Neuropathic pain: quality-of-life impact, costs and cost effectiveness of therapy

Placebo and nocebo effects in the neurological practice

Knowledge of placebo and nocebo effects is essential to identify their influence on the results in clinical practice and clinical trials, and thereby properly interpret their results. It is known that the gold standard of clinical trials research is the double-blind, placebo-controlled, randomized clinical study. The objective of this review is to distinguish specific from non-specific effects, so that the presence of positive effects in the group that received placebo (placebo effect) and the presence of adverse effects in the group receiving placebo (nocebo effect) lead to confounding in interpreting the results. Placebo and nocebo effects have been considered in neurological diseases such as depression, pain, headache, multiple sclerosis, epilepsy. As placebo and nocebo effects are also present in clinical practice, the purpose of this review is to draw attention to their influence on neurological practice, calling attention to the development of measures that can minimize them.

Treatment of localized neuropathic pain of different etiologies with the 5% lidocaine medicated plaster - a case series

Objective

To assess the efficacy and safety of the topical 5% lidocaine medicated plaster in the treatment of localized neuropathic pain.

Study design

This was a case series at an Austrian pain clinic, using retrospective analysis.

Patients and methods

Data of 27 patients treated for localized neuropathic pain with the 5% lidocaine medicated plaster were retrospectively analyzed. Assessment included changes in overall pain intensity, in intensity of different pain qualities, and of hyperalgesia and allodynia, and changes in sleep quality.

Results

Patients (17 female, ten male; mean age 53.4±11.4 years) presented mainly with dorsalgia (16 patients) or postoperative/posttraumatic pain (seven patients); one patient suffered from both. The mean overall pain intensity prior to treatment with lidocaine medicated plaster was 8.4±1.2 on the 11-point Likert scale. In the majority of cases, the lidocaine plaster was applied concomitantly with preexisting pain medication (81.5% of the patients). During the 6-month observation period, overall mean pain intensity was reduced by almost 5 points (4.98) to 3.5±2.6. Substantial reductions were also observed for neuralgiform pain (5 points from 7.9±2.6 at baseline) and burning pain (3 points from 5.2±4.1). Sleep quality improved from 4.6±2.6 at baseline to 5.5±1.8. Stratification by pain diagnosis showed marked improvements in overall pain intensity for patients with dorsalgia or postoperative/posttraumatic pain. The lidocaine plaster was well tolerated.

Conclusion

Overall, topical treatment with the 5% lidocaine medicated plaster was associated with effective pain relief and was well tolerated.

Antinociceptive properties of physalins from Physalis angulata

Pain is the most common reason a patient sees a physician. Nevertheless, the use of typical painkillers is not completely effective in controlling all pain syndromes; therefore further attempts have been made to develop improved analgesic drugs. The present study was undertaken to evaluate the antinociceptive properties of physalins B (1), D (2), F (3), and G (4) isolated from Physalis angulata in inflammatory and centrally mediated pain tests in mice. Systemic pretreatment with 1-4 produced dose-related antinociceptive effects on the writhing and formalin tests, traditional screening tools for the assessment of analgesic drugs. On the other hand, only 3 inhibited inflammatory parameters such as hyperalgesia, edema, and local production of TNF-α following induction with complete Freund's adjuvant. Treatment with 1, 3, and 4 produced an antinociceptive effect on the tail flick test, suggesting a centrally mediated antinociception. Reinforcing this idea, 2-4 enhanced the mice latency reaction time during the hot plate test. Mice treated with physalins did not demonstrate motor performance alterations. These results suggest that 1-4 present antinociceptive properties associated with central, but not anti-inflammatory, events and indicate a new pharmacological property of physalins.

Migraine and reward system-or is it aversive?

Migraine is a debilitating neurological disorder with grave consequences for both the individual and society. This review will focus on recent literature investigating how brain structures implicated in reward and aversion contribute to the genesis of migraine pain. There exist many overlapping and interacting brain regions within pain and reward circuitry that contribute to negative affect and subjective experience of pain. The emotional component of pain has been argued to be a greater metric of quality of life than its sensory component, and thus understanding the processes that influence this pain characteristic is essential to developing novel treatment strategies for mitigating migraine pain. We emphasize and provide evidence that abnormalities within the mesolimbic cortical reward pathways contribute to migraine pain and that there are structural and functional neuroplasticity within the overlapping brain regions common to both pain and reward.

Does the kappa opioid receptor system contribute to pain aversion?

The kappa opioid receptor (KOR) and the endogenous peptide-ligand dynorphin have received significant attention due the involvement in mediating a variety of behavioral and neurophysiological responses, including opposing the rewarding properties of drugs of abuse including opioids. Accumulating evidence indicates this system is involved in regulating states of motivation and emotion. Acute activation of the KOR produces an increase in motivational behavior to escape a threat, however, KOR activation associated with chronic stress leads to the expression of symptoms indicative of mood disorders. It is well accepted that KOR can produce analgesia and is engaged in chronic pain states including neuropathic pain. Spinal studies have revealed KOR-induced analgesia in reversing pain hypersensitivities associated with peripheral nerve injury. While systemic administration of KOR agonists attenuates nociceptive sensory transmission, this effect appears to be a stress-induced effect as anxiolytic agents, including delta opioid receptor agonists, mitigate KOR agonist-induced analgesia. Additionally, while the role of KOR and dynorphin in driving the dysphoric and aversive components of stress and drug withdrawal has been well characterized, how this system mediates the negative emotional states associated with chronic pain is relatively unexplored. This review provides evidence that dynorphin and the KOR system contribute to the negative affective component of pain and that this receptor system likely contributes to the high comorbidity of mood disorders associated with chronic neuropathic pain.

