Chronic pain after spinal injury: interference with sleep and daily activities

Neuropathic Pain and Spinal Cord Injury: Phenotypes and Pharmacological Management

Chronic neuropathic pain is a complicated condition after a spinal cord injury (SCI) that often has a lifelong and significant negative impact on life after the injury; therefore, improved pain management is considered a significant and unmet need. Neuropathic pain mechanisms are heterogeneous and the difficulty in determining their individual contribution to specific pain types may contribute to poor treatment outcomes in this population. Thus, identifying human neuropathic pain phenotypes based on pain symptoms, somatosensory changes, or cognitive and psychosocial factors that reflect specific spinal cord or brain mechanisms of neuropathic pain is an important goal. Once a pain phenotype can be reliably replicated, its relationship with biomarkers and clinical treatment outcomes can be analyzed, and thereby facilitate translational research and further the mechanistic understanding of individual differences in the pain experience and in clinical trial outcomes. The present article will discuss clinical aspects of SCI-related neuropathic pain, neuropathic pain phenotypes, pain mechanisms, potential biomarkers and pharmacological interventions, and progress regarding how defining neuropathic pain phenotypes may lead to more targeted treatments for these difficult pain conditions.

Outcomes and reflections on a consensus-building workshop for developing a spinal cord injury-related chronic pain research agenda

Context/ Objective: Chronic pain following spinal cord injury (SCI) is a prevalent secondary health condition that significantly impacts quality of life (QoL). Although growing, the number of available effective pain management approaches for SCI is limited. Recognizing the need to "kick-start" activity on this topic, a consensus-building workshop on developing a research agenda for SCI-related chronic pain was held in 2006 with an expert panel. The present paper describes the processes of the consensus-workshop and its associated outcomes towards advancing the research agenda for SCI-related pain in Canada. A commentary on the current state of knowledge regarding SCI-related pain is also provided.

METHODS

Thirty-nine stakeholders (researchers, clinicians, policy-makers, SCI advocates, and people with SCI) attended the consensus-workshop. A modified Delphi approach was employed to gain consensus on identifying the top five SCI pain research priorities for improving QoL post-SCI. As well, project planning along with infrastructure support opportunities were discussed.

RESULTS

The top five pain research priorities were: 1) pain management and treatment; 2) measurement tools; 3) health services policy and advocacy; 4) knowledge transfer; and 5) mechanisms of pain. Recommendations related to the priorities and related resources were generated, and pilot work was initiated.

CONCLUSIONS

The consensus workshop provided an initial roadmap for research on SCI-related chronic pain, and supported five pilot projects on the identified priorities. Reflections on the current research landscape in Canada and abroad suggest increased activity towards addressing pain post-SCI but evidence-based approaches are still lacking.

Multiple mediation path model of pain's cascading influence on physical disability in individuals with SCI from Colombia, South America

BACKGROUND

Research has begun to document the bivariate connections between pain in individuals with spinal cord injury (SCI) and various aspects of health related quality of life (HRQOL), such as fatigue, social functioning, mental health, and physical functioning.

OBJECTIVE

The purpose of this study was to construct and test a theoretical path model illuminating the stage-wise and sequential (cascading) HRQOL pathways through which pain increases physical disability in individuals with SCI in a sample from Colombia, South America. It was hypothesized that increased pain would lead to decreased energy, which would lead to decreased mental health and social functioning, which both would lead to emotional role limitations, which finally would lead to physical role limitations.

METHODS

A cross-sectional study assessed individuals with SCI (n = 40) in Neiva, Colombia. Participants completed a measure indexing various aspects of HRQOL.

RESULTS

The path model overall showed excellent fit indices, and each individual path within the model was statistically significant. Pain exerted significant indirect effects through all possible mediators in the model, ultimately suggesting that energy, mental health, social functioning, and role limitations-emotional were likely pathways through which pain exerted its effects on physical disability in individuals with SCI.

CONCLUSIONS

These findings uncover several potential nodes for clinical intervention which if targeted in the context of rehabilitation or outpatient services, could result in salubrious direct and indirect effects reverberating down the theoretical causal chain and ultimately reducing physical disability in individuals with SCI.

