Gabapentin effect on neuropathic pain compared among patients with spinal cord injury and different durations of symptoms

The effect of neuropathic pain treatments on pain interference following spinal cord injury: A systematic review

CONTEXT

Neuropathic pain is a common and debilitating condition following SCI. While treatments for neuropathic pain intensity have been reviewed, the impact on pain interference has not been summarized.

OBJECTIVE

To systematically review the effect of neuropathic pain interventions on pain interference in individuals with spinal cord injury.

METHODS

This systematic review included randomized controlled trials and quasi-experimental (non-randomized) studies which assessed the impact of an intervention on pain interference in individuals with spinal cord injury and neuropathic pain. Articles were identified by searching MEDLINE (1996 to April 11, 2022), EMBASE (1996 to April 11, 2022), PsycInfo (1987 to April, week 2, 2022). Studies were assessed for methodologic quality using a modified GRADE approach and were given quality of evidence (QOE) scores on a 4-point scale ranging from very low to high.

RESULTS

Twenty studies met the inclusion criteria. These studies fell into the following categories: anticonvulsants (n = 2), antidepressants (n = 1), analgesics (n = 1), antispasmodics (n = 1), acupuncture (n = 2), transcranial direct current stimulation (n = 1), active cranial electrotherapy stimulation (n = 2), transcutaneous electrical nerve stimulation (n = 2), repetitive transcranial magnetic stimulation (n = 1), functional electrical stimulation (n = 1), meditation and imagery (n = 1), self-hypnosis and biofeedback (n = 1), and interdisciplinary pain programs (n = 4).

CONCLUSION

When considering studies of moderate to high quality, pregabalin, gabapentin, intrathecal baclofen, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation (in 1 of 2 studies) were shown to have beneficial effects on pain interference. However, due to the low number of high-quality studies further research is required to confirm the efficacy of these interventions prior to recommending their use to reduce pain interference.

Biodegradable nanoparticles targeting circulating immune cells reduce central and peripheral sensitization to alleviate neuropathic pain following spinal cord injury

ABSTRACT

Neuropathic pain is a critical source of comorbidity following spinal cord injury (SCI) that can be exacerbated by immune-mediated pathologies in the central and peripheral nervous systems. In this article, we investigate whether drug-free, biodegradable, poly(lactide- co -glycolide) (PLG) nanoparticle treatment mitigates the development of post-SCI neuropathic pain in female mice. Our results show that acute treatment with PLG nanoparticles following thoracic SCI significantly reduces tactile and cold hypersensitivity scores in a durable fashion. Nanoparticles primarily reduce peripheral immune-mediated mechanisms of neuropathic pain, including neuropathic pain-associated gene transcript frequency, transient receptor potential ankyrin 1 nociceptor expression, and MCP-1 (CCL2) chemokine production in the subacute period after injury. Altered central neuropathic pain mechanisms during this period are limited to reduced innate immune cell cytokine expression. However, in the chronic phase of SCI, nanoparticle treatment induces changes in both central and peripheral neuropathic pain signaling, driving reductions in cytokine production and other immune-relevant markers. This research suggests that drug-free PLG nanoparticles reprogram peripheral proalgesic pathways subacutely after SCI to reduce neuropathic pain outcomes and improve chronic central pain signaling.

Combination Drug Therapy for the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (NP) is an increasingly prevalent disease and leading cause of disability which is challenging to treat. Several distinct classes of drugs are currently used for the treatment of chronic NP, but each drug targets only narrow components of the underlying pathophysiological mechanisms, bears limited efficacy, and comes with dose-limiting side effects. Multimodal therapies have been increasingly proposed as potential therapeutic approaches to target the multiple mechanisms underlying nociceptive transmission and modulation. However, while preclinical studies with combination therapies showed promise to improve efficacy over monotherapy, clinical trial data on their efficacy in specific populations are lacking and increased risk for adverse effects should be carefully considered. Drug-drug co-crystallization has emerged as an innovative pharmacological approach which can combine two or more different active pharmaceutical ingredients in a single crystal, optimizing pharmacokinetic and physicochemical characteristics of the native molecules, thus potentially capitalizing on the synergistic efficacy between classes of drugs while simplifying adherence and minimizing the risk of side effects by reducing the doses. In this work, we review the current pharmacological options for the treatment of chronic NP, focusing on combination therapies and their ongoing developing programs and highlighting the potential of co-crystals as novel approaches to chronic NP management.

Cortical Mechanisms Underlying Immersive Interactive Virtual Walking Treatment for Amelioration of Neuropathic Pain after Spinal Cord Injury: Findings from a Preliminary Investigation of Thalamic Inhibitory Function

BACKGROUND

Neuropathic pain following spinal cord injury (SCI) affects approximately 60% of individuals with SCI. Effective pharmacological and non-pharmacological treatments remain elusive. We recently demonstrated that our immersive virtual reality walking intervention (VRWalk) may be effective for SCI NP. Additionally, we found that SCI NP may result from a decrease in thalamic γ-aminobutyric-acid (GABA), which disturbs central sensorimotor processing.

OBJECTIVE

While we identified GABAergic changes associated with SCI NP, a critical outstanding question is whether a decrease in SCI NP generated by our VRWalk intervention causes GABA content to rise.

METHOD

A subset of participants (n = 7) of our VRWalk trial underwent magnetic resonance spectroscopy pre- and post-VRWalk intervention to determine if the decrease in SCI NP is associated with an increase in thalamic GABA.

RESULTS

The findings revealed a significant increase in thalamic GABA content from pre- to post-VRWalk treatment.

CONCLUSION

While the current findings are preliminary and should be interpreted with caution, pre- to post-VRWalk reductions in SCI NP may be mediated by pre- to post-treatment increases in thalamic GABA by targeting and normalizing maladaptive sensorimotor cortex reorganization. Understanding the underlying mechanisms of pain recovery can serve to validate the efficacy of home-based VR walking treatment as a means of managing pain following SCI. Neuromodulatory interventions aimed at increasing thalamic inhibitory function may provide more effective pain relief than currently available treatments.

