Stimulation of the central and peripheral nervous system for the control of pain

Effects of somatostatin, a somatostatin agonist, and an antagonist, on a putative migraine trigger pathway

OBJECTIVE

To determine whether somatostatin (SST) could be a cortico-brainstem neurotransmitter involved in producing the headache of migraine.

BACKGROUND

There is evidence to support the idea that a cortico-brainstem-trigeminal nucleus neuraxis might be responsible for producing migraine headache; we have suggested that SST may be one of the neurotransmitters involved.

METHODS

Rats were anesthetised and prepared for recording neurons in either the periaqueductal gray matter (PAG) or nucleus raphe magnus (NRM), as well as the trigeminal nucleus caudalis (TNC). The dura mater and facial skin were stimulated electrically or mechanically. SST, the SST agonist L054264 and the SST antagonist CYN54806 were injected intravenously, by microinjection, or by iontophoresis into the PAG or NRM. Cortical neuronal activity was provoked by cortical spreading depression (CSD) or light flash (LF) and was monitored by recording cortical blood flow (CBF).

RESULTS

Intravenous injection of SST: (a) selectively decreased the responses of TNC neurons to stimulation of the dura, but not skin, for up to 5 h; (b) decreased the ongoing discharge rate of TNC neurons while simultaneously increasing the discharge rate of neurons in either brainstem nucleus and; (c) prevented, or reversed, the effect of CSD and LF on brainstem and trigeminal neuron discharge rates. CSD and LF decreased the discharge rate of neurons in both brainstem nuclei and increased the discharge rate of TNC neurons. These effects were reversed by L054264 and mimicked by CYN54806. Injections of L054264 into the PAG or NRM reduced the response of TNC neurons to dural stimulation and skin stimulation differentially, depending on the nucleus injected. Injections of CYN54806 into either brainstem nucleus potentiated the responses of TNC neurons to dural and skin stimulation, but without a marked differential effect.

CONCLUSIONS

These results imply that SST could be a neurotransmitter in a pathway responsible for migraine pain.

The Impact of Hot Spring Hydrotherapy on Pain Perception and Dysfunction Severity in Patients with Chronic Low Back Pain: A Systematic Review and Meta-Analysis

Background

Chronic Low Back Pain (CLBP) is a prevalent global health issue, leading to prolonged discomfort and functional limitations. Hot spring hydrotherapy, which utilizes mineral-rich, warm spring water, offers a unique physical therapy that holds promise in alleviating CLBP symptoms.

Objective

This meta-analysis aims to assess the effectiveness of hot spring hydrotherapy in improving CLBP symptoms, encompassing pain intensity, functional disability, quality of life, and medication usage.

Methods

A systematic review and meta-analysis were conducted by searching relevant literature in multiple databases. Included studies compared hot spring hydrotherapy with control interventions or other treatments. Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated for pain intensity, functional disability, medication usage, and quality of life.

Results

A total of 16 studies met the inclusion criteria, involving 1656 participants with chronic low back pain across various countries. The meta-analysis demonstrated that hot spring hydrotherapy was effective in reducing pain intensity (SMD = -0.901, 95% CI [-1.777, -0.025], P < 0.05) and improving functional disability (SMD = -3.236, 95% CI [-4.898, -1.575], P < 0.0001) in CLBP patients. Hot spring hydrotherapy also resulted in a significant reduction in medication usage (P < 0.05). Subgroup analysis showed that the effects of hot spring hydrotherapy were more pronounced in patients aged 60 and above, while no significant differences were observed in patients below 60 years of age, single hot Spring Hydrotherapy help improve patients' quality of life.

Conclusion

Hot spring hydrotherapy is an effective intervention for improving CLBP symptoms, including pain intensity, functional disability, and medication usage. It is particularly beneficial for CLBP patients aged 60 and above. These findings support the integration of hot spring hydrotherapy into the treatment approach for CLBP, although further research is needed to determine its efficacy in younger patients and to explore the underlying mechanisms of its therapeutic effects.

Prospero Id

CRD42023430860.

Effect of Repetitive Peripheral Magnetic Stimulation on Patients With Low Back Pain: A Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The purpose of this meta-analysis was to investigate the effects of repetitive peripheral magnetic stimulation (rPMS) on pain intensity, functional mobility, and kinesiophobia in individuals with low back pain (LBP).

DATA SOURCES

The PubMed, Physiotherapy Evidence Database, Embase, Cochrane Library, and Web of Science databases were systematically searched from inception until November 25, 2022.

STUDY SELECTION

Eligible randomized controlled trials contained information on the population (LBP), intervention (rPMS), and outcomes (pain intensity, functional mobility, and kinesiophobia). Participants in the rPMS intervention group were compared with those in sham or other control groups. Two independent researchers searched for, screened, and qualified the articles.

DATA EXTRACTION

Two independent researchers extracted key information from each eligible study. The authors' names, year of publication, setting, total sample size, rPMS parameters, baseline/mean difference (MD), and 95% confidence interval (CI) were extracted using a standardized form, and the methodological quality was assessed using the Physiotherapy Evidence Database score and GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) system.

DATA SYNTHESIS

Of 733 studies identified, 6 randomized controlled trials (n = 139) were included for meta-analysis. Compared with sham rPMS or other therapy, rPMS showed significant efficacy in reducing pain intensity (visual analog scale: MD, -1.89; 95% CI, -3.32 to -0.47; P<.05; very low-quality evidence). Significant efficacy was also found in terms of functional disability (Oswestry Disability Index: MD, -8.39; 95% CI, -13.65 to -3.12; P<.001; low-quality evidence). However, there was no statistically significant between-group difference on the Tampa scale of kinesiophobia (MD, -1.81; 95% CI, -7.60 to 3.98; P>.05; very low-quality evidence).

CONCLUSIONS

This meta-analysis found very low- to low-quality evidence that rPMS can be used to reduce pain intensity and improve functional disability in individuals with LBP. However, no significant effect of rPMS on kinesiophobia was found.

