Effects of spinal cord stimulation with “standard clinical” and higher frequencies on peripheral blood flow in rats

Improvement of brain perfusion in patients with chronic brain ischemia at epidural spinal cord electrical stimulation

Objective

Increasing life expectancy and aging of the population is accompanied by a steady increase in the number of elderly patients with chronic cerebral ischemia and age-related cognitive impairment associated with cerebral hypoperfusion and microangiopathy. The aim of this study was to identify long-term changes in cerebral blood flow (CBF) in patients with chronic cerebral ischemia at the epidural electrical stimulation of the spinal cord (SCS).

Materials and methods

Changes in cerebral blood flow were studied according to CT perfusion in 59 patients (aged 55–78 years) with vertebrogenic pain syndromes and chronic cerebral ischemia during epidural electrical stimulation of the spinal cord at the cervical (C3–C5) and lower thoracic (Th9–Th10) levels.

Results

In all patients, on the 5th day of trial SCS, an increase in cerebral blood flow by from 58.6 ± 1.13 ml/100 ml/min to 64.8 ± 1.21 ml/100 ml/min (p < 0.01) with stimulation at the Th9-Th10 level and from 58.8 ± 1.12 ml/100 ml/min to 68.2 ± 1.42 ml/100 ml/min (p < 0, 01) with stimulation at the C3-C5 level. These changes in brain perfusion were preserved during the follow-up examination 1 year after the implantation of chronic SCS system. The greatest increase in CBF was registered in the frontotemporal regions, subcortical structures and white matter of the brain. Changes in cerebral perfusion did not correlate with the degree of reduction in the severity of the accompanying pain syndrome. The change in CBF in the control group (32 patients) in all periods was not statistically significant.

Conclusion

Our results show that SCS is accompanied by a persistent improvement in brain perfusion, which may be potentially useful for developing methods for reducing age-related vascular disorders in the elderly.

[Chronic spinal stimulation in treatment of lower limb critical ischaemia syndrome]

Obliterating peripheral artery disease is a commonly occurring pathological condition, most often resulting from an atherosclerotic lesion of vessels with progressive narrowing of their lumens. The consequences of decompensation of chronic arterial insufficiency such as ischaemic pain, claudication, and trophic impairments are in some instances difficult to treat, despite using multicomponent medicamentous therapy and/or performing revascularizing interventions. This article describes a clinical case report regarding the use of spinal stimulation in a patient presenting with stage IV chronic lower limb ischaemia according to the Fontaine classification. This is accompanied and followed by depicting the dynamics of the laboratory, instrumental, and clinical parameters over a two-year follow-up period. In order to explain the choice of the intervention and the causes of the described picture, discussed are the existing theories of the mechanisms of action of spinal stimulation. To this is added a literature review of using this method in treatment of lower limb critical ischaemia when performing reconstructive angiosurgical treatment is unavailable. Mention is also made of the incidence and types of probable complications, as well as possibilities and limitations of the method.

Dorsal Root Ganglion Stimulation in Experimental Painful Diabetic Polyneuropathy: Delayed Wash-Out of Pain Relief After Low-Frequency (1Hz) Stimulation

OBJECTIVE

Up until now there is little data about the pain relieving effect of different frequency settings in DRGS. The aim of this study was to compare the pain relieving effect of DRGS at low-, mid-, and high-frequencies and Sham-DRGS in an animal model of painful diabetic neuropathy (PDPN).

MATERIAL AND METHODS

Diabetes mellitus was induced by an intraperitoneal injection of streptozotocin in 8-week-old female Sprague-Dawley rats (n = 24; glucose ≥15 mmol/L: n = 20; mechanical hypersensitivity: n = 15). Five weeks later, a DRGS device was implanted at the L5 DRG. Ten animals were included for stimulation, alternating 30 minutes of low (1 Hz)-, mid (20 Hz)-, and high (1000 Hz)-frequencies and Sham-DRGS during four days, with a pulse width of 0.2 msec (average amplitude: 0.19 ± 0.01 mA), using a randomized cross-over design. The effect on mechanical hypersensitivity of the hind paw to von Frey filaments was evaluated.