A Systematic Review of the Interventions for Management of Pain in Patients After Spinal Cord Injury

Chronic pain is a very common problem in patients with spinal cord injury (SCI) as it affects 80% of these patients, which negatively affects their quality of life. Despite many advantages that exist in the management of any type of pain (neuropathic, nociceptive, mixed) in these patients, there is no cure, and the analgesic effect of some treatments is inadequate. This study aims to conduct an evidence-based systematic review regarding the various interventions used for the management of pain after SCI. The PubMed, Physiotherapy Evidence Database (PEDro), and Cochrane Library databases were searched from 1969 to 2023. The risk of bias was assessed using the PEDro scoring system. A total of 57 studies met the inclusion criteria and were included in this systematic review. Among the different interventions at present, 18 studies examined the role of oral medications, 11 studies examined the role of minimally invasive methods (injection and infusion), 16 studies investigated physiotherapy and alternative treatments, and 12 studies examined the role of repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and cranial electrotherapy stimulation (CES) in the management of pain in patients after SCI. Gabapentin and pregabalin are very effective in managing chronic neuropathic pain after SCI, and pregabalin also seems to reduce anxiety and sleep disturbances in the patients. It is noteworthy that lamotrigine, valproate, and carbamazepine do not have an analgesic effect, but mirogabalin is a novel and promising drug. Antidepressants (selective serotonin reuptake inhibitors and serotonin and noradrenaline reuptake inhibitors) did not reduce the pain of the patients, although some studies showed an efficacy of amitriptyline especially in depressed patients and tramadol should be considered short-term with caution. Also, tDCS and rTMS reduced pain. Moreover, botulinum toxin type A, lidocaine, ketamine, and intrathecal baclofen significantly reduced pain intensity, although the sample of the studies was small. Physiotherapy and alternative treatments seem to relieve pain, and transcutaneous electrical nerve stimulation had the greatest reduction of pain intensity. In conclusion, several pharmaceutical and non-pharmaceutical methods exist, which can reduce pain in patients after SCI. The type of intervention can be considered by the physician depending on the patients' preference, age, medical history, type of pain, and associated symptoms. However, more studies with greater samples and with better methodological quality should be conducted.

Inhibition of NKCC1 in spinal dorsal horn and dorsal root ganglion results in alleviation of neuropathic pain in rats with spinal cord contusion

Previous studies have confirmed the relationship between chloride homeostasis and pain. However, the role of sodium potassium chloride co-transporter isoform 1 (NKCC1) in dorsal horn and dorsal root ganglion neurons (DRGs) in spinal cord injury (SCI)-induced neuropathic pain (NP) remains inconclusive. Therefore, we aimed to explore whether suppression of NKCC1 in the spinal cord and DRGs alleviate the NP of adult rats with thoracic spinal cord contusion. Thirty adult female Sprague-Dawley rats (8 week-old, weighing 250-280 g) were randomly divided into three groups with ten animals in each group (sham, SCI, and bumetanide groups). The paw withdrawal mechanical threshold and paw withdrawal thermal latency were recorded before injury (baseline) and on post-injury days 14, 21, 28, and 35. At the end of experiment, western blotting (WB) analysis, quantitative real-time Polymerase Chain Reaction (PCR) and immunofluorescence were performed to quantify NKCC1 expression. Our results revealed that NKCC1 protein expression in the spinal cord and DRGs was significantly up-regulated in rats with SCI. Intraperitoneal treatment of bumetanide (an NKCC1 inhibitor) reversed the expression of NKCC1 in the dorsal horn and DRGs and ameliorated mechanical ectopic pain and thermal hypersensitivities in the SCI rats. Our study demonstrated the occurrence of NKCC1 overexpression in the spinal cord and DRGs in a rodent model of NP and indicated that changes in the peripheral nervous system also play a major role in promoting pain sensitization after SCI.

Limb accelerations during sleep are related to measures of strength, sensation, and spasticity among individuals with spinal cord injury

BACKGROUND

To evaluate the relationship between measures of neuromuscular impairment and limb accelerations (LA) collected during sleep among individuals with chronic spinal cord injury (SCI) to provide evidence of construct and concurrent validity for LA as a clinically meaningful measure.

METHODS

The strength (lower extremity motor score), sensation (summed lower limb light touch scores), and spasticity (categorized lower limb Modified Ashworth Scale) were measured from 40 adults with chronic (≥ 1 year) SCI. Demographics, pain, sleep quality, and other covariate or confounding factors were measured using self-report questionnaires. Each participant then wore ActiGraph GT9X Link accelerometers on their ankles and wrist continuously for 1-5 days to measure LA from movements during sleep. Regression models with built-in feature selection were used to determine the most relevant LA features and the association to each measure of impairment.

RESULTS

LA features were related to measures of impairment with models explaining 69% and 73% of the variance (R²) in strength and sensation, respectively, and correctly classifying 81.6% (F1-score = 0.814) of the participants into spasticity categories. The most commonly selected LA features included measures of power and frequency (frequency domain), movement direction (correlation between axes), consistency between movements (relation to recent movements), and wavelet energy (signal characteristics). Rolling speed (change in angle of inclination) and movement smoothness (median crossings) were uniquely associated with strength. When LA features were included, an increase of 72% and 222% of the variance was explained for strength and sensation scores, respectively, and there was a 34% increase in spasticity classification accuracy compared to models containing only covariate features such as demographics, sleep quality, and pain.

CONCLUSION

LA features have shown evidence of having construct and concurrent validity, thus demonstrating that LA are a clinically-relevant measure related to lower limb strength, sensation, and spasticity after SCI. LA may be useful as a more detailed measure of impairment for applications such as clinical prediction models for ambulation.

Coexistence of chronic hyperalgesia and multilevel neuroinflammatory responses after experimental SCI: a systematic approach to profiling neuropathic pain

Background

People with spinal cord injury (SCI) frequently develop neuropathic pain (NP) that worsens disability and diminishes rehabilitation efficacy. Chronic NP is presently incurable due to poor understanding of underlying mechanisms. We hypothesized that multilocus neuroinflammation (NIF) might be a driver of SCI NP, and tested it by investigating whether NP coexisted with central NIF, neurotransmission (NTM), neuromodulation (NML) and neuroplasticity (NPL) changes post-SCI.