Effect of Peripheral Magnetic Stimulation on Acute and Chronic Pain After Surgery: A Systematic Review and Meta-Analysis

Peripheral magnetic stimulation (PMS) is a potentially promising modality to help manage postoperative pain. We systematically reviewed the effect of PMS on acute and chronic postoperative pain. MEDLINE, Cochrane CENTRAL, EMBASE, ProQuest Dissertations, and clinical trials.gov were searched from inception until May 2021. We included studies of any study design that included patients ≥18 years of age undergoing any type of surgery that administered PMS within the perioperative period and evaluated postoperative pain. Seventeen randomized controlled trials and 1 nonrandomized clinical trial were included into the review. Thirteen out of the 18 studies found a positive effect with PMS on postoperative pain scores. In our meta-analysis, peripheral magnetic stimulation was more efficacious than sham or no intervention within the first 7 postoperative days (mean difference [MD] -1.64 on a 0 to 10 numerical rating score, 95% confidence interval [CI] -2.08 to -1.20, I2 = 77%, 6 studies, 231 patients). This was also true at 1 and 2 months after surgery (MD -1.82, 95% CI -2.48 to -1.17, I2 = 0%, 3 studies, 104 patients; and MD -1.96, 95% CI -3.67 to -.26, I2 = 84%, 3 studies, 104 patients, respectively). A difference was not seen with persistent pain at 6 and 12-months after surgery, acute postoperative opioid consumption, or adverse events between groups. Results are limited by heterogeneity and generally low-quality studies, as well as low or very low quality of evidence. High-quality and adequately blinded trials are needed to definitively confirm the benefits of peripheral magnetic stimulation administered in the perioperative period. PERSPECTIVE: This review evaluates the efficacy and safety of PMS on postoperative pain. The results help elucidate PMS' role in postoperative pain management and identify gaps where more research is required.

Ultrasound-guided repetitive pulsed peripheral magnetic stimulation provides pain relief in refractory glossopharyngeal neuralgia: A case report

Aims

Repetitive peripheral magnetic stimulation (rPMS) is a novel nonpharmacological treatment modality. This noninvasive approach can stimulate peripheral nerves to provide analgesia through neuromodulation. We report the first case of ultrasound-guided rPMS to treat a case of severe refractory glossopharyngeal neuralgia.

Methods

A 70-year-old female with an 8-year history of glossopharyngeal neuralgia reported refractory pain unresponsive to pharmacological and interventional treatments. After consenting to treatment, the patient received high-frequency rPMS in three different sessions using intermittent theta burst stimulation below motor thresholds. rPMS was applied over the skin directed at the glossopharyngeal nerve identified using ultrasound guidance. Session 1 included 20 min of continuous treatment, session 2 included 40 min of treatment (two 20-min treatments separated by a 10-min break), session 3 included 40 min of treatment (similar to Session 2) repeated daily for 5 days. Pre- and postintervention pain levels were collected with a daily 1-week pain diary and pain questionnaires.

Results

Session 1 led to an immediate 30% decrease in pain after treatment. Session 2 led to a 75% decrease in pain immediately after treatment that remained reduced for approximately 2 days. Session 3 produced complete pain relief immediately after treatment and remained lower for 5 days after treatment and returned to baseline levels at 1 week.

Conclusion

rPMS provided immense but temporary relief in a severe case of refractory glossopharyngeal neuralgia. Further work is needed to determine the most effective regimen to treat complex pain disorders in the head and neck.

Outcome of Surgical Treatments of Chronic Pain Caused by Trigeminal Neuropathy

BACKGROUND

Trigeminal neuropathy represents a subset of several facial pain syndromes that are difficult to diagnose and treat. Although many surgical modalities are available, outcomes remain suboptimal. The aim of this study is to present our experience in management of trigeminal neuropathy with a focus on the effectiveness and long-term efficacy of the different surgical procedures.

METHODS

A single-center retrospective cohort study was conducted from December 2012 until February 2020.

RESULTS

Twenty-eight patients (19 females, 9 males) were included in this study. They had 40 surgical interventions. At last follow-up, 1 patient (33.3%) treated by spinal cord stimulation (SCS) had no pain recurrence and 2 patients (66.6%) had their devices removed because of therapeutic failure. Median time to pain recurrence after SCS was 19.5 months (interquartile range [IQR], 29.79 months). Six patients were treated with peripheral nerve stimulation (PNS). At last follow-up, 2 patients had satisfactory pain relief, whereas half of the patients had no improvement. For the 17 patients treated with computed tomography-guided trigeminal tractotomy/nucleotomy, true failure occurred 7 times in 6 patients. Median time to pain recurrence was 5.6 months (IQR, 6.2). Of the 6 patients treated with caudalis DREZ, 3 (50%) had satisfactory pain relief for >1 year and the median time to pain recurrence was 3.9 months (IQR, 29.53).

CONCLUSIONS

Trigeminal neuropathy is a difficult to treat entity of facial pain syndromes. The long-term efficacy of available interventions does not meet patients' satisfaction. More organized prospective studies with longer follow-up are needed to define the patient population best served by each surgical modality.

Dorsal root entry zone procedure and other surgeries for pain

Pain is a very common symptom that often serves a protective function. It is typically treated medically. When pain becomes chronic and intractable, it no longer serves a protective function and often requires more aggressive forms of treatment. Many types of surgeries can be performed for the management of pain. These surgeries can involve ablation (destruction) or augmentation (stimulation or facilitation) of some part of the nervous system. In many of these surgeries, neurophysiologic intraoperative monitoring (NIOM) is not needed, however, in others neuromonitoring serves a mapping and monitoring purpose. The prototype of pain surgery for this chapter is the dorsal root entry zone (DREZ) procedure. Both mapping and monitoring can help improve lesioning precision and outcomes in this surgery. In this chapter, the DREZ procedures and other surgeries for primarily pain relief in which NIOM is used are discussed. Surgeries, such as spinal stenosis, in which pain relief is important but not the sole purpose, are not discussed here and are covered elsewhere.

