median of 16s; SCS 5 weeks: median of 7s). Phasic and accommodating right atrial neuronal somata displayed similar passive and active membrane properties in vitro, whether derived from sham or either chronic SCS group. Synaptic efficacy was differentially enhanced in accommodating (not phasic) IC neurons by chronic SCS. Taken together these data indicate that chronic SCS therapy modifies IC neuronal stochastic inter-connectivity in atrial fibrillation suppression by altering synaptic function without directly targeting the transmembrane properties of individual IC neuronal somata.

Is Constant Current or Constant Voltage Spinal Cord Stimulation Superior for the Suppression of Nociceptive Visceral and Somatic Stimuli? A Rat Model

This study compares the effects of constant current (CC) and constant voltage (CV) spinal cord stimulation (SCS) at various frequencies and intensities on standard nociceptive measurements in rats, the visceromotor reflex (VMR) and neuronal activity, during noxious visceral and somatic stimuli. Abdominal muscle electromyographic activity changes were measured to indicate VMR, and extracellular activity of L6-S2 spinal neurons was recorded during somatic (pinching) and noxious visceral stimulation (colorectal distension [CRD], 60 mmHg) in anesthetized rats. A stimulating (unipolar ball) electrode at L2-L3 delivered CC- or CV-SCS at varied frequencies and intensities. CC-SCS reduced VMR evoked by CRD significantly more than CV-SCS (p < 0.05). For neuronal activity, high-frequency CC-SCS (40 and 100 Hz) and CV-SCS (100 Hz) effectively reduced intraspinal somatic nociceptive transmission more than low-frequency SCS (2 Hz). No significant differences were observed between the effects of CC- and CV-SCS on spontaneous activity and nociceptive responses of spinal neurons to noxious CRD following short- (five to ten minutes) or long-term (20-30 min) SCS. Although high-frequency CC- and CV-SCS may be more useful for the management of somatic pain, CC-SCS may be more effective for treating complex pain systems like visceral hypersensitivity.

Spinal Cord Stimulation Improves Ventricular Function and Reduces Ventricular Arrhythmias in a Canine Postinfarction Heart Failure Model

Spinal cord stimulation (SCS) reduces the incidence of ventricular tachyarrhythmias in experimental models. This study investigated the effects of long-term SCS on ventricular function in a postinfarction canine heart failure model. In stage 1, dogs underwent implantable cardioverter-defibrillator implantation and embolization of the left anterior descending artery followed by right ventricular pacing (240 ppm) for 3 weeks to produce heart failure. In stage 2, 28 surviving animals were assigned to the SCS (delivered at the T4/T5 spinal region for 2 hours 3 times a day), medicine (MED; carvedilol therapy at 12.5 mg PO BID), or control (CTRL; no therapy) group for the initial phase 1 study. In a subsequent phase 2 study, 32 stage 1 survivors were equally randomized to the SCS, MEDS (carvedilol plus ramipril 2.5 mg PO QD), SCS plus MEDS (concurrent therapy), or CTRL group. Animals were monitored for 5 weeks (phase 1) or 10 weeks (phase 2). In stage 3, all phase 1 animals underwent circumflex artery balloon occlusion for 1 hour. In the SCS group, left ventricular ejection fraction was 65+/-5% at baseline, 17+/-3% at the end of stage 1, and 47+/-7% at the end of stage 2. In the MED group, left ventricular ejection fraction was 61+/-4% at baseline, 18+/-3% at the end of stage 1, and 34+/-4% at the end of stage 2. In the CTRL group, left ventricular ejection fraction was 64+/-5% at baseline, 19+/-5% at the end of stage 1, and 28+/-3% at the end of stage 2. Left ventricular ejection fraction was significantly improved in the SCS compared with the MED and CTRL groups (P<0.001 for both). The mean number of spontaneous nonsustained ventricular tachyarrhythmias during stage 2 and the occurrence of ischemic ventricular tachyarrhythmias during stage 3 also were significantly decreased in the SCS (27+/-17 and 27%, respectively; P<0.03) and MED (58+/-42 and 33%; P<0.05) versus CTRL (88+/-52 and 76%) group. After 10 weeks in the phase 2 studies, the greatest recovery in ejection fraction was noted in the SCS (52+/-5%) and SCS+MEDS (46+/-4%) groups compared with the MEDS (38+/-2%) and CTRL (31+/-4%) groups. SCS significantly improved cardiac contractile function and decreased ventricular arrhythmias in canine heart failure.