Methods

Female Sprague–Dawley rats (230–250 g) with T10 compression or laminectomy were evaluated for physical conditions, coordinated hindlimb functions, neurological reflexes, and mechanical/thermal sensitivity thresholds at 1 day post-injury (p.i.) and weekly thereafter. Eight weeks p.i., central nervous system tissues were histochemically and immunohistochemically characterized for parameters/markers of histopathology and NIF/NTM/NML/NPL. Also analyzed was the correlative relationship between levels of selected biomarkers and thermosensitivity thresholds via statistical linear regression.

Results

SCI impaired sensorimotor functions, altered reflexes, and produced spontaneous pain signs and hypersensitivity to evoked nociceptive, mechanical, and thermal inputs. Only injured spinal cords exhibited neural lesion, microglia/astrocyte activation, and abnormal expression of proinflammatory cytokines, as well as NIF/NTM/NML/NPL markers. Brains of SCI animals displayed similar pathophysiological signs in the gracile and parabrachial nuclei (GrN and PBN: sensory relay), raphe magnus nucleus and periaqueduct gray (RMN and PAG: pain modulation), basolateral amygdala (BLA: emotional-affective dimension of pain), and hippocampus (HPC: memory/mood/neurogenesis). SCI augmented sensory NTM/NPL (GrN and PBN); increased GAD67 (PAG) level; reduced serotonin (RMN) and fear-off neuronal NTR2 (BLA) expressions; and perturbed neurogenesis (HPC).

Conclusion

T10 compression caused chronic hyperalgesia that coexisted with NIF/NTM/NML/NPL responses at multilevel neuroaxis centers. The data have provided multidimensional biomarkers as new mechanistic leads to profile SCI NP for therapeutic/therapy development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02628-2.

On the therapeutic targets and pharmacological treatments for pain relief following spinal cord injury: A mechanistic review

Spinal cord injury (SCI) is globally considered as one of the most debilitating disorders, which interferes with daily activities and life of the affected patients. Despite many developments in related recognizing and treating procedures, post-SCI neuropathic pain (NP) is still a clinical challenge for clinicians with no distinct treatments. Accordingly, a comprehensive search was conducted in PubMed, Medline, Scopus, Web of Science, and national database (SID and Irandoc). The relevant articles regarding signaling pathways, therapeutic targets and pharmacotherapy of post-SCI pain were also reviewed. Data were collected with no time limitation until November 2020. The present study provides the findings on molecular mechanisms and therapeutic targets, as well as developing the critical signaling pathways to introduce novel neuroprotective treatments of post-SCI pain. From the pathophysiological mechanistic point of view, post-SCI inflammation activates the innate immune system, in which the immune cells elicit secondary injuries. So, targeting the critical signaling pathways for pain management in the SCI population has significant importance in providing new treatments. Indeed, several receptors, ion channels, excitatory neurotransmitters, enzymes, and key signaling pathways could be used as therapeutic targets, with a pivotal role of n-methyl-D-aspartate, gamma-aminobutyric acid, and inflammatory mediators. The current review focuses on conventional therapies, as well as crucial signaling pathways and promising therapeutic targets for post-SCI pain to provide new insights into the clinical treatment of post-SCI pain. The need to develop innovative delivery systems to treat SCI is also considered.

The Efficacy, Adverse Events & Withdrawal Rates of the Pharmacological Management of Chronic Spinal Cord Injury Pain: A Systematic Review & Meta-Analysis

OBJECTIVE

To establish the efficacy of medications, incidence of adverse events (AE) and withdrawal rates (WR) of the pharmacological management of chronic spinal cord injury (SCI) pain.

METHODOLOGY

PubMed, MEDLINE, Embase, CINAHL, Web of Science, CENTRAL and PsycINFO were searched (November 2017) and updated (January 2020). Two independent review authors screened and identified papers for inclusion.

RESULTS

Twenty-one studies met inclusion for efficacy analysis and 17 for AEs and WR analysis; no additional paper were included from the up dated 2020 search. Treatments were divided into 6 categories: anticonvulsants (n = 6), antidepressants (n = 3), analgesics (n = 8), anti-spasticity (n = 2), cannabinoids (n = 1) and other (n = 2). Trials of anticonvulsants, antidepressants, and cannabinoids included long-term follow-up trials (2 weeks- 4 months), and analgesics, anti-spasticity, among others were short term trials (0-2 days). Effectiveness for NP was found for Pregabalin (3/3 studies) and Lidocaine (2/3 studies). Studies using Ketamine also reported effectiveness (2/2) but the quality of these papers was rated as poor. Most frequently reported AEs included dizziness, dry mouth, nausea and constipation. Pregabalin had a higher risk of somnolence (RR 3.15, 95% CI 2.00-4.98) and dizziness (RR 2.9, 95% CI 1.58-5.30). Ketamine had a higher risk of reduced vision (RR 9.00, 95% CI 0.05-146.11), dizziness (RR 8.33, 95% CI 1.73-40.10) and somnolence (RR 7.00, 95% CI 1.73-40.1). WRs ranged from: 18.4% (antidepressants), 0-30% (anticonvulsants), 0-10% (anti-spasticity), 0-48% (analgesics), 28.6% (cannabinoids) and 0-22.2% (other).

CONCLUSION

Pregabalin was found to be effective for NP versus placebo. Cannabinoids was ineffective for NP. AEs are a common cause for withdrawal. The nature of AEs was poorly reported and should be improved in future RCT's.

Toward Improving the Prediction of Functional Ambulation After Spinal Cord Injury Though the Inclusion of Limb Accelerations During Sleep and Personal Factors

OBJECTIVE

To determine if functional measures of ambulation can be accurately classified using clinical measures; demographics; personal, psychosocial, and environmental factors; and limb accelerations (LAs) obtained during sleep among individuals with chronic, motor incomplete spinal cord injury (SCI) in an effort to guide future, longitudinal predictions models.

DESIGN

Cross-sectional, 1-5 days of data collection.

SETTING

Community-based data collection.

PARTICIPANTS

Adults with chronic (>1 year), motor incomplete SCI (N=27).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Ambulatory ability based on the 10-m walk test (10MWT) or 6-minute walk test (6MWT) categorized as nonambulatory, household ambulator (0.01-0.44 m/s, 1-204 m), or community ambulator (>0.44 m/s, >204 m). A random forest model classified ambulatory ability using input features including clinical measures of strength, sensation, and spasticity; demographics; personal, psychosocial, and environmental factors including pain, environmental factors, health, social support, self-efficacy, resilience, and sleep quality; and LAs measured during sleep. Machine learning methods were used explicitly to avoid overfitting and minimize the possibility of biased results.