[Treatment of sciatic posttraumatic neuropathy with chronic neuromodulation and endoscopic technics]

OBJECTIVE

Sciatic nerve injury in the deep gluteal space is a major clinical problem due to microsurgical manipulations in this region are limited in scope. We offer new endoscopic approach to the sciatic nerve in the deep gluteal space which allows to perform microsurgical manipulations, neurophysiological mapping and electrode installation for the chronic nerve stimulation.

MATERIAL AND METHOD

3 patients with sciatic neuropathy have been operated. Before the operation they suffered from neuropathic pain in the the posterior thigh and calf, reaching 7-8 points on the visual analog scale (VAS). Paresis of triceps surae and biceps femur also was occurred. We performed endoscopic approach to the deep gluteal space through a small incision under the gluteal fold. Microsurgical external and internal decompression of sciatic nerve was performed under the endoscopic control. Next, intra-trunk nerve mapping was performed to visualize sensory fibers. Cylindrical electrodes for chronic neurostimulation were directly placed on the sensory fibers of sciatic nerve.

RESULTS

Pain relief was obtained in all cases after activating the simulator, the patient noted a 50% reduction in pain. Muscle straight restoration was observed in all cases 2-3 months later. The clinical effect was stable in the follow up (6 months).

CONCLUSION

This technique, combining minimal invasiveness and intraoperative neurophysiological control, makes it possible to optimally position the electrode, both to achieve positive analgesic effect and for potential restoration of nerve function.

Glioblastoma single-cell microRaman analysis under stress treatments

Glioblastoma multiforme (GBM) is the most frequent malignant brain tumor characterized by highly heterogeneous subpopulations. In order to reveal the heterogeneous cell response, single cell analysis is an essential requirement. In this study, optical microscopy and Raman microspectroscopy were used to follow the stress response of U251 single cells adherent on a silicon substrate. Cultured cells on silicon substrate were treated with hydrogen peroxide to promote apoptosis. Under these conditions expected changes occurred after a few hours and were revealed by the reduction of cytochrome c, lipid, nucleic acid and protein Raman signals: this ensured the possibility to analyse U251 cell line as grown on Si substrate, and to monitor the response of single cells to stress conditions. As a consequence, we used microRaman to monitor the effects induced by nutrient depletion: a fast change of Raman spectra showed two different sub-populations of sensible and resistant U251 cells. Furthermore, spectral variations after DMSO addition were associated to volume changes and confirmed by morphological analysis. Thus, our results highlight the sensitivity of Raman microspectroscopy to detect rapid variations of macromolecule concentration due to oxidative stress and/or cell volume changes at the single cell level.

Peripheral Nerve Field Stimulation Therapy for Patients With Thoracic Pain: A Prospective Study

OBJECTIVE

Relative to the number of patients suffering chronic lumbar and cervical pain, fewer patients suffer persistent thoracic pain. Consequently there is less literature, with smaller sample sizes, reporting treatment of this cohort. Here, we assess peripheral nerve field stimulation (PNfS) as a potential treatment for chronic thoracic pain.

MATERIALS AND METHODS

This study included 20 consecutive chronic thoracic pain sufferers that responded successfully to PNfS trial. The patients were subsequently implanted with permanent eight-contact electrode linear percutaneous leads within their major area of pain. Patients were followed up at 12 months for outcome reporting. All 20 patients were considered in the statistical analysis, despite removal of three devices prior to follow up.

RESULTS

The average baseline pre-treatment Numerical Pain Rating Scale (NPRS) score was 7.75 ± 1.4. Following PNfS, the mean NPRS score was 2.25 ±2.14, reflecting a significant average improvement of 5.5 ± 3.31. Three patients were explanted prior to follow up: the first gained excellent thoracic pain relief but pain at the Implantable Pulse Generator (IPG) site could not be overcome, the second achieved excellent pain relief but the PNfS was removed due to recurrent infection and in the final instance, the intervention offered only poor relief and the device removed.

CONCLUSION

PNfS is an effective intervention for intractable disabling thoracic pain, offering sustained and worthwhile pain relief, for the overwhelming majority of the cohort. This may be especially true when considering a combined treatment approach of PNfS and analgesic use to manage remnant pain.

The Proper Use of Neurostimulation for Hand Pain

Upper extremity neuropathic pain states greatly impact patient functionality and quality of life, despite appropriate surgical intervention. This article focuses on the advanced therapies that may improve pain care, including advanced treatment strategies that are available. The article also surveys therapies on the immediate horizon, such as spinal cord stimulation, peripheral nerve stimulation, and dorsal root ganglion spinal cord stimulation. As these therapies evolve, so too will their placement within the pain care algorithm grounded by a foundation of evidence to improve patient safety and management of patients with difficult neuropathic pain.

Self-organization of "fibro-axonal" composite tissue around unmodified metallic micro-electrodes can form a functioning interface with a peripheral nerve: A new direction for creating long-term neural interfaces

INTRODUCTION

A long-term peripheral neural interface is an area of intense research. The use of electrode interfaces is limited by the biological response to the electrode material.

METHODS

We created an electrode construct to harbor the rat sciatic nerve with interposition of autogenous adipose tissue between the nerve and the electrode. The construct was implanted for 10 weeks.

RESULTS

Immunohistochemistry showed a unique laminar pattern of axonal growth layered between fibro-collagenous tissue, forming a physical interface with the tungsten micro-electrode. Action potentials transmitted across the intrerface showed mean conduction velocities varying between 6.99 ± 2.46 and 20.14 ± 4 m/s.

CONCLUSIONS

We have demonstrated the feasibility of a novel peripheral nerve interface through modulation of normal biologic phenomena. It has potential applications as a chronic implantable neural interface.

Silicon substrate as a novel cell culture device for myoblast cells

BACKGROUND

Tissue and organ regeneration via transplantation of cell bodies in-situ has become an interesting strategy in regenerative medicine. Developments of cell carriers to systematically deliver cell bodies in the damage site have fall shorten on effectively meet this purpose due to inappropriate release control. Thus, there is still need of novel substrate to achieve targeted cell delivery with appropriate vehicles. In the present study, silicon based photovoltaic (PV) devices are used as a cell culturing substrate for the expansion of myoblast mouse cell (C2C12 cells) that offers an atmosphere for regular cell growth in vitro. The adherence, viability and proliferation of the cells on the silicon surface were examined by direct cell counting and fluorescence microscopy.

