Diagnosis and treatment of neuropathic pain

Mu-opioid receptor and receptor tyrosine kinase crosstalk: Implications in mechanisms of opioid tolerance, reduced analgesia to neuropathic pain, dependence, and reward

Despite the prevalence of opioid misuse, opioids remain the frontline treatment regimen for severe pain. However, opioid safety is hampered by side-effects such as analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, or reward. These side effects promote development of opioid use disorders and ultimately cause overdose deaths due to opioid-induced respiratory depression. The intertwined nature of signaling via μ-opioid receptors (MOR), the primary target of prescription opioids, with signaling pathways responsible for opioid side-effects presents important challenges. Therefore, a critical objective is to uncouple cellular and molecular mechanisms that selectively modulate analgesia from those that mediate side-effects. One such mechanism could be the transactivation of receptor tyrosine kinases (RTKs) via MOR. Notably, MOR-mediated side-effects can be uncoupled from analgesia signaling via targeting RTK family receptors, highlighting physiological relevance of MOR-RTKs crosstalk. This review focuses on the current state of knowledge surrounding the basic pharmacology of RTKs and bidirectional regulation of MOR signaling, as well as how MOR-RTK signaling may modulate undesirable effects of chronic opioid use, including opioid analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, and reward. Further research is needed to better understand RTK-MOR transactivation signaling pathways, and to determine if RTKs are a plausible therapeutic target for mitigating opioid side effects.

Evaluation of the effects of different hemostatic agent applications on mental nerve

PURPOSE

Evaluating the effect of ABS (Ankaferd Blood Stopper^®), Tranexamic Acid (Transamin^®) and Thrombin-Containing Hemostatic Matrix (Floseal^®) on the mental nerve of rats by using histopathologic and immunohistochemical analyses.

MATERIALS AND METHODS

40 Wistar Albino rats were used. Rats were randomly selected into 4 groups as Control (G1), ABS (G2), Tranexamic Acid (G3) and Thrombin-Containing Hemostatic Matrix (G4). In the control group G1, the left mental nerve was exposed and 0.3 ml of sterile saline was applied for 5 min, then closed with suture. In the other three groups, the left mental nerve was exposed and 0.3 ml ABS, Tranexamic Acid and Floseal was applied to groups, respectively. After 5 min, wounds were closed with suture. Immunohistochemical and histopathologic examinations were performed on mental nerves after 28 days.

RESULTS

The total histopathologic and immunohistochemical semiquantitative scores were significantly higher in ABS (G2) compared to Control (G1), Tranexamic Acid (G3) and Thrombin-Containing Hemostatic Matrix (G4) (P < 0.05). Myelin thickness were significantly lower in G2 compared to G1, G2 and G3 (P < 0.05). G3 has the most reliable results compared to G2 and G4 (P < 0.05).

CONCLUSION

The study results suggest that ABS has neurotoxic effects and should not be used close to the nerve, and thrombin-containing hemostatic matrix should be used carefully. Tranexamic acid, on the other hand, was found to be the most reliable hemostatic agent for use in close proximity to neural tissues. Further studies are required to determine the efficacy of the hemostatic agents on peripheral nerve degeneration.

Future Treatment of Neuropathic Pain in Spinal Cord Injury: The Challenges of Nanomedicine, Supplements or Opportunities?

Neuropathic pain (NP) is a common chronic condition that severely affects patients with spinal cord injuries (SCI). It impairs the overall quality of life and is considered difficult to treat. Currently, clinical management of NP is often limited to drug therapy, primarily with opioid analgesics that have limited therapeutic efficacy. The persistence and intractability of NP following SCI and the potential health risks associated with opioids necessitate improved treatment approaches. Nanomedicine has gained increasing attention in recent years for its potential to improve therapeutic efficacy while minimizing toxicity by providing sensitive and targeted treatments that overcome the limitations of conventional pain medications. The current perspective begins with a brief discussion of the pathophysiological mechanisms underlying NP and the current pain treatment for SCI. We discuss the most frequently used nanomaterials in pain diagnosis and treatment as well as recent and ongoing efforts to effectively treat pain by proactively mediating pain signals following SCI. Although nanomedicine is a rapidly growing field, its application to NP in SCI is still limited. Therefore, additional work is required to improve the current treatment of NP following SCI.

Sustained Release In Situ Thermogelling Hydrogel of Cerebrolysin for Treatment of Facial Nerve Axotomy in Rats

PURPOSE

The most essential principle in managing facial nerve (FN) injury is proper diagnosis and early treatment. This study evaluated local application of different concentrations and injection intervals of Cerebrolysin hydrogel (CBLH) for facial nerve axotomy (FNA) treatment. We hypothesized that local application of CBLH may provide a sustained release of Cerebrolysin and enhance neural regeneration.

METHODS

The authors implemented a randomized, controlled, blinded animal study. The sample was composed of the right FN. Functionally, eye-blink reflex was evaluated 2 and 4 weeks postoperatively. All rats were euthanized after 4 weeks, and nerve regeneration was evaluated histopathologically and immunohistochemically (IHC) with antibody against neurofilament (anti-NF) and S100 proteins. Descriptive and correlation statistics were computed, and the P value was set at .05.

RESULTS

The sample was composed of 72 adult male rats equally allocated into 8 groups. Groups I and V served as control groups and were injected with phosphate buffered saline once and four times, respectively. Rest of the groups were injected with 5%, 10%, and 15% CBLH once in groups II, III, IV and weekly in groups VI, VII, and VIII. CBLH showed statistically significant FN regeneration by enhancing Schwann and axonal growth compared to control group especially with single injection of 10%, 15%, and 5% 4-time injections, where the P value was less than .001. Significant improvement of eye-blink reflex was correlated with structural improvement associated with CBLH.

CONCLUSION

Finally, CBLH enhanced nerve regeneration and rehabilitation after FNA in rats. Therefore, it could be considered as an alternative treatment of FNA. More experimental and clinical trials should be considered to detect the effectiveness of CBLH in neural regeneration.