RESULTS

The combination of LA, clinical, and demographic features resulted in the highest classification accuracies for both functional ambulation outcomes (10MWT=70.4%, 6MWT=81.5%). Adding LAs, personal, psychosocial, and environmental factors, or both increased the accuracy of classification compared with the clinical/demographic features alone. Clinical measures of strength and sensation (especially knee flexion strength), LA measures of movement smoothness, and presence of pain and comorbidities were among the most important features selected for the models.

CONCLUSIONS

The addition of LA and personal, psychosocial, and environmental features increased functional ambulation classification accuracy in a population with incomplete SCI for whom improved prognosis for mobility outcomes is needed. These findings provide support for future longitudinal studies that use LA; personal, psychosocial, and environmental factors; and advanced analyses to improve clinical prediction rules for functional mobility outcomes.

Pharmacological treatment of central neuropathic pain: consensus of the Brazilian Academy of Neurology

ABSTRACT Background: Central neuropathic pain (CNP) is often refractory to available therapeutic strategies and there are few evidence-based treatment options. Many patients with neuropathic pain are not diagnosed or treated properly. Thus, consensus-based recommendations, adapted to the available drugs in the country, are necessary to guide clinical decisions. Objective: To develop recommendations for the treatment of CNP in Brazil. Methods: Systematic review, meta-analysis, and specialists opinions considering efficacy, adverse events profile, cost, and drug availability in public health. Results: Forty-four studies on CNP treatment were found, 20 were included in the qualitative analysis, and 15 in the quantitative analysis. Medications were classified as first-, second-, and third-line treatment based on systematic review, meta-analysis, and expert opinion. As first-line treatment, gabapentin, duloxetine, and tricyclic antidepressants were included. As second-line, venlafaxine, pregabalin for CND secondary to spinal cord injury, lamotrigine for CNP after stroke, and, in association with first-line drugs, weak opioids, in particular tramadol. For refractory patients, strong opioids (methadone and oxycodone), cannabidiol/delta-9-tetrahydrocannabinol, were classified as third-line of treatment, in combination with first or second-line drugs and, for central nervous system (CNS) in multiple sclerosis, dronabinol. Conclusions: Studies that address the treatment of CNS are scarce and heterogeneous, and a significant part of the recommendations is based on experts opinions. The CNP approach must be individualized, taking into account the availability of medication, the profile of adverse effects, including addiction risk, and patients' comorbidities.

Prolonged Analgesia by Spinal Cord Stimulation Following a Spinal Injury Associated With Activation of Adult Neural Progenitors

OBJECTIVES

Responses of spinal progenitors to spinal cord stimulation (SCS) following spinal cord injury (SCI) in rats were assessed to reveal their potential contribution to SCS-induced analgesia.

METHODS

Spinal epidural electrodes were implanted in rats at T12 rostral to a quadrant dorsal horn injury at T13. Further groups additionally received either a microlesion to the dorsolateral funiculus (DLF) or gabapentin (10 mg/kg). SCS was performed at 25 Hz for 10 minutes on day 4 (early SCS) and at 10 Hz for 10 minutes on day 8 (late SCS) after injury. Paw withdrawal threshold (PWT) was measured before injury, 30 minutes before or after SCS, and before cull on day 14, followed by immunostaining assessment.

RESULTS

Paw withdrawal thresholds in uninjured animals (51.0 ± 4.0 g) were markedly reduced after SCI (17.3 ± 2.2 g). This was significantly increased by early SCS (38.5 ± 5.2 g, P < 0.01) and further enhanced by late SCS (50.9 ± 1.9 g, P < 0.01) over 6 days. Numbers of neural progenitors expressing nestin, Sox2, and doublecortin (DCX) in the spinal dorsal horn were increased 6 days after SCS by 6-fold, 2-fold, and 2.5-fold, respectively (P < 0.05 to 0.01). The elevated PWT evoked by SCS was abolished by DLF microlesions (48.9 ± 2.6 g vs. 19.0 ± 3.9 g, P < 0.01) and the number of nestin-positive cells was reduced to the level without SCS (P < 0.05). Gabapentin enhanced late SCS-induced analgesia from 37.0 ± 3.9 g to 54.0 ± 0.8 g (P < 0.01) and increased gamma-aminobutyric acid (GABA)-ergic neuronal marker vesicular GABA transporter-positive newborn cells 2-fold (P < 0.01).

CONCLUSIONS

Spinal progenitor cells appear to be activated by SCS via descending pathways, which may be enhanced by gabapentin and potentially contributes to relief of SCI-induced neuropathic pain.

Pregabalin and gabapentin in neuropathic pain management after spinal cord injury: a systematic review and meta-analysis

Neuropathic pain after spinal cord injury (SCI) has a significant negative impact on the patients’ quality of life. The objective of this systematic review is to examine the safety and efficacy of pregabalin (PGB) and gabapentin (GBP) in the treatment of neuropathic pain due to SCI. PubMed, the Cochrane Library, Embase, Scopus, and the Web of Science were searched up to December 2018. The reference lists of key and review studies were reviewed for additional citations. The quality of the studies was evaluated using the Cochrane Collaboration’s tools for assessing the risk of bias. A meta-analysis was performed for primary and secondary outcomes. Eight studies were eligible for inclusion. Meta-analysis of PGB vs. placebo showed that PGB was effective for neuropathic pain (standardized mean difference [SMD] = −0.40; 95% confidence interval [CI]: −0.78, −0.01), anxiety (MD = −0.68; 95% CI: −0.77, −0.59), depression (mean difference [MD] = −0.99; 95% CI: −1.08, −0.89), and sleep interference (MD = −1.08; 95% CI: −1.13, −1.02). Also, GBP was more effective than a placebo for reducing pain. No significant difference was observed between the efficacy of the two drugs (MD = −0.37; 95% CI: −1.67, 0.93). There was no significant difference between the two drugs for discontinuation due to adverse events (risk ratio = 3.00; 95% CI: 0.81, 11.15). PGB and GBP were effective vs. placebos in decreasing neuropathic pain after SCI. Also, there was no significant difference between the two drugs for decreasing pain and adverse events.