Spinal cord stimulation in sympathetically maintained complex regional pain syndrome type I with severe disability. A prospective clinical study

Background and purpose: In this prospective trial we assessed the long-term effect of spinal cord stimulation (SCS) on the improvement of functional status in complex regional pain syndrome type I (CRPS I). Methods: A prerequisite for eligibility to SCS treatment was the responsiveness of patients to sympathetic nerve block. In 29 patients with chronic sympathetically maintained CRPS I, the efficacy of SCS on deep pain, allodynia and functional disability was determined. Pain intensity was estimated during SCS free intervals of 45 min (inactivation test) every 3 months and compared with that under SCS treatment. Results: On SCS treatment, both deep pain and allodynia could be permanently reduced from 10 to 0–2 on a 10 cm visual analogue scale (VAS) ( p < 0.01). During the inactivation tests, reoccurrence of pain up to 8 VAS (quartiles 6–8) was measured. Considerable impairments in daily living activities, objectified by the pain disability index, were also restored ( p < 0.01). After a follow-up period of 35.6 ± 21 months, 12 of 16 patients with affected upper limb showed significant increase of the fist grip strength from 0 to 0.35 (quartiles 0.1–0.5) kg compared with 0.9 (quartiles 0.7–1.1) kg on the unaffected side ( p < 0.01). Eight of ten patients with lower limb disability resumed walking without crutches. Previous pain medication could be significantly reduced ( p < 0.01). Conclusions: As a result of permanent pain relief under long-term SCS combined with physiotherapy, the functional status and the quality of life could be significantly improved in sympathetically maintained CRPS I.

Acute vs. Prolonged Screening for Spinal Cord Stimulation in Chronic Pain

Spinal cord stimulation (SCS) was performed to test the hypothesis that pain relief data during acute (15 minute intraoperative) and prolonged (5day) SCS screening have equivalent predictive value for long-term successful SCS control of chronic low back pain and/or lower extremity pain. A retrospective series of patients with chronic low back and/or lower extremity pain underwent either percutaneous or open (ie, laminectomy) SCS implantation during which acute intraoperative followed by prolonged screening trials for percentage pain relief (%PR) were performed. Data were analyzed for (a) correlation between positive predictive value (PPV) of acute and prolonged SCS screening for %PR and (b) PPV of acute vs. prolonged screening %PR for long-term SCS %PR. Fifty-four patients (male/female=38/16; mean age±SEM=54.2± 2.0years) underwent thoracic (T) (mean level=T9.1± 0.4) percutaneous (n=33) and laminectomy (n= 21) implantation of SCS for acute (15 minute intraoperative) and prolonged (5.0±0.3 days) SCS screening of pain relief. Correlation between successful (>50%PR) pain relief during acute (n=53/54, PPV=98%) and prolonged (n=47/52, PPV=90%) screening was significant (Spearman Rank Correlation Coefficient, SRCC =0.462, p<0.01). After permanent SCS implantation, at mean follow-up=9.4±1.5months, acute and prolonged SCS screening %PR PPV's were each statistically significant for predicting long-term SCS relief of chronic pain (n=31/38, PPV=82% and n=31/36, PPV=86%, SRCC=0.462 and 0.433, respectively, p<0.01). We conclude that successful pain relief during acute SCS screening is highly correlated with successful prolonged SCS screening of chronic low back and/or lower extremity pain relief. Acute and prolonged SCS screening appear to have equivalent predictive value for successful long-term SCS control of chronic low back and/or lower extremity pain. These preliminary results suggest potential justification for eliminating prolonged and retaining acute (intraoperative) SCS screening for selection of permanent SCS implantation candidates.