RESULTS

All DRGS frequencies resulted in a complete reversal of mechanical hypersensitivity and "a clinically relevant reduction" was achieved in 70-80% of animals. No significant differences in maximal pain relieving effect were found between the different frequency treatments (p = 0.24). Animals stimulated at 1000 and 20 Hz returned to baseline mechanical hypersensitivity values 15 and 30 min after stimulation cessation, respectively, while animals stimulated at 1 Hz did not.

CONCLUSIONS

These results show that DRGS is equally effective when applied at low-, mid-, and high-frequency in an animal model of PDPN. However, low-frequency-(1 Hz)-DRGS resulted in a delayed wash-out effect, which suggests that this is the most optimal frequency for pain therapy in PDPN as compared to mid- and high-frequency.

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.

Dependence of c-fos Expression on Amplitude of High-Frequency Spinal Cord Stimulation in a Rodent Model

OBJECTIVES

Clinical high-frequency spinal cord stimulation (hfSCS) (>250 Hz) applied at subperception amplitudes reduces leg and low back pain. This study investigates, via labeling for c-fos-a marker of neural activation, whether 500 Hz hfSCS applied at amplitudes above and below the dorsal column (DC) compound action potential (CAP) threshold excites dorsal horn neurons.

MATERIALS AND METHODS

DC CAP thresholds in rats were determined by applying single biphasic pulses of SCS to T₁₂ -T₁₃ segments using pulse widths of 40 or 200 μsec via a ball electrode placed over the left DC and increasing amplitude until a short latency CAP was observed on the L₅ DC and sciatic nerve. The result of this comparison allowed us to substitute sciatic nerve CAP for DC CAP. SCS at T₁₂ -T₁₃ was applied continuously for two hours using: sham or hfSCS at 500 Hz SCS, 40 μsec pulse width, and 50, 70, 90, or 140% CAP threshold. Spinal cord slices from T₁₁ -L₁ were immunolabeled for c-fos, and the number of c-fos-positive cells was quantified.

RESULTS

500 Hz hfSCS applied at 90 and 140% CAP threshold produced substantial (≥6 c-fos + neurons on average per slice per segment) c-fos expression in more segments between T₁₁ and L₁ than did sham stimulation (p < 0.025, 90% CAP; p < 0.001, 140% CAP, Fisher's Exact Tests) and resulted in more c-fos-positive neurons on average per slice per segment ipsilateral to than contralateral to the SCS electrode at 70, 90, and 140% CAP threshold (p < 0.01, Wilcoxon Signed Rank Tests).

CONCLUSIONS

The finding of enhanced c-fos expression in the ipsilateral superficial dorsal horn provides evidence for activation/modulation of neuronal circuitry associated with subperception hfSCS.

Burst Spinal Cord Stimulation in Peripherally Injured Chronic Neuropathic Rats: A Delayed Effect

OBJECTIVE

Two well-known spinal cord stimulation (SCS) paradigms, conventional (Con) and burst SCS, are hypothesized to exert their antinociceptive effects through different stimulation-induced mechanisms. We studied the course of the behavioral antinociceptive effect during 60 minutes of SCS and 30 minutes post-SCS in a rat model of chronic neuropathic pain.

METHODS

Animals underwent a unilateral partial sciatic nerve ligation, after which quadripolar electrodes were implanted into the epidural space at vertebral level T13 (n = 43 rats). While receiving either Con SCS or biphasic burst SCS, the pain behavior of the rats was assessed by means of paw withdrawal thresholds (WTs) in response to the application of von Frey monofilaments.

RESULTS

After 15 minutes of Con SCS (n = 21), WTs significantly differed from baseline (P = 0.04), whereas WTs of the burst SCS group (n = 22) did not. After 30 minutes of SCS, WTs of the Con SCS and burst SCS groups reached similar levels, both significantly different from baseline, indicating a comparable antinociceptive effect for these SCS paradigms. Yet, the WTs of the burst SCS group were still significantly increased compared with baseline at 30 minutes post-stimulation, whereas the WTs of the Con SCS group were not.

CONCLUSIONS

To conclude, biphasic burst SCS results in a delayed antinociceptive effect after onset of the stimulation, as compared with Con SCS, in a chronic neuropathic pain model. Furthermore, biphasic burst SCS seems to exhibit a delayed wash-out of analgesia after stimulation is turned off.