Chiari malformation and syringomyelia

Chiari malformation was first described over a century ago, and consists of posterior fossa anomalies that generally share the feature of cerebellar tonsillar descent through the foramen magnum. Our understanding of this disorder was initially based on autopsy studies, and has been greatly enhanced by the advent of MRI. The surgical management of Chiari anomalies has also evolved in a parallel fashion. Although the exact surgical technique varies among individual surgeons, the goals of surgery remain constant and consist of relieving brainstem compression and cranial nerve distortion, restoring the normal flow of CSF across the foramen magnum, and reducing the size of any associated syrinx cavity. Syrinx cavities are most commonly associated with Chiari anomalies, yet primary spinal syringomyelia (PSS) can be caused by traumatic, infectious, degenerative, and other etiologies that cause at least a partial CSF flow obstruction in the spinal subarachnoid space. As with syringomyelia associated with Chiari anomalies, the main goal of PSS surgery is to reestablish CSF flow across the area of obstruction. In addition to MRI, myelography with CT can be very helpful in the evaluation and management of these patients by identifying focal regions of CSF obstruction that may be amenable to surgical intervention. Future directions for the treatment of Chiari anomalies and syringomyelia include the application of advanced imaging techniques, more widespread use of genetic evaluation, large-scale outcome studies, and the further refinement of surgical technique.

Repeated Sigma-1 Receptor Antagonist MR309 Administration Modulates Central Neuropathic Pain Development After Spinal Cord Injury in Mice

Up to two-thirds of patients affected by spinal cord injury (SCI) develop central neuropathic pain (CNP), which has a high impact on their quality of life. Most of the patients are largely refractory to current treatments, and new pharmacological strategies are needed. Recently, it has been shown that the acute administration of the σ1R antagonist MR309 (previously developed as E-52862) at 28 days after spinal cord contusion results in a dose-dependent suppression of both mechanical allodynia and thermal hyperalgesia in wild-type CD-1 Swiss female mice. The present work was addressed to determine whether MR309 might exert preventive effects on CNP development by repeated administration during the first week after SCI in mice. To this end, the MR309 (16 or 32 mg/kg i.p.) modulation on both thermal hyperalgesia and mechanical allodynia development were evaluated weekly up to 28 days post-injury. In addition, changes in pro-inflammatory cytokine (TNF-α, IL-1β) expression and both the expression and activation (phosphorylation) of the N-methyl-D-aspartate receptor subunit 2B (NR2B-NMDA) and extracellular signal-regulated kinases (ERK1/2) were analyzed. The repeated treatment of SCI-mice with MR309 resulted in significant pain behavior attenuation beyond the end of the administration period, accompanied by reduced expression of central sensitization-related mechanistic correlates, including extracellular mediators (TNF-α and IL-1β), membrane receptors/channels (NR2B-NMDA) and intracellular signaling cascades (ERK/pERK). These findings suggest that repeated MR309 treatment after SCI may be a suitable pharmacologic strategy to modulate SCI-induced CNP development.

CRMP2 and voltage-gated ion channels: potential roles in neuropathic pain

Neuropathic pain represents a significant and mounting burden on patients and society at large. Management of neuropathic pain, however, is both intricate and challenging, exacerbated by the limited quantity and quality of clinically available treatments. On this stage, dysfunctional voltage-gated ion channels, especially the presynaptic N-type voltage-gated calcium channel (VGCC) (Cav2.2) and the tetrodotoxin-sensitive voltage-gated sodium channel (VGSC) (Nav1.7), underlie the pathophysiology of neuropathic pain and serve as high profile therapeutic targets. Indirect regulation of these channels holds promise for the treatment of neuropathic pain. In this review, we focus on collapsin response mediator protein 2 (CRMP2), a protein with emergent roles in voltage-gated ion channel trafficking and discuss the therapeutic potential of targetting this protein.

Adverse cognitive effect of gabapentin in individuals with spinal cord injury: preliminary findings

Study design

Prospective observational cohort study.

Objectives

To assess the effects of gabapentin on neuropsychological variables including memory, attention, and executive function in individuals with spinal cord injury.

Setting

Santa Clara Valley Medical Center inpatient spinal cord injury unit.

Methods

Ten patients (three females, seven males) with traumatic spinal cord injury underwent testing, with a mean age of 35.6 years (range 19-59, SD ±15.74). There were five patients with tetraplegia and five with paraplegia. Nine tests to assess neuropsychological function and two tests to assess pain were performed at 1 week post initiation of therapy, and at 4 weeks post initiation of therapy. The neuropsychological tests assessed aspects of memory, attention, and executive function.

Results

The average score for six out of the nine neuropsychological items administered at 1 week post initiation of gabapentin displayed a decrease in cognitive function when compared to baseline. The average score for five out of nine neuropsychological items improved from 1 week post initiation of treatment to 4 weeks post initiation of treatment.

Conclusions

Gabapentin therapy is associated with a tangible decline in memory, executive function, and attention in individuals with spinal cord injury. However, owing to small sample size, loss of patient follow-up at the 4 week post-treatment assessment, and lack of a control group, we cannot definitively state that any decreases in cognition are solely attributable to treatment with gabapentin.

Central Mechanisms Mediating Thrombospondin-4-induced Pain States

Peripheral nerve injury induces increased expression of thrombospondin-4 (TSP4) in spinal cord and dorsal root ganglia that contributes to neuropathic pain states through unknown mechanisms. Here, we test the hypothesis that TSP4 activates its receptor, the voltage-gated calcium channel Cavα2δ1 subunit (Cavα2δ1), on sensory afferent terminals in dorsal spinal cord to promote excitatory synaptogenesis and central sensitization that contribute to neuropathic pain states. We show that there is a direct molecular interaction between TSP4 and Cavα2δ1 in the spinal cord in vivo and that TSP4/Cavα2δ1-dependent processes lead to increased behavioral sensitivities to stimuli. In dorsal spinal cord, TSP4/Cavα2δ1-dependent processes lead to increased frequency of miniature and amplitude of evoked excitatory post-synaptic currents in second-order neurons as well as increased VGlut2- and PSD95-positive puncta, indicative of increased excitatory synapses. Blockade of TSP4/Cavα2δ1-dependent processes with Cavα2δ1 ligand gabapentin or genetic Cavα2δ1 knockdown blocks TSP4 induced nociception and its pathological correlates. Conversely, TSP4 antibodies or genetic ablation blocks nociception and changes in synaptic transmission in mice overexpressing Cavα2δ1 Importantly, TSP4/Cavα2δ1-dependent processes also lead to similar behavioral and pathological changes in a neuropathic pain model of peripheral nerve injury. Thus, a TSP4/Cavα2δ1-dependent pathway activated by TSP4 or peripheral nerve injury promotes exaggerated presynaptic excitatory input and evoked sensory neuron hyperexcitability and excitatory synaptogenesis, which together lead to central sensitization and pain state development.