Maladaptive reorganization following SCI: The role of body representation and multisensory integration

In this review we focus on maladaptive brain reorganization after spinal cord injury (SCI), including the development of neuropathic pain, and its relationship with impairments in body representation and multisensory integration. We will discuss the implications of altered sensorimotor interactions after SCI with and without neuropathic pain and possible deficits in multisensory integration and body representation. Within this framework we will examine published research findings focused on the use of bodily illusions to manipulate multisensory body representation to induce analgesic effects in heterogeneous chronic pain populations and in SCI-related neuropathic pain. We propose that the development and intensification of neuropathic pain after SCI is partly dependent on brain reorganization associated with dysfunctional multisensory integration processes and distorted body representation. We conclude this review by suggesting future research avenues that may lead to a better understanding of the complex mechanisms underlying the sense of the body after SCI, with a focus on cortical changes.

Patterns and Impact of Electronic Health Records-Defined Depression Phenotypes in Spine Surgery

BACKGROUND

Preoperative depression is a risk factor for poor outcomes after spine surgery.

OBJECTIVE

To understand effects of depression on spine surgery outcomes and healthcare resource utilization.

METHODS

Using IBM's MarketScan Database, we identified 52 480 patients who underwent spinal fusion. Retained patients were classified into 6 depression phenotype groups based on International Classification of Disease, 9th/10th Revision (ICD-9/10) codes and use/nonuse of antidepressant medications: major depressive disorder (MDD), other depression (OthDep), antidepressants for other psychiatric condition (PsychRx), antidepressants for physical (nonpsychiatric) condition (NoPsychRx), psychiatric condition only (PsychOnly), and no depression (NoDep). We analyzed baseline demographics, comorbidities, healthcare utilization/payments, and chronic opioid use.

RESULTS

Breakdown of groups in our cohort: MDD (15%), OthDep (12%), PsychRx (13%), NonPsychRx (15%), PsychOnly (12%), and NoDep (33%). Postsurgery: increased outpatient resource utilization, admissions, and medication refills at 1, 2, and 5 yr in the NoDep, PsychOnly, NonPsychRx, PsychRx, and OthDep groups, and highest in MDD. Postoperative opioid usage rates remained unchanged in MDD (44%) and OthDep (36%), and reduced in PsychRx (40%), NonPsychRx (31%), and PsychOnly (20%), with greatest reduction in NoDep (13%). Reoperation rates: 1 yr after index procedure, MDD, OthDep, PsychRx, NonPsychRx, and PsychOnly had more reoperations compared to NoDep, and same at 2 and 5 yr. In NoDep patients, 45% developed new depressive phenotype postsurgery.

CONCLUSION

EHR-defined classification allowed us to study in depth the effects of depression in spine surgery. This increased understanding of the interplay of mental health will help providers identify cohorts at risk for high complication rates, and health care utilization.

The antioxidant N-(2-mercaptopropionyl)-glycine (tiopronin) attenuates expression of neuropathic allodynia and hyperalgesia

The current pharmacotherapy of neuropathic pain is inadequate as neuropathic pain involves varied clinical manifestations with multifactorial etiology, modulated by a cascade of physical and molecular events leading to different clinical presentations of pain. There is an accumulating evidence of the involvement of oxidative stress in neuropathy, and antioxidants have shown promise in mitigating neuropathic pain syndromes. To explore the evidence supporting this beneficial proclivity of antioxidants, this study investigated the antinociceptive effectiveness of N-(2-mercaptopropionyl)glycine or tiopronin, a well-recognized aminothiol antioxidant, in a refined chronic constriction injury (CCI) rat model of neuropathic pain. Tiopronin (10, 30, and 90 mg/kg, i.p.) and pregabalin (30 mg/kg, i.p.) were administered daily after CCI surgery. The neuropathic paradigms of mechanical/cold allodynia and mechanical/heat hyperalgesia were assessed on days 3, 7, 14, and 21 post-nerve ligation. At the end of study, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were estimated in the sciatic nerve, dorsal root ganglion, and spinal cord for assessing the extent of oxidative stress. The expression of neuropathic nociception was attenuated by tiopronin which was observed as a significant attenuation of CCI-induced allodynia and hyperalgesia. Tiopronin reversed the neuronal oxidative stress by significantly reducing MDA, and increasing SOD, CAT, and GSH levels. Pregabalin also showed similar beneficial propensity on CCI-induced neuropathic aberrations. These findings suggest prospective neuropathic pain attenuating efficacy of tiopronin and further corroborated the notion that antioxidants are effective in mitigating the development and expression of neuropathic pain and underlying neuronal oxidative stress.

Effectiveness of warm needling acupuncture for pain relief in patients with diabetic peripheral neuropathy: A protocol of systematic review

BACKGROUND

Warm needling acupuncture (WNA) has been widely utilized for pain management in patients with diabetic peripheral neuropathy (DPN). However, its results are still inconsistent, and no systematic review has specifically addressed this issue. Thus, this systematic review will comprehensively and systematically investigate the effectiveness and safety of WNA for pain relief in DPN.

METHODS

A comprehensive literature search of MEDLINE, EMBASE, Cochrane Library, Web of Science, Scopus, Allied and Complementary Medicine Database, CBM database, and China National Knowledge Infrastructure will be performed for randomized controlled trials that report WNA for pain relief in patients with DPN. All electronic databases will be searched from initial to the present without limitations of language and publication status. Two investigators will independently screen papers, collect data, and assess study quality. Cochrane risk of bias tool will be used for study quality assessment, and evidence quality will be evaluated using Grading of Recommendations Assessment, Development and Evaluations approach. RevMan 5.3 software will be applied for running statistical analysis.

RESULTS

This study will summarize the evidence for the effectiveness and safety of WNA for the management of pain in patients with DPN.

CONCLUSIONS

The findings of this study may provide helpful evidence to judge whether WNA for pain relief in DPN is effective or not.

Hydroethanolic Stem Bark Extract of Burkea africana Attenuates Vincristine-Induced Peripheral Neuropathy in Rats

Context. The stem bark of the savanna tree Burkea africana (Hook) (family: Leguminosae) is used in the Ghanaian traditional medicine for the management of various pain-related diseases.