Femoral vascular conductance and peroneal muscle sympathetic nerve activity responses to acute epidural spinal cord stimulation in humans

NEW FINDINGS

What is the central question of this research? Does acute spinal cord stimulation increase vascular conductance and decrease muscle sympathetic nerve activity in the lower limbs of humans? What is the main finding and its importance? Acute spinal cord stimulation led to a rapid rise in femoral vascular conductance, and peroneal muscle sympathetic nerve activity demonstrated a delayed reduction that was not associated with the initial increase in femoral vascular conductance. These findings suggest that neural mechanisms in addition to attenuated muscle sympathetic nerve activity might be involved in the initial increase in femoral vascular conductance during acute spinal cord stimulation.

ABSTRACT

Clinical cases have indicated an increase in peripheral blood flow after continuous epidural spinal cord stimulation (SCS) and that reduced muscle sympathetic nerve activity (MSNA) might be a potential mechanism. However, no studies in humans have directly examined the effects of acute SCS (<60 min) on vascular conductance and MSNA. In study 1, we tested the hypothesis that acute SCS (<60 min) of the thoracic spine would lead to increased common femoral vascular conductance, but not brachial vascular conductance, in 11 patients who previously underwent surgical SCS implantation for management of neuropathic pain. Throughout 60 min of SCS, common femoral artery conductance was elevated and significantly different from brachial artery conductance [in millilitres per minute: 15 min, change (Δ) 26 ± 37 versus Δ-2 ± 19%; 30 min, Δ28 ± 45 versus Δ0 ± 26%; 45 min, Δ48 ± 43 versus Δ2 ± 21%; 60 min, Δ36 ± 61 versus Δ1 ± 24%; and 15 min post-SCS, Δ51 ± 64 versus Δ6 ± 33%; P = 0.013]. A similar examination in a patient with cervical SCS revealed minimal changes in vascular conductance. In study 2, we examined whether acute SCS reduces peroneal MSNA in a subset of SCS patients (n = 5). The MSNA burst incidence in response to acute SCS gradually declined and was significantly reduced at 45 and 60 min of SCS (in bursts per 100 heart beats: 15 min, Δ-1 ± 12%; 30 min, Δ-14 ± 12%; 45 min, Δ-19 ± 16%; 60 min, Δ-24 ± 18%; and 15 min post-SCS: Δ-11 ± 7%; P = 0.015). These data demonstrate that acute SCS rapidly increases femoral vascular conductance and reduces peroneal MSNA. The gradual reduction in peroneal MSNA observed during acute SCS suggests that neural mechanisms in addition to attenuated MSNA might be involved in the acute increase in femoral vascular conductance.

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

Objectives

This 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.

Methods

Mechanical 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).

Results

Average 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.

Discussion

We 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.

Spinal Cord Stimulation Alters Protein Levels in the Cerebrospinal Fluid of Neuropathic Pain Patients: A Proteomic Mass Spectrometric Analysis

OBJECTIVES

Electrical neuromodulation by spinal cord stimulation (SCS) is a well-established method for treatment of neuropathic pain. However, the mechanism behind the pain relieving effect in patients remains largely unknown. In this study, we target the human cerebrospinal fluid (CSF) proteome, a little investigated aspect of SCS mechanism of action.

METHODS

Two different proteomic mass spectrometry protocols were used to analyze the CSF of 14 SCS responsive neuropathic pain patients. Each patient acted as his or her own control and protein content was compared when the stimulator was turned off for 48 hours, and after the stimulator had been used as normal for three weeks.

RESULTS

Eighty-six proteins were statistically significantly altered in the CSF of neuropathic pain patients using SCS, when comparing the stimulator off condition to the stimulator on condition. The top 12 of the altered proteins are involved in neuroprotection (clusterin, gelsolin, mimecan, angiotensinogen, secretogranin-1, amyloid beta A4 protein), synaptic plasticity/learning/memory (gelsolin, apolipoprotein C1, apolipoprotein E, contactin-1, neural cell adhesion molecule L1-like protein), nociceptive signaling (neurosecretory protein VGF), and immune regulation (dickkopf-related protein 3).

