Temporary abolition of pain in man

Role of transcutaneous electric nerve stimulation in the management of trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia typically involves nerves supplying teeth, jaws and face of older females. Though the etiology is usually obscure, different treatment modalities have been tried for it viz. medicinal treatment, injection alcohol, peripheral neurectomy, rhizotomy, and microvascular decompression etc. Transcutaneous electric nerve stimulation (TENS) is an emerging and promising option for management of such patients.

AIMS AND DESIGN

The present study was designed with an aim to study the efficacy of TENS in management of trigeminal neuralgia.

MATERIALS AND METHODS

The study was conducted on 30 patients of trigeminal neuralgia confirmed by diagnostic nerve block. They were given bursts of TENS for 20-40 days over the path of the affected nerve and subsequently evaluated at 1 month and 3 month intervals by visual analogue scale (VAS), verbal pain scale (VPS), a functional outcome scales for main daily activities like sleep, chewing, talking, or washing face.

RESULTS

The results showed that, on VAS, the score decreased from 8.9 (Pre TENS) to 3.1 at 1 month and 1.3 at 3 months, and on VPS, the score decreased from 3.5 (Pre TENS) to 1.2 at 1 month and 0.3 at 3 months. Similarly, a considerable decrease in scores was seen on functional outcome scale for different activities. No side effects like irritation or redness of skin were seen in any of the patients.

CONCLUSIONS

Thus, TENS was found to be a safe, easily acceptable, and non-invasive outdoor patient department procedure for management of trigeminal neuralgia.

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.

Assessing the effectiveness and cost effectiveness of subcutaneous nerve stimulation in patients with predominant back pain due to failed back surgery syndrome (SubQStim study): study protocol for a multicenter randomized controlled trial

BACKGROUND

Chronic radicular pain can be effectively treated with spinal cord stimulation, but this therapy is not always sufficient for chronic back pain. Subcutaneous nerve stimulation (SQS) refers to the placement of percutaneous leads in the subcutaneous tissue within the area of pain. Case series data show that failed back surgery syndrome (FBSS) patients experience clinically important levels of pain relief following SQS and may also reduce their levels of analgesic therapy and experience functional well-being. However, to date, there is no randomized controlled trial evidence to support the use of SQS in FBSS.

METHODS/DESIGN

The SubQStim study is a multicenter randomized controlled trial comparing SQS plus optimized medical management ('SQS arm') versus optimized medical management alone ('OMM arm') in patients with predominant back pain due to FBSS. Up to 400 patients will be recruited from approximately 33 centers in Europe and Australia and will be randomized 1:1 to the SQS or OMM arms. After 9 months, patients who fail to reach the primary outcome will be allowed to switch treatments. Patients will be evaluated at baseline (prior to randomization) and at 1, 3, 6, 9, 12, 18, 24, and 36 months after randomization. The primary outcome is the proportion of patients at 9 months with a ≥50% reduction in back pain intensity compared to baseline. The secondary outcomes are: back and leg pain intensity score, functional disability, health-related quality of life, patient satisfaction, patient global impression of change, healthcare resource utilization/costs, cost-effectiveness analysis and adverse events. Outcomes arms will be compared between SQS and OMM arms at all evaluation points up to and including 9 months. After the 9-month assessment visit, the main analytic focus will be to compare within patient changes in outcomes relative to baseline.

DISCUSSION

The SubQStim trial began patient recruitment in November 2012. Recruitment is expected to close in late 2014.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01711619.

Neuromodulation for cephalgias

Headaches (cephalgias) are a common reason for patients to seek medical care. There are groups of patients with recurrent headache and craniofacial pain presenting with malignant course of their disease that becomes refractory to pharmacotherapy and other medical management options. Neuromodulation can be a viable treatment modality for at least some of these patients. We review the available evidence related to the use of neuromodulation modalities for the treatment of medically refractory craniofacial pain of different nosology based on the International Classification of Headache Disorders, 2(nd) edition (ICHD-II) classification. This article also reviews the scientific rationale of neuromodulation application in management of cephalgias.