Defining Major Depressive Disorder Cohorts Using the EHR: Multiple Phenotypes Based on ICD-9 Codes and Medication Orders

Background

Major Depressive Disorder (MDD) is one of the most common mental illnesses and a leading cause of disability worldwide. Electronic Health Records (EHR) allow researchers to conduct unprecedented large-scale observational studies investigating MDD, its disease development and its interaction with other health outcomes. While there exist methods to classify patients as clear cases or controls, given specific data requirements, there are presently no simple, generalizable, and validated methods to classify an entire patient population into varying groups of depression likelihood and severity.

Methods

We have tested a simple, pragmatic electronic phenotype algorithm that classifies patients into one of five mutually exclusive, ordinal groups, varying in depression phenotype. Using data from an integrated health system on 278,026 patients from a 10-year study period we have tested the convergent validity of these constructs using measures of external validation, including patterns of psychiatric prescriptions, symptom severity, indicators of suicidality, comorbidity, mortality, health care utilization, and polygenic risk scores for MDD.

Results

We found consistent patterns of increasing morbidity and/or adverse outcomes across the five groups, providing evidence for convergent validity.

Limitations

The study population is from a single rural integrated health system which is predominantly white, possibly limiting its generalizability.

Conclusion

Our study provides initial evidence that a simple algorithm, generalizable to most EHR data sets, provides categories with meaningful face and convergent validity that can be used for stratification of an entire patient population.

The efficiency of ozone therapy and low-level laser therapy in rat facial nerve injury

PURPOSE

Comparison of low-level laser therapy (LLLT) and ozone therapy (OT) methods for the treatment of facial nerve injury (FNI) in rats, evaluated by histomorphometric measurement analysis.

MATERIALS AND METHODS

Thirty rats were randomly divided into control (C), LLLT, and OT groups. The left facial nerves (FNs) of all rats (n = 30) were used in this study. These were held in a surgical clamp for 30 s to create neuropathic damage. The non-injured right FNs of the rats in the control group formed the fourth, sham (S) group in this study (n = 10). Therefore the total number of evaluated samples was 40. The injured FNs of rats in the control group were left to heal spontaneously, whereas LLLT was applied for 21 consecutive days (output 100 mW/cm² and wavelength 850 nm) and OT (2 ml; 80 μm/ml) once every 2 days for 21 days.

RESULTS

After histomorphological evaluation, the OT group revealed statistically significant outcomes following FNI compared with the OT and control groups in terms of branching of nerve fibers (p = 0.003), nerve fiber diameters (p = 0.0398), nerve fiber areas (p = 0.042), and axon numbers (p = 0.0327). Although the LLLT group revealed a better healing process than the control group, the outcome was not statistically significant in terms of branching of nerve fibers (p = 0.6804), nerve fiber diameters (p = 0.7424), nerve fiber areas (p = 0.7048), and axon numbers (p = 0.7588).

CONCLUSIONS

OT resulted in statistically significant differences in outcome when compared with the LLLT and control groups, and provided a safe and effective treatment for FNI in rats. OT could therefore be considered as an alternative treatment of FNI. Clinical studies should now be performed to establish whether comparable results can be achieved in humans.

Mental imagery training for treatment of central neuropathic pain: a narrative review

Mental imagery is a quasi-perceptual experience in the absence of external stimuli. This concept has intrigued psychologists, sportspersons, neurologists and other scientists for over a decade now. Imagery has been used in rehabilitation and the results have been promising. Researchers refer to this as healing the body through the mind. However, the challenge is lack of standardized protocols, homogeneity and consistency in application of mental imagery in different populations. The purpose of this review is to discuss and understand the role of mental imagery in the treatment of central neuropathic pain (CNP). Treatment options of CNP are inadequate and their benefits are short lived. We conducted an extensive search on various databases using combinations of different keywords and reviewed the available literature in this area. We were able to finalize twelve studies where mental imagery was used for treating CNP in spinal cord injury (SCI), stroke and multiple sclerosis. However, the methodology and techniques of mental imagery training used in these studies were non-homogeneous and inconsistent. This review provides a guiding framework to further explore the different techniques of mental imagery and their roles in treating CNP.

Persistent socket pain postenucleation and post evisceration: a systematic review

PURPOSE

To investigate causes, diagnostics and treatment modalities for persistent socket pain (PSP) after enucleation and evisceration.

METHODS

A systematic search was undertaken in accordance with the PRISMA Statement, in PubMed, Embase.com and Thomson Reuters/Web of Science. We searched for relevant papers until the 28th of July 2016. Inclusion criteria were (1) patients with a history of enucleation or evisceration, (2) PSP, (3) report of the cause and/or used diagnostics and/or treatment modality, (4) full text in English, Dutch or Spanish language. Excluded were (1) review articles, (2) comments, and publications concerning, (3) nonhumans, (4) exenterated patients, (5) acute postoperative pain, or (6) periorbital pain without pain in the socket. Given the lack of high quality evidence from randomized controlled trials, we examined all available evidence from primary observational studies and assessed quality within this lower level of evidence.

RESULTS

A total of 32 studies were included. Causes of PSP found were prosthesis-related (n = 5), dry socket (n = 2), trochleitis (n = 3), compression of the trigeminal nerve (n = 2), implant-related (n = unknown), inflammation (n = 5), surgery-related (n = 4), neuromas (n = 8), malignant tumours (n = 3), psychiatric/psychosocial (n = 2), phantom pain (n = 149), rarer entities (n = 3) or unknown (n = 14). Nonsurgical treatments suffice for conditions as trochleitis, prosthesis-related pain, dry socket and for phantom pain. Other causes of pain may require more invasive treatments such as implant removal.

CONCLUSION

Careful history and examination can give some direction in the diagnostic procedure; however, PSP is probably multifactorial and the specific origin(s) may remain uncertain. Implant replacement can be an effective treatment. Studies to identifiy less invasive procedures are required.