CONCLUSION

Previously unknown effects of SCS on levels of proteins involved in neuroprotection, nociceptive signaling, immune regulation, and synaptic plasticity are demonstrated. These findings, in the CSF of neuropathic pain patients, expand the picture of SCS effects on the neurochemical environment of the human spinal cord. An improved understanding of SCS mechanism may lead to new tracks of investigation and improved treatment strategies for neuropathic pain.

Spinal cord stimulation in experimental chronic painful diabetic polyneuropathy: Delayed effect of High-frequency stimulation

Background

Spinal cord stimulation (SCS) has been shown to provide pain relief in painful diabetic polyneuropathy (PDPN). As the vasculature system plays a great role in the pathophysiology of PDPN, a potential beneficial side‐effect of SCS is peripheral vasodilation, with high frequency (HF) SCS in particular. We hypothesize that HF‐SCS (500 Hz), compared with conventional (CON) or low frequency (LF)‐SCS will result in increased alleviation of mechanical hypersensitivity in chronic experimental PDPN.

Methods

Diabetes was induced in 8‐week‐old female Sprague–Dawley rats with an intraperitoneal injection of 65 mg/kg of streptozotocin (n = 44). Rats with a significant decrease in mechanical withdrawal response to von Frey filaments over a period of 20 weeks were implanted with SCS electrodes (n = 18). Rats were assigned to a cross‐over design with a random order of LF‐, CON‐, HF‐ and sham SCS and mechanical withdrawal thresholds were assessed with von Frey testing.

Results

Compared with sham treatment, the average 50% WT score for 5 Hz was 4.88 g higher during stimulation (p = 0.156), and 1.77 g higher post‐stimulation (p = 0.008). CON‐SCS resulted in 50% WT scores 5.7 g, and 2.51 g higher during (p = 0.064) and after stimulation (p < 0.004), respectively. HF‐SCS started out with an average difference in 50% WT score compared with sham of 1.87 g during stimulation (p = 0.279), and subsequently the steepest rise to a difference of 5.47 g post‐stimulation (p < 0.001).

Conclusions

We demonstrated a delayed effect of HF‐SCS on mechanical hypersensitivity in chronic PDPN animals compared with LF‐, or CON‐SCS.

Significance

This study evaluates the effect of SCS frequency (5–500 Hz) on mechanical hypersensitivity in the chronic phase of experimental PDPN. High frequency (500 Hz) – SCS resulted in a delayed effect‐ on pain‐related behavioural outcome in chronic PDPN.

High-frequency electrical stimulation can be a complementary therapy to promote nerve regeneration in diabetic rats

The purpose of this study was to evaluate whether 1 mA of percutaneous electrical stimulation (ES) at 0, 2, 20, or 200 Hz augments regeneration between the proximal and distal nerve stumps in streptozotocin diabetic rats. A10-mm gap was made in the diabetic rat sciatic nerve by suturing the stumps into silicone rubber tubes. Normal animals were used as the controls. Starting 1 week after transection, ES was applied between the cathode placed at the distal stump and the anode at the proximal stump every other day for 3 weeks. At 4 weeks after surgery, the normal controls and the groups receiving ES at 20, and 200 Hz had a higher success percentage of regeneration compared to the ES groups at 0 and 2 Hz. In addition, quantitative histology of the successfully regenerated nerves revealed that the groups receiving ES at a higher frequency, especially at 200 Hz, had a more mature structure with more myelinated fibers compared to those in the lower-frequency ES groups. Similarly, electrophysiology in the ES group at 200 Hz showed significantly shorter latency, larger amplitude, larger area of evoked muscle action potentials and faster conduction velocity compared to other groups. Immunohistochemical staining showed that ES at a higher frequency could significantly promote calcitonin gene-related peptide expression in lamina I-II regions in the dorsal horn and recruit a higher number of macrophages in the diabetic distal sciatic nerve. The macrophages were found that they could stimulate the secretion of nerve growth factor, platelet-derived growth factor, and transforming growth factor-β in dissected sciatic nerve segments. The ES at a higher frequency could also increase cutaneous blood flow in the ipsilateral hindpaw to the injury. These results indicated that a high-frequency ES could be necessary to heal severed diabetic peripheral nerve with a long gap to be repaired.