Differential effects of subcutaneous electrical stimulation (SQS) and transcutaneous electrical nerve stimulation (TENS) in rodent models of chronic neuropathic or inflammatory pain

OBJECTIVES

Electrical stimulation has been used for many years for the treatment of pain. Present-day research demonstrates that stimulation targets and parameters impact the induction of specific pain-modulating mechanisms. New targets are increasingly being investigated clinically, but the scientific rationale for a particular target is often not well established. This present study compares the behavioral effects of targeting peripheral axons by electrode placement in the subcutaneous space vs. electrode placement on the surface of the skin in a rodent model.

MATERIALS AND METHODS

Rodent models of inflammatory and neuropathic pain were used to investigate subcutaneous electrical stimulation (SQS) vs. transcutaneous electrical nerve stimulation (TENS). Electrical parameters and relative location of the leads were held constant under each condition.

RESULTS

SQS had cumulative antihypersensitivity effects in both inflammatory and neuropathic pain rodent models, with significant inhibition of mechanical hypersensitivity observed on days 3-4 of treatment. In contrast, reduction of thermal hyperalgesia in the inflammatory model was observed during the first four days of treatment with SQS, and reduction of cold allodynia in the neuropathic pain model was seen only on the first day with SQS. TENS was effective in the inflammation model, and in agreement with previous studies, tolerance developed to the antihypersensitivity effects of TENS. With the exception of a reversal of cold hypersensitivity on day 1 of testing, TENS did not reveal significant analgesic effects in the neuropathic pain rodent model.

CONCLUSIONS

The results presented show that TENS and SQS have different effects that could point to unique biologic mechanisms underlying the analgesic effect of each therapy. Furthermore, this study is the first to demonstrate in an animal model that SQS attenuates neuropathic and inflammatory-induced pain behaviors.

Acupuncture transcutaneous electrical nerve stimulation reduces discomfort associated with barostat-induced rectal distension: A randomized-controlled study

AIM: To explore the effectiveness of acupuncture transcutaneous electrical nerve stimulation (Acu-TENS), a non-invasive modality in reduction of rectal discomfort during barostat-induced rectal distension.

METHODS: Forty healthy subjects were randomized to receive 45 min of either Acu-TENS or placebo-TENS (no electrical output) over acupuncture points Hegu (large-intestine 4), Neiguan (pericardium 6) and Zusanli (stomach 36). A balloon catheter attached to a dual-drive barostat machine was then inserted into the subjects’ rectum. A step-wise (4 mmHg) increase in balloon pressure was induced until maximal tolerable or 48 mmHg. Visual analogue scale and a 5-point subjective discomfort scale (no perception, first perception of distension, urge to defecate, discomfort/pain and extreme pain) were used to assess rectal discomfort at each distension pressure. Blood beta-endorphin levels were measured before, immediately after intervention, at 24 mmHg and at maximal tolerable distension pressure.

RESULTS: There was no difference in the demographic data and baseline plasma beta-endorphin levels between the two groups. Perception threshold levels were higher in the Acu-TENS group when compared to the placebo group, but the difference reached statistical significance only at the sensations “urge to defecate” and “pain”. The distension pressures recorded at the “urge to defecate” sensation for the Acu-TENS and placebo-TENS groups were 28.0 ± 4.5 mmHg and 24.6 ± 5.7 mmHg, respectively (P = 0.043); and the pressures recorded for the “pain” sensation for these two groups were 36.0 ± 4.2 mmHg and 30.5 ± 4.3 mmHg respectively (P = 0.002). Compared to the placebo group, a higher number of participants in the Acu-TENS group tolerated higher distension pressures (> 40 mmHg) (65% in Acu-TENS vs 25% in placebo, P = 0.02). The plasma beta-endorphin levels of the Acu-TENS group were significantly higher than that of the placebo group at barostat inflation pressure of 24 mmHg (1.31 ± 0.40 ng/mL vs 1.04 ± 0.43 ng/mL, P = 0.044) and at maximal inflation pressure (1.46 ± 0.53 ng/mL vs 0.95 ± 0.38 ng/mL, P = 0.003).

CONCLUSION: Acu-TENS reduced rectal discomfort during barostat-induced rectal distension and concurrently associated with a rise in beta-endorphin level.