Diagnosis and pharmacologic management of neuropathic pain among patients with chronic low back pain

Chronic low back pain consists of both nociceptive and neuropathic mechanisms and can be classified as a mixed pain syndrome. Neuropathic component of chronic low back pain has often been under-recognized and under-treated by the physicians. Recent studies have demonstrated that approximately 20%-55% of chronic low back pain patients have neuropathic pain symptoms. An altered peripheral, spinal, and supraspinal processing of pain arising as a result of a lesion affecting the nerves system are the major contributor to neuropathic low back pain. The clinical evaluation is still the gold standard for assessment and diagnosis of neuropathic low back pain. Although diagnosis can be difficult due to the lack of reliable gold standard diagnostic test for neuropathic low back pain, screening tools may help non-specialists, in particular, to identify potential patients with neuropathic low back pain who require further diagnostic evaluation and pain management. Several screening tools for neuropathic pain have been developed and tested with different patient populations. Among the screening tools, the painDETECT questionnaire and the Standardized Evaluation of Pain are validated in patients with low back pain. The Standardized Evaluation of Pain may lead to more effective in discriminating between neuropathic and nociceptive pain in patients with low back pain according to the higher rate of sensitivity and its validity in patients with low back pain. However, the most appropriate approach is still to combine findings on physical and neurologic examinations and patient’s report in distinguishing neuropathic pain from nociceptive pain. The clinical examination including bedside sensory tests is still the best available tool for assessment and diagnosis neuropathic pain among patients with chronic low back pain. Due to the fact that chronic low back pain consists of both nociceptive and neuropathic mechanisms, a multimodal treatment approach is more rational in the management of patients with chronic low back pain. Therefore, combination therapy including drugs with different mechanisms of action should be given to the patients with chronic low back pain.

Increased methylation of the MOR gene proximal promoter in primary sensory neurons plays a crucial role in the decreased analgesic effect of opioids in neuropathic pain

BACKGROUND

The analgesic potency of opioids is reduced in neuropathic pain. However, the molecular mechanism is not well understood.

RESULTS

The present study demonstrated that increased methylation of the Mu opioid receptor (MOR) gene proximal promoter (PP) in dorsal root ganglion (DRG) plays a crucial role in the decreased morphine analgesia. Subcutaneous (s.c.), intrathecal (i.t.) and intraplantar (i.pl.), not intracerebroventricular (i.c.v.) injection of morphine, the potency of morphine analgesia was significantly reduced in nerve-injured mice compared with control sham-operated mice. After peripheral nerve injury, we observed a decreased expression of MOR protein and mRNA, accompanied by an increased methylation status of MOR gene PP, in DRG. However, peripheral nerve injury could not induce a decreased expression of MOR mRNA in the spinal cord. Treatment with 5-aza-2'-deoxycytidine (5-aza-dC), inhibited the increased methylation of MOR gene PP and prevented the decreased expression of MOR in DRG, thereby improved systemic, spinal and periphery morphine analgesia.

CONCLUSIONS

Altogether, our results demonstrate that increased methylation of the MOR gene PP in DRG is required for the decreased morphine analgesia in neuropathic pain.

Is an easy and reliable diagnosis of localized neuropathic pain (LNP) possible in general practice? Development of a screening tool based on IASP criteria

BACKGROUND AND OBJECTIVE

Neuropathic pain (NP) is a common type of chronic pain in which 60% of patients present with localized symptoms. Early diagnosis of NP is often a challenge in primary care. Moreover, so far no standard diagnostic procedure for localized NP (LNP) is available. To help general practitioners, a screening tool was developed and evaluated.

RESEARCH DESIGN AND METHODS

The development of the screening tool was based on the grading system principles for NP proposed by the IASP, focusing on medical history and distribution of painful symptoms and sensory signs. It was tested by 31 general practitioners and evaluated against the NP diagnosis of three pain specialists as reference in a single center prospective study in Spain using a cohort study design including an adult population of chronic pain patients. This design avoids spectrum bias where the spectrum of disease is not correctly reflected in the study population.

MAIN OUTCOME MEASURES

General practitioners rated usefulness, simplicity, and time requirements of the tool. Diagnostic accuracy was expressed by sensitivity, specificity, and positive and negative predictive values.

RESULTS

General practitioners consecutively screened 2079 chronic pain patients (mean age 60.7 ± 11.1 years, 69.9% female). Using the tool, 394 patients were diagnosed with LNP. Screening including sensory examination took 7 min (median). General practitioners rated the tool as useful (24/31; 77.4%) or very useful (7/31; 22.6%) for diagnosing LNP and facilitating clinical practice (30/31; 96.8%). Under daily practice conditions, sensitivity and specificity of the tool for detecting LNP was 46.7% and 86.6%, respectively.

CONCLUSIONS

The proposed screening tool was shown to be easy and useful for detecting NP and LNP in chronic pain patients as a fast first assessment tool in primary care, thus facilitating the choice of a topical treatment. LIMITATIONS AND STRENGTHS: The drop-out rate was high but was accounted for by using correction factors in the diagnostic accuracy calculations. A strength is the unselected chronic patient population: spectrum of disease correctly reflects day-to-day clinical practice and is not biased. Diagnostic accuracy of the tool therefore appears to be realistic.

Atorvastatin as novel treatment for neuropathic pain: a case report

INTRODUCTION

Managing neuropathic pain can be very challenging, with standard medical therapies often providing inadequate relief. It has recently been reported in the literature that statins alleviate neuropathic pain in the rat model. We present a case report in which an above-the-knee amputee achieved relief of his neuropathic stump pain with atorvastatin.

CASE REPORT

We describe the case of a 50-year-old man with a 12-year history of chronic neuropathic stump pain and sporadic phantom limb pain following an above-the-knee amputation. For 11 years the pain was managed with gabapentin 300 mg 3 times daily plus oxycodone 10 mg twice daily. He autonomously weaned himself to gabapentin 300 mg once daily and oxycodone 10 mg once daily, exacerbating his stump pain in the process. After starting atorvastatin 20 mg once daily for hypercholesterolemia, he immediately experienced decreased intensity of his stump pain, but his phantom pain persisted at its usual intensity.

