Contemporary management of neuropathic pain for the primary care physician

Mechanical Effects of a Specific Neurodynamic Mobilization of the Superficial Fibular Nerve: A Cadaveric Study

CONTEXT

A specific neurodynamic mobilization for the superficial fibular nerve (SFN) has been suggested in the reference literature for manual therapists to evaluate nerve mechanosensitivity in patients. However, no authors of biomechanical studies have examined the ability of this technique to produce nerve strain. Therefore, the mechanical specificity of this technique is not yet established.

OBJECTIVES

To test whether this examination and treatment technique produced nerve strain in the fresh frozen cadaver and the contribution of each motion to total longitudinal strain.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

MAIN OUTCOME MEASURE(S)

A differential variable reluctance transducer was inserted in 10 SFNs from 6 fresh cadavers to measure strain during the mobilization. A specific sequence of plantar flexion, ankle inversion, straight-leg raise position, and 30° of hip adduction was applied to the lower limb. The mobilization was repeated at 0°, 30°, 60°, and 90° of the straight-leg raise position to measure the effect of hip-flexion position.

RESULTS

Compared with a resting position, this neurodynamic mobilization produced a significant amount of strain in the SFN (7.93% ± 0.51%, P < .001). Plantar flexion (59.34% ± 25.82%) and ankle inversion (32.80% ± 21.41%) accounted for the biggest proportions of total strain during the mobilization. No difference was noted among different hip-flexion positions. Hip adduction did not significantly contribute to final strain (0.39% ± 10.42%, P > .05), although high variability among limbs existed.

CONCLUSIONS

Ankle motion should be considered the most important factor during neurodynamic assessment of the SFN for distal entrapment. These results suggest that this technique produces sufficient strain in the SFN and could therefore be evaluated in vivo for correlation with mechanosensitivity.

Glutamatergic systems in neuropathic pain and emerging non-opioid therapies

Neuropathic pain, a disease of the somatosensory nervous system, afflicts many individuals and adequate management with current pharmacotherapies remains elusive. The glutamatergic system of neurons, receptors and transporters are intimately involved in pain but, to date, there have been few drugs developed that therapeutically modulate this system. Glutamate transporters, or excitatory amino acid transporters (EAATs), remove excess glutamate around pain transmitting neurons to decrease nociception suggesting that the modulation of glutamate transporters may represent a novel approach to the treatment of pain. This review highlights and summarizes (1) the physiology of the glutamatergic system in neuropathic pain, (2) the preclinical evidence for dysregulation of glutamate transport in animal pain models, and (3) emerging novel therapies that modulate glutamate transporters. Successful drug discovery requires continuous focus on basic and translational methods to fully elucidate the etiologies of this disease to enable the development of targeted therapies. Increasing the efficacy of astrocytic EAATs may serve as a new way to successfully treat those suffering from this devastating disease.

Tocotrienol-Rich Vitamin E (Tocovid) Improved Nerve Conduction Velocity in Type 2 Diabetes Mellitus Patients in a Phase II Double-Blind, Randomized Controlled Clinical Trial

Diabetic peripheral neuropathy (DPN) is the most common microvascular complication of diabetes that affects approximately half of the diabetic population. Up to 53% of DPN patients experience neuropathic pain, which leads to a reduction in the quality of life and work productivity. Tocotrienols have been shown to possess antioxidant, anti-inflammatory, and neuroprotective properties in preclinical and clinical studies. This study aimed to investigate the effects of tocotrienol-rich vitamin E (Tocovid Suprabio^TM) on nerve conduction parameters and serum biomarkers among patients with type 2 diabetes mellitus (T2DM). A total of 88 patients were randomized to receive 200 mg of Tocovid twice daily, or a matching placebo for 12 months. Fasting blood samples were collected for measurements of HbA1c, renal profile, lipid profile, and biomarkers. A nerve conduction study (NCS) was performed on all patients at baseline and subsequently at 2, 6, 12 months. Patients were reassessed after 6 months of washout. After 12 months of supplementation, patients in the Tocovid group exhibited highly significant improvements in conduction velocity (CV) of both median and sural sensory nerves as compared to those in the placebo group. The between-intervention-group differences (treatment effects) in CV were 1.60 m/s (95% CI: 0.70, 2.40) for the median nerve and 2.10 m/s (95% CI: 1.50, 2.90) for the sural nerve. A significant difference in peak velocity (PV) was also observed in the sural nerve (2.10 m/s; 95% CI: 1.00, 3.20) after 12 months. Significant improvements in CV were only observed up to 6 months in the tibial motor nerve, 1.30 m/s (95% CI: 0.60, 2.20). There were no significant changes in serum biomarkers, transforming growth factor beta-1 (TGFβ-1), or vascular endothelial growth factor A (VEGF-A). After 6 months of washout, there were no significant differences from baseline between groups in nerve conduction parameters of all three nerves. Tocovid at 400 mg/day significantly improve tibial motor nerve CV up to 6 months, but median and sural sensory nerve CV in up to 12 months of supplementation. All improvements diminished after 6 months of washout.