Recombinant neural progenitor transplants in the spinal dorsal horn alleviate chronic central neuropathic pain

Neuropathic pain induced by spinal cord injury (SCI) is clinically challenging with inadequate long-term treatment options. Partial pain relief offered by pharmacologic treatment is often counterbalanced by adverse effects after prolonged use in chronic pain patients. Cell-based therapy for neuropathic pain using GABAergic neuronal progenitor cells (NPCs) has the potential to overcome untoward effects of systemic pharmacotherapy while enhancing analgesic potency due to local activation of GABAergic signaling in the spinal cord. However, multifactorial anomalies underlying chronic pain will likely require simultaneous targeting of multiple mechanisms. Here, we explore the analgesic potential of genetically modified rat embryonic GABAergic NPCs releasing a peptidergic NMDA receptor antagonist, Serine-histogranin (SHG), thus targeting both spinal hyperexcitability and reduced inhibitory processes. Recombinant NPCs were designed using either lentiviral or adeno-associated viral vectors (AAV2/8) encoding single and multimeric (6 copies of SHG) cDNA. Intraspinal injection of recombinant cells elicited enhanced analgesic effects compared with nonrecombinant NPCs in SCI-induced pain in rats. Moreover, potent and sustained antinociception was achieved, even after a 5-week postinjury delay, using recombinant multimeric NPCs. Intrathecal injection of SHG antibody attenuated analgesic effects of the recombinant grafts suggesting active participation of SHG in these antinociceptive effects. Immunoblots and immunocytochemical assays indicated ongoing recombinant peptide production and secretion in the grafted host spinal cords. These results support the potential for engineered NPCs grafted into the spinal dorsal horn to alleviate chronic neuropathic pain.

Inflammatory Stress Effects on Health and Function After Spinal Cord Injury

Background: Injury to the spinal cord produces immediate, adaptive inflammatory responses that can exacerbate the initial injury and lead to secondary damage. Thus far, researchers and clinicians have focused on modulating acute inflammation to preserve sensorimotor function. However, this singular approach risks overlooking how chronic inflammation negatively impacts the broader health of persons with a spinal cord injury (SCI). Objective: The aim of this monograph was to discuss interrelated processes causing persistent inflammatory stress after SCI, along with associated health risks. We review archetypal factors that contribute to a chronic inflammatory state, including response to injury, acute infection, and autonomic dysreflexia. Secondary complications producing and exacerbating inflammation are also discussed, including pain, depression, obesity, and injury to the integumentary and skeletal systems. Finally, we discuss the role of bacteria and the gut microbiome in this process and then conclude with a discussion on how a pro-inflammatory phenotype promotes an elevated risk for cardiovascular disease after injury. Conclusions: Effectively managing chronic inflammation should be a high priority for clinicians and researchers who seek to improve the health and life quality of persons with SCI. Chronic inflammation worsens secondary medical complications and amplifies the risk for cardiometabolic disorders after injury, directly impacting both the quality of life and mortality risk after SCI. Inflammation can worsen pain and depression and even hinder neurological recovery. It is, therefore, imperative that countermeasures to chronic inflammation are routinely considered from the point of initial injury and proceeding throughout the lifespan of the individual with SCI.

Living With Chronic Pain After Spinal Cord Injury: A Mixed-Methods Study

OBJECTIVE

To identify the relative importance of positive (facilitators) and negative (barriers) contributors to living with chronic pain after spinal cord injury (SCI).

DESIGN

Mixed-methods: (1) Qualitative (n=35): individual, semistructured, open-ended interviews identifying facilitator/barrier themes; (2) Quantitative (n=491): converting the most common themes into statements and quantifying agreement with these in an online survey to determine relative importance, underlying dimensions, and their associations with perceived difficulty in dealing with pain.

SETTING

University-based research setting and general community.

PARTICIPANTS

Volunteers (N=526) with SCI experiencing moderate to severe chronic pain.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Interview guides, facilitator/barrier statements, and pain inventories.

RESULTS

Exploratory factor analyses reduced agreement ratings into 4 facilitators (information regarding pain and treatments, resilience, coping, medication use) and 5 barriers (poor health care communication, pain impact and limitations, poor communication about pain, difficult nature of pain, treatment concerns). Greater "pain impact and limitations," "difficult nature of pain," "poor communication from provider," lower "resilience," greater "medication use," and younger age predicted greater difficulty in dealing with pain (r=.75; F=69.02; P<.001).

CONCLUSIONS

This study revealed multiple facilitators and barriers to living with chronic pain after SCI. The principal barrier, "poor health care communication," indicated that consumers do not receive adequate information from their health care providers regarding pain. "Information regarding pain and treatments" had greater agreement scores and factor loadings than all other facilitators, indicating that most participants view provider-patient communication and educational efforts regarding pain and pain management as priorities and critical needs. Further initiatives in these areas are important for improving pain management post-SCI.

Changes in pain and quality of life in depressed individuals with spinal cord injury: does type of pain matter?