CONCLUSIONS

More studies are needed to characterize the analgesic effects of statins better. In patients who have neuropathic pain refractory to traditional treatment options or, rather, decline traditional treatment options, statin therapy may be helpful.

Characteristics of neuropathic pain in patients with spinal cord injury

Objective

To characterize neuropathic pain in patients with spinal cord injury (SCI) according to classification used in the study by Baron et al. (Baron classification), a classification of neuropathic pain based on the mechanism. To also compare the patterns of neuropathic pain in SCI patients with those in patients with other etiologies and to determine the differences in patterns of neuropathic pain between the etiologies.

Methods

This was a descriptive cross-sectional study. We used the Baron classification to investigate the characteristics of neuropathic pain in SCI. Sixty-one SCI patients with neuropathic pain (The Leeds assessment of neuropathic symptoms and signs score ≥12) were enrolled in this study between November 2012 and August 2013, after excluding patients <20 of age, patients with visual analog scale (VAS) score <3, pregnant patients, and patients with systemic disease or pain other than neuropathic pain.

Results

The most common pain characteristic was pricking pain followed by electrical pain and numbness. The mean VAS score of at-level neuropathic pain was 7.51 and that of below-level neuropathic pain was 6.83. All of the patients suffered from rest pain, but 18 (54.6%) patients with at-level neuropathic pain and 20 (50.0%) patients with below-level neuropathic pain suffered from evoked pain. There was no significant difference in between at-level and below-level neuropathic pains.

Conclusion

The result was quite different from the characteristics of post-herpetic neuralgia, but it was similar to the characteristics of diabetic neuropathy as shown in the study by Baron et al., which means that sensory nerve deafferentation may be the most common pathophysiologic mechanism of neuropathic pain after SCI. Since in our study, we included short and discrete symptoms and signs based on diverse mechanisms, our results could be helpful for determining further evaluation and treatment.

A preliminary report on stem cell therapy for neuropathic pain in humans

Objective

Mesenchymal stem cells (MSCs) have been shown in animal models to attenuate chronic neuropathic pain. This preliminary study investigated if: i) injections of autologous MSCs can reduce human neuropathic pain and ii) evaluate the safety of the procedure.

Methods

Ten subjects with symptoms of neuropathic trigeminal pain underwent liposuction. The lipoaspirate was digested with collagenase and washed with saline three times. Following centrifugation, the stromal vascular fraction was resuspended in saline, and then transferred to syringes for local injections into the pain fields. Outcome measures at 6 months assessed reduction in: i) pain intensity measured by standard numerical rating scale from 0–10 and ii) daily dosage requirements of antineuropathic pain medication.

Results

Subjects were all female (mean age 55.3 years ± standard deviation [SD] 14.67; range 27–80 years) with pain symptoms lasting from 4 months to 6 years and 5 months. Lipoaspirate collection ranged from 102–214 g with total cell numbers injected from 33 million to 162 million cells. Cell viability was 62%–91%. There were no systemic or local tissue side effects from the stem cell therapy (n=41 oral and facial injection sites). Clinical pain outcomes showed that at 6 months, 5/9 subjects had reduced both pain intensity scores and use of antineuropathic medication. The mean pain score pre-treatment was 7.5 (SD 1.58) and at 6 months had decreased to 4.3 (SD 3.28), P=0.018, Wilcoxon signed-rank test. Antineuropathic pain medication use showed 5/9 subjects reduced their need for medication (gabapentin, P=0.053, Student’s t-test).

Conclusion

This preliminary open-labeled study showed autologous administration of stem cells for neuropathic trigeminal pain significantly reduced pain intensity at 6 months and is a safe and well tolerated intervention.

Emerging drugs for neuropathic pain

INTRODUCTION

Neuropathic pain is a costly and disabling condition, which affects up to 8% of the population. Available therapies often provide incomplete pain relief and treatment-related side effects are common. Preclinical neuropathic pain models have facilitated identification of several promising targets, which have progressed to human clinical phases of evaluation.

AREAS COVERED

A systematic database search yielded 25 new molecular entities with specified pharmacological mechanisms that have reached Phase II or III clinical trials. These include calcium channel antagonists, vanilloid receptor antagonists, potassium channel agonists, NMDA antagonists, novel opioid receptor agonists, histamine H3 receptor antagonists, a novel sodium channel antagonist, serotonin modulators, a novel acetylcholine receptor agonist, α-2b adrenoreceptor agonist, cannabinoid CB2 receptor agonist, nitric oxide synthase inhibitor, orexin receptor antagonist, angiotensin II 2 antagonist, imidazoline I2 receptor agonist, apoptosis inhibitor and fatty acid amide hydrolase inhibitor.

EXPERT OPINION

Although the diversity of pharmacological mechanisms of interest emphasise the complexity of neuropathic pain transmission, the considerable number of agents under development reflect a continued enthusiasm in drug development for neuropathic pain. Ongoing enhancements in methodology of both preclinical and clinical research and closer translation in both directions are expected to more efficiently identify new agents, which will improve the management of neuropathic pain.

Assessment and management of neuropathic pain in primary care

SUMMARY Most patients with neuropathic pain present and are managed in primary care. It is generally a long-term condition associated with poor physical, psychological and social health. Assessment and pharmacological treatment algorithms, specifically designed for primary care, are now available. The focus should be on taking a good medical history and clinical examination, and with the knowledge of the patient's current and past medical history, the general practitioner can diagnose possible neuropathic pain and initiate treatment while awaiting specialist assessment (if required). Specific nonpharmaceutical interventions, though popular with patients, have thus far demonstrated limited effectiveness. General practitioners, with their long-term relationship with patients, have a central role in improving the diagnosis and management of neuropathic pain.