RESULTS

It was found that on the silicon surface, cells proliferated over 7 days showing normal morphology, and expressed their biological activities. Cell culture on silicon substrate reveals their attachment and proliferation over the surface of the PV device. After first day of culture, cell viability was 88% and cell survival remained above 86% as compared to the seeding day after the seventh day. Furthermore, the DAPI staining revealed that the initially scattered cells were able to eventually build a cellular monolayer on top of the silicon substrate.

CONCLUSIONS

This study explored the biological applications of silicon based PV devices, demonstrating its biocompatibility properties and found useful for culture of cells on porous 2-D surface. The incorporation of silicon substrate has been efficaciously revealed as a potential cell carrier or vehicle in cell growth technology, allowing for their use in cell based gene therapy, tissue engineering, and therapeutic angiogenesis.

Peripheral trigeminal nerve field stimulation: report of 6 cases

OBJECT

Peripheral nerve field stimulation has been successfully used for many neuropathic syndromes. However, it has been reported as a treatment for trigeminal neuropathic pain or persistent idiopathic facial pain only in the recent years.

METHODS

The authors present a review of the literature and their own series of 6 patients who were treated with peripheral nerve stimulation for facial neuropathic pain, reporting excellent pain relief and subsequent better social relations and quality of life.

RESULTS

On average, pain scores in these patients decreased from 10 to 2.7 on the visual analog scale during a 17-month follow-up (range 0-32 months). The authors also observed the ability to decrease trigeminal pain with occipital nerve stimulation, clinically confirming the previously reported existence of a close anatomical connection between the trigeminal and occipital nerves (trigeminocervical nucleus).

CONCLUSIONS

Peripheral nerve field stimulation of the trigeminal and occipital nerves is a safe and effective treatment for trigeminal neuropathic pain and persistent idiopathic facial pain, when patients are strictly selected and electrodes are correctly placed under the hyperalgesia strip at the periphery of the allodynia region.

Treatment of digit ulcers in a patient with Buerger's disease by using cervical spinal cord stimulation -a case report-

Buerger's disease (thromboangiitis obliterans) is known as a segmental inflammatory vasculitis that involves the small-sized and medium-sized arteries, veins, and nerves. Most effective treatment for Buerger's disease is smoking cessation. Except for the cessation of tobacco use, surgical revascularization is available in severe ischemia and a distal target vessel. Amputation has been used as the last treatment option of the disease up to the present. Increasing limb survival and decreasing amputation rate is important. This case describes the use of spinal cord stimulation (SCS) in patient with Buerger's disease and its effect is not only the complete healing of ulcers but also amputation is not performed.

Thromboangiitis Obliterans (Buerger's Disease)-Current Practices

Thromboangiitis obliterans (TAO) is a nonatherosclerotic, segmental inflammatory disease that most commonly affects the small and medium-sized arteries and veins in the upper and lower extremities. Cigarette smoking has been implicated as the main etiology of the disease. In eastern parts of the world TAO forms 40-60% of peripheral vascular diseases. Clinical features and angiographic finding are the basis of early diagnosis of TAO. Abstinence from smoking is the only definitive treatment to prevent disease progression. Medical management in form of aspirin, pentoxyfylline, cilostazol, and verapamil increase pain-free walking distance in intermittent claudication, but long term usage fails to prevent disease progression in patients who continue to smoke. Surgical treatment in form of revascularization, lumbar sympathectomy, omentopexy, and Ilizarov techniques help reduce pain and promote healing of trophic changes. Newer treatment modalities like spinal cord stimulation, prostacyclin, bosentan, VEGF, and stem cell therapy have shown promising results. Latest treatment options include peripheral mononuclear stem cell, and adipose tissue derived mononuclear stem cells have been shown to be effective in preventing disease progression, decrease major amputation rates, and improving quality of life.

Trigeminal branch stimulation for intractable neuropathic pain: technical note

Intractable neuropathic facial pain resulting from injury to the peripheral branches of the trigeminal nerve presents a significant challenge for neurologists, pain specialists, and neurosurgeons. In this paper, we describe our technique of peripheral nerve stimulation of the infraorbital and supraorbital nerves to treat patients with medically intractable facial pain. Stimulation of the infraorbital and supraorbital nerves is performed using percutaneously inserted electrodes that are positioned in the epifascial plane, traversing the course of the infraorbital or supraorbital nerves. The temporary electrodes are inserted under fluoroscopic guidance and are anchored to the skin. A trial lasting a few days is followed, if successful, by insertion of a permanent electrode that is tunneled under the skin behind the ear toward the infraclavicular pocket, which houses the implantable pulse generator. Our technique of electrode insertion to stimulate the infraorbital or supraorbital nerves has been successfully used in several patients with neuropathic trigeminal pain of various etiologies. In patients who underwent permanent electrode implantation, stimulation resulted in long lasting pain relief; complications were rare and minor. We conclude that trigeminal branch stimulation is a simple technique that can be used in selected patients with neuropathic pain in the distribution of the infraorbital or supraorbital nerves. This procedure may provide relief of medically intractable pain, without the need for destructive procedures or more central modulation approaches.