OBJECTIVE

To examine the association of neuropathic and nociceptive pain severity and interference with quality of life (QoL) in persons with spinal cord injury (SCI) who underwent a randomized controlled 12-week trial of an antidepressant to treat depression. A secondary objective was to assess the effect of changes in pain on mobility and physical independence.

DESIGN

Multivariable ANCOVA models controlling for relevant demographic covariates, treatment condition, and baseline pain and QoL were used.

SETTING

Six rehabilitation centers.

PARTICIPANTS

Of the 133 persons who were randomized into the trial, 108 provided pain severity and interference ratings through follow-up.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

The Satisfaction with Life Scale and the physical and mental component summary scores of the 12-Item Short-Form Health Survey (SF-12). Secondary outcome measures included the mobility and physical independence subscales of the Craig Handicap Assessment and Reporting Technique (CHART).

RESULTS

Broadly, few associations between pain and QoL were evident. Results revealed relationships between lower baseline nociceptive pain interference and higher satisfaction with life and mental health-related QoL at 12 weeks. Similarly, lower neuropathic pain interference was associated with change in physical independence, but unrelated to mobility.

CONCLUSIONS

Pain interference over time may be differentially related to QoL outcomes based on the type of pain following SCI, but overall, there were no extensive relationships between pain and QoL in this sample of depressed persons with SCI.

Targeting inflammation as a treatment modality for neuropathic pain in spinal cord injury: a randomized clinical trial

Background

The purpose of the present study was to examine the effectiveness of an anti-inflammatory intervention as a treatment for neuropathic pain following spinal cord injury (SCI).

Methods

This randomized, parallel-group, controlled clinical trial (NCT02099890) examined 20 participants with varying levels and severities of SCI, randomized (3:2) to either a 12-week anti-inflammatory diet, or control group. Outcome measures consisted of self-determined indices of pain as assessed using the neuropathic pain questionnaire (NPQ) and markers of inflammation as assessed by various pro- and anti-inflammatory cytokines, as well as the eicosanoids PGE2 and LTB4.

Results

A significant group × time interaction was found for sensory pain scores (p < 0.01). A Mann-Whitney test revealed that the change scores (3-month baseline) were significantly different between groups for IFN-y (U = 13.0, p = 0.01), IL-1β (U = 14.0, p = 0.01), and IL-2 (U = 12.0, p = 0.01). A Friedman test revealed the treatment group had a significant reduction in IFN-y (x² = 8.67, p = 0.01), IL-1β (x² = 17.78, p < 0.01), IL-6 (x² = 6.17, p < 0.05), while the control group showed no significant change in any inflammatory mediator. A stepwise backward elimination multiple regression analysis showed that the change in sensory neuropathic pain was a function of the change in the proinflammatory cytokines IL-2 and IFN-y, as well as the eicosanoid PGE2 (R = 0.689, R² = 0.474).

Conclusions

Overall, the results of the study demonstrate the efficacy of targeting inflammation as a means of treating neuropathic pain in SCI, with a potential mechanism relating to the reduction in proinflammatory cytokines and PGE2.

Trial registration

ClinicalTrials.gov, NCT02099890

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0625-4) contains supplementary material, which is available to authorized users.

Training-Induced Functional Gains following SCI

We previously demonstrated that daily, hour-long training sessions significantly improved both locomotor (limb kinematics, gait, and hindlimb flexor-extensor bursting patterns) and nonlocomotor (bladder function and at-level mechanical allodynia) functions following a moderate contusive spinal cord injury. The amount of training needed to achieve this recovery is unknown. Furthermore, whether this recovery is induced primarily by neuronal activity below the lesion or other aspects related to general exercise is unclear. Therefore, the current study objectives were to (1) test the efficacy of 30 minutes of step training for recovery following a clinically relevant contusion injury in male Wistar rats and (2) test the efficacy of training without hindlimb engagement. The results indicate that as little as 30 minutes of step training six days per week enhances overground locomotion in male rats with contusive spinal cord injury but does not alter allodynia or bladder function. Thirty minutes of forelimb-only exercise did not alter locomotion, allodynia, or bladder function, and neither training protocol altered the amount of in-cage activity. Taken together, locomotor improvements were facilitated by hindlimb step training for 30 minutes, but longer durations of training are required to affect nonlocomotor systems.

Pain relief and functional improvement in patients with neuropathic pain associated with spinal cord injury: an exploratory analysis of pregabalin clinical trials

Background

Characterizing relationships between pain relief and function can inform patient management decisions. This analysis explored graphically the relationship between pain relief and functional improvement in patients with neuropathic pain associated with spinal cord injury in two clinical trials of pregabalin.