Best practices in the treatment of neuropathic pain

SUMMARY Neuropathic pain is a complex pain syndrome that remains difficult to treat. Patients fail to obtain satisfactory relief despite receiving pharmacological agents. Neuropathic pain has a significant impact on health-related quality of life. A multidisciplinary approach is recommended in the treatment of neuropathic pain. Preventative, nonpharmacological and pharmacological treatments are suggested in the management of neuropathic pain. Interventional options, such as spinal cord stimulation, intrathecal drug delivery, intravenous infusions therapies, and sympathetic nerve block, should be considered in patients with refractory neuropathic pain.

Quality improvement in neurology: Distal symmetric polyneuropathy quality measures

Peripheral neuropathy is a common neurologic disorder, affecting 2% to 8% of the population in population-based studies with confirmation by neurologist examination. These prevalence numbers are remarkably stable across developed countries. In 1999, 8.6% of Medicare beneficiaries had neuropathy as a primary or secondary diagnosis, and the cost of treatment was estimated at $3.5 billion (Consumer Price Index adjusted to 2013 $4.9 billion), which did not include outpatient medications. Peripheral neuropathy has many causes and varies in regard to its clinical manifestations and severity. Distal symmetric polyneuropathy (DSP) is the most common pattern of peripheral neuropathy generally and the most common phenotype of neuropathy due to diabetes. Reported prevalence rates of DSP among diabetic patients range from 15% to 37% across large population-based studies, and the prevalence among those with impaired glucose tolerance has been reported to be 11%. DSP can result in weakness, sensory loss, pain, autonomic dysfunction, gait impairment, falls, disability, and impaired quality of life.

Effectiveness and tolerability of low-dose oral oxycodone/naloxone added to anticonvulsant therapy for noncancer neuropathic pain: an observational analysis

BACKGROUND

Opioids may alleviate chronic neuropathic pain (NP), but are considered second/third-line analgesia due to their poor gastrointestinal (GI) tolerability. A fixed combination of prolonged-release oxycodone and naloxone (OXN) has been developed to overcome the GI effects. The aim of this analysis was to evaluate analgesic effectiveness and tolerability of low-dose OXN in patients with moderate-to-severe noncancer NP despite analgesia.

METHODS

This retrospective observation of consecutive adult patients, treated open-label for 8 weeks at a single Italian centre, evaluated effectiveness (pain intensity numerical rating scale [NRS], Patients' Global Impression of Change [PGIC], Douleur Neuropathique 4 inventory [DN4] and Chronic Pain Sleep Inventory [CPSI]), doses of daily OXN and adjuvant medication, rescue paracetamol use, bowel function index (BFI), laxative use, and safety.

RESULTS

Of 200 patients (mean age 65.9 years; 54% female) with NP included in the analysis; 97% completed 8 weeks' treatment. At the observation start, all patients were taking anticonvulsants and complained of constipation, and 60% were receiving opioids. Pain intensity and DN4 score decreased significantly by endpoint (NRS p < 0.0001; DN4 p < 0.0001) and need for rescue analgesics abated. Reduction in pain intensity throughout the observation was similar regardless of NP aetiology. According to PGIC, 87.8% of patients were much/extremely improved, CPSI (p < 0.0001) and BFI were significantly improved (p < 0.0001) and laxative use decreased. No differences were found between patients <65 years vs those ≥65 years. OXN was generally well tolerated.

STUDY LIMITATIONS

Study limitations including the retrospective observational design, the lack of a control group and the single-centre design may limit the generalizability of our findings.

CONCLUSIONS

Low-dose OXN (25.0 ± 12.5 mg/day) added to anticonvulsants was highly effective in controlling noncancer NP of varied aetiology, with reduced need for rescue analgesia and improved quality of sleep, and was well tolerated, with improved bowel function and reduced laxative use. The efficacy and tolerability of OXN demonstrated in this real-world setting suggest its utility in this difficult to manage patient population.

CLINICAL CHARACTERISTICS OF NEUROPATHIC PAIN IN PATIENTS WITH CARPAL TUNNEL SYNDROME

The purpose of this study was to identify the clinical characteristics of neuropathic pain in patients with carpal tunnel syndrome. We retrospectively reviewed 143 hands in 127 patients with carpal tunnel syndrome. The neuropathic pain was determined by using the painDETECT as a self-administered psychometric questionnaire to distinguish neuropathic pain. There were no significant differences in the characteristics of the patients with and without neuropathic pain. However, there were significant differences in the pain scores between those with and without neuropathic pain (p < 0.01). Furthermore, there was a significant difference between the existence of night pain in these patients (p < 0.01). Based on the results of the current study, we conclude that it is important to be aware of, and consider the existence of neuropathic pain during the treatment of patients with carpal tunnel syndrome with night pain or a high score on the numerical rating scales of pain.

Protective Effect of Agaricus brasiliensis on STZ-Induced Diabetic Neuropathic Pain in Rats

Objective. The present investigation examined the neuroprotective effect of Agaricus brasiliensis (AbS) against STZ-induced diabetic neuropathic pain in laboratory rats. STZ-induced diabetic rats were administered orally with AbS. Body weight, serum glucose, and behavioral parameters were measured before and at the end of the experiment to see the effect of AbS on these parameters. After 6 weeks of treatments, all animals were sacrificed to study various biochemical parameters. Treatment with AbS 80 mg/kg in diabetic animals showed significant increase in body weight, pain threshold, and paw withdrawal threshold and significant decrease in serum glucose, LPO and NO level, Na-K-ATPase level, and TNF- α and IL-1 β level as compared to vehicle treated diabetic animals in dose and time dependent manner. AbS can offer pain relief in PDN. This may be of potential benefit in clinical practice for the management of diabetic neuropathy.

Diabetic neuropathy

Diabetic neuropathy (DN) is the most common and troublesome complication of diabetes mellitus, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care. The clinical assessment of diabetic peripheral neuropathy and its treatment options are multifactorial. Patients with DN should be screened for autonomic neuropathy, as there is a high degree of coexistence of the two complications. A review of the clinical assessment and treatment algorithms for diabetic neuropathy, painful neuropathy, and autonomic dysfunction is provided.