Peripheral nerve stimulation in treatment of intractable postherpetic neuralgia

Objective.  This case report presents an application of peripheral nerve stimulation to a patient with intractable postherpetic neuralgia that conventional treatment failed to ameliorate. Methods.  The patient underwent an uneventful peripheral nerve stimulator trial with placement of two temporal eight-electrode percutaneous leads (Octrode leads, Advanced Neuromodulation Systems, Plano, TX, USA) into the right subscapular and right paraspinal area of the upper thoracic region. Results.  Upon experiencing excellent pain relief over the next two weeks, the patient underwent implantation of permanent leads two weeks later and reported sustained pain relief. Conclusion. Peripheral nerve stimulation offers an alternative treatment option for intractable pain associated with postherpetic neuralgia, especially for elderly patients where treatment options are limited due to existing comorbidities. Further studies are warranted.

Occipital nerve stimulation for the treatment of occipital neuralgia-eight case studies

Objective.  The aim of this study was to examine the hypothesis that subcutaneous occipital stimulation influences pain due to occipital neuralgia. Materials and Methods.  Between 2001 and 2004 eight patients with intractable occipital neuralgia were referred to our center. Their records were reviewed. Each patient was interviewed over the telephone. They were all offered a trial of stimulation using a percutaneous lead over 1 week. If they achieved 50% pain reduction a permanent lead was implanted. The impact of occipital stimulation was measured by pain score, analgesic requirements, and employment status. Results.  Seven proceeded to a permanent stimulator. There was a reduction in the visual analog score postimplantation in five of the seven patients. The total quantity of opiates taken after implantation showed a marked reduction. Of the seven who had a permanent implant two acquired full-time employment. Conclusion.  Occipital neuralgia is a useful and reversible treatment for intractable occipital neuralgia.

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.

Regenerative scaffold electrodes for peripheral nerve interfacing

Advances in neural interfacing technology are required to enable natural, thought-driven control of a prosthetic limb. Here, we describe a regenerative electrode design in which a polymer-based thin-film electrode array is integrated within a thin-film sheet of aligned nanofibers, such that axons regenerating from a transected peripheral nerve are topographically guided across the electrode recording sites. Cultures of dorsal root ganglia were used to explore design parameters leading to cellular migration and neurite extension across the nanofiber/electrode array boundary. Regenerative scaffold electrodes (RSEs) were subsequently fabricated and implanted across rat tibial nerve gaps to evaluate device recording capabilities and influence on nerve regeneration. In 20 of these animals, regeneration was compared between a conventional nerve gap model and an amputation model. Characteristic shaping of regenerated nerve morphology around the embedded electrode array was observed in both groups, and regenerated axon profile counts were similar at the eight week end point. Implanted RSEs recorded evoked neural activity in all of these cases, and also in separate implantations lasting up to five months. These results demonstrate that nanofiber-based topographic cues within a regenerative electrode can influence nerve regeneration, to the potential benefit of a peripheral nerve interface suitable for limb amputees.

Peripheral nerve stimulation for the treatment of postamputation pain--a case report

Many amputees suffer from postamputation pain, which can be extremely debilitating, decrease quality of life, increase the risk of depression, and negatively affect interpersonal relationships and the ability to work. Present methods of treatment, including medications, are often unsatisfactory in reducing postamputation pain. Electrical stimulation of the nerve innervating the painful area could reduce the pain, but peripheral nerve stimulation is rarely used to treat postamputation pain because present methods require invasive surgical access and precise placement of the leads in close proximity (≤ 2 mm) with the nerve. The present study investigated a novel approach to peripheral nerve stimulation in which a lead was placed percutaneously a remote distance (> 1 cm) away from the femoral nerve in a patient with severe residual limb pain (RLP) 33 years following a below-knee amputation. Electrical stimulation generated ≥ 75% paresthesia coverage, reduced RLP by > 60%, and improved quality of life outcomes as measured by the pain interference scale of the Brief Pain Inventory-Short Form (100% reduction in pain interference), Pain Disability Index (74% reduction in disability), and the Patient Global Impression of Change (very much improved) during a 2-week home trial. There were no adverse events. The ability to generate significant paresthesia coverage and pain relief with a single lead inserted percutaneously and remotely from the target nerve holds promise for providing relief of postamputation pain.

