Long-term effects of spinal cord stimulation in chronic pain syndromes

Summary A total of 50 patients with chronic pain syndromes were selected for treatment with spinal cord stimulation. Correct positioning of electrodes was obtained in 44 patients, leading to an initial alleviation of pain in 25 patients. In 6 patients, electrodes (though still effective in 4) had to be removed because of surgical complications within the first 5 months of use. Only 8 patients had at least some beneficial effect lasting for more than 3 years. The long-term results in patients with more severe psychological disturbances were no worse than those of the other patients.     

Recommendations for patient selection in spinal cord stimulation

Studies have shown that spinal cord stimulation (SCS) can reduce chronic pain by at least 50% over prolonged periods, improve function and quality-of-life, reduce requirements for healthcare resources and enable return to work in appropriately selected patients. However, SCS does not provide pain relief in all patients and is an expensive, labor intensive and invasive procedure with complications and ongoing management that requires specialists with specific skills and judgment. Multidisciplinary selection of appropriate patients for SCS is essential to achieve maximal benefit from the procedure. The aim of the article is to provide a clinical practice guide to the likely effectiveness of SCS in treating various types of chronic pain, as supported by the literature. The article will summarize indications and contraindications for SCS, provide guidance on the selection and timing for referral, and highlight the benefits and complications associated with the procedure.     

脊髓和马尾神经损伤后慢性神经源性疼痛外科治疗策略

目的 探讨脊髓和马尾神经损伤后慢性神经源性疼痛的神经外科治疗策略.方法 脊髓和马尾神经损伤后慢性神经源性疼痛20例,年龄28～81岁,病程8个月～50年.共行镇痛手术23次,其中,脊髓背根入髓区显微外科切开术19次,脊髓电刺激术3次,鞘内靶控输注系统植入术1次.采用视觉模拟评分（VAS）来评估手术疗效,以术后疼痛缓解大于75%为疗效优秀,疼痛缓解50%～75%为良好,疼痛缓解小于50%为差.结果 随访6个月～4年,10例疼痛消失,停用镇痛剂,生活质量改善;7例疼痛明显减轻,VAS 2～4分,其中,5例停用镇痛剂,2例镇痛剂使用量明显下降,生活质量改善;3例疼痛无明显改善.结论 脊髓背根入髓区显微外科切开术和脊髓电刺激术对脊髓和马尾神经损伤后慢性神经源性疼痛患者疗效满意,但其适应证有差别,应根据患者的损伤节段、损伤程度和疼痛部位等具体情况选择手术方式.     

Spinal cord stimulation for neuropathic pain

Spinal cord stimulation (SCS) is used for more than 40 years to treat localized chronic medically refractory neuropathic pain involving limb(s) and trunk. The most frequent indications remain complex regional pain syndrome (CRPS) failed back surgery syndrome (FBSS), and peripheral neuropathy. Stimulation-induced paresthesias, perceived by the patient, prevent blinded evaluation and increase the placebo effect, decreasing the credibility of the tonic SCS efficacy. Retrospective studies reported that about 50% of the patients are improved more than 50% at short-term, but long-term improvement is less. Several comparative randomized trials (RCT) are now available. In CRPS, a RCT demonstrated the superiority of SCS plus physiotherapy compared to physiotherapy alone. In FBSS, two RCTs have shown that SCS was superior to reoperation and conventional medical treatment, (CMM) respectively. New stimulation waveforms, namely burst, high frequency (10 KHz) stimulation and close-loop SCS, have been proposed recently to avoid the perception of paresthesias and/or increase the pain relief. RCTs in FBSS have suggested that these new SCS modalities were as least as efficient than conventional tonic SCS and perhaps slightly superior. Two RCTs confirmed SCS efficacy in painful diabetic neuropathy in comparison with CMM. Complications are frequent (hardware dysfunction or migration, superficial infection) but exceptionally serious. Consequently, the risk/benefit ratio is favorable to SCS, considering that chronic pain patients undergoing this procedure are usually resistant to all the other therapies.     