A study of electrode placement at the cervical and upper thoracic nerve roots using an anatomic trans-spinal approach

Objective. Since 1996 we have placed temporary catheters at the cervical nerve roots in chronic pain patients for the treatment of radiculopathy and complex regional pain syndrome. We investigated the possibility of placing electrodes both at the cervical spinal nerve and dorsal root ganglion for the purpose of neuromodulation. Methods. Anatomic and technical feasibility studies were performed on 4 human cadavers to examine the placement of electrodes at the cervical nerve roots. We proposed a novel trans-spinal approach to the cervical and upper thoracic nerve roots. We tested various approaches and insertion techniques. We collected radiographic images of the essential steps involved in this technique. Results. Successful placement was accomplished in 3 of the 4 cadavers at the C3, C4, C5, C6, C7, C8, T1, and T2 nerve roots. For placement at C5 to T2, we used a trans-spinal approach entering at the corresponding contralateral interlaminar space. However, due to the anatomy of the cervical nerve roots, vertebral artery, cervical plexus, and occiput, it was necessary to use a different technique for the upper cervical nerve roots. For placement at the C3 and C4 nerve roots, we made the initial insertion between the C1 and C2 lamina using curved needles which were advanced in a caudal direction transversing the median plane of the spine to arrive at the contralateral inter vertebral foramen of either C3 or C4. We were unable to cannulate either C1 or C2 in any of the cadavers. The required equipment included fluoroscopy, contrast dye, directable guide wires, electrodes, and curved needles. Conclusions. In human cadavers, a percutaneous technique was successful in the placement of neurostimulator electrodes at the cervical and upper thoracic nerve roots using a novel trans-spinal approach. New smaller electrode systems that can be placed in a transforaminal position safely may be needed.

Technical performance of percutaneous and laminectomy leads analyzed by modeling

The objective of this study was to compare the technical performance of laminectomy and percutaneous spinal cord stimulation leads with similar contact spacing by computer modeling. Monopolar and tripolar (guarded cathode) stimulation with both lead types in a low-thoracic spine model was simulated using UT-SCS software. Dorsal column and dorsal root fiber thresholds were calculated as well as the area of recruited fibers in the dorsal columns, the rostrocaudal span of recruited dorsal root fibers and the energy consumption at discomfort threshold. Tripolar stimulation is superior to monopolar stimulation in the recruitment of the dorsal columns, a percutaneous lead recruits a ∼12% larger dorsal column area than a laminectomy lead does. This difference is reduced when the contact spacing of the lead models is the same. A percutaneous lead with significant wire impedance (140 Ohms) consumes ∼115-240% more energy, whereas the same lead with negligible wire impedance consumes ∼40-85% more energy. A deterioration of all performance parameters is predicted when a percutaneous lead is placed more dorsally in the epidural tissue. When positioned next to the dura mater, a percutaneous lead has a similar performance (fiber recruitment in the dorsal columns and the dorsal roots) as a laminectomy lead with similar contact spacing, but substantially higher energy consumption. The superior clinical performance of the laminectomy lead is most probably due to the difference in volume and insertion technique of the two lead types.

Peripheral nerve field stimulation: is age an indicator of outcome?

Objective.  This study aims to assess peripheral nerve field stimulation as a treatment option for chronic pain and test for indicators of outcome. Materials and Methods.  We reviewed all patients permanently implanted with peripheral nerve field stimulators over the past 24 months. A questionnaire was used to assess outcomes. Results.  Twenty-seven questionnaires were sent out and 23/27 responded. A significant average decrease of 4.02 visual analog scale points was observed. The average pain decrease for the low back was 3.77 points and 5.9 for occipital implants. An age effect was detected; younger patients (<60 years) reported an average pain relief of 4.79 points while older patients (>61 years) reported an average pain relief decrement of only 2.83 points. Most patients reported decreases in analgesic use after treatment. Pain relief was significantly and highly correlated with reduced analgesic intake and patient satisfaction. Conclusion.  Peripheral nerve field stimulation is a safe, reversible, and effective treatment option for patients with chronic pain, particularly those under 60 years.

Spinal Cord Stimulation and the Induction of c-fos and Heat Shock Protein 72 in the Central Nervous System of Rats

For more than a decade, spinal cord stimulation (SCS) has been used as an adjuvant treatment for patients who are unresponsive to conventional therapies for angina pectoris. Many studies showed that SCS has both electro-analgesic and anti-ischemic effects. Nonetheless, the biological substrates by which SCS acts have not yet been unraveled, although recently areas in the brain have been described that show changes in blood flow, following SCS, and during provocation of angina. In search of a putative mechanism of action of SCS, we hypothesized that SCS affects processing of nociceptive information within the central nervous system (CNS). Moreover, it may alter the limbic system activity that maintains the balance between sympathetic and parasympathetic activity in the heart. Hence, we have developed a rat model to investigate its suitability for studying the induction of neural activity during SCS. To characterize neural activity, we used the expression of both the immediate early gene c-fos and the heat shock protein 72 (HSP72). c-Fos was used to identify structures in the CNS affected by SCS, and HSP72 was applied in order to ascertain whether SCS might operate as a stressor. In 20 halothane-anesthetized male Wistar rats, two electrodes were placed epidurally, one at the C7 level and the other at the T2 level. Two days after surgery, the rats were either stimulated "treated" animals, n = 10) or used as controls ("unstimulated" = "sham," n = 10) in random order. Furthermore, we studied the effect of SCS on behavior in five treated and five control rats. Three hours after stimulation, the rats were euthanized and the brain and spinal cord were removed. The treated group showed regional increased c-fos expression in regions of the limbic system (periaqueductal gray, paraventricular hypothalamic nucleus, paraventricular thalamic nucleus, central amygdala, agranular and dysgranular insular cortex, (peri)ambiguus, nucleus tractus solitarius, and spinal cord) that are involved in the processing of pain and cardiovascular regulation, among other things. Moreover, in both treated rats and controls, HSP72-expression was found in the endothelium of the enthorhinal cortex, the amygdala, and the ventral hypothalamus, but not in the neurons. Finally, treated animals were significantly more alert and active than controls. In conclusion, the rat model we developed appears to be suitable for studying potential mechanisms through which SCS may act. In addition, SCS affects c-fos expression in specific parts of the brain known to be involved in regulation of pain and emotions. HSP72-expression is limited to the endothelium of certain parts of the CNS and thereby excludes physical stress effects as a potential mechanism of SCS.