Effects of Electroacupuncture at BL60 on Formalin-Induced Pain in Rats

Acupuncture was used to treat symptoms of pain in the ancient orient. The present study was conducted to determine the effects of electroacupuncture (EA) at the BL60 acupoint on male Sprague-Dawley rats. Each rat received EA at BL60 acupoint before formalin injection. Behavioral responses were recorded using a video camera and c-Fos immunohistochemistry was performed thereafter. Treatment of EA at BL60 significantly inhibited flinching behavior and c-fos expression induced by formalin injection into the paw, compared to a control group. These results suggest that electroacupuncture at BL60 acupoint may be effective in relieving inflammatory pain.

Pain management for women in labour: an overview of systematic reviews

BACKGROUND

The pain that women experience during labour is affected by multiple physiological and psychosocial factors and its intensity can vary greatly.  Most women in labour require pain relief. Pain management strategies include non-pharmacological interventions (that aim to help women cope with pain in labour) and pharmacological interventions (that aim to relieve the pain of labour).

OBJECTIVES

To summarise the evidence from Cochrane systematic reviews on the efficacy and safety of non-pharmacological and pharmacological interventions to manage pain in labour. We considered findings from non-Cochrane systematic reviews if there was no relevant Cochrane review.

METHODS

We searched the Cochrane Database of Systematic Reviews (The Cochrane Library 2011, Issue 5), The Cochrane Database of Abstracts of Reviews of Effects (The Cochrane Library 2011, Issue 2 of 4), MEDLINE (1966 to 31 May 2011) and EMBASE (1974 to 31 May 2011) to identify all relevant systematic reviews of randomised controlled trials of pain management in labour. Each of the contributing Cochrane reviews (nine new, six updated) followed a generic protocol with 13 common primary efficacy and safety outcomes. Each Cochrane review included comparisons with placebo, standard care or with a different intervention according to a predefined hierarchy of interventions. Two review authors extracted data and assessed methodological quality, and data were checked by a third author. This overview is a narrative summary of the results obtained from individual reviews.

MAIN RESULTS

We identified 15 Cochrane reviews (255 included trials) and three non-Cochrane reviews (55 included trials) for inclusion within this overview. For all interventions, with available data, results are presented as comparisons of: 1. Intervention versus placebo or standard care; 2. Different forms of the same intervention (e.g. one opioid versus another opioid); 3. One type of intervention versus a different type of intervention (e.g. TENS versus opioid). Not all reviews included results for all comparisons. Most reviews compared the intervention with placebo or standard care, but with the exception of opioids and epidural analgesia, there were few direct comparisons between different forms of the same intervention, and even fewer comparisons between different interventions. Based on these three comparisons, we have categorised interventions into: " What works" ,"What may work", and "Insufficient evidence to make a judgement".WHAT WORKSEvidence suggests that epidural, combined spinal epidural (CSE) and inhaled analgesia effectively manage pain in labour, but may give rise to adverse effects. Epidural, and inhaled analgesia effectively relieve pain when compared with placebo or a different type of intervention (epidural versus opioids). Combined-spinal epidurals relieve pain more quickly than traditional or low dose epidurals. Women receiving inhaled analgesia were more likely to experience vomiting, nausea and dizziness.When compared with placebo or opioids, women receiving epidural analgesia had more instrumental vaginal births and caesarean sections for fetal distress, although there was no difference in the rates of caesarean section overall. Women receiving epidural analgesia were more likely to experience hypotension, motor blockade, fever or urinary retention. Less urinary retention was observed in women receiving CSE than in women receiving traditional epidurals. More women receiving CSE than low-dose epidural experienced pruritus.  WHAT MAY WORKThere is some evidence to suggest that immersion in water, relaxation, acupuncture, massage and local anaesthetic nerve blocks or non-opioid drugs may improve management of labour pain, with few adverse effects.  Evidence was mainly limited to single trials. These interventions relieved pain and improved satisfaction with pain relief (immersion, relaxation, acupuncture, local anaesthetic nerve blocks, non-opioids) and childbirth experience (immersion, relaxation, non-opioids) when compared with placebo or standard care. Relaxation was associated with fewer assisted vaginal births and acupuncture was associated with fewer assisted vaginal births and caesarean sections.INSUFFICIENT EVIDENCEThere is insufficient evidence to make judgements on whether or not hypnosis, biofeedback, sterile water injection, aromatherapy, TENS, or parenteral opioids are more effective than placebo or other interventions for pain management in labour. In comparison with other opioids more women receiving pethidine experienced adverse effects including drowsiness and nausea. 