Conventional and kilohertz-frequency spinal cord stimulation produces intensity- and frequency-dependent inhibition of mechanical hypersensitivity in a rat model of neuropathic pain

BACKGROUND

Spinal cord stimulation (SCS) is a useful neuromodulatory technique for treatment of certain neuropathic pain conditions. However, the optimal stimulation parameters remain unclear.

METHODS

In rats after L5 spinal nerve ligation, the authors compared the inhibitory effects on mechanical hypersensitivity from bipolar SCS of different intensities (20, 40, and 80% motor threshold) and frequencies (50, 1 kHz, and 10 kHz). The authors then compared the effects of 1 and 50 Hz dorsal column stimulation at high- and low-stimulus intensities on conduction properties of afferent Aα/β-fibers and spinal wide-dynamic-range neuronal excitability.

RESULTS

Three consecutive daily SCS at different frequencies progressively inhibited mechanical hypersensitivity in an intensity-dependent manner. At 80% motor threshold, the ipsilateral paw withdrawal threshold (% preinjury) increased significantly from pre-SCS measures, beginning with the first day of SCS at the frequencies of 1 kHz (50.2 ± 5.7% from 23.9 ± 2.6%, n = 19, mean ± SEM) and 10 kHz (50.8 ± 4.4% from 27.9 ± 2.3%, n = 17), whereas it was significantly increased beginning on the second day in the 50 Hz group (38.9 ± 4.6% from 23.8 ± 2.1%, n = 17). At high intensity, both 1 and 50 Hz dorsal column stimulation reduced Aα/β-compound action potential size recorded at the sciatic nerve, but only 1 kHz stimulation was partially effective at the lower intensity. The number of actions potentials in C-fiber component of wide-dynamic-range neuronal response to windup-inducing stimulation was significantly decreased after 50 Hz (147.4 ± 23.6 from 228.1 ± 39.0, n = 13), but not 1 kHz (n = 15), dorsal column stimulation.

CONCLUSIONS

Kilohertz SCS attenuated mechanical hypersensitivity in a time course and amplitude that differed from conventional 50 Hz SCS, and may involve different peripheral and spinal segmental mechanisms.

Comparison of burst and tonic spinal cord stimulation on spinal neural processing in an animal model

OBJECTIVES

Spinal cord stimulation (SCS) using bursts of pulses suppressed neuropathic pain as well or better than tonic stimulation and limited the incidences of parasthesias. The present translational study explored possible differences in mechanisms of burst and tonic SCS on nociceptive spinal networks and/or the gracile nucleus supraspinal relay.

MATERIALS AND METHODS

Visceromotor reflexes (VMRs, a nociceptive response) or extracellular activity of either L6-S2 spinal neurons or gracile nucleus neurons were recorded during noxious somatic stimulation (pinching) and visceral stimulation (colorectal distension [CRD]) in anesthetized rats. A stimulating (unipolar, ball) electrode at L2-L3 delivered 40 Hz burst or tonic SCS at different intensities relative to motor threshold (MT).

RESULTS

Average MTs for burst SCS were significantly lower than for tonic SCS. Burst SCS reduced the VMR more than tonic SCS. After high-intensity SCS (90% MT), spinal neuronal responses to CRD and pinch were reduced similarly for burst and tonic SCS. At low-intensity SCS (60% MT), only burst SCS significantly decreased the nociceptive somatic response. Tonic but not burst SCS significantly increased spontaneous activity of neurons in the gracile nucleus.

CONCLUSION

Based on the clinically relevant burst versus tonic parameters used in this study, burst SCS is more efficacious than tonic SCS in attenuating visceral nociception. Burst and tonic SCS also suppress lumbosacral neuronal responses to noxious somatic and visceral stimuli; however, burst SCS has a greater inhibitory effect on the neuronal response to noxious somatic stimuli than to noxious visceral stimuli. Reduced or abolished paresthesia in patients may be due in part to burst SCS not increasing spontaneous activity of neurons in the gracile nucleus.