Median Nerve Stimulation in a Patient with Complex Regional Pain Syndrome Type II

A 54-year-old man experienced injury to the second finger of his left hand due to damage from a paintball gun shot 8 years prior, and the metacarpo-phalangeal joint was amputated. He gradually developed mechanical allodynia and burning pain, and there were trophic changes of the thenar muscle and he reported coldness on his left hand and forearm. A neuroma was found on the left second common digital nerve and was removed, but his symptoms continued despite various conservative treatments including a morphine infusion pump on his left arm. We therefore attempted median nerve stimulation to treat the chronic pain. The procedure was performed in two stages. The first procedure involved exposure of the median nerve on the mid-humerus level and placing of the electrode. The trial stimulation lasted for 7 days and the patient's symptoms improved. The second procedure involved implantation of a pulse generator on the left subclavian area. The mechanical allodynia and pain relief score, based on the visual analogue scale, decreased from 9 before surgery to 4 after surgery. The patient's activity improved markedly, but trophic changes and vasomotor symptom recovered only moderately. In conclusion, median nerve stimulation can improve chronic pain from complex regional pain syndrome type II.

Peripheral subcutaneous stimulation for the treatment of intractable postherpetic neuralgia: two case reports and literature review

Postherpetic neuralgia (PHN) is a common cause of chronic pain in the elderly. Antidepressants, anticonvulsants, and opioids may reduce discomfort in many patients, while others have pain intractable to all forms of therapy. We present a novel treatment approach for intractable PHN utilizing percutaneous peripheral nerve stimulation. Two cases are described in which an 80-year-old man and a 67-year-old woman with intractable PHN, lasting 2 and 10 years, respectively, were effectively treated with implantation of two octapolar leads in the lateral thoracic region. These cases suggest that peripheral nerve stimulation may offer an alternative treatment option for intractable pain associated with PHN especially in the elderly where treatment options are limited because of existing comorbidities.

Bidirectional interfaces with the peripheral nervous system

Considerable scientific and technological efforts have been devoted to develop neuroprostheses and hybrid bionic systems that link the human nervous system with electronic or robotic prostheses, with the main aim of restoring motor and sensory functions in disabled patients. Such developments have also the potential to be applied to normal human beings to improve their physical capabilities for bidirectional control and feedback of machines. A number of neuroprostheses use interfaces with peripheral nerves or muscles for neuromuscular stimulation and signal recording. This chapter provides a general overview of the peripheral neural interfaces available and their use from research to clinical application in controlling artificial and robotic prostheses and in developing neuroprostheses. Extraneural electrodes, such as cuff and epineurial electrodes, provide simultaneous interface with many axons in the nerve, whereas intrafascicular, penetrating, and regenerative electrodes may selectively contact small groups of axons within a nerve fascicle. Biological and technical issues are reviewed relative to the problems of electrode design and tissue injury. The last sections review different strategies for the use of peripheral neural interfaces in biomedical applications.

Peripheral nerve stimulation for neuropathic pain

Peripheral nerve stimulation (PNS) has been used for treatment of neuropathic pain for more than 40 years. Recent resurgence of interest to this elegant surgical modality came from the introduction of less invasive implantation techniques and the wider acceptance of neuromodulation as a treatment of medically refractory cases. This article reviews the literature on the use of PNS for neuropathic pain and describes current indications and hardware choices in frequent use. Published experience indicates that neuropathic pain responds to PNS in many patients. PNS works well in both established indications, such as post-traumatic and postsurgical neuropathy, occipital neuralgia, and complex regional pain syndromes, and in relatively new indications for neuromodulation, such as migraines and daily headaches, cluster headaches, and fibromyalgia. Future research and growing clinical experience will help in identifying the best candidates for PNS, choosing the best procedure and best hardware for each individual patient, and defining adequate expectations for patients and pain specialists.

Analgesic and antinociceptive effects of peripheral nerve neurostimulation in an advanced human experimental model

Electrical peripheral nerve neurostimulation (PNS) is reported to be an effective pain treatment. An objective proof of antinociceptive effect is lacking. The human experimental study addressed PNS effects on nociception and pain by electrophysiology and psychophysics. In 23 healthy volunteers, 39 sessions were conducted. Three experiments (PNS ipsilateral, PNS contralateral, Control) consisted of 13 sessions each. Conditioning PNS (100 Hz) of left (PNS ipsilateral) or right (PNS contralateral) superficial radial nerve trunk evoked non-painful, tingling sensations on the hand dorsum. Local cutaneous anesthesia at PNS site provided for preferential nerve trunk stimulation. Cortical laser-evoked potentials (LEP) after painful stimulation at left hand dorsum were recorded together with mechanical and thermal perception thresholds at the same site before (T1), during (T2), and after (T3) PNS or a no stimulation period (Control). Mechanical and thermal perception decreased in the anesthetized area. Late LEP amplitude decreased independently of PNS site. Exclusively under ipsilateral PNS, N2 latency increased and laser ratings decreased. Mechanical detection threshold transiently increased during ipsilateral PNS at hand dorsum. PNS induced strong reduction of mechanical perception due to peripheral collision of orthodromic (test stimulus) and antidromic (PNS) selective Abeta fiber excitation. Delay of N2 component and reduction of laser pain were specific to ipsilateral PNS. Divergent and common effects of ipsilateral and contralateral PNS suggest a combination of peripheral and central antinociceptive mechanisms. The study in man documents inhibition of nociception and pain by PNS and provides with an experimental model for future objectives in neuromodulation.

The current range of neuromodulatory devices and related technologies

The pace of technology dictates changes in every aspect of human life. Medical profession is not an exception. The development of sophisticated electronic devices has radically influenced diagnosis and therapy. Today neurosurgical science is revolutionized with numerous implanted and non-implanted devices that modulate and stimulate the nervous system. Physicians, patients and non-technical experts involved in this field need to understand the core mechanisms and the main differences of this technology so that they can use it effectively. It will take years until clinicians reach a "consensus" about the use of these devices, but in the course of action objective information about the current status of the methods and equipment, and the technical, biological, and financial complications that arise in practice will speed up their public approval and acceptance.