AUTHORS' CONCLUSIONS

Most methods of non-pharmacological pain management are non-invasive and appear to be safe for mother and baby, however, their efficacy is unclear, due to limited high quality evidence. In many reviews, only one or two trials provided outcome data for analysis and the overall methodological quality of the trials was low. High quality trials are needed.There is more evidence to support the efficacy of pharmacological methods, but these have more adverse effects. Thus, epidural analgesia provides effective pain relief but at the cost of increased instrumental vaginal birth.It remains important to tailor methods used to each woman's wishes, needs and circumstances, such as anticipated duration of labour, the infant's condition, and any augmentation or induction of labour.A major challenge in compiling this overview, and the individual systematic reviews on which it is based, has been the variation in use of different process and outcome measures in different trials, particularly assessment of pain and its relief, and effects on the neonate after birth. This made it difficult to pool results from otherwise similar studies, and to derive conclusions from the totality of evidence. Other important outcomes have simply not been assessed in trials; thus, despite concerns for 30 years or more about the effects of maternal opioid administration during labour on subsequent neonatal behaviour and its influence on breastfeeding, only two out of 57 trials of opioids reported breastfeeding as an outcome. We therefore strongly recommend that the outcome measures, agreed through wide consultation for this project, are used in all future trials of methods of pain management.

DBS and electrical neuro-network modulation to treat neurological disorders

The use of neuromodulatory techniques in the treatment of neurological disorders is expanding and now includes devices targeting the motor cortex, basal ganglia, spinal cord, peripheral nervous system, and autonomic nervous system. In this chapter, we review and discuss the current and past literature as well as review indications for each of these devices in the ongoing management of many common neurological diseases including chronic pain, Parkinson's disease, tremor, dystonia, and epilepsy. We also discuss and update mechanisms of deep brain stimulation and electrical neuro-network modulation.

Supraorbital transcutaneous neurostimulation has sedative effects in healthy subjects

Background

Transcutaneous neurostimulation (TNS) at extracephalic sites is a well known treatment of pain. Thanks to recent technical progress, the Cefaly^® device now also allows supraorbital TNS. During observational clinical studies, several patients reported decreased vigilance or even sleepiness during a session of supraorbital TNS. We decided therefore to explore in more detail the potential sedative effect of supraorbital TNS, using standardized psychophysical tests in healthy volunteers.

Methods

We performed a double-blind cross-over sham-controlled study on 30 healthy subjects. They underwent a series of 4 vigilance tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale, d2 test). Each subject was tested under 4 different experimental conditions: without the neurostimulation device, with sham supraorbital TNS, with low frequency supraorbital TNS and with high frequency supraorbital TNS.

Results

As judged by the results of three tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale) there was a statistically significant (p < 0.001) decrease in vigilance and attention during high frequency TNS, while there were no changes during the other experimental conditions. Similarly, performance on the d2 test was impaired during high frequency TNS, but this change was not statistically significant.

Conclusion

Supraorbital high frequency TNS applied with the Cefaly^® device decreases vigilance in healthy volunteers. Additional studies are needed to determine the duration of this effect, the underlying mechanisms and the possible relation with the stimulation parameters. Meanwhile, this effect opens interesting perspectives for the treatment of hyperarousal states and, possibly, insomnia.

Temporary sacral nerve stimulation alters rectal sensory function: a physiological study

BACKGROUND

The indications for sacral nerve stimulation are increasing, but the mechanism remains poorly understood.

OBJECTIVE

This study aimed to examine the effect of sacral nerve stimulation on rectal compliance and rectal sensory function.

DESIGN

This was a prospective study.

SETTINGS

This study took place at a university teaching hospital.

PATIENTS

Twenty-three consecutive consenting patients (22 female; median age, 49 y) undergoing temporary sacral nerve stimulation for fecal incontinence were prospectively studied. Clinical response was assessed by the use of bowel diaries and Wexner scores.

MAIN OUTCOME MEASURES

Anal manometry, rectal compliance, volume and pressure thresholds to rectal distension (barostat), and rectal Doppler mucosal blood flow were measured before and at the end of stimulation.