Gut microbiota regulates neuropathic pain: potential mechanisms and therapeutic strategy

Neuropathic pain (NP) is a sustained and nonreversible condition characterized by long-term devastating physical and psychological damage. Therefore, it is urgent to identify an effective treatment for NP. Unfortunately, the precise pathogenesis of NP has not been elucidated. Currently, the microbiota-gut-brain axis has drawn increasing attention, and the emerging role of gut microbiota is investigated in numerous diseases including NP. Gut microbiota is considered as a pivotal regulator in immune, neural, endocrine, and metabolic signaling pathways, which participates in forming a complex network to affect the development of NP directly or indirectly. In this review, we conclude the current understanding of preclinical and clinical findings regarding the role of gut microbiota in NP and provide a novel therapeutic method for pain relief by medication and dietary interventions.

Does a Rehabilitation Program of Aerobic and Progressive Resisted Exercises Influence HIV-Induced Distal Neuropathic Pain?

OBJECTIVE

Distal symmetrical polyneuropathy is a common neurological sequela after HIV, which leads to neuropathic pain and functional limitations. Rehabilitation programs with exercises are used to augment pharmacological therapy to relieve pain but appropriate and effective exercises are unknown. This study explored the safety and effect of moderate-intensity aerobic exercises and progressive resisted exercises for HIV-induced distal symmetrical polyneuropathy neuropathic pain.

DESIGN

A randomized pretest, posttest of 12 wks of aerobic exercise or progressive resisted exercise compared with a control. Outcome measures were assessed using the subjective periphery neuropathy, brief peripheral neuropathy screening, and numeric pain rating scale. Pain was assessed at baseline, 6 and 12 wks. Data between groups were compared using Kruskal-Wallis, Mann-Whitney U test, and within-groups Friedman and Wilcoxon signed rank tests.

RESULTS

There were 136 participants (mean [SD] age = 36.79 [8.23] yrs) and the exercise groups completed the protocols without any adverse effects. Pain scores within and between aerobic exercise and progressive resisted exercise groups showed significant improvement (P < 0.05) from baseline to 6 and 12 wks compared with the control (P > 0.05).

CONCLUSIONS

This study supports a rehabilitation program of moderate-intensity aerobic exercise and progressive resisted exercise being safe and effective for reducing neuropathic pain and is beneficial with analgesics for HIV-induced distal symmetrical polyneuropathy.

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%).

Neuropathic pain: principles of diagnosis and treatment

Neuropathic pain is caused by disease or injury of the nervous system and includes various chronic conditions that, together, affect up to 8% of the population. A substantial body of neuropathic pain research points to several important contributory mechanisms including aberrant ectopic activity in nociceptive nerves, peripheral and central sensitization, impaired inhibitory modulation, and pathological activation of microglia. Clinical evaluation of neuropathic pain requires a thorough history and physical examination to identify characteristic signs and symptoms. In many cases, other laboratory investigations and clinical neurophysiological testing may help identify the underlying etiology and guide treatment selection. Available treatments essentially provide only symptomatic relief and may include nonpharmacological, pharmacological, and interventional therapies. Most extensive evidence is available for pharmacological treatment, and currently recommended first-line treatments include antidepressants (tricyclic agents and serotonin-norepinephrine reuptake inhibitors) and anticonvulsants (gabapentin and pregabalin). Individualized multidisciplinary patient care is facilitated by careful consideration of pain-related disability (eg, depression and occupational dysfunction) as well as patient education; repeat follow-up and strategic referral to appropriate medical/surgical subspecialties; and physical and psychological therapies. In the near future, continued preclinical and clinical research and development are expected to lead to further advancements in the diagnosis and treatment of neuropathic pain.