Auricular vagus nerve stimulation enhances central serotonergic function and inhibits diabetic neuropathy development in Zucker fatty rats

Painful neuropathy is a frequent comorbidity in diabetes. Zucker diabetic fatty (fa/fa) rats develop type 2 diabetes spontaneously with aging and show nociceptive hypersensitivity at the age of 13 weeks. In preclinical and clinical studies, the treatment of diabetic neuropathy is challenging, but complementary medicine such as transcutaneous auricular vagus nerve stimulation (taVNS) appears beneficial to the relief of neuropathic pain. However, the mechanism behind the effectiveness of taVNS remains unclear. In this study, we show that daily 30-min taVNS (2/15 Hz, 2 mA) for consecutive 27 days effectively inhibited the development of nociceptive hypersensitivity in Zucker diabetic fatty rats as detected by thermal hyperalgesia and mechanical allodynia in hindpaw. We also demonstrated that this beneficial effect in nociceptive behavior is related to an elevated serotonin (5-HT) plasma concentration and an upregulated expression of 5-HT receptor type 1A (5-HT1AR) in hypothalamus. We conclude that daily 30-min taVNS sessions lessen diabetic neuropathy development by enhancing serotonergic function in genetically diabetes prone individuals.

Perspective

This article presents taVNS as a new approach to inhibit the development of diabetic neuropathy in genetically prone individuals. This approach could potentially help clinicians who seek to avoid the complication of neuropathic pain in diabetic patient or to relieve the pain if there was one.

Antiallodynic and antihyperalgesic activities of zerumbone via the suppression of IL-1β, IL-6, and TNF-α in a mouse model of neuropathic pain

Background

Neuropathic pain is a debilitating condition that severely affects the quality of life for those with this pain condition, and treatment for pain relief is greatly sought-after. Zerumbone (Zer), a sesquiterpene compound isolated from the rhizomes of a Southeast Asian ginger plant, Zingiber zerumbet (L.) Roscoe ex Smith. (Zingiberaceae), showed antinociceptive and antiinflammatory properties when previously tested on models of nociception and inflammation.

Objective

This study investigated the effects of prophylactic administration of zerumbone on allodynia and hyperalgesia in a mouse model of chronic constriction injury (CCI)-induced neuropathic pain.

Methods

Intraperitoneal administration of Zer (5–50 mg/kg) from day 1 post-surgery was carried out to identify the onset and progression of the pain condition. Responses toward mechanical and cold allodynia, and mechanical and thermal hyperalgesia were assessed on days 3, 5, 7, 9, 11, and 14 post-surgery. Blood plasma and spinal cord levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and IL-10 were screened using enzyme-linked immunosorbent assay on day 15.

Results

Zer (10 and 50 mg/kg) attenuated pain symptoms on all days of behavioral testing without any signs of sedation in the rotarod test. ED₅₀ values for mechanical allodynia, cold allodynia, thermal hyperalgesia, and mechanical hyperalgesia were 9.25, 9.507, 8.289, and 9.801 mg/kg, respectively. Blood plasma and spinal levels of IL-1β, IL-6, and tumor necrosis factor-α but not IL-10 were significantly (p<0.05) suppressed by zer treatment.

Discussion and conclusion

Zer exhibits its antiallodynic and antihyperalgesic properties via reduced sensitization at nociceptor neurons possibly through the suppression of inflammatory mediators. Zer may prove to be a novel and beneficial alternative for the management of neuropathic pain.

Acupuncture for the Treatment of Peripheral Neuropathy: A Systematic Review and Meta-Analysis

OBJECTIVES

Neuropathy and its associated pain pose great therapeutic challenges. While there has been a recent surge in acupuncture use and research, little remains known about its effects on nerve function. This review aims to assess the efficacy of acupuncture in the treatment of neuropathy of various etiologies.

METHODS

The Medline, AMED, Cochrane, Scopus, CINAHL, and clintrials.gov databases were systematically searched from inception to July 2015. Randomized controlled trials (RCTs) assessing acupuncture's efficacy for poly- and mononeuropathy were reviewed. Parallel and crossover RCTs focused on acupuncture's efficacy were reviewed and screened for eligibility. The Scale for Assessing Scientific Quality of Investigations in Complementary and Alternative Medicine was used to assess RCT quality. RCTs with score of >9 and active control treatments such as sham acupuncture or medical therapy were included.

RESULTS

Fifteen studies were included: 13 original RCTs, a long-term follow-up, and a re-analysis of a prior RCT. The selected RCTs studied acupuncture for neuropathy caused by diabetes, Bell's palsy, carpal tunnel syndrome, human immunodeficiency virus (HIV), and idiopathic conditions. Acupuncture regimens, control conditions, and outcome measures differed among studies, and various methodological issues were identified. Still, the majority of RCTs showed benefit for acupuncture over control in the treatment of diabetic neuropathy, Bell's palsy, and carpal tunnel syndrome. Acupuncture is probably effective in the treatment of HIV-related neuropathy, and there is insufficient evidence for its benefits in idiopathic neuropathy. Acupuncture appears to improve nerve conduction study parameters in both sensory and motor nerves. Meta-analyses were conducted on all diabetic neuropathy and Bell's palsy individual subject data (six RCTs; a total of 680 subjects) using a summary estimate random effects model, which showed combined odds ratio of 4.23 (95% confidence interval 2.3-7.8; p < 0.001) favoring acupuncture over control for neuropathic symptoms.

CONCLUSIONS

Acupuncture is beneficial in some peripheral neuropathies, but more rigorously designed studies using sham-acupuncture control are needed to characterize its effect and optimal use better.

Postherpetic neuralgia, diabetic neuropathy, and trigeminal neuralgia - Chronic peripheral neuropathic pain in 58,480 rural Italian primary care patients

Introduction:

Chronic peripheral neuropathic pain (CPNP) is a condition due to peripheral nervous system diseases or injury, but its prevalence is unknown in Italian primary care.

Aim:

The aim of this study is to assess the prevalence of CPNP in a rural primary care area in Northern Italy.

Materials and Methods:

A multicenter audit study was carried out in a rural area in Northern Italy with 113 participating general practitioners (GPs) seeing 58,480 patients >18 years during 3 months. Patients who for any reason attended GPs’ surgeries and had symptoms suggestive of neuropathic pain (NP) were given the NP diagnostic questionnaire “Douleur Neuropathique en 4 Questions” (DN4) and recorded their pain level on a visual analog scale (VAS).