RESULTS

Sixteen patients (70%) had a favorable clinical response. Median anal squeeze pressures increased with stimulation from 40 (range, 6-156) cmH2O to 64 (range, 16-243) cmH2O. Median rectal compliance did not significantly change with stimulation (prestimulation: 11.5 (range, 7.9-21.8) mL/mmHg, poststimulation: 12.4 (range, 6.2-22) mL/mmHg, P = .941). Rectal wall pressures associated with urge (baseline: 15.4 (range, 11-26.7) mmHg, poststimulation: 19 (range, 11.1-42.7) mmHg, P = .054) and maximal tolerated thresholds (baseline: 21.6 (8.5-31.9) mmHg, poststimulation: 27.1 (14.3-43.3) mmHg, P = .023) significantly increased after stimulation. Rectal Doppler mucosal blood flow did not significantly change with stimulation (baseline: 125.8 (69.9-346.8), poststimulation: 112.4 (50.2-404.1), P = .735). Changes in anal resting pressure and rectal wall pressures with stimulation were evident only in responders; however, changes in anal squeeze pressures were evident in both responders and nonresponders.

LIMITATIONS

The study reports results following short-term stimulation in a small but homogenous group of patients. A larger long-term study will follow.

CONCLUSION

Temporary sacral nerve stimulation does not change rectal compliance, but is associated with significant changes to the pressure thresholds of rectal distension. This, together with the observation that outcome is not related to sphincter integrity, supports the hypothesis of an afferent-mediated mechanism of action.

Computational functions of neurons and circuits signaling injury: relationship to pain behavior

The basic circuitry of the "pain pathway" mediating transmission of information from the periphery to the brain is well known, consisting of specialized sensory fibers known as nociceptors projecting to specific spinal cord neurons, which in turn project on to the thalamus and cerebral cortex. Here we survey some of the unique properties of these circuits, such as peripheral and central sensitization, and the segmental and descending modulatory control of synaptic transmission. We also review evidence indicating dissociation between nociceptor activity and behavioral indications of pain. Together, these considerations point to the need for a more quantitative approach to the nociceptive system, specifically the interactions at peripheral, spinal, and supraspinal levels as well as between them, to more fully understand how the activity in nociceptive neurons individually and collectively is related to the pain response.

Restoration of locomotive function in Parkinson's disease by spinal cord stimulation: mechanistic approach

Specific motor symptoms of Parkinson's disease (PD) can be treated effectively with direct electrical stimulation of deep nuclei in the brain. However, this is an invasive procedure, and the fraction of eligible patients is rather low according to currently used criteria. Spinal cord stimulation (SCS), a minimally invasive method, has more recently been proposed as a therapeutic approach to alleviate PD akinesia, in light of its proven ability to rescue locomotion in rodent models of PD. The mechanisms accounting for this effect are unknown but, from accumulated experience with the use of SCS in the management of chronic pain, it is known that the pathways most probably activated by SCS are the superficial fibers of the dorsal columns. We suggest that the prokinetic effect of SCS results from direct activation of ascending pathways reaching thalamic nuclei and the cerebral cortex. The afferent stimulation may, in addition, activate brainstem nuclei, contributing to the initiation of locomotion. On the basis of the striking change in the corticostriatal oscillatory mode of neuronal activity induced by SCS, we propose that, through activation of lemniscal and brainstem pathways, the locomotive increase is achieved by disruption of antikinetic low-frequency (<30 Hz) oscillatory synchronization in the corticobasal ganglia circuits.

What's new in the diagnosis and treatment of peripheral nerve entrapment neuropathies

Entrapment neuropathies can be common conditions with the potential to cause significant disability. Correct diagnosis is essential for proper management. This article is a review of recent developments related to diagnosis and treatment of various common and uncommon nerve entrapment disorders. When combined with classical peripheral nerve examination techniques, innovations in imaging modalities have led to more reliable diagnoses. Moreover, innovations in conservative and surgical techniques have been controversial as to their effects on patient outcome, but randomized controlled trials have provided important information regarding common operative techniques. Treatment strategies for painful peripheral neuropathies are also reviewed.