Mechanisms of spinal cord stimulation in neuropathic pain

Abstract

The understanding of the mode of action of spinal cord stimulation (SCS) as treatment of neuropathic pain is still fragmentary. SCS evolved from the gate-control theory postulating a spinal modulation of noxious inflow, but there is little evidence that SCS influences nociceptive pain; pain relief in peripheral vascular disease and angina pectoris is presumably secondary to other SCS effects. In man, SCS may effectively abolish both continuous and evoked pain (tactile/thermal allodynia) whereas induced, acute nociceptive pain is unaffected. Recent SCS studies performed on rat models of mononeuropathy have demonstrated a preferential effect on AB fiber mediated functions, and the hyperexcitability of wide-dynamic-range dorsal horn neurons was attenuated. These effects were coupled to increased release of CABA and reduced glutamate and aspartate release in the dorsal horn. Intrathecal administration of GABA, baclofen and adenosine enhanced the SCS effect on tactile allodynia even in previously non-responsive rats. Preliminary results indicate that gabapentin may have a similar effect. GABAergic and adenosine-related mechanisms conceivably represent only examples of a number of putative receptor systems involved in SCS. Clinical trials have been initiated exploring the possibility to improve the efficacy of SCS by concomitant pharmacotherapy. [Neurol Res 2000; 22: 28S-292]     

Thalamic EEG recordings in patients with chronic pain

Summary Thalamic EEG recordings were made in 10 patients; the therapeutic goal of the implantation was the electrical stimulation treatment for pain. The patients' ages ranged from 37 to 72 years; seven patients had thalamic pain (Dejerine-Roussy syndrome), two had chronic spinal arachnoiditis and one had facial anaesthesia dolorosa.Platinum-iridium electrodes were stereotaxically inserted; the ventrobasal complex of the thalamus including the ventral posterior zone was the target of the implant.Excessive thalamic slowing was found in four of seven patients with Dejerine-Roussy syndrome and also in two of three cases with other causes of pain. One patient had marked rhythmical intermittent delta activity in the thalamus which was often triggered by arousing stimuli. Thalamic spindle activity was sometimes noted without concomitant spindle activity on the scalp and would occasionally occur in states of early drowsiness.A condensed version of this paper was presented at the meeting of the American EEG Society, June 22–25, 1977, Miami, Fla.     

Opioid use and spinal cord stimulation therapy: The long game

Spinal cord stimulation (SCS) has been considered as an alternative therapy to reduce opioid requirements in certain chronic pain disorders. However, information on long-term opioid consumption patterns and their impact on SCS device explantation is lacking. We conducted a retrospective study of 45 patients to characterize long-term patterns of opioid usage after SCS implantation. Daily morphine equivalent dosage (MED) increased, decreased, and remained the same in 40%, 40%, and 20% of patients at 1-year follow-up, respectively. Twelve (27%) underwent explantation due to treatment failure at a median of 18 months after implantation. Pre-operative opioid status (naïve vs. active use) was not associated with explantation (18% vs. 29%, p = 0.699) and neither was the daily MED change status (i.e. increased, decreased, unchanged) at 1-year (p = 0.499, 1.000, 0.735, respectively). Following explantation, reduction in the daily MED was seen in 92% of patients with dosages falling below pre-operative baseline in nine. Among the opioid naïve patients, 55% were on opioids at last follow-up (average 32.4 ± 14.6 months). Our results indicate that daily opioid consumption does not decrease in most patients 1-year after SCS implantation. Furthermore, post-operative evaluation beyond 1-year is necessary to assess the efficacy and durability of SCS therapy as well as its impact on opioid requirement. Lastly, rigorous patient selection and pre-operative risk assessment for misuse and dependence are paramount to improving outcome after SCS implantation.     

高颈段脊髓电刺激促醒颅脑创伤昏迷一例并文献复习

目的 研究高颈段脊髓电刺激对颅脑创伤昏迷的促醒作用.方法 观察1例重型颅脑创伤患者高颈段脊髓电刺激术后清醒时间、脑电图、诱发电位及脑血流的变化.结果 患者术后2个月逐渐清醒,脑电图逐渐转为正常α节律,诱发电位潜伏期延长逐渐改善,脑血流明显增加.结论 高颈段脊髓电刺激可能通过增加脑血流、恢复正常的神经电生理活动促醒颅脑创伤昏迷患者.

Abstract：

Objective To study the awoking effect of high cervical spinal cord stimulation on comatose patients with traumatic brain injury.Methods Recovery time,electroencephalogram(EEG),evoked patentials,cerebral blood perfusion after cervical spinal cord stimulation in a comatose patient were investigated.Results The patient emerged form conla at 2 months after spinal cord stimulation treatment.EEG gradually turned into a normal(rhythm,evoked potentials latency improved,and cerebral blood perfusion increased significantly.Conclusions High cervical spinal cord stimulation exerts its beneficial effects to comatose patients with traumatic brain injury by increasing cerebral blood perfusion and restoring normal cerebral electrical activity.     