Results:

Chronic NP was established by a DN4 score of ≥4 and a VAS pain score of ≥40 mm for >6 months together with a clinical diagnosis in 448 (254 women and 194 men) out of 58,480 patients giving a prevalence of 0.77%. 179 patients (0.31%) had diabetes neuropathy, 142 (0.24%) had postherpetic pain, 41 (0.07%) had trigeminal neuralgia, 27 (0.05%) had NP postinjury, 27 (0.05%) had NP caused by nerve entrapments, 11 (0.02%) had NP triggered by systemic diseases, and 21 (0.04%) had NP of unknown etiology.

Conclusions:

The prevalence of CPNP in this population of primary care attenders in a rural area in Northern Italy was 0.77%. Diabetes neuropathy (0.31%) and postherpetic pain (0.24%) were the two most common subgroups of NP, followed by trigeminal neuralgia (0.07%).

Combination strategy of PARP inhibitor with antioxidant prevent bioenergetic deficits and inflammatory changes in CCI-induced neuropathy

Neuropathic pain, a debilitating pain condition and the underlying pathogenic mechanisms are complex and interwoven amongst each other and still there is scant information available regarding therapies which promise to treat the condition. Evidence indicate that oxidative/nitrosative stress induced poly (ADP-ribose) polymerase (PARP) overactivation initiate neuroinflammation and bioenergetic crisis culminating into neurodegenerative changes following nerve injury. Hence, we investigated the therapeutic effect of combining an antioxidant, quercetin and a PARP inhibitor, 4-amino 1, 8-naphthalimide (4-ANI) on the hallmark deficits induced by chronic constriction injury (CCI) of sciatic nerve in rats. Quercetin (25 mg/kg, p.o.) and 4-ANI (3 mg/kg, p.o.) were administered either alone or in combination for 14 days to examine sciatic functional index, allodynia and hyperalgesia using walking track analysis, Von Frey, acetone spray and hot plate tests respectively. Malondialdehyde, nitrite and glutathione levels were estimated to detect oxidative/nitrosative stress; mitochondrial membrane potential and cytochrome c oxidase activity to assess mitochondrial function; NAD & ATP levels to examine the bioenergetic status and levels of inflammatory markers were evaluated in ipsilateral sciatic nerve. Quercetin and 4-ANI alone improved the pain behaviour and biochemical alterations but the combination therapy demonstrated an appreciable reversal of CCI-induced changes. Nitrotyrosine and Poly ADP-Ribose (PAR) immunopositivity was decreased and nuclear factor erythroid 2-related factor (Nrf-2) levels were increased significantly in micro-sections of the sciatic nerve and dorsal root ganglion (DRG) of treatment group. These results suggest that simultaneous inhibition of oxidative stress-PARP activation cascade may potentially be useful strategies for management of trauma induced neuropathic pain.

Continuous neurophatic orofacial pain: A retrospective study of 23 cases

Background

To determine the clinical characteristics of Continuous Neuropathic Orofacial Pain in patients that suffer Persistent Idiopathic Facial Pain (PIFP), Painful Post-Traumatic Trigeminal Neuropathy (PPTTN) or Burning Mouth Syndrome (BMS) and to describe their treatment.

Material and Methods

A retrospective observational study was made, reviewing the clinical history of the patients diagnosed with Continuous Neuropathic Orofacial Pain between 2004 and 2011 at the Orofacial Pain Unit of the Master of Oral Surgery and Implantology of the University of Barcelona and at the Orofacial Pain Unit of the Teknon Medical Center of Barcelona.

Results

The average age of the patients with Continuous Neuropathic Orofacial Pain was 54.5, with a clear female predominance (86.9%, n=20). Of all patients, 60.9% (n=14) were suffering a PIFP, 21.7% (n=5) had a BMS and 17.4% (n=4) were presenting a PPTTN. The pain quality described by the patients with Continuous Neuropathic Orofacial Pain was oppressive (43.47%, n=10), widely represented by patients with PIFP, and burning (39.13%, n=9) being the only quality that described patients with BMS. The treatment carried out with the patients was only pharmacologic. The most used drugs for the treatment of PIFP and PPTTN were clonazepam (50%, n=9) and amitriptyline (44.44%, n=8). However, a 55.5% (n=10) of the patients with PIFP or PPTTN required the association of two or more drugs for a correct pain control. All the patients with BMS responded satisfactorily to clonazepam.

Conclusions

Continuous Neuropathic Orofacial Pain is a little known condition among the general population, physicians and dentists. This favors a late diagnosis and inaccurate treatments which entail unnecessary suffering. It is important to inform both the general population and health professionals concerning this painful condition.

Key words:Continuous neuropathic orofacial pain, persistent idiopathic facial pain, painful post-traumatic trigeminal neuropathy, burning mouth syndrome, atypical odontalgia.

Antiallodynic and antihyperalgesic effects of zerumbone on a mouse model of chronic constriction injury-induced neuropathic pain

Neuropathic pain is a chronic condition that is difficult to be treated. Current therapies available are either ineffective or non-specific thus requiring newer treatment approaches. In this study, we investigated the antiallodynic and antihyperalgesic effects of zerumbone, a bioactive sesquiterpene from Zingiber zerumbet in chronic constriction injury (CCI)-induced neuropathic pain animal model. Our findings showed that single and repeated dose of intra-peritoneal administration of zerumbone (5, 10, 50, 100 mg/kg) significantly attenuated the CCI-induced neuropathic pain when evaluated using the electronic von Frey anesthesiometer, cold plate, Randall-Selitto analgesiometer and the Hargreaves plantar test. Zerumbone significantly alleviated tactile and cold allodynia as well as mechanical and thermal hyperalgesia. Our findings are in comparison to the positive control drugs thatused gabapentin (20 mg/kgi.p.) and morphine (1 mg/kgi.p.). Together, these results showed that the systemic administration of zerumbone produced marked antiallodynic and antihyperalgesic effects in the CCI-induced neuropathic pain in mice and may serve as a potential lead compound for further analysis.