Ultrasound-guided, percutaneous peripheral nerve stimulation: technical note

BACKGROUND

Peripheral nerve stimulation is a form of neuromodulation that applies electric current to peripheral nerves to induce stimulation paresthesias within the painful areas.

OBJECTIVE

To report a method of ultrasound-guided, percutaneous peripheral nerve stimulation. This technique utilizes real-time imaging to avoid injury to adjacent vascular structures during minimally invasive placement of peripheral nerve stimulator electrodes.

MATERIAL AND METHODS

We describe a patient that presented with chronic, bilateral foot pain following multiple foot surgeries, for whom a comprehensive, pain management treatment strategy had failed. We utilized ultrasound-guided, percutaneous tibial nerve stimulation at a thigh level to provide durable pain relief on the right side, and open peripheral nerve stimulation on the left.

RESULTS

The patient experienced appropriate stimulation paresthesias and excellent pain relief on the plantar aspect of the right foot with the percutaneous electrode. On the left side, we were unable to direct the stimulation paresthesias to the sole of the foot, despite multiple electrode repositionings. A subsequent, open placement of a left tibial nerve stimulator was performed. This revealed that the correct electrode position against the tibial nerve was immediately adjacent to the popliteal artery, and was thus not appropriate for percutaneous placement.

CONCLUSION

We describe a method of ultrasound-guided peripheral nerve stimulation that avoids the invasiveness of electrode placement via an open procedure while providing excellent pain relief. We further describe limitations of the percutaneous approach when navigating close to large blood vessels, a situation more appropriately managed with open peripheral nerve stimulator placement. Ultrasound-guided placement may be considered for patients receiving peripheral nerve stimulators placed within the deep tissues, and not easily placed in a blind fashion.

Spinal cord stimulation: the types of neurostimulation devices currently being used, and what radiologists need to know when evaluating their appearance on imaging

Neural stimulation is increasingly used as a treatment for chronic pain. Common indications for spinal cord stimulation include chronic neuropathic and oncological pain, intractable angina, or chronic pain secondary to vascular disease. It is estimated that up to 4 million patients may be candidates for the therapy. Therefore, it is likely that an increasing number of patients will have spinal neurostimulation devices implanted over the coming years. Because radiography and computed tomography are the primary imaging modalities used to evaluate the proper positioning of these devices, radiologists should be familiar with their appearance. The purpose of this article is to discuss the types of neurostimulation devices currently being used and to demonstrate their respective imaging appearances.

Restoration of locomotive function in Parkinson's disease by spinal cord stimulation: mechanistic approach

Specific motor symptoms of Parkinson's disease (PD) can be treated effectively with direct electrical stimulation of deep nuclei in the brain. However, this is an invasive procedure, and the fraction of eligible patients is rather low according to currently used criteria. Spinal cord stimulation (SCS), a minimally invasive method, has more recently been proposed as a therapeutic approach to alleviate PD akinesia, in light of its proven ability to rescue locomotion in rodent models of PD. The mechanisms accounting for this effect are unknown but, from accumulated experience with the use of SCS in the management of chronic pain, it is known that the pathways most probably activated by SCS are the superficial fibers of the dorsal columns. We suggest that the prokinetic effect of SCS results from direct activation of ascending pathways reaching thalamic nuclei and the cerebral cortex. The afferent stimulation may, in addition, activate brainstem nuclei, contributing to the initiation of locomotion. On the basis of the striking change in the corticostriatal oscillatory mode of neuronal activity induced by SCS, we propose that, through activation of lemniscal and brainstem pathways, the locomotive increase is achieved by disruption of antikinetic low-frequency (<30 Hz) oscillatory synchronization in the corticobasal ganglia circuits.

Prospective clinical study of a new implantable peripheral nerve stimulation device to treat chronic pain

OBJECTIVES

To evaluate clinical use of the StimRouter, an investigational implanted peripheral nerve stimulator for treating chronic neuropathic pain, using the median nerve as a model for that general application.

METHODS

Eight patients with carpal tunnel syndrome and chronic pain despite both carpal tunnel release and treatment with oral pain medications were enrolled in a single-center, open-label trial after institutional review board approval. Primary endpoints were successful implantation near the target peripheral nerve and safety. All 8 patients were implanted temporarily at the median nerve in at least one arm and 2 patients were implanted bilaterally, with 10 implants total. Each implant was considered a separate "patient." For 5 days, all patients received 6 hours of daily transdermal electrical stimulation targeting the median nerve. Pain was measured at baseline, during implant, and after explant.