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.

Neuralgia pós-herpética: dois casos clínicos

A neuralgia pós-herpética (NPH) é a complicação mais frequente do herpes-zóster, caracterizando-se pela presença de dor tipo neuropática de distribuição dermatômica, após manifestação prévia de um quadro agudo de herpes-zóster, geralmente um mês depois do surgimento das vesículas. O objetivo do presente relato é apresentar dois casos clínicos de NPH e suas respostas a diferentes tratamentos. O primeiro caso apresentou intolerância à amitriptilina e uma boa resposta clínica à gabapentina na dosagem de 900 mg/dia. O segundo caso apresentou intolerância à capsaicina, mas apresentou boa resposta à combinação da pregabalina com lidocaína tópica. A gabapentina, a pregabalina e a lidocaína tópica são tratamentos eficazes para o tratamento da neuralgia pós-herpética. Todas essas recomendações vão ao encontro dos tratamentos utilizados pelos médicos de família nos dois casos apresentados neste estudo. 

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.

Effective management of intractable neuropathic pain using an intrathecal morphine pump in a patient with acute transverse myelitis

Transverse myelitis is a rare inflammatory myelopathy characterized by loss of motor and sensory function below the affected level of the spinal cord, and causes neurogenic bowel and bladder. Occasionally, it also causes neuropathic pain with spasticity. Traditional therapies for neuropathic pain are multiple, including multimodal analgesic regimens, antiepileptic or antidepressant medications, opioids, sympathetic blocks, and spinal cord stimulation. Persistent neuropathic pain can cause emotional distress by affecting sleep, work, recreation, and emotional well-being. Here we report the case of a patient suffering from intractable neuropathic pain following acute transverse myelitis that was not relieved by combinations of nonsteroidal anti-inflammatory, anti-epileptic, antidepressant, and opioid medications, or by acupuncture. Implantation of an intrathecal morphine pump controlled the pain successfully without side effects, and enabled the patient to embark on intensive rehabilitation. The patient's muscle strength has improved significantly and the patient may soon be able to use a walker with minimal assistance.

H-reflex and clinical examination in the diagnosis of diabetic polyneuropathy

OBJECTIVES

To determine among adult patients with type-2 diabetes mellitus the proportion diagnosed with diabetic polyneuropathy (DPN) by clinical evaluation and by the Hoffmann reflex (H-reflex). In addition, the predictive value of the H-reflex in the diagnosis of DPN was evaluated.

METHODS

Studies were carried out on 150 adult patients referred for neuropathy screening. Diagnostic criteria for DPN were at least two abnormalities in clinical neurophysiological examinations and electrophysiological testing (H-reflex and nerve conduction velocity). Logistic regression analysis was performed to identify unique contributions of study characteristics to positive versus negative outcomes.

RESULTS

H-reflex was absent in 39.3% (59/150) and latency was prolonged in 43.3% (65/150) of patients. Ulnar nerve motor branch nerve conduction showed prolonged latency in 9.3% (14/150) of patients. Logistic regression analysis indicated that the H-reflex was significantly associated with positive outcomes.

CONCLUSION

The H-reflex could have a predictive value in DPN, providing more quantitative information regarding diagnosis than conventional nerve conduction studies.

A gastroretentive gabapentin formulation for the treatment of painful diabetic peripheral neuropathy: efficacy and tolerability in a double-blind, randomized, controlled clinical trial

AIMS

A randomized, double-blind, placebo-controlled study was conducted in 147 patients to determine the efficacy and safety of a gastroretentive formulation of gabapentin (G-GR) in treating painful diabetic peripheral neuropathy (DPN).

METHODS

Diabetic patients with symmetrical painful symptoms in distal extremities for 1-5 years and a baseline average daily pain (ADP) score of ≥4 received G-GR 3000mg, as a single evening daily dose (G-GR-QD) or a divided dose (G-GR-DD, 1200mg AM/1800mg PM), or placebo for 4 weeks. G-GR was titrated from 300 to 3000mg/day over 2 weeks, followed by 2 additional weeks at 3000mg/day. Efficacy measures included changes from baseline to Week 4 in ADP score and average daily sleep interference score (SIS).