Neuropathic cancer pain: What we are dealing with? How to manage it?

Cancer pain is a serious health problem, and imposes a great burden on the lives of patients and their families. Pain can be associated with delay in treatment, denial of treatment, or failure of treatment. If the pain is not treated properly it may impair the quality of life. Neuropathic cancer pain (NCP) is one of the most complex phenomena among cancer pain syndromes. NCP may result from direct damage to nerves due to acute diagnostic/therapeutic interventions. Chronic NCP is the result of treatment complications or malignancy itself. Although the reason for pain is different in NCP and noncancer neuropathic pain, the pathophysiologic mechanisms are similar. Data regarding neuropathic pain are primarily obtained from neuropathic pain studies. Evidence pertaining to NCP is limited. NCP due to chemotherapeutic toxicity is a major problem for physicians. In the past two decades, there have been efforts to standardize NCP treatment in order to provide better medical service. Opioids are the mainstay of cancer pain treatment; however, a new group of therapeutics called coanalgesic drugs has been introduced to pain treatment. These coanalgesics include gabapentinoids (gabapentin, pregabalin), antidepressants (tricyclic antidepressants, duloxetine, and venlafaxine), corticosteroids, bisphosphonates, N-methyl-D-aspartate antagonists, and cannabinoids. Pain can be encountered throughout every step of cancer treatment, and thus all practicing oncologists must be capable of assessing pain, know the possible underlying pathophysiology, and manage it appropriately. The purpose of this review is to discuss neuropathic pain and NCP in detail, the relevance of this topic, clinical features, possible pathology, and treatments of NCP.

Electroacupuncture and lumbar transplant of GDNF-secreting fibroblasts synergistically attenuate hyperalgesia after sciatic nerve constriction

Electroacupuncture (EA) has been shown to induce potent analgesic effects on neuropathic pain in both patients and rodents. Cell therapy to release antinociceptive agents near the pain processing centers of the spinal cord is a promising next step in the development of treatment modalities. This study investigated the effects of the combination of EA and cell therapy by glial cell line-derived neurotrophic factor (GDNF) on neuropathic pain in rats. The hyperalgesic state was induced by chronic constriction injury (CCI) of the sciatic nerve and fibroblasts genetically modified to secrete bioactive GDNF (FBs-GDNF) were used for cell therapy. Fifty-eight rats with neuropathic pain were randomly divided into five groups (CCI+PBS, n = 11; CCI+FBs-GDNF, n = 12; CCI+EA+PBS, n = 11; CCI+EA+FBs-pLNCX2, n = 12; CCI+EA+FBs-GDNF, n = 12). On the 7th day after CCI, the rats received intrathecal transplantation of FBs-GDNF or control fibroblasts (FBs-pLNCX2). In the meantime, EA was administered once every other day from the 7th day after CCI surgery for 21 days. The paw withdrawal latency (PWL) to radiant heat was measured every other day. The results showed that the ipsilateral PWL of the rats from all three EA treatment groups significantly increased starting on the 12th day compared with the PBS control group. Strikingly, the group which received EA treatment and FBs-GDNF transplantation (CCI+EA+FBs-GDNF) showed a significantly decreased thermal hyperalgesia after 2 weeks post CCI surgery compared with the groups which received EA treatment and FBs-pLNCX2 transplantation (CCI+EA+FBs-pLNCX2) or PBS (CCI+EA+PBS) as well as the FBs-GDNF transplantation group without EA treatment (CCI+FBs-GDNF). Our data suggest that EA and cell therapy can synergistically attenuate hyperalgesia in neuropathic pain rats.

Effects of histamine on spontaneous neuropathic pain induced by peripheral axotomy

The present study was designed to investigate the effects of histamine on spontaneous neuropathic pain (NP) induced by peripheral axotomy. Rats and mice were subjected to complete transection of the left sciatic and saphenous nerves to induce spontaneous NP (the neuroma model). Rats were then treated with drugs once daily for 30 days (histidine and loratadine, i.p.) or 21 days (histamine, i.c.v.). Autotomy behavior was scored daily until day 50 post-operation (PO). On days 14 to 21 PO, some rats in the control group were subjected to single-fiber recording. Autotomy behavior was also monitored daily in histidine decarboxylase (the key enzyme for histamine synthesis) knockout (HDC(-/-)) and wild-type mice for 42 days. We found that both histidine (500 mg/kg) (a precursor of histamine that increases histamine levels in the tissues) and histamine (50 μg/5 μL) significantly suppressed autotomy behavior in rats. HDC(-/-) mice lacking endogenous histamine showed higher levels of autotomy than the wild-type. In addition, the analgesic effect of histidine was not antagonized by loratadine (a peripherally-acting H1 receptor antagonist), while loratadine alone significantly suppressed autotomy. Electrophysiological recording showed that ectopic spontaneous discharges from the neuroma were blocked by systemic diphenhydramine (an H1 receptor antagonist). Our results suggest that histamine plays an important role in spontaneous NP. It is likely that histamine in the central nervous system is analgesic, while in the periphery, via H1 receptors, it is algesic. This study justifies the avoidance of a histamine-rich diet and the use of peripherally-acting H1 receptor antagonists as well as agents that improve histamine action in the central nervous system in patients with spontaneous NP.

Treatment of painful peripheral neuropathy

Neuropathic pain management is an important aspect in the management of painful peripheral neuropathy. Anticonvulsants and antidepressants have been studied extensively and are often used as first-line agents in the management of neuropathic pain. In this article, data from multiple randomized controlled studies on painful peripheral neuropathies are summarized to guide physicians in treating neuropathic pain. Treatment is a challenge given the diverse mechanisms of pain and variable responses in individuals. However, most patients derive pain relief from a well-chosen monotherapy or well-designed polypharmacy that combines agents with different mechanisms of action.