RESULTS

Two patients experienced clinically meaningful (>or=30%) pain reduction throughout the entire 5-day treatment period. Apparent carryover effect in pain reduction also was observed after daily stimulation. After explant, pain returned to baseline, increasing 36.8% to 45.6% relative to average reduced pain with daily stimulation. No significant or unexpected adverse events occurred. Mean patient study satisfaction was 96%, and 100% of patients indicated a preference for permanent implant.

DISCUSSION

Temporary implant of the StimRouter device resulted in both pain reduction and reduced use of oral opioid pain medication during the 5-day stimulation period. The results suggest that permanent implant of the StimRouter System may be safe and effective for treating chronic peripheral neuropathic pain.

Hi-TENS combined with PCA-morphine as post caesarean pain relief

OBJECTIVES

to examine effectiveness and overall opiate consumption between high-sensory transcutaneous electrical nerve stimulation (Hi-TENS) combined with patient-controlled analgesia with morphine and patient-controlled analgesia with morphine alone following elective (e.g. scheduled) caesarean birth.

DESIGN

randomised, controlled study.

SETTING

a county hospital in south-west Sweden.

PARTICIPANTS

42 multiparous women.

MEASUREMENTS AND FINDINGS

participants were randomly assigned and connected to patient-controlled analgesia with morphine alone or in combination with Hi-TENS apparatus. Levels of morphine consumed were calculated every third hour during the first 24 hours post partum. Pain and sedation were assessed by visual analogue scale at one, three, six, nine, 12 and 24 hours post partum. Total consumption of morphine differed significantly between the groups: morphine with TENS was 16.2 ± 12.6 mg and morphine alone was 33.1 ± 20.9 mg (p = 0.007). Assessment of pain relief showed no significant difference. Sedation differed significantly between the groups (p = 0.045), especially between three and 12 hours post partum (p = 0.011).

KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

pain relief from a combination of Hi-TENS and patient-controlled analgesia with morphine was as effective as patient-controlled analgesia with morphine alone, produced less sedation and reduced morphine use by approximately 50%. Women undergoing a caesarean section should be given the opportunity to make an informed choice about post operative pain relief before surgery. A presumed benefit of this treatment combination is that the mother is more alert and better able to interact with her newborn during the first hours after birth without drowsiness due to large doses of opiates.

Ultrasound-guided permanent implantation of peripheral nerve stimulation (PNS) system for neuropathic pain of the extremities: original cases and outcomes

OBJECTIVE

Our objective is to describe our experience applying a minimally invasive, ultrasound-assisted technique for peripheral nerve stimulation (PNS) trial and permanent implantation in patients with neuropathic extremity pain.

DESIGN

Retrospective case series and review of the literature. Setting. Tertiary referral center and academic medical center.

PATIENTS

Patients with upper or lower extremity neuropathic pain resistant to other therapies who responded to an ultrasound-guided peripheral nerve block at a proximal location. Interventions. Ultrasound-assisted through-the-needle placement of percutaneous neurostimulation electrodes on target major peripheral nerves for fully percutaneous trial, staged trial or permanent implantation of PNS system. A PNS trial period of 3-7 days was used.

OUTCOME MEASURES

Pain relief at last follow-up, complications, therapeutic limitations due to technique as applied. Results. Six of eight (75%) patients and 7/9 (78%) peripheral nerves had a successful trial and underwent permanent PNS system implantation using a minimally invasive, ultrasound-assisted technique from November 2007 to December 2008. All but one patient with an implanted PNS system had > or =50% pain relief at last follow-up and 3/7 (43%) permanent systems were associated with > or =80% relief. Loss of paresthesia required revision to dual-lead systems in upper extremity radial nerve PNS. Infection led to explant in one case.

CONCLUSIONS

In a small series of patients, a minimally invasive, ultrasound-assisted technique for PNS trial, and permanent PNS implantation proved feasible. Patients without adequate analgesia during neurostimulation trial avoided surgical incision and those undergoing permanent implantation were not subjected to the potential morbidity associated with nerve dissection.