Neuromodulation of the cingulum for neuropathic pain after spinal cord injury. Case report

The authors present a case in which high-frequency electrical stimulation of the cingulum using standard deep brain stimulation (DBS) technology resulted in pain relief similar to that achieved with cingulotomy and superior to that achieved with periventricular gray matter (PVG) stimulation. This patient had a complete spinal cord injury at the C-4 level and suffered from medically refractory neuropathic pain. He underwent placement of bilateral cingulum and unilateral PVG DBS electrodes and a 1-week blinded stimulation trial prior to permanent implantation of a pulse generator. During the stimulation trial, the patient's pain level was assessed using a visual analog scale, and pain medication usage was recorded. During this period the patient was blinded to stimulation parameters. Stimulation of the cingulum provided better pain control than PVG stimulation or medication alone. The authors believe that cingulum stimulation can benefit patients with severe neuropathic pain that is refractory to other treatments. Advantages over cingulotomy include reversibility and the ability to adjust stimulation parameters for optimum efficacy.

Hardware failures in spinal cord stimulation (SCS) for chronic benign pain of spinal origin

Spinal cord stimulation (SCS) has become an established clinical option for treatment of refractory chronic pain not related to cancer. Current hardware and implantation techniques for SCS are already highly developed and continuously improving, however equipment failures over the course of the long-term treatment are still encountered in a relatively high proportion of treated cases. Percutaneous SCS electrodes seem to be particularly prone to dislocation and insulation failures. This review summarizes the experience of the authors with management of hardware failures and their causes in patients treated with SCS for chronic pain of benign origin. The published literature is critically surveyed and discussed.

Peripheral nerve stimulation for the treatment of chronic pain

The aim of this retrospective study is to evaluate the role of the implanted peripheral nerve stimulator in patients with pain in a peripheral nerve distribution. The current study is the largest in the literature that examines the role of the implantable peripheral nerve stimulator in the chronic pain patient. Our patient sample included 38 patients (with 41 nerve stimulators), consisting of 19 males and 19 females with a mean age of 44 years (SD=11 years). Four groups of etiologic factors were identified; blunt or sharp nerve trauma (14/38), iatrogenic injuries from surgery (9/38), inadvertent injection of a nerve (9/38) and post surgery for entrapment or tumour (8/38). Stimulation was attempted in 45 patients, but an initial trial failed in 4. Mean follow-up time from implantation of the stimulator was 31 months (SD=19 months). Compensation benefit was an issue in 29 cases (76%). Outcome following implantation was assessed based on pain criteria, narcotic usage and return to normal function/ work. Relief from preoperative pain was judged as good (>50% relief) by 23/38 patients (61%). A total of 15 patients reported fair or poor results (39%). Six patients required removal of their stimulators (15%) due to infection or reduction of pain control after an initial good result. A statistically significant decrease in reported pain level was found postoperatively (p<0.05). Workers' compensation patients have equivalent outcomes to non-compensable patients (p>0.05). Eighteen of 38 (47%) patients reported a significant improvement in their activity levels following stimulator implant. In conclusion, over 60% of patients had a significant improvement in their pain and lifestyle following implantation of peripheral nerve stimulators. We therefore conclude that peripheral nerve stimulation can be useful in decreasing pain in well selected patients with severe pain in the distribution of a peripheral nerve.

Late outcome of spinal cord stimulation for unreconstructable and limb-threatening lower limb ischemia

OBJECTIVES

To determine whether the initial benefits of spinal cord stimulation (SCS) treatment for critical limb ischemia (CLI) persist over years.

DESIGN

Analysis of data prospectively collected for every CLI patient receiving permanent SCS. Follow-up range 12 to 98 months (mean 46+/-23, median 50 months).

POPULATION

87 patients (28% stage III, 72%stage IV) with unreconstructable CLI due (83%) or not (17%) to atherosclerosis and with an initial sitting/supine transcutaneous pO2 gradient >15 mmHg.

METHODS

Assessment of actuarial patient survival (PS), limb salvage (LS) and amputation-free patient survival (AFPS). Analysis of the impact of 15 risk factors on long-term outcomes using the Fischer's exact test for categorical variables and the t test for continuous variables.

RESULTS

Follow-up was complete for patient and limb survival. A single non-atherosclerotic patient died during follow-up. Among atherosclerotic patients PS decreased from 88% at 1y, to 76% at 3y, 64% at 5y and 57% at 7y. LS reached 84% at 1y, 78% at 2y, 75% at 3y and remained stable thereafter. Diabetes was found to affect LS (p<0.05) and heart disease to reduce PS (p<0.01). AFPS was reduced in heart patients (p<0.01), diabetics (p<0.05) and in patients with previous stroke (p<0.05).

CONCLUSIONS

In CLI patients the beneficial effects of SCS persist far beyond the first year of treatment and major amputation becomes infrequent after the second year.

Peripheral nerve stimulation for the treatment of neuropathic craniofacial pain

Treatment of neuropathic pain in the region of head and face presents a challenging problem for pain specialists. In particular, those patients who do not respond to conventional treatment modalities usually continue to suffer from pain due to lack of reliable medical and surgical approaches. Peripheral nerve stimulation (PNS) has been used for treatment of neuropathic pain for many decades, but only recently it has been systematically applied to the craniofacial region. Here we summarize published experience with PNS in treatment of craniofacial pain and discuss some technical details of the craniofacial PNS procedure.

Cervical spinal cord stimulation in cerebral ischemia

Spinal cord stimulation (SCS) is a well established therapy in the treatment for chronic pain. SCS has also been shown to increase peripheral blood flow and is now an accepted treatment in the management of ischemic limb pain and angina. There is a growing body of evidence that cervical spinal cord stimulation also increases cerebral blood flow (CBF) in both animal and human models. SCS could potentially impact on the treatment of cerebral vasospasm and stroke by an increase in CBEF The utility of SCS is also being explored in novel applications such as adjunctive tumor therapy, where resistance to therapy conferred by tissue hypoxia may be ameliorated by CBF augmentation.