Painful decisions for senior pets

Osteoarthritis and cancer are the inevitable consequences of aging and significantly contribute to the cause of death in cats and dogs. Managing the pain associated with these disease states is the veterinarian’s mandate. Many treatment modalities and agents are available for patient management; however, it is only with an understanding of disease neurobiology and a mechanism-based approach to problem diagnosis that the clinician can offer patients an optimal quality of life based on evidence-based best medicine. When treating pain, knowledge is still our best weapon.

Chemotherapy-induced peripheral neuropathy. Part II. Prevention

The incidence of chemotherapy-induced peripheral neuropathy (CIPN) in the population of cancer patients is estimated at 3-7% in cytostatic monotherapy and as high as 38% in the case of polytherapy. While testing drugs that may reduce the damage to the peripheral nervous system, particular attention should be paid to their protective action against the severe and painful complication in the patient. Another aspect, perhaps a more important one, is the confidence that application of preventive drugs will not exert a significant impact on progression of the neoplastic disease or the effectiveness of the causal treatment. Many drugs have been tested for prevention of CIPN; however, none of them have thus far been irrefutably proven to possess preventive properties. No guidelines on chemotherapy-induced peripheral neuropathy preventive action have been established, either. This article is an attempt to present reports from the available literature about the possibilities of prevention of CIPN.

Clinical characteristics and patterns of healthcare utilization in patients with painful neuropathic disorders in UK general practice: a retrospective cohort study

BACKGROUND

Clinical characteristics and patterns of healthcare utilization in patients with painful neuropathic disorders (PNDs) who are under the care of general practitioners (GPs) in the UK are not well understood.

METHODS

Using a large electronic UK database, we identified all adults (age ≥ 18 years) with any GP encounters between 1 January 2006-31 December 2006 at which a diagnosis of PND was noted ("PND patients"). An age-and gender-matched comparison group also was constituted consisting of randomly selected patients with one or more GP encounters-but no mention of PNDs-during this period. Characteristics and patterns of healthcare utilization of patients in the two groups were then examined over the one-year study period.

RESULTS

The study sample consisted of 31,688 patients with mention of PNDs and an equal number of matched comparators; mean age was 56 years, and 62% were women. The prevalence of various comorbidities was higher among patients in the PND group, including digestive disorders (31% vs. 17% for comparison group), circulatory disorders (29% vs. 22%), and depression (4% vs. 3%) (all p < 0.01). Receipt of prescriptions for pain-related pharmacotherapy also was higher among PND patients, including nonsteroidal anti-inflammatory drugs (56% of PND patients had one or more such prescriptions vs. only 22% in the comparison group), opioids (49% vs. 12%), tricyclic antidepressants (20% vs. 1%), and antiepileptics (12% vs. 1%) (all p < 0.01). PND patients also averaged significantly more GP visits (22.8 vs. 14.2) and referrals to specialists (2.8 vs. 1.4) over one year (both comparisons p < 0.01).

CONCLUSIONS

Patients with PNDs under the care of GPs in the UK have relatively high levels of use of healthcare services and pain-related pharmacotherapy.

Painful peripheral neuropathies

BACKGROUND AND OBJECTIVES

Painful neuropathies are common and often difficult to treat. The objective of this report was to review the subject to facilitate diagnosis and pain relief.

CONTENTS

The classification, causes, type of fibers involved, manifestations, diagnosis, adjuvant tests, questionnaires used in the diagnosis, and treatment are described.

CONCLUSIONS

The subject is very broad and involves several causes and treatments that often should be combined to obtain adequate pain control.

Preliminary assessment of a neuropathic pain treatment and referral algorithm for patients with cancer

CONTEXT

The purpose of this case series study was to pilot test an evidence-based neuropathic pain (NP) treatment and referral algorithm for use by oncology nurses when managing cancer-related NP.

OBJECTIVES

The primary study objective was to assess patient-reported outcomes (pain severity, changes in activities of daily living, and satisfaction) resulting from algorithm use.

METHODS

Outpatients (n=20) with cancer-related NP scores ≥4 on a 0-10 numeric rating scale participated in the study. NP assessment, treatment, and referral to ancillary providers were guided by an evidence-based NP algorithm that was implemented by oncology nurse practitioners. Based on efficacy evidenced through randomized clinical trials published at the time of study implementation, the following drugs were included in the algorithm: lidocaine patch, gabapentin, oxycodone, tramadol, morphine, methadone, duloxetine, pregabalin, and nortriptyline. Recommendations for starting dose, dose escalation, drug combinations, treatment duration, and contraindications were included for first-tier drugs. Patient-reported outcomes (pain severity, functional capacity, and satisfaction) were assessed monthly over 12 weeks.

RESULTS

Average NP severity (P=0.001), general activity (P<0.001), mood (P=0.002), walking ability (P=0.01), ability to perform normal work (P=0.002), relationships (P=0.002), sleep (P=0.01), life enjoyment (P<0.001), and patient satisfaction (P=0.003) all improved by 12 weeks.

CONCLUSION

Evidence from this pilot study suggests that NP evidence-based treatment may result in improved symptoms, function, and patient satisfaction. A randomized controlled trial is needed to further assess algorithm efficacy.

Pharmacological treatment of neuropathic cancer pain: a comprehensive review of the current literature

Neuropathic cancer pain (NCP), commonly encountered in clinical practice, may be cancer-related, namely resulting from nervous system tumor invasion, surgical nerve damage during tumor removal, radiation-induced nerve damage and chemotherapy-related neuropathy, or may be of benign origin, unrelated to cancer. A neuropathic component is evident in about 1/3 of cancer pain cases. Although from a pathophysiological perspective NCP may differ from chronic neuropathic pain (NP), such as noncancer-related pain, clinical practice, and limited publications have shown that these two pain entities may share some treatment modalities. For example, co-analgesics have been well integrated into cancer pain-management strategies and are often used as First-Line options for the treatment of NCP. These drugs, including antidepressants and anticonvulsants, are recommended by evidence-based guidelines, whereas, others such as lidocaine patch 5%, are supported by randomized, controlled, clinical data and are included in guidelines for restricted conditions treatment. The vast majority of these drugs have already been proven useful in the management of benign NP syndromes. Treatment decisions for patients with NP can be difficult. The intrinsic difficulties in performing randomized controlled trials in cancer pain have traditionally justified the acceptance of drugs already known to be effective in benign NP for the management of malignant NP, despite the lack of relevant high quality data. Interest in NCP mechanisms and pharmacotherapy has increased, resulting in significant mechanism-based treatment advances for the future. In this comprehensive review, we present the latest knowledge regarding NCP pharmacological management.