Validity and reliability of the Japanese version of the painDETECT questionnaire: a multicenter observational study

Objectives

The aim of this study was to evaluate the validity and reliability of the Japanese version of the painDETECT questionnaire (PDQ-J).

Materials and Methods

The translation of the original PDQ into Japanese was achieved according to the published guidelines. Subsequently, a multicenter observational study was performed to evaluate the validity and reliability of PDQ-J, including 113 Japanese patients suffering from pain.

Results

Factor analysis revealed that the main component of PDQ-J comprises two determinative factors, which account for 62% of the variance observed. Moreover, PDQ-J revealed statistically significant correlation with the intensity of pain (Numerical Rating Scale), Physical Component Score, and Mental Component Score of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). The Cronbach alpha for the total score was 0.78 and for the main component was 0.80. In the analysis of test–retest method, the intraclass correlation coefficient between the two scores was 0.94.

Conclusions

We demonstrated the validity and reliability of PDQ-J. We encourage researchers and clinicians to use this tool for the assessment of patients who suffer suspected neuropathic pain.

Pregabalin versus gabapentin in the management of peripheral neuropathic pain associated with post-herpetic neuralgia and diabetic neuropathy: a cost effectiveness analysis for the Greek healthcare setting

BACKGROUND

The anticonvulsants pregabalin and gabapentin are both indicated for the treatment of peripheral neuropathic pain. The decision on which treatment provides the best alternative, should take into account all aspects of costs and outcomes associated with the two therapeutic options. The objective of this study was to examine the cost - effectiveness of the two agents in the management of patients with painful diabetic neuropathy or post - herpetic neuralgia, under the third party payer perspective in Greece.

METHODS

The analysis was based on a dynamic simulation model which estimated and compared the costs and outcomes of pregabalin and gabapentin in a hypothetical cohort of 1,000 patients suffering from painful Diabetic Peripheral Neuropathy (DPN) or Post-Herpetic Neuralgia (PHN). In the model, each patient was randomly allocated an average pretreatment pain score, measured using an eleven-point visual analogue scale (0 - 10) and was "run through" the model, simulating their daily pain intensity and allowing for stochastic calculation of outcomes, taking into account medical interventions and the effectiveness of each treatment.

RESULTS

Pregabalin demonstrated a reduction in days with moderate to severe pain when compared to gabapentin. During the 12 weeks the pregabalin arm demonstrated a 0.1178 (SE 0.0002) QALY gain, which proved to be 0.0063 (SE 0.0003) higher than that in the gabapentin arm. The mean medication cost per patient was higher for the pregabalin arm when compared to the gabapentin arm (i.e. €134.40) over the 12 week treatment period. However, this higher cost was partially offset by the reduced direct medical costs (i.e. the cost of specialist visits, the cost of diagnostic tests and the other applied interventions). Comparing costs with respective outcomes, the ICERs for pregabalin versus gabapentin were €13 (95%CI: 8 - 18) per additional day with no or mild pain and €19,320 (95%CI: 11,743 - 26,755) per QALY gained.

CONCLUSIONS

Neuropathic pain carries a great disease burden for patients and society and, is also, associated with a significant economic burden. The treatment of pain associated with DPN and PHN with pregabalin is a cost-effective intervention for the social security in Greece compared to gabapentin. Thus, these findings need to be taken into consideration in the decision - making process when considering which therapy to use for the treatment of neuropathic pain.

Effects of axonal ion channel dysfunction on quality of life in type 2 diabetes

OBJECTIVE

Pharmacological agents for diabetic peripheral neuropathy (DN) target a number of mechanisms, including sodium channel function and γ-aminobutyric acid-minergic processes. At present, prescription is undertaken on a trial-and-error basis, leading to prolonged medication trials and greater healthcare costs. Nerve-excitability techniques are a novel method of assessing axonal ion channel function in the clinical setting. The aim of this study was to determine the effects of axonal ion channel dysfunction on neuropathy-specific quality-of-life (QoL) measures in DN.

RESEARCH DESIGN AND METHODS

Fifty-four patients with type 2 diabetes mellitus underwent comprehensive neurologic assessment, nerve-conduction studies, and nerve-excitability assessment. Neuropathy severity was assessed using the Total Neuropathy Score. Neuropathy-specific QoL was assessed using a DN-specific QoL questionnaire (Neuropathy-Specific Quality of Life Questionnaire [NeuroQoL]). Glycosylated hemoglobin and BMI were recorded in all patients.

RESULTS

NeuroQoL scores indicated significant QoL impairment (mean 9.08 ± 5.93). Strength-duration time constant (SDTC), an excitability parameter reflecting sodium channel function, was strongly correlated with QoL scores (r = 0.545; P < 0.005). SDTC was prolonged in 48.6% of patients who experienced neuropathic symptoms. A significant correlation was also noted between SDTC and neuropathy severity (r = 0.29; P < 0.05). This relationship was strengthened when looking specifically at patients with clinically graded neuropathy (r = 0.366; P < 0.05).

CONCLUSIONS

The current study has demonstrated an association between markers of sodium channel function and QoL in DN. The study demonstrates that excitability techniques may identify patients in whom altered sodium channel function may be the dominant abnormality. The findings suggest that excitability techniques may have a role in clinical decision making regarding neuropathic treatment prescription.

Peripheral neuropathy induces cutaneous hypersensitivity in chronically spinalized rats

BACKGROUND/OBJECTIVES

The present study was aimed at the issue of whether peripheral nerve injury-induced chronic pain is maintained by supraspinal structures governing descending facilitation to the spinal dorsal horn, or whether altered peripheral nociceptive mechanisms sustain central hyperexcitability and, in turn, neuropathic pain. We examined this question by determining the contribution of peripheral/spinal mechanisms, isolated from supraspinal influence(s), in cutaneous hypersensitivity in an animal model of peripheral neuropathy.