A new method for spatially selective, non-invasive activation of neurons: concept and computer simulation

Currently available non-invasive neurostimulation devices, using skin electrodes or externally applied magnetic coils, are not capable of producing a local stimulation maximum deep inside a homogeneous conductor, because of a fundamental limitation inherent to the Laplace equation. In this paper, a new neurostimulation method (the DeepFocus method) is presented, which avoids this limitation by using an indirect method of producing electric currents inside tissues: First, cylinder-shaped ferromagnetic rotating disks of non-permanent magnetic material are placed near the skin and magnetized by a non-rotating magnetic coil. Each of the disks rotates at high speed around its own axis of symmetry, thus producing a purely electric Lorentz force field having a non-zero divergence outside the disk, and therefore giving rise to charge accumulations inside the tissues. Subsequently, the magnetic field is switched off suddenly, causing a re-distribution of charge, and hence short-lived electrical currents, which can be used to activate neurons. Two magnet configurations are presented in this paper, and analyzed by computer simulation, showing that the DeepFocus method produces a maximum current density (the 'focus') deep inside the conducting body. The field strength thus created in the focus (7.9 V/m) is strong enough to activate thick myelinated fibers, but can be kept below the threshold for C-fibers, which makes the new method a possible tool for pain mitigation by targeted neurostimulation.

Mechanisms of spinal cord stimulation in ischemia

OBJECT

The goal of this study was to assess the duration of neuroprotection after SCS. Nearly 40 years after the first description of spinal cord stimulation (SCS), the mechanisms underlying its physiological effects remain unclear. It is known that SCS affects activity in the nervous system on a broad scale. Local neurohumoral changes within the dorsal horn of the spinal cord have been described, as have changes in cortical activation in a number of brain regions. Spinal cord stimulation has even been found to have profound effects on sympathetic vascular tone, a discovery that has led to its use in ameliorating blood flow in the limbs, heart, and brain.

METHODS

In an effort to delineate the limits of neuroprotection offered by SCS, the authors have studied its use in an experimental model of permanent middle cerebral artery (MCA) occlusion in rats. The investigators applied SCS in a delayed fashion 3, 6, or 9 hours after MCA occlusion. The results are reported and mechanisms underlying the physiological effects of SCS are reviewed, with particular attention being paid to the effect of SCS on cerebral blood flow in the setting of cerebral ischemia.

CONCLUSIONS

The authors found that SCS applied as late as 6 hours postischemia significantly reduces stroke volumes, whereas SCS applied 9 hours after ischemia fails to reduce stroke injury.

A critical review of interfaces with the peripheral nervous system for the control of neuroprostheses and hybrid bionic systems

Considerable scientific and technological efforts have been devoted to develop neuroprostheses and hybrid bionic systems that link the human nervous system with electronic or robotic prostheses, with the main aim of restoring motor and sensory functions in disabled patients. A number of neuroprostheses use interfaces with peripheral nerves or muscles for neuromuscular stimulation and signal recording. Herein, we provide a critical overview of the peripheral interfaces available and trace their use from research to clinical application in controlling artificial and robotic prostheses. The first section reviews the different types of non-invasive and invasive electrodes, which include surface and muscular electrodes that can record EMG signals from and stimulate the underlying or implanted muscles. Extraneural electrodes, such as cuff and epineurial electrodes, provide simultaneous interface with many axons in the nerve, whereas intrafascicular, penetrating, and regenerative electrodes may contact small groups of axons within a nerve fascicle. Biological, technological, and material science issues are also reviewed relative to the problems of electrode design and tissue injury. The last section reviews different strategies for the use of information recorded from peripheral interfaces and the current state of control neuroprostheses and hybrid bionic systems.

Spinal cord stimulation: a seven-year audit

OBJECTIVE

To evaluate the outcome and complications of spinal cord stimulation (SCS) for chronic neuropathic pain in an Australian population.

MATERIALS AND METHODS

An independent researcher retrospectively examined the records of 138 patients trialing SCS between 1995 and 2002 at our institution. Information collected included pain relief, ability to perform activities of daily living (ADLs), return to work and reduction in opiate analgesia. Clinical, psychological, demographic and financial data were also collected.

RESULTS

Of 138 patients who trialed SCS, 103 (74.7%) achieved a greater than 50% reduction in their pain and proceeded to permanent implantation. At 1 year following permanent implantation, 84.4% of these still had a reduction in their pain by greater than 50%. The majority of patients, 59.1%, stated that their analgesia was good (50-74% pain reduction). All patients required opiate analgesics prior to SCS implantation, but this fell to 54.6% after SCS implantation. Additionally, 73.6% had a significant improvement in their ability to perform ADLs and 24% of patients were able to return to work.

CONCLUSION

SCS is an effective treatment in the control of chronic neuropathic pain, particularly in combination with comprehensive medical management within a multidisciplinary pain management centre.

Repetitive magnetic stimulation A novel therapeutic approach for myofascial pain syndrome

The aim of this study was to evaluate the short, medium and long-term effects of peripheral repetitive magnetic stimulation (rMS) on myofascial pain compared with transcutaneous electrical nerve stimulation (TENS).Fifty-three subjects with myofascial trigger points (TPs) at the level of the superior trapezius muscle were allocated randomly to three groups. The first group (n=17) was treated with rMS, the second (n=18) with TENS and the third (n=18) received a placebo treatment. Each treatment consisted of ten daily 20-minute sessions. Patients were evaluated before and immediately following treatment, and at one and three months after the end of treatment. Outcome measures were: the "neck pain and disability visual analogue scale" (NPDVAS), an algometric evaluation of pain, an evaluation of the TP characteristics, and the range of cervical bending and rotation contralateral to the affected trapezius muscle. At the end of treatment, the rMS group showed a significant improvement in the NPDVAS, algometry, TP characteristics, and cervical contralateral rotation. This improvement also persisted at one and three months post-therapy. After treatment, the TENS group showed significant improvement in the same outcome measures except for algometry. At the one month follow-up visit, this improvement had returned to non significant levels in all outcome measures with the exception of NPDVAS. No significant effect of TENS was seen at the three-month follow-up visit. The placebo group showed no significant improvement in any measure. Our results strongly suggest that at medium and longer term intervals peripheral rMS may be more effective than TENS for the treatment of myofascial pain.