Temperature increases by kilohertz frequency spinal cord stimulation

Introduction

Kilohertz frequency spinal cord stimulation (kHz-SCS) deposits significantly more power in tissue compared to SCS at conventional frequencies, reflecting increased duty cycle (pulse compression). We hypothesize kHz-SCS increases local tissue temperature by joule heat, which may influence the clinical outcomes.

Long-term potentiation in spinal nociceptive systems--how acute pain may become chronic

Chronic pain is a major problem since it is difficult to treat and the understanding of the underlying neurobiology is sparse. The mechanisms underpinning the transition of acute into chronic pain remain unclear. However, long-term potentiation (LTP) in spinal nociceptive systems may be one such mechanism. Here, we briefly review the literature regarding LTP in spinal nociceptive systems including our own data on LTP in deep convergent nociceptive neurons. Furthermore, we discuss the role of this phenomenon in understanding the neurobiology of chronic pain and the possible therapeutic implications.     

Dorsal cord stimulation (D.C.S.) in treatment of chronic non-neoplastic pain

We describe a series of patients with chronic non-neoplastic pain of different etiologies in whom temporary percutaneous stimulations of the dorsal cord allowed us to select the cases suitable for implantation with a definitive neurostimulating device. The technique and results are reported.

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Sommario Gli autori descrivono una serie di pazienti affetti da dolore cronico non tumorale di eziologie differenti; in questi pazienti la stimolazione temporanea del midollo spinale per via percutanea ha permesso di selezionare i casi candidati all'impianto definitivo degli elettrodi epidurali midollari. La tecnica e i risultati sono descritti.

     

Descending volleys generated by efficacious epidural motor cortex stimulation in patients with chronic neuropathic pain

Epidural motor cortex stimulation (EMCS) is a therapeutic option for chronic, drug-resistant neuropathic pain, but its mechanisms of action remain poorly understood. In two patients with refractory hand pain successfully treated by EMCS, the presence of implanted epidural cervical electrodes for spinal cord stimulation permitted to study the descending volleys generated by EMCS in order to better appraise the neural circuits involved in EMCS effects. Direct and indirect volleys (D- and I-waves) were produced depending on electrode polarity and montage and stimulus intensity. At low-intensity, anodal monopolar EMCS generated D-waves, suggesting direct activation of corticospinal fibers, whereas cathodal EMCS generated I2-waves, suggesting transsynaptic activation of corticospinal tract. The bipolar electrode configuration used in chronic EMCS to produce maximal pain relief generated mostly I3-waves. This result suggests that EMCS induces analgesia by activating top–down controls originating from intracortical horizontal fibers or interneurons but not by stimulating directly the pyramidal tract. The descending volleys elicited by bipolar EMCS are close to those elicited by transcranial magnetic stimulation using a coil with posteroanterior orientation. Different pathways are activated by EMCS according to stimulus intensity and electrode montage and polarity. Special attention should be paid to these parameters when programming EMCS for pain treatment.     

The effect of locomotor training combined with functional electrical stimulation in chronic spinal cord injured subjects: walking and reflex studies

With the new developments in traumatology medicine, the majority of spinal cord injuries sustained are clinically incomplete and the proportion is likely to continue to rise. Thus, it is necessary to continue to develop new treatment and rehabilitation strategies and understand the factors that can enhance recovery of walking following spinal cord injury (SCI). One new development is the use of functional electrical stimulation (FES) device to assist locomotion. The objective of this review is to present findings from some recent studies on the effect of long-term locomotor training with FES in subjects with SCI. Promising results are shown in all outcome measures of walking, such as functional mobility, speed, spatio–temporal parameters, and the physiological cost of walking. Furthermore, the change in the walking behavior could be associated with plasticity in the CNS organization, as seen by the modification of the stretch reflex and changes in the corticospinal projection to muscles of the lower leg. In conclusion, recovery of walking is an increasing possibility for a large number of people with SCI. New modalities of treatment have become available for this population but most still need to be evaluated for their efficacy. This review has focused on FES assisted walking as a therapeutic modality in subjects with chronic SCI, but it is envisaged that the care and recovery of SCI in the early phase of recovery could also be improved.     

Prediction of central neuropathic pain in spinal cord injury based on EEG classifier

Objectives

To create a classifier based on electroencephalography (EEG) to identify spinal cord injured (SCI) participants at risk of developing central neuropathic pain (CNP) by comparing them with patients who had already developed pain and with able bodied controls.