METHODS

Adult rats were spinalized at T8-T9; 8 days later, peripheral neuropathy was induced by implanting a 2-mm polyethylene cuff around the left sciatic nerve. Hind paw withdrawal responses to mechanical or thermal plantar stimulation were evaluated using von Frey filaments or a heat lamp, respectively.

RESULTS

Spinalized rats without cuff implantation exhibited a moderate decrease in mechanical withdrawal threshold on ~day 10 (P < 0.05) and in thermal withdrawal threshold on ~day 18 (P < 0.05). However, cuff-implanted spinalized rats developed a more rapid and significant decrease in mechanical (~day 4; P < 0.001) and thermal (~day 10; P < 0.05) withdrawal thresholds that remained significantly decreased through the duration of the study.

CONCLUSIONS

Our findings demonstrate an aberrant peripheral/spinal mechanism that induces and maintains thermal and to a greater degree tactile cutaneous hypersensitivity in the cuff model of neuropathic pain, and raise the prospect that altered peripheral/spinal nociceptive mechanisms in humans with peripheral neuropathy may have a pathologically relevant role in both inducing and sustaining neuropathic pain.

Considerations for neuropathic pain conditions in life care planning

Significant progress has been made in assessing and managing neuropathic pain. Newer, more effective treatments with minimal side effects are available. Despite advances in treatments, neuropathic pain remains a multifaceted phenomenon that can be difficult to alleviate. Diagnosis, mechanisms of injury, and treatment recommendations are critical components of life care plans for patients with neuropathic pain. A clear understanding of the underlying issues and careful coordination with neurologists and other treatment providers are key to providing optimal life care plans. Understanding that pain treatments vary over time and by individual patient is integral to comprehensive life care planning.

Can treatment success with 5% lidocaine medicated plaster be predicted in cancer pain with neuropathic components or trigeminal neuropathic pain?

An expert group of 40 pain specialists from 16 countries performed a first assessment of the value of predictors for treatment success with 5% lidocaine-medicated plaster in the management of cancer pain with neuropathic components and trigeminal neuropathic pain. Results were based on the retrospective analysis of 68 case reports (sent in by participants in the 4 weeks prior to the conference) and the practical experience of the experts. Lidocaine plaster treatment was mostly successful for surgery or chemotherapy-related cancer pain with neuropathic components. A dose reduction of systemic pain treatment was observed in at least 50% of all cancer pain patients using the plaster as adjunct treatment; the presence of allodynia, hyperalgesia or pain quality provided a potential but not definitively clear indication of treatment success. In trigeminal neuropathic pain, continuous pain, severe allodynia, hyperalgesia, or postherpetic neuralgia or trauma as the cause of orofacial neuropathic pain were perceived as potential predictors of treatment success with lidocaine plaster. In conclusion, these findings provide a first assessment of the likelihood of treatment benefits with 5% lidocaine-medicated plaster in the management of cancer pain with neuropathic components and trigeminal neuropathic pain and support conducting large, well-designed multicenter studies.

Surgically induced neuropathic pain: understanding the perioperative process

Nerve damage takes place during surgery. As a consequence, significant numbers (10%-40%) of patients experience chronic neuropathic pain termed surgically induced neuropathic pain (SNPP). The initiating surgery and nerve damage set off a cascade of events that includes both pain and an inflammatory response, resulting in "peripheral and central sensitization," with the latter resulting from repeated barrages of neural activity from nociceptors. In affected patients, these initial events produce chemical, structural, and functional changes in the peripheral and central nervous systems (CNS). The maladaptive changes in damaged nerves lead to peripheral manifestations of the neuropathic state-allodynia, sensory loss, shooting pains, etc, that can manifest long after the effects of the surgical injury have resolved. The CNS manifestations that occur are termed "centralization of pain" and affect sensory, emotional, and other (eg, cognitive) systems as well as contributing to some of the manifestations of the chronic pain syndrome (eg, depression). Currently there are no objective measures of nociception and pain in the perioperative period. As such, intermittent or continuous pain may take place during and after surgery. New technologies including direct measures of specific brain function of nociception and new insights into preoperative evaluation of patients including genetic predisposition, appear to provide initial opportunities for decreasing the burden of SNPP, until treatments with high efficacy and low adverse effects that either prevent or treat pain are discovered.

Treatment options in paraneoplastic disorders of the peripheral nervous system

OPINION STATEMENT

Paraneoplastic disorders of the peripheral nervous system (PNS) are the most frequent manifestation of paraneoplasia. As with the central nervous system, two categories of immune mechanisms are distinguished. On one side, antibodies toward intracellular antigens (HuD and CV2-CRMP5) occur with subacute sensory neuronopathy or sensorimotor neuropathy probably depending on a T cell mediated disorder (group 1). On the other side, the Lambert-Eaton myasthenic syndrome (LEMS) and peripheral nerve hyperexcitability (PNH) occur with antibodies to cell membrane antigens, respectively, the voltage gated calcium channel and CASPR2 proteins, which are responsible for the disease (group 2). Treatment recommendation mostly depends on class IV studies. Three lines of therapeutics can be proposed, namely tumor, immunomodulatory and symptomatic treatments. Cancer treatment is crucial since an early tumor cure is the best way to stabilize patients in group 1 and improve those in group 2. This implies the use of an efficient strategy for cancer diagnosis. With group 2 symptomatic treatment including 3,4 diaminopyridine for LEMS and carbamazepine for PNH may suffice to obtain good quality remission. Immunomodulatory treatments like IVIg and plasma exchange, which have a well-established efficacy in antibody dependent diseases, may be used as second line treatments. Rituximab, for which there is only little evidence in this context, may be kept in a third line for severe refractory patients. With group 1 patients, who frequently develop an evolving and disabling disorder, bolus of methylprednisolone and or IVIg may be recommended while searching for and treating the tumor. If the tumor is not found and the patient deteriorates, monthly pulses of cyclophosphamide may stabilize the patients. Antidepressants and antiepileptic drugs efficacious in the treatment of neuropathic pain are to be used as symptomatic treatment when necessary. The choice is then based on the cost effectiveness and tolerance of these drugs.