Oral Local Anesthesia Successfully Ameliorated Neuropathic Pain in an Upper Limb Suggesting Pain Alleviation through Neural Plasticity within the Central Nervous System: A Case Report

Neural blockades are considered an alternative to pharmacotherapy for neuropathic pain although these blockades elicit limited effects. We encountered a patient with postbrachial plexus avulsion injury pain, which was refractory to conventional treatments but disappeared temporarily with the administration of the local anesthetic lidocaine around the left mandibular molar tooth during dental treatments. This analgesic effect on neuropathic pain by oral local anesthesia was reproducible. Under conditions of neuropathic pain, cerebral somatotopic reorganization in the sensorimotor cortices of the brain has been observed. Either expansion or shrinkage of the somatotopic representation of a deafferentated body part correlates with the degree of neuropathic pain. In our case, administration of an oral local anesthetic shrank the somatotopic representation of the mouth, which is next to the upper limb representation and thereby expanded the upper limb representation in a normal manner. Consequently, oral local anesthesia improved the pain in the upper limb. This case suggests that pain alleviation through neural plasticity within the brain is related to neural blockade.

Electroacupuncture Zusanli (ST36) on Release of Nitric Oxide in the Gracile Nucleus and Improvement of Sensory Neuropathies in Zucker Diabetic Fatty Rats

The purpose of these studies was to examine the effects of electroacupuncture (EA) Zusanli (ST36) on release of nitric oxide (NO) in the gracile nucleus (GN) and determine if functional neuropathic changes were modified by EA ST36-induced NO in the nucleus in Zucker diabetic fatty (ZDF) rats. The foot withdrawal responses to mechanical, thermal and cold stimuli were measured before and after EA stimulation. A microdialysis probe was implanted in the GN and dialysate samples were collected 20 min before, during and after EA ST36. Total nitrate and nitrite (NO_x⁻) concentrations in the samples were quantified by using chemiluminescence. The baseline dialysate NO_x⁻ concentrations in the GN were decreased in ZDF rats compared to lean control (LC) rats (P < .05). In ZDF rats, dialysate NO_x⁻ releases in the GN were markedly increased during EA ST36, whereas in LC rats, the releases were moderately enhanced at 20–40 min after EA ST36. The withdrawal latencies to mechanical, cold and thermal stimuli were significantly improved 20 min after EA ST36 both in LC and ZDF rats, but not altered by non-acupoint stimulation. The withdrawal latencies to EA ST36 were further potentiated by 3-morpholinyl-sydnoneimine and inhibited by N^G-Propyl-l-arginine infused into the GN in ZDF rats (P < .05). These results show that EA ST36 increases NO release in the GN, and NO in the nucleus modifies withdrawal latencies to mechanical, cold, and thermal nociception stimuli. Data suggest that EA ST36 induces NO release in the GN, which contributes to improvement of sensory neuropathies in rats.

Palliative care for the cancer patient

Palliation of symptoms to optimize QOL is the foundation of cancer care regardless of stage of disease or level of anticancer treatment. Patients commonly experience pain, constipation, nausea, vomiting, dyspnea, fatigue, and delirium. Many valid clinical tools are available to the primary care clinician to screen for symptoms, assess severity, measure treatment response, and elicit the patient's subjective symptom experience. Although there is limited evidence regarding the relative efficacy of symptom interventions from randomized controlled trials, clinical practice guidelines are available.

Word Choices of Advanced Cancer Patients: Frequency of Nociceptive and Neuropathic Pain

The purpose of this study was to determine if nociceptive and/or neuropathic pain in advanced cancer patients could be identified by word selections made on the McGill Melzack Pain Questionnaire. Theoretical definitions for nociceptive and neuropathic pain provided a framework for categorizing the word descriptors in the McGill Melzack Pain Questionnaire's sensory and miscellaneous dimensions. A description study design was used to group word frequencies by primary site and pain type. The participants were 76 advanced cancer patients who received home-based hospice services. A wide range of word choices for lung cancer patients supported both nociceptive and neuropathic pain. Individuals with colon and liver cancer selected words that described 2 types of nociceptive (visceral, somatic) pain, while those with prostate cancer noted somatic pain. A set frequency was not reached by individuals with breast, pancreatic, gastric, and other advanced cancers. This study provided evidence that advanced cancer patients select words that describe nociceptive and neuropathic pain types.

Orofacial pain and neurosensory disorders and dysfunction in cancer patients

Orofacial pain and altered nerve sensation may be the initial sign of oropharyngeal or nasopharyngeal cancer. This article focuses on the most common orofacial pain conditions and neurosensory alterations that affect cancer patients, such as neuropathic pain, muscle spasm or contractures, mucositis, and increased or decreased sensory discrimination in the affected area. The various pharmacotherapeutic modalities for cancer pain management ranging from non steroidal anti-inflammatory drugs (NSAIDs) for mild pain to opioids for severe pain are discussed in detail.

Update on pharmacotherapy guidelines for treatment of neuropathic pain

Neuropathic pain encompasses a myriad of painful disease states that are often hard to treat, especially with one single medication. In the comprehensive treatment of neuropathic pain, the concept of complex polypharmacy is a rational approach, accompanied by physical and mental health therapies. Medications primarily used for neuropathic pain generally fall into the categories of anticonvulsants, antidepressants, opioids, and topical agents. Generally, most first-line medications used today show a response rate of approximately 30% to 50% reduction in pain in up to 50% of patients treated. There is no "gold standard" in regard to one medication for neuropathic pain. Some new medications have emerged during the past few years that help to augment the armamentarium of medications used in neuropathic pain. This paper reviews the definition of neuropathic pain and introduces the reader to the evidence-based literature on these new medications available for the treatment of neuropathic pain.