Management of Neuropathic Pain Associated with Spinal Cord Injury

Spinal cord injury (SCI) is an injury to the spinal cord that leads to varying degrees of motor and/or sensory deficits and paralysis. Chronic pain of both neuropathic and nociceptive type is common and contributes to reduced quality of life. The aim of the review is to provide current clinical understanding as well as discuss and evaluate efficacy of pharmacological interventions demonstrated in the clinical studies. The review was based on literature search in PubMed and Medline with words "neuropathic pain" and "spinal cord injury". The review included clinical studies and not experimental data nor case reports. A limited number of randomized and placebo-controlled studies concerning treatment options of neuropathic pain after SCI were identified. Amitriptyline, a tricyclic antidepressant and the antiepileptic drugs, gabapentin and pregabalin, are most studied with demonstrated efficacy, and considered to be the primary choice. Opioids have demonstrated conflicting results in the clinical studies. In addition, administration route used in the studies as well as reported side effects restrict everyday use of opioids as well as ketamine and lidocaine. Topical applications of capsaicin or lidocaine as well as intradermal injections of Botulinum toxin are new treatment modalities that are so far not studied on SCI population and need further studies. Non-pharmacological approaches may have additional effect on neuropathic pain. Management of pain should always be preceded by thorough clinical assessment of the type of pain. Patients need a follow-up to evaluate individual effect of applied measures. However, the applied management does not necessarily achieve satisfactory pain reduction. Further clinical studies are needed to evaluate the effect of both established and novel management options.

Adjunctive, pain-modifying, analgesic drugs

Outside the realm of nonsteroidal antiinflammatory drug(NSAID) and opioid exist a broad range of medications that exert an analgesic effect, or otherwise modify and protect against pain, by manipulating various targets along the nociceptive pathway. Strength of evidence for dogs and cats can vary widely, and this article will review the available literature that may guide clinical usage in these species.

Gabapentinoids are effective in decreasing neuropathic pain and other secondary outcomes after spinal cord injury: a meta-analysis

OBJECTIVE

To examine the effectiveness of gabapentin and pregabalin in diminishing neuropathic pain and other secondary conditions in individuals with spinal cord injury (SCI).

DATA SOURCES

A systematic search was conducted using multiple databases for relevant articles published from 1980 to June 2013.

STUDY SELECTION

Controlled and uncontrolled trials involving gabapentin and pregabalin for treatment of neuropathic pain, with ≥3 subjects and ≥50% of study population with SCI, were included.

DATA EXTRACTION

Two independent reviewers selected studies based on inclusion criteria and then extracted data. Pooled analysis using Cohen's d to calculate standardized mean difference (SMD), SE, and 95% confidence interval (CI) for primary (pain) and secondary outcomes (anxiety, depression, sleep interference) was conducted.

DATA SYNTHESIS

Eight studies met inclusion criteria. There was a significant reduction in the intensity of neuropathic pain at <3 months (SMD=.96±.11; 95% CI, .74-1.19; P<.001) and between 3 and 6 months (SMD=2.80±.18; 95% CI, 2.44-3.16; P<.001). A subanalysis found a significant decrease in pain with gabapentin (SMD=1.20±.16; 95% CI, .88-1.52; P<.001) and with pregabalin (SMD=1.71±.13; 95% CI, 1.458-1.965; P<.001). A significant reduction in other SCI secondary conditions, including sleep interference (SMD=1.46±.12; 95% CI, 1.22-1.71; P<.001), anxiety (SMD=1.05±.12; 95% CI, .81-1.29; P<.001), and depression (SMD=1.22±.13; 95% CI, .967-1.481; P<.001) symptoms, was shown. A significantly higher risk of dizziness (risk ratio [RR]=2.02, P=.02), edema (RR=6.140, P=.04), and somnolence (RR=1.75, P=.01) was observed.

CONCLUSIONS

Gabapentin and pregabalin appear useful for treating pain and other secondary conditions after SCI. Effectiveness comparative to other analgesics has not been studied. Patients need to be monitored closely for side effects.

Challenging the catechism of therapeutics for chronic neuropathic pain: Targeting CaV2.2 interactions with CRMP2 peptides

Chronic neuropathic pain management is a worldwide concern. Pharmaceutical companies globally have historically targeted ion channels as the therapeutic catechism with many blockbuster successes. Remarkably, no new pain therapeutic has been approved by European or American regulatory agencies over the last decade. This article will provide an overview of an alternative approach to ion channel drug discovery: targeting regulators of ion channels, specifically focusing on voltage-gated calcium channels. We will highlight the discovery of an anti-nociceptive peptide derived from a novel calcium channel interacting partner - the collapsin response mediator protein 2 (CRMP2). In vivo administration of this peptide reduces pain behavior in a number of models of neuropathic pain without affecting sympathetic-associated cardiovascular activity, memory retrieval, sensorimotor function, or depression. A CRMP2-derived peptide analgesic, with restricted access to the CNS, represents a completely novel approach to the treatment of severe pain with an improved safety profile. As peptides now represent one of the fastest growing classes of new drugs, it is expected that peptide targeting of protein interactions within the calcium channel complex may be a paradigm shift in ion channel drug discovery.

Long-term effect of pulsed radiofrequency on chronic cervical radicular pain refractory to repeated transforaminal epidural steroid injections

OBJECTIVE

The article aims to evaluate the long-term effectiveness and safety of pulsed radiofrequency (PRF) on the dorsal root ganglion (DRG) in patients with chronic cervical radicular pain refractory to repeated transforaminal epidural steroid injections (TFESIs).

DESIGN

This is a prospective observational study.