A randomized controlled pilot study of a cognitive-behavioral therapy approach for painful diabetic peripheral neuropathy

The purpose of the present pilot study was to assess the efficacy of cognitive-behavioral therapy (CBT) for painful diabetic peripheral neuropathy. This was a randomized, treatment as usual (TAU), controlled, nonblinded intervention pilot study with a 4-month follow-up conducted in a VA medical center. It was hypothesized that participants who received CBT, as compared to those who received TAU, would report significant decreases on self-report measures of pain severity, interference, and depressive symptoms from pretreatment to 4-month follow-up. Participants meeting inclusion criteria were randomly assigned to 1 of the study conditions. Of the 20 eligible participants, 12 were randomized to CBT and 8 were randomized to TAU. Participants randomized to CBT showed significant decreases on measures of pain severity (B = -.54) and pain interference (B = -.77) from pretreatment to 4-month follow-up. There were no significant changes in the TAU participants' scores on measures of pain severity (B = .00) or pain interference (B = -.09). Neither CBT nor TAU participants showed significant changes in their levels of depressive symptoms from pretreatment to 4-month follow-up. CBT may be an effective treatment approach for reducing pain severity and interference associated with painful diabetic peripheral neuropathy.

PERSPECTIVE

The results of this study suggest that engaging patients in CBT for painful diabetic peripheral neuropathy may provide them the skills to become more active and experience less pain.

Swim therapy reduces mechanical allodynia and thermal hyperalgesia induced by chronic constriction nerve injury in rats

OBJECTIVE

Neuropathic pain is common and often difficult to treat because it generally does not respond well to the currently available pain medications or nerve blocks. Recent studies in both humans and animals have suggested that exercise may induce a transient analgesia and reduce acute pain in normal healthy individuals. We examined whether swim therapy could alleviate neuropathic pain in rats.

DESIGN

Rats were trained to swim over a 2-week period in warm water. After the rats were trained, neuropathic pain was induced by constricting the right sciatic nerve, and regular swimming was resumed. The sensitivity of each hind paw was monitored using the Hargreaves test and von Frey test to evaluate the withdrawal response thresholds to heat and touch.

RESULTS

The paw ipsilateral to the nerve ligation expressed pain-like behaviors including thermal hyperalgesia and mechanical allodynia. Regular swim therapy sessions significantly reduced the mechanical allodynia and thermal hyperalgesia. Swim therapy had little effect on the withdrawal thresholds for the contralateral paw. In addition, swim therapy alone did not alter the thermal or mechanical thresholds of normal rats.

CONCLUSIONS

The results suggest that regular exercise, including swim therapy, may be an effective treatment for neuropathic pain caused by nerve injuries. This study, showing that swim therapy reduces neuropathic pain behavior in rats, provides a scientific rationale for clinicians to test the efficacy of exercise in the management of neuropathic pain. It may prove to be a safe and cost-effective therapy in a variety of neuropathic pain states.

Guidelines in the management of diabetic nerve pain: clinical utility of pregabalin

Diabetic peripheral neuropathy is a common complication of diabetes. It presents as a variety of syndromes for which there is no universally accepted unique classification. Sensorimotor polyneuropathy is the most common type, affecting about 30% of diabetic patients in hospital care and 25% of those in the community. Pain is the reason for 40% of patient visits in a primary care setting, and about 20% of these have had pain for greater than 6 months. Chronic pain may be nociceptive, which occurs as a result of disease or damage to tissue with no abnormality in the nervous system. In contrast, neuropathic pain is defined as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system." Persistent neuropathic pain interferes significantly with quality of life, impairing sleep and recreation; it also significantly impacts emotional well-being, and is associated with depression, anxiety, and noncompliance with treatment. Painful diabetic peripheral neuropathy is a difficult-to-manage clinical problem, and patients with this condition are more apt to seek medical attention than those with other types of diabetic neuropathy. Early recognition of psychological problems is critical to the management of pain, and physicians need to go beyond the management of pain per se if they are to achieve success. This evidence-based review of the assessment of the patient with pain in diabetes addresses the state-of-the-art management of pain, recognizing all the conditions that produce pain in diabetes and the evidence in support of a variety of treatments currently available. A search of the full Medline database for the last 10 years was conducted in August 2012 using the terms painful diabetic peripheral neuropathy, painful diabetic peripheral polyneuropathy, painful diabetic neuropathy and pain in diabetes. In addition, recent reviews addressing this issue were adopted as necessary. In particular, reports from the American Academy of Neurology and the Toronto Consensus Panel on Diabetic Neuropathy were included. Unfortunately, the results of evidence-based studies do not necessarily take into account the presence of comorbidities, the cost of treatment, or the role of third-party payers in decision-making. Thus, this review attempts to give a more balanced view of the management of pain in the diabetic patient with neuropathy and in particular the role of pregabalin.

Painful diabetic polyneuropathy: approach to diagnosis and management

OBJECTIVES

To provide a current overview of the diagnostic work-up and management of painful diabetic polyneuropathy (PDPN).

METHODS

A review covering the literature from 2004 to 2011, which describes the tools designed to diagnose neuropathic pain and assess its severity, including self-administered questionnaires, validated laboratory tests and simple handheld screening devices, and the evidence-based therapeutic approaches to PDPN.

RESULTS

The clinical aspects, pathogenesis, and comorbidities of PDPN, as well as its impact on health related quality of life (HR-QoL), are the main drivers for the management of patients with suspected PDPN. PDPN treatment consists first of all in improving glycemic control and lifestyle intervention. A number of symptomatic pharmacological agents are available for pain control: tricyclic antidepressants and selective serotonin norepinephrine reuptake inhibitors (venlafaxine and duloxetine), α2-delta ligands (gabapentin and pregabalin), opioid analgesics (tramadol and oxycodone), and agents for topical use, such as lidocaine patch and capsaicin cream. With the exception of transcutaneous electrical nerve stimulation, physical treatment is not supported by adequate evidence.