RESULTS

A significantly larger decrease in ADP score was observed in the G-GR-QD dose group compared with placebo (-2.50 versus -1.30; p=0.002). A ≥50% reduction in ADP score was achieved in 34.8% of G-GR-QD recipients compared with 7.8% of placebo recipients (p=0.001). Similar results were observed for changes in SIS. The incidences of dizziness and somnolence, commonly associated with gabapentin, were low.

CONCLUSIONS

Once-daily G-GR was effective and well tolerated for the treatment of pain due to DPN.

Evaluation of Transcutaneous Electrical Nerve Stimulation as a Treatment of Neck Pain due to Musculoskeletal Disorders

BACKGROUND

This study was designed to evaluate transcutaneous electrical nerve stimulation (TENS) as a treatment for neck pain due to musculoskeletal disorders within the context of a physiotherapy treatment.

METHODS

Thirty subjects with neck pain were randomly allocated to two groups, treated with either TENS (n = 15) or placebo (n = 15). Each subject received one session for one hour. All subjects were evaluated before, during treatment, after switch off and again a week after by using Myometer machine. All subjects completed the follow-up assessment. Subjects referred for out-subjects' physiotherapy department, fulfilling the inclusion and exclusion criteria, took part in the study.

RESULTS

The assessments were compared and used to measure outcome treatment. Improvement in their condition was measured in terms of a reduction in the individual's level of pain during the week after the end of the first session. At the end of the first session, the study showed that 11 subjects (73%) in the treatment and 7 subjects (43%) in the control groups had gained marked improvement. These results are statistically highly significant, (P = 0.01) at the end of the follow-up assessment.

CONCLUSIONS

A conclusion could be drawn that a single intense TENS treatment is an effective treatment for neck pain due to musculoskeletal disorders. On the other hand, TENS showed an effective pain relief with subjects who have a mild neck pain rather than those with severe symptoms.

KEYWORDS

Musculoskeletal disorders; Transcutaneous electrical nerve stimulation; Neck pain.

Effects of high-velocity, low-amplitude manipulation on catalase activity in men with neck pain

OBJECTIVE

The aim of this study was to identify the influence of high-velocity, low-amplitude (HVLA) manipulation on lipid peroxidation and catalase activity in subjects with neck pain who answered the Neck Disability Index and quadruple visual scale questionnaires.

METHODS

Twenty-two men (mean age, 38 years) with neck pain were recruited through radio and newspaper advertisements in the local media. Every patient received 6 sessions of HVLA manipulation, 3 times a week for 2 weeks. Blood samples were drawn from the cubital vein before treatment in the first session and after the third and sixth sessions. The quadruple visual scale was used with the same scheme. The Neck Disability Index questionnaire was applied before the beginning of treatment and after the last session. Catalase activity and lipoperoxidation were measured in erythrocyte samples.

RESULTS

Results showed no change in lipid peroxidation. Nevertheless, the catalase activity was increased by HVLA manipulation. The same treatment reduced pain perception and disability in these subjects.

CONCLUSION

The present study has shown that catalase activity of the erythrocytes, but not lipoperoxidation, increased after 6 sessions of HVLA manipulation treatment in men with neck pain. The results support the beneficial role of HVLA in the treatment of patients with neck pain.

CT guided percutaneous cryoneurolysis for post thoracotomy pain syndrome: early experience and effectiveness

RATIONALE AND OBJECTIVES

The aim of this study was to determine the effect of cryoablation on pain levels in patients with histories of post-thoracotomy pain syndrome.

MATERIALS AND METHODS

Eighteen patients were included in this retrospective review. Preprocedural and immediate postprocedural pain scores were recorded, as well as several months after the procedures.

RESULTS

The average preprocedural pain score was 7.5 +/- 2.0, which decreased to 1.2 +/- 1.9 immediately after the procedure. After a mean follow-up period of 51 days, the average pain score was 4.1 +/- 1.7. The difference between preprocedural and postprocedural pain scores was statistically significant by Wilcoxon's rank sum test.

CONCLUSION

Cryoneurolysis of the intercostal nerves statistically significantly decreased pain scores in patients with post-thoracotomy pain syndrome.