METHODS

We retrospectively reviewed data on 112 subjects who had received repeated TFESIs for cervical radicular pain. Twenty-nine of those 112 patients continued to complain of persistent cervical radicular pain, despite an average of three repeated TFESIs. Among 29 patients with sustained arm pain of over 4 on the numerical rating scale (NRS), a total of 21 patients were included prospectively. Those 21 patients underwent PRF on the symptomatic cervical DRG and were evaluated carefully for neurologic deficits and side effects. The clinical outcomes were measured via NRS for arm pain before treatment, and 1, 3, 6, and 12 months after treatment. Successful pain relief was defined as a 50% or more reduction in the NRS score as compared with the pretreatment score. After 12 months, patients' satisfaction levels with treatment were determined.

RESULTS

Fourteen of the 21 patients (66.7%) after cervical PRF stimulation reported pain relief of 50% or more at the 3-month and 12-month follow-up periods, respectively. Fifteen of the 21 patients (71.4%) were satisfied with their outcome at 12 months' posttreatment. No serious adverse effects were observed.

CONCLUSION

Application of PRF to the DRG appears to be an effective and relatively safe intervention technique for chronic cervical radicular pain refractory to repeated TFESIs.

Role of NKCC1 and KCC2 in the development of chronic neuropathic pain following spinal cord injury

Neuropathic pain is a common problem following spinal cord injury (SCI). Effective analgesic therapy has been hampered by the lack of knowledge about the mechanisms underlying post-SCI neuropathic pain. Current evidence suggests GABAergic spinal nociceptive processing is a critical functional node in this complex phenotype, representing a potential target for therapeutic intervention. Normal GABA neurotransmission is dependent on precise regulation of the level of intracellular chloride, which is determined by the coordinated activities of two cation/chloride cotransporters (CCCs) in the SLC12 family: the inwardly directed Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) and outwardly directed K(+)-Cl(-) cotransporter isoform 2 (KCC2). Inhibition of NKCC1 with its potent antagonist bumetanide reduces pain behavior in rats following SCI. Moreover, the injured spinal cord tissues exhibit a significant transient upregulation of NKCC1 protein and a concurrent downregulation of KCC2 protein. Thus, imbalanced function of NKCC1 and KCC2 may contribute to the induction and maintenance of the chronic neuropathic pain following SCI.

A systematic review of pharmacologic treatments of pain after spinal cord injury

OBJECTIVE

To conduct a systematic review of published research on the pharmacologic treatment of pain after spinal cord injury (SCI).

DATA SOURCES

MEDLINE, CINAHL, EMBASE, and PsycINFO databases were searched for articles published 1980 to June 2009 addressing the treatment of pain post SCI. Randomized controlled trials (RCTs) were assessed for methodologic quality using the Physiotherapy Evidence Database (PEDro) assessment scale, whereas non-RCTs were assessed by using the Downs and Black (D&B) evaluation tool. A level of evidence was assigned to each intervention by using a modified Sackett scale.

STUDY SELECTION

The review included RCTs and non-RCTs, which included prospective controlled trials, cohort, case series, case-control, pre-post studies, and post studies. Case studies were included only when there were no other studies found.

DATA EXTRACTION

Data extracted included the PEDro or D&B score, the type of study, a brief summary of intervention outcomes, the type of pain, the type of pain scale, and the study findings.

DATA SYNTHESIS

Articles selected for this particular review evaluated different interventions in the pharmacologic management of pain after SCI. Twenty-eight studies met inclusion criteria; there were 21 randomized controlled trials; of these, 19 had level 1 evidence. Treatments were divided into 5 categories: anticonvulsants, antidepressants, analgesics, cannabinoids, and antispasticity medications.

CONCLUSIONS

Most studies did not specify participants' types of pain, making it difficult to identify the type of pain being targeted by the treatment. Anticonvulsant and analgesic drugs had the highest levels of evidence and were the drugs most often studied. Gabapentin and pregabalin had strong evidence (5 level 1 RCTs) for effectiveness in treating post-SCI neuropathic pain as did intravenous analgesics (lidocaine, ketamine, and morphine), but the latter only had short-term benefits. Tricyclic antidepressants only showed benefit for neuropathic pain in depressed persons. Intrathecal baclofen reduced musculoskeletal pain associated with spasticity; however, there was conflicting evidence for the reduction in neuropathic pain. Studies assessing the effectiveness of opioids were limited and revealed only small benefits. Cannabinoids showed conflicting evidence in improving spasticity-related pain. Clonidine and morphine when given together had a significant synergistic neuropathic pain-relieving effect.

Does pain mediate the pain interference with sleep problem in chronic pain? Findings from studies for management of diabetic peripheral neuropathic pain with duloxetine

Although sleep problems are common in patients with chronic pain, it is unclear whether pain mediates (causes) impaired sleep. The relationship between pain and sleep has been difficult to investigate because of the potential confounds of depression and somnolence. This report used clinical trials data for duloxetine in the management of diabetic peripheral neuropathic pain (DPNP) to investigate the direction of this association. Data were pooled from three double-blind, randomized, placebo-controlled, 12-week trials of patients with DPNP without mood disorder (n=1,139). DPNP patients reporting somnolence and those who were receiving sedating concomitant medications were removed from the analyses (n=93). Efficacy measures included weekly mean scores for average daily pain severity, night pain severity, and pain interference with sleep. Duloxetine at 60 and 120 mg per day separated from placebo for average pain and night pain improvement as early as one week after treatment began, whereas sleep interference improvement separated from placebo at the three visits it was assessed (Weeks 4, 8, and 12). Change in sleep interference was moderately to strongly correlated (P<0.001) with changes in average pain (r=0.46) and nighttime pain severity (r=0.53). These results confirm the association between the improvement in daily pain and nighttime pain, and improvement in sleep interference for a large population without depression or somnolence. Although this association cannot establish causality, these results provide some evidence for the possibility that pain may mediate the sleep problem associated with DPNP and perhaps chronic pain in general.

Symptom burden in persons with spinal cord injury

OBJECTIVE

To determine (1) the frequency, severity, and reported course of 7 symptoms in persons with spinal cord injury (SCI) and (2) the association between these symptoms and patient functioning.

DESIGN

Postal survey.

SETTING

Community.