DISCUSSION

As efficacy and tolerability of current therapy for PDPN are not ideal, the need for a better approach in management further exists. Novel compounds should be developed for the treatment of PDPN.

Are treatment benefits in neuropathic pain reflected in the Self Assessment of Treatment questionnaire?

BACKGROUND/OBJECTIVE

The Self Assessment of Treatment (SAT) questionnaire was developed to reflect key patient reported outcomes of Neuropathic Pain (NP) treatments. This study aimed to understand how patients perceived the relevance and ease of understanding of the questions in the SAT and to recommend modifications based on patient and clinician interviews.

METHODS

Semi-structured interviews were conducted with clinicians and NP patients to provide information regarding treatment attributes and the impact of pain. Patients were debriefed on the SAT, a 5-item scale evaluating pain, activity level, quality of life (QoL) and satisfaction with treatment (recommend treatment and undergo treatment again). The SAT has a recall period reflecting back to the start of treatment. The qualitative analysis software ATLAS.ti 5.0 was used to analyze patient transcripts. Changes to the SAT were integrated into the questionnaire for a second round of debriefing interviews.

RESULTS

Three NP clinicians and 44 patients (20 painful diabetic neuropathy, 16 HIV-associated neuropathy and 8 post herpetic neuralgia) with a mean age of 60.3 (12.3) years and an even gender distribution were interviewed. Patient treatment experience included anticonvulsants (73%), antidepressants (34%), opioids (25%), and topical medications (41%). Pain descriptors and treatment attributes were similar across the three NP groups. Pain relief was judged the most important treatment attribute, followed by ability to undertake activities. Sleep improvement was another important attribute. Activity limitations and QOL were perceived as too broad and non-specific, and were split into 3 concepts each (activity limitations was split into self care, daily and physical activities and QOL was split into sleep, emotions, and social function). A 7-day recall period was introduced. The item stem and response options were made consistent, and a baseline and follow-up questionnaires were developed (except for the satisfaction items) to enable monitoring onset of treatment benefit and change over time.

CONCLUSIONS

The content validity of the revised SAT was improved by the qualitative research, and NP treatment benefits are reflected in a more consistent fashion by the changes. Baseline and follow-up versions make it possible to perform assessments of change over time.

Neuropathic pain

Neuropathic pain is a clinical entity that presents unique diagnostic and therapeutic challenges. This chapter addresses the classification, epidemiology, pathophysiology, diagnosis, and treatment of neuropathic pain syndrome. Neuropathic pain can be distinguished from nociceptive pain based on clinical signs and symptoms. Although neuropathic pain presents a significant burden to individuals and society, a more accurate assessment of resource utilization, costs, and impairments associated with neuropathic pain would facilitate appropriate planning of healthcare policies. The underlying pathophysiology of neuropathic pain is not well defined. Several theories regarding the mechanism of neuropathic pain have been proposed, including central and peripheral nervous system sensitization, deafferentation, neurogenic inflammation, and the wind up theory. Neuropathic pain is a clinical diagnosis and requires a systematic approach to assessment, including a detailed history, physical examination, and appropriate diagnostic testing. The mainstay of treatment for neuropathic pain is pharmacological, including the use of antidepressants, antiepileptics, topical anesthetics, and opioids. Nonpharmacological treatments include psychological approaches, physical therapy, interventional therapy, spinal cord stimulation, and surgical procedures. Neuropathic pain is difficult to treat, but a combination of therapies may be more effective than monotherapy. Clinical practice guidelines provide an evidence-based approach to the treatment of neuropathic pain.

Burden of illness associated with painful diabetic peripheral neuropathy among adults seeking treatment in the US: results from a retrospective chart review and cross-sectional survey

BACKGROUND

The purpose of this study was to characterize the burden of illness among adult subjects with painful diabetic peripheral neuropathy (pDPN) seeking treatment in the US.

METHODS

This observational study recruited 112 subjects with pDPN during routine visits from general practitioner and specialist sites. Subjects completed a one-time questionnaire, which included demographics, symptom duration, health care resource use, out-of-pocket costs, employment status, and validated measures that assessed pain, functioning, sleep, anxiety and depression, health status, and productivity. Investigators completed a case report form based on a 6-month retrospective chart review to capture clinical information, pDPN-related treatments, and other pDPN-related health care resource use over the past 6 months. Annualized costs were extrapolated based on reported 6-month health care resource use.

RESULTS

The mean age of the subjects was 61.1 years, 52.7% were female, and 17.9% were in paid employment. The most common comorbid conditions were sleep disturbance/insomnia (43.8%), depressive symptoms (41.1%), and anxiety (35.7%). The mean pain severity score was 5.2 (0-10 scale), and 79.5% reported moderate or severe pain. The mean pain interference with function score was 5.0 (0-10 scale) overall, with 2.0 among mild, 5.1 among moderate, and 7.0 among severe. The mean Medical Outcomes Study sleep problems index score was 48.5 (0-100 scale). The mean health state utility score was 0.61. Among subjects employed for pay, mean overall work impairment was 43.6%. Across all subjects, mean overall activity impairment was 52.3%. In total, 81.3% were prescribed at least one medication for their pDPN; 50.9% reported taking at least one nonprescription medication. Adjusted mean annualized total direct and indirect costs per subject were $4841 and $9730, respectively. Outcomes related to pain interference with function, sleep, health status, activity impairment, prescription medication use, and direct and indirect costs were significantly worse among subjects with more severe pain (P < 0.0020).

CONCLUSION

Subjects with pDPN exhibited high pain levels, which were associated with poor sleep, function, and productivity. Health care resource utilization in pDPN was prevalent and costs increased with greater pain severity. The burden of pDPN was greater among subjects with greater pain severity.