Guidelines for the Pharmacological Treatment of Peripheral Neuropathic Pain: Expert Panel Recommendations for the Middle East Region

Neuropathic pain (NeP) has been the focus of extensive basic and clinical research over the past 20 years. This has led to an increased understanding of underlying pathophysiological mechanisms and the development of new therapeutic agents, as well as a clearer definition of the role of established medications. To date there are no published treatment guidelines for NeP in the Middle East. A multidisciplinary panel of Middle East and international experts met to review critically and reach a consensus on how best to apply evidence-based guidelines for the treatment of NeP (mainly peripheral NeP) in the Middle East. The expert panel recommended pregabalin, gabapentin and secondary amine tricyclic antidepressants (nortriptyline and desipramine) as first-line treatments for peripheral NeP. Serotonin-norepinephrine reuptake inhibitor antidepressants, tramadol and controlled-release opioid analgesics were recommended as second-line treatments. There is a need to increase diagnostic awareness of NeP, use validated screening questionnaires and undertake more treatment research in the Middle East region.

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.

Psychological aspects of patients with Fabry disease

The Minnesota Muliphasic Personality Inventory (MMPI-2) is widely used in chronic illness and chronic pain populations to assess psychological functioning. We report the results of the first investigation using the MMPI-2 to assess psychological aspects of patients with Fabry disease. Fabry disease, an X-linked lysosomal storage disorder, is a multisystem progressive disease affecting the kidney, heart, and central nervous system, and is particularly associated with chronic symptoms including pain. In this study, 28 patients with Fabry disease completed the MMPI-2 and a background questionnaire. Fabry disease patients scored significantly higher than the MMPI-2 normative sample on seven clinical scales (Hs, D, Hy, Pd, Pa, Pt, Sc) and two validity scales (L, F). Individuals with elevated scores on the Hs, D, and Hy scales tend to have somatic complaints, sadness, and emotional distress. Under stress, they may experience an increase in physical symptoms. Elevated Pd, Pa, Pt, and Sc scales suggest social maladjustment, suspiciousness, and feelings of isolation. An elevated L scale suggests defensiveness; a high score on F suggests emotional turmoil. When compared with cohorts of patients with Gaucher disease (GD), chronic heart disease (CRHD), and chronic pain, the Fabry disease patients had significantly higher scores than GD patients and CRHD patients on numerous clinical (Hs, D, Si), and validity (F) scales underscoring the relative amount of suffering and pain experienced by Fabry disease patients. No significant differences on any MMPI-2 scales were found between the Fabry disease patients and the pain patients, suggesting that Fabry disease patients may be comparable to pain patient populations.

An optimal protocol to analyze the rat spinal cord proteome

Since the function of the spinal cord depends on the proteins found there, better defing the normal Spinal Cord Proteome is an important and challenging task. Although brain and cerebrospinal fluid samples from patients with different central nervous system (CNS) disorders have been studied, a thorough examination of specific spinal cord proteins and the changes induced by injury or associated to conditions such as neurodegeneration, spasticity and neuropathies has yet to be performed. In the present study, we aimed to describe total protein content in the spinal cord of healthy rats, employing different proteomics tools. Accordingly, we have developed a fast, easy, and reproducible sequential protocol for protein extraction from rat spinal cords. We employed conventional two dimensional electrophoresis (2DE) in different pH ranges (eg. 4–7, 3–11 NL) combined with identification by mass spectrometry (MALDI-TOF/TOF), as well as first dimension protein separation combined with Liquid Chromatography Mass Spectrometry/Mass Spectrometry (LC-MS/MS) to maximise the benefits of this technology. The value of these techniques is demonstrated here by the identification of several proteins known to be associated with neuroglial structures, neurotransmission, cell survival and nerve growth in the central nervous system. Furthermore this study identified many spinal proteins that have not previously been described in the literature and which may play an important role as either sensitive biomarkers of dysfunction or of recovery after Spinal Cord Injury.

A study on electrocardiographic changes secondary to the use of tricyclic antidepressants in patients with chronic pain

BACKGROUND AND OBJECTIVES

Tricyclic antidepressants (TCAs) are widely used as analgesics in chronic lumbar pain and neuropathic pain. The objective of this study was to evaluate the electrocardiographic changes in patients with chronic pain treated with amitriptyline or imipramine.