Neural mechanisms of spinal cord stimulation

Neuromodulation, specifically spinal cord stimulation (SCS), relieves pain and improves organ function. This chapter discusses the limited information presently available about the underlying mechanisms that explain the beneficial effects of treating patients with SCS. Where applicable, information is presented about translational research that illustrates the importance of collaboration between clinicians, basic scientists, and engineers. This chapter presents the infant stage of studies that attempt to explain the mechanisms which come into play for treating neuropathic pain, ischemic pain in peripheral vascular disease, and diseases of the visceral organs, specifically the gastrointestinal tract and the heart. The basic science studies will demonstrate how SCS acts on various pain syndromes and diseases via multiple pathways in the central nervous system as well as in somatic structures and visceral organs.

The effect of spinal cord stimulation frequency in experimental painful diabetic polyneuropathy

BACKGROUND

Spinal cord stimulation (SCS) has been shown to be an effective treatment for painful diabetic polyneuropathy (PDP). An increase of efficacy is needed since only 67% of patients benefit from SCS. This study aimed to develop an animal model for SCS in PDP and study the effect of various stimulation frequencies on the functional outcome. As the pathophysiology of PDP is complex, including vasoconstriction and nerve injury, the frequency of SCS may result in different outcomes.

METHODS

Diabetes mellitus was induced by an intraperitoneal injection of streptozotocin in 8-week-old female Sprague-Dawley rats (n=76; glucose >15 mmol/L; n=51). A SCS device was implanted at level Th13 4 weeks later. SCS of the dorsal columns was applied for 30 min and the effect on mechanical hypersensitivity was evaluated.

RESULTS

Mechanical hypersensitivity developed in 26 rats, which were included (low-frequency, n=6; mid-frequency, n=8; high frequency, n=9; and sham, n=3). SCS of the dorsal columns was applied for 40 min, and the effect on mechanical hypersensitivity was evaluated. In all treatment groups, SCS resulted in reversal of mechanical hypersensitivity and a clinically relevant reduction was achieved in 70% of animals. No differences in efficacy were found between the different treatment groups.

CONCLUSIONS

The pain-relieving effect of SCS in PDP was studied in an experimental model. Our study shows that SCS on mechanical hypersensitivity in PDP rats is equally effective when applied at low, mid and high frequency.

Spinal cord stimulation: neurophysiological and neurochemical mechanisms of action

Chronic neuropathic pain can significantly reduce quality of life and place an economic burden on individuals and society. Spinal cord stimulation (SCS) is an alternative approach to the treatment of neuropathic pain when standard pharmacological agents have failed. However, an improved understanding of the mechanisms by which SCS inhibits pain is needed to enhance its clinical utility. This review summarizes important findings from recent studies of SCS in animal models of neuropathic pain, highlights current understanding of the spinal neurophysiological and neurochemical mechanisms by which SCS produces an analgesic effect, and discusses the potential clinical applicability of these findings and future directions for research.

Electrical stimulation improves peripheral nerve regeneration in streptozotocin-induced diabetic rats

We discuss if percutaneous electrical stimulation (ES) at 1 mA and 2 Hz after peripheral nerve transection could enhance axonal regeneration and functional recovery in diabetic animals.

METHODS

Four groups of adult rats (group A: normal rats; group B: normal rats with ES; group C: streptozotocin- induced diabetic rats; and group D: streptozotocin-induced diabetic rats with ES) were subjected to sciatic nerve section followed by repair using silicone rubber conduits across a 10-mm gap. Rats in groups B and D received ES for 15 minutes every other day for three weeks. The groups A and C received no ES.

RESULTS

At four weeks after surgery in groups B and D, immunohistochemical staining showed that lamina I and II regions in the dorsal horn ipsilateral to the injury were significantly calcitonin gene-related peptide-immunolabeled, and a significantly higher number of macrophages were recruited in the distal sciatic nerve compared with group C. In groups A, B, and D, electrophysiological results showed higher levels of reinnervation with significantly shorter latencies and faster nerve conductive velocities, and the histologic evaluations showed relatively larger mean values of myelinated axon densities and endoneurial areas compared with group C.

CONCLUSIONS

Thus, the ES may improve the recovery of a severe peripheral nerve injury in diabetic animals, which could be considered as a supplementary treatment in diabetic neurotrauma.