INTERVENTION

A survey that included measures of the frequency, severity, and recalled course of pain, fatigue, numbness, weakness, shortness of breath, vision loss, and memory loss, as well as a measure of community integration and psychologic functioning was mailed to a sample of persons with SCI. One hundred forty-seven usable surveys were returned (response rate, 43% of surveys mailed).

MAIN OUTCOME MEASURES

The frequency and average severity of each symptom was computed, and the frequencies of each type of reported course were noted. Analyses estimated the associations among the symptoms, and between symptom severity and measures of patient functioning.

RESULTS

The most common symptoms were pain, weakness, fatigue, and numbness. All symptoms were reported to remain the same or to get worse more often than they were reported to improve once they began. Pain, weakness, fatigue, and memory loss were the symptoms most closely associated with patient functioning.

CONCLUSIONS

Patients with SCI must deal with a number of secondary complications in addition to any disability caused by the injury itself. Of 7 symptoms studied, pain, weakness, and fatigue appeared to be most common and most closely linked to patient social and mental health functioning. Research is needed to identify the causal relationships between perceived symptoms and quality of life in patients with SCI and to identify effective treatments for those symptoms shown to impact patient functioning.

The treatment of neuropathic pain

Neuropathic pain is responsible for a significant amount of the morbidity associated with generalized and focal peripheral neuropathies. It is a consequence of alterations in neuronal function, chemistry, and structure that occur secondary to nerve injury. These manifestations of neuronal plasticity occur in the peripheral nerve, spinal cord, and brain. A variety of agents from diverse pharmacologic classes, the so-called adjuvant analgesics, have been used to treat neuropathic pain. These include antidepressants, first- and second-generation anticonvulsants, antiarrhythmic agents, topical agents, N-methyl-D-aspartate receptor antagonists, and opioid analgesics. The use of these adjuvant analgesics, either alone or in combination, should result in the alleviation of neuropathic pain in most patients. Recent advances in the understanding of pain mechanisms at multiple central nervous system levels should pave the way toward more effective treatment modalities.

Practical considerations in the assessment and treatment of pain in adults with physical disabilities

Adults aging with physical disabilities experience a variety of pain disorders that affect their functionality and QOL. It is important that clinicians caring for this population be knowledgeable about this common symptom and be able to perform a thorough history and physical examination. In addition, it is imperative to have a good working knowledge of the strengths and limitations of the treatments available.

Sleep disorders: an overview

Although sleep disorders medicine is a relatively young discipline, understanding of the diagnosis, pathophysiology, and treatment of sleep disorders is evolving at a rapid pace. This overview discusses the history of the development of sleep disorders medicine, tracing changes in the diagnostic classification of sleep disorders as well as the role of polysomnography in diagnosis. This evolution is most evident for insomnia, one of the major sleep disturbances. The accumulation of epidemiologic data on the prevalence and temporal course of insomnia and emerging information regarding its pathophysiology derived from laboratory assessments have led to the development of new therapeutic approaches for primary insomnia and insomnia associated with medical and psychiatric disorders.

A treatment algorithm for neuropathic pain

BACKGROUND

Neuropathic pain is a chronic pain syndrome caused by drug-, disease-, or injury-induced damage or destruction of sensory neurons within the dorsal root ganglia of the peripheral nervous system. Characteristic clinical symptoms include the feeling of pins and needles; burning, shooting, and/or stabbing pain with or without throbbing; and numbness. Neuronal hyperexcitability represents the hallmark cellular mechanism involved in the underlying pathophysiology of neuropathic pain. Although the primary goal is to alleviate pain, clinicians recognize that even the most appropriate treatment strategy may be, at best, only able to reduce pain to a more tolerable level.

OBJECTIVE

The purpose of this review is to propose a treatment algorithm for neuropathic pain that health care professionals can logically follow and adapt to the specific needs of each patient. The algorithm is intended to serve as a general guide to assist clinicians in optimizing available therapeutic options.

METHODS

A comprehensive review of the literature using the PubMed, MEDLINE, Cochrane, and Toxnet databases was conducted to design and develop a novel treatment algorithm for neuropathic pain that encompasses agents from several drug classes, including antidepressants, antiepileptic drugs, topical antineuralgic agents, narcotics, and analgesics, as well as various treatment options for refractory cases.

RESULTS

Any of the agents in the first-line drug classes (tricyclic antidepressants, antiepileptic drugs, topical antineuralgics, analgesics) may be used as a starting point in the treatment of neuropathic pain. If a patient does not respond to treatment with at least 3 different agents within a drug class, agents from a second drug class may be tried. When all first-line options have been exhausted, narcotic analgesics or refractory treatment options may provide some benefit. Patients who do not respond to monotherapy with any of the first- or second-line agents may respond to combination therapy or may be candidates for referral to a pain clinic. Because the techniques used at pain clinics tend to be invasive, referrals to these clinics should be reserved for patients who are truly refractory to all forms of pharmacotherapy.

CONCLUSIONS

Neuropathic pain continues to be one of the most difficult pain conditions to treat. With the proposed algorithm, clinicians will have a framework from which to design a pain treatment protocol appropriate for each patient. The algorithm will also help streamline referrals to specialized pain clinics, thereby reducing waiting list times for patients who are truly refractory to traditional pharmacotherapy.

Pharmacologic Management Part 2: Lesser-Studied Neuropathic Pain Diseases

This second part of a review of the pharmacologic management of neuropathic pain diseases describes the current treatment options for three lesser-studied neuropathic syndromes: Central poststroke pain, spinal cord injury, and complex regional pain syndrome II. Diagnosis can be difficult in patients with these syndromes, because the pain experienced is much greater and of a different type than would normally be expected following a stroke or injury to the spinal cord or a peripheral nerve. Even when an accurate and timely diagnosis is made, treatment options are limited and frequently suboptimal. However, the results of published trials do support the use of anticonvulsants and/or tricyclic antidepressants as first-line pharmacotherapy in these three neuropathic pain syndromes. To maximize treatment outcomes, future research must: Continue to more fully elucidate the relationship between the signs and symptoms of pain and the underlying pathophysiology; Delineate the natural history of central poststroke pain, spinal cord injury, and complex regional pain syndrome; Identify patient-related factors that may indicate an increased risk of developing neuropathic pain following stroke or nerve injury; Investigate emerging treatments that target underlying pain mechanisms.