Thermogram in spinal cord stimulation with complex regional pain syndrome and a review of the literature

Introduction: Spinal cord stimulation (SCS) is an efficient procedure for treatment of intractable pain. Methods: We present a patient who underwent SCS lead placement for severe left lower extremity pain. The patient had experienced good pain. He underwent thermographic imaging before, just after and ten days later of procedure. Results: Thermogram study revealed from blue color (hypothermic) pattern at before procedure to reddish or pink color (hyperthermic) pattern at ten days later. Discussion: SCS may be increase microcirculation and seems to have sympatholytic effects. Conclusion: We experienced that improvement of blood flow as result of SCS in CRPS.     

Segmental hypersensitivity and spinothalamic function in spinal cord injury pain

The mechanisms underlying central pain following spinal cord injury (SCI) are unsettled. The purpose of the present study was to examine differences in spinothalamic tract function below injury level and evoked pain in incomplete SCI patients with neuropathic pain below injury level (central pain) versus those without such pain. A clinical examination, quantitative sensory testing and magnetic resonance imaging (MRI) were performed in 10 SCI patients with below-level pain and in 11 SCI patients without neuropathic pain. Patients with and without pain had similar reductions of mechanical and thermal detection thresholds below injury level. SCI patients with central pain had sensory hypersensitivity in dermatomes corresponding to the lesion level more frequently than SCI patients without pain, but this may in part be explained by the exclusion of at-level spontaneous pain in the pain-free group. The rostral-caudal extent of the lesion measured by MRI did not differ between the two patient groups, and there were no statistically significant differences in any of the predefined areas of interest on the axial plane images. This study suggests that neuronal hyperexcitability plays a key role in central SCI pain and furthermore - in contrast to previous findings - that loss of spinothalamic functions does not appear to be a predictor for central neuropathic pain in spinal cord injury.     

脊髓电刺激治疗复杂区域性疼痛综合征

目的探讨脊髓电刺激术（spinal cord stimulation,SCS）治疗复杂性区域性疼痛综合征（complex regional pain syndrome,CRPS）的有效性。方法回顾性分析4例CRPS病例,其均经脊髓电刺激手术治疗并随访1年以上,采用视觉模拟疼痛评分（VAS）评估疼痛转归。结果病人术后VAS评分平均降低5．4,3例病人疼痛缓解大于50％,无手术并发症。结论SCS能够安全、有效地治疗CRPS。、     

脊髓背根入髓区毁损术治疗脊髓和马尾神经损伤后疼痛

目的 探讨脊髓和马尾神经损伤后疼痛的神经外科治疗方法、效果和安全性.方法 脊髓和马尾神经损伤后疼痛患者14例,年龄28～72岁,病程8个月-28年;疼痛位于下肢感觉减退和缺失区,为烧灼、压榨或痉挛样疼痛,视觉模拟疼痛评分(Visual analogy scale,VAS)8～10分;均伴有不同程度的下肢肌力下降.14例患者共行脊髓背根入髓区(dorsal root entry zone,DREZ)毁损术15次.结果 随访3个月-3年.6例疼痛消失,5例疼痛明显减轻,停用或少量使用镇痛剂,VAS 2～4分;3例疼痛无明显改善.所有病例无严重手术并发症.结论 DREZ毁损术对脊髓和马尾神经损伤后慢性神经病理性疼痛安全有效.     

Generating artificial sensations with spinal cord stimulation in primates and rodents

For patients who have lost sensory function due to a neurological injury such as spinal cord injury (SCI), stroke, or amputation, spinal cord stimulation (SCS) may provide a mechanism for restoring somatic sensations via an intuitive, non-visual pathway. Inspired by this vision, here we trained rhesus monkeys and rats to detect and discriminate patterns of epidural SCS. Thereafter, we constructed psychometric curves describing the relationship between different SCS parameters and the animal's ability to detect SCS and/or changes in its characteristics. We found that the stimulus detection threshold decreased with higher frequency, longer pulse-width, and increasing duration of SCS. Moreover, we found that monkeys were able to discriminate temporally- and spatially-varying patterns (i.e. variations in frequency and location) of SCS delivered through multiple electrodes. Additionally, sensory discrimination of SCS-induced sensations in rats obeyed Weber's law of just-noticeable differences. These findings suggest that by varying SCS intensity, temporal pattern, and location different sensory experiences can be evoked. As such, we posit that SCS can provide intuitive sensory feedback in neuroprosthetic devices.