Use of a spinal cord stimulator for treatment of Martorell hypertensive ulcer

Martorell ulcer is a specific disease entity characterized by multiple small homogeneous, symmetrical lesions, although single lesions are observed as well, most commonly located on the anterolateral aspect of the lower leg. The pain associated to these lesions is disproportionate to their size.Martorell ulcer designates a specific disease entity that occurs predominantly in middle-aged women with poorly controlled hypertension in the form of skin ulcers on the anterolateral aspect of the lower legs. The lesions initially appear as small, painful blisters which may or may not be associated with trauma. The pathophysiology of Martorell ulcer is assumed to be related to hypertension-induced arteriole changes in the dermis. The pain is often disproportionate, and the symptoms are not relieved by rest or elevation.Spinal cord stimulation (SCS) is an accepted evidence-based therapy for the treatment of chronic ischemic pain. Spinal cord stimulation is used as a therapeutic tool in the management of this disease not only for symptomatic pain control but also for accelerating the healing process through its effects on causal mechanisms. The beneficial effects of SCS when used to treat ischemic pain include pain relief, decreased infarction or ulcer size, decreased oxygen requirements, and increased claudication distance. Clinical and basic studies indicate that these beneficial effects are mainly associated with an increase or redistribution of blood flow to the ischemic area and/or normalization of the activity in the nervous system.We present the case of a 71-year-old woman diagnosed with Martorell ulcer in the acute phase of the disease. The patient was treated with SCS to achieve both pain relief and healing of the cutaneous ulcer.

Spinal cord stimulation for Raynaud's syndrome: long-term alleviation of bilateral pain with a single cervical lead

INTRODUCTION

  Spinal cord stimulation (SCS) has been described in a variety of neuropathic and vasospastic pain conditions including Raynaud's syndrome.

METHODS

  We report here the outcome of single lead SCS in the case of a 49-year-old woman with severe Raynaud's syndrome, which had failed to respond to medical therapy.

RESULTS

  With a single quadripolar cervical lead in midline position at the C2/C3 level sustained pain relief of the bilateral pain was accomplished. Pain scores sank from 7/10 to 2-3/10 on the nominal analog scale and remained stable more than nearly four years by now.

CONCLUSIONS

  Treatment of bilateral pain in Raynaud's syndrome with SCS in a single technique is feasible. Advantages and disadvantages as compared with stimulation with bilateral leads are discussed.

Spinal cord stimulation for patients with inoperable chronic critical leg ischemia

BACKGROUND

Because of the prevalence of diabetes, the treatment of diabetic foot is still challenging. Even an exactly proved effective and practical method can't be listed except vascular surgery which is not a long-term way for it. Spinal cord stimulation (SCS) is a very promising option in the treatment algorithm of inoperable chronic critical leg ischemia (CLI).

DATA SOURCES

We searched Pubmed database with key words or terms such as "spinal cord stimulation", "ischemic pain" and "limb ischemia" appeared in the last five years.

RESULTS

The mechanism of SCS is unclear. Two theories have emerged to interpret the benefits of SCS. Pain relief from SCS can be confirmed by a majority of the studies, while limb salvage and other more ambitious improvements have not come to an agreement. The complications of SCS are not fatal, but most of them are lead migration, lead connection failure, and local infection.

CONCLUSIONS

SCS is a safe, promising treatment for patients with inoperable CLI. It is effective in pain reduction compared with traditional medical treatment.

The effect of spinal cord stimulation on seizure susceptibility in rats

OBJECTIVES

Spinal cord stimulation (SCS) activates the thalamus, which may be involved in generation of seizures. SCS may therefore influence seizure susceptibility. We investigated the effect of SCS on seizure susceptibility when performed at low frequency (4 Hz) and a frequency in the typical range of SCS treatment (54 Hz).

MATERIALS AND METHODS

Rats were divided in three groups: control (N = 8), 4 Hz SCS (N = 6), and 54 Hz SCS (N = 8). Tonic-clonic seizures were induced by 10-min intravenous infusion of pentylenetetrazole (PTZ). SCS was started 5 min prior to PTZ infusion and continued for 5 min after infusion offset. Seizure susceptibility was accessed via the latency, number, and total duration of seizures.

RESULTS

Four Hz SCS significantly increased seizure susceptibility. Fifty-four Hz SCS produced a nonsignificant trend toward decreased seizure susceptibility.

CONCLUSIONS

Low-frequency SCS is proconvulsive in rats. Further research needs to investigate if this also applies to humans.