METHODS

Forty patients, ages 26 to 81 years (57.27 +/- 13.65 years) of both genders (female 19, male 21), with neuropathic syndromes (lumbosciatalgia, postlaminectomy syndromes, and postherpetic neuritis, among others) participated in this study; 60% had cardiovascular diseases; 30% had changes in the ECG (RBBB, LBBB, first-degree AVB, LAHB, or PVCs). Three ECGs were done in each patient: one ECG was done before beginning treatment, and 30 and 60 days after beginning treatment evaluating PR, QRS, QT QTc, DQT DQTc, and HR. Thirty-two patients were on amitriptyline and eight on imipramine. The mean dose at the end of the study was 54.29 mg of amitriptyline and 46.87 mg of imipramine.

RESULTS

Analysis of electrocardiographic parameters after the use of TCAs showed that amitriptyline caused a transitory increase in heart rate in females (p = 0.049), and the duration of the QRS in patients 60 years or older and patients with cardiopathies (p = 0.01). In patients who received 75 mg of amitriptyline, the QTc interval was greater when compared to that of patients who received 25 mg of the drug (p = 0.0044). The increase in those parameters demonstrated the effects of amitriptyline on cardiac conduction; however, clinical compromise was not seen, since they remained within normal limits (QRS < 110 msec and QTc < 470 msec).

CONCLUSIONS

The chronic use of TACs proved to be safe and effective, and it did not show changes in cardiac conduction with clinical repercussion.

Increased peripheral nerve excitability and local NaV1.8 mRNA up-regulation in painful neuropathy

BACKGROUND

Neuropathic pain caused by peripheral nerve injury is a chronic disorder that represents a significant clinical challenge because the pathological mechanisms have not been fully elucidated. Several studies have suggested the involvement of various sodium channels, including tetrodotoxin-resistant NaV1.8, in affected dorsal root ganglion (DRG) neurons. We have hypothesized that altered local expression of NaV1.8 in the peripheral axons of DRG neurons could facilitate nociceptive signal generation and propagation after neuropathic injury.

RESULTS

After unilateral sciatic nerve entrapment injury in rats, compound action potential amplitudes were increased in both myelinated and unmyelinated fibers of the ipsilateral sciatic nerve. Tetrodotoxin resistance of both fiber populations and sciatic nerve NaV1.8 immunoreactivity were also increased. Further analysis of NaV1.8 distribution revealed that immunoreactivity and mRNA levels were decreased and unaffected, respectively, in the ipsilateral L4 and L5 DRG; however sciatic nerve NaV1.8 mRNA showed nearly an 11-fold ipsilateral increase. Nav1.8 mRNA observed in the sciatic nerve was likely of axonal origin since it was not detected in non-neuronal cells cultured from nerve tissue. Absence of changes in NaV1.8 mRNA polyadenylation suggests that increased mRNA stability was not responsible for the selective peripheral mRNA increase. Furthermore, mRNA levels of NaV1.3, NaV1.5, NaV1.6, NaV1.7, and NaV1.9 were not significantly different between ipsilateral and contralateral nerves. We therefore propose that selective NaV1.8 mRNA axonal transport and local up-regulation could contribute to the hyperexcitability of peripheral nerves in some neuropathic pain states.

CONCLUSION

Cuff entrapment injury resulted in significantly elevated axonal excitability and increased NaV1.8 immunoreactivity in rat sciatic nerves. The concomitant axonal accumulation of NaV1.8 mRNA may play a role in the pathogenesis of this model of neuropathic pain.

Diabetic peripheral neuropathic pain: recognition and management

The occurrence of diabetic peripheral neuropathy (DPN) is linked to poor glycemic control over time. While most people never develop diabetic peripheral neuropathic pain (DPNP) as a consequence of DPN, enough of them do that we must have effective options for the management of this disabling condition. Two years ago there were no formally approved medications for the treatment of DPNP, and now there are two medications with Food and Drug Administration approval for DPNP. One of these medications, duloxetine has been established to significantly improve pain and to address depression by its reuptake inhibition of norepinephrine and serotonin. This article examines the epidemiology of DPNP, its underlying pathogenesis, necessary evaluation methods, and treatment options available with a focus on the role of duloxetine.