Methods

This was a post hoc analysis of two randomized, double-blind, clinical trials in patients who were treated with pregabalin (n=181) or placebo (n=172) for neuropathic pain associated with spinal cord injury. The bivariate relationship between percent pain relief and absolute change in the functional outcomes with placebo and pregabalin was evaluated graphically using scatter plots, and loess curves illustrated the extent of the relationship between pain and function. Linear trend analysis evaluated the statistical significance of these relationships using Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT)-based thresholds of pain reduction (<15%, 15% <30%, 30% to <50%, and ≥50%). Outcome measures included modified Brief Pain Inventory pain interference with function in one of the studies and the Medical Outcomes Study Sleep Scale (an 11-point Numeric Rating Scale) and the Hospital Anxiety and Depression Scale (HADS) for the pooled studies.

Results

Data ellipses showed a shift with pregabalin relative to placebo toward greater improvement with increasing pain relief for all outcome measures except HADS. Loess curves suggested a relationship between increased pain relief and improved function except for HADS, with the clearest relationship observed for sleep. Linear trend analysis showed significant relationships between pain and Medical Outcomes Study Sleep Scale (P<0.0001) and between pain and function on the modified Brief Pain Inventory Interference Index and most individual items (P<0.05).

Conclusion

Greater functional improvements were generally achieved at higher levels of clinically significant pain reduction. Pregabalin resulted in shifts from placebo toward greater functional improvement with greater pain relief.

The impact of pain on health-related quality of life 3 months after stroke

BACKGROUND

Pain is common in stroke; however, its impacts on health-related quality of life (HRQoL) are unclear due to the limitations of previous studies.

OBJECTIVES

The current study aims to examine and compare the demographic and clinical characteristics of Chinese stroke patients with and without pain and explore the correlations between poststroke pain and HRQoL.

METHOD

Four hundreds and forty-one participants recruited in an acute stroke unit in a regional hospital. They were assessed 3 months after the index stroke with the following instruments. HRQoL was measured using the Short Form-12 (SF-12). The Chinese version of the Faces Pain Rating Scale-Revised (FPS-R) was used to determine the presence and intensity of pain. The demographic and clinical characteristics of patients were obtained using Barthel Index (BI), Fatigue Severity Scale (FSS), Geriatric Depression Scale (GDS), Anxiety subscale of the Hospital Anxiety and Depression Scale (HADSA), Instrumental Activities of Daily Living (IADL), Mini Mental State Examination (MMSE), Modified Rankin Scale (MRS), and National Institutes of Health Stroke Scale (NIHSS).

RESULTS

Of all participants screened, 167 reported pain and 69 had novel pain. The pain group had significantly lower physical component summary (PCS) scores after adjusting for sex, education, DSM-IV depression and BI, GDS, HADSA, and FSS scores. The FPS score was negatively correlated with a lower PCS score in patients with pain and with novel pain.

CONCLUSION

The presence and intensity of pain have significant negative effects on HRQoL in stroke survivors. Interventions for pain could make a valuable contribution to improving HRQoL in stroke survivors.

Evaluation of pain and its effect on quality of life and functioning in men with spinal cord injury

Background

Pain is one of the most important consequences of spinal cord injury (SCI). It may affect several aspects of life, especially the quality of life (QoL). Hence, this study was conducted to establish an understanding of pain and its correlates and effects on patients with SCI in our community.

Methods

In a cross-sectional study, 58 male veterans suffering from SCI were admitted to our center for a regular follow-up. Demographic and SCI-related descriptive information were gathered using a self-reported questionnaire. To evaluate the patients' pain quality and the effect of pain on daily life, a questionnaire in 3 parts of lumbar, cervical and shoulder pain was administered. EuroQoL questionnaire and General Health Questionnaire (GHQ) 12 were also used to assess the patients' QoL.

Results

The mean age of the participants was 45.91 ± 6.69 with mean injury time of 25.54 ± 5.91. forty-four patients (75.9%) reported pain, including lumbar pain (63%), cervical pain (39%) and shoulder pain (51%). The presence of pain was associated with lower QoL. Patients with lumbar pain reported a significant amount of pain affecting their daily life and this effect was higher in patients with lower GHQ score or anxiety/depressive disorder.

Conclusions

Musculoskeletal pain, is a common complaint in veterans with SCI and is inversely associated with functioning and general health status. Lumbar and shoulder pain affects patient's daily living more than cervical pain.

Development and validation of the English Pain Interference Index and Pain Interference Index-Parent report

OBJECTIVE

Measurement of pain interference in children is challenged by a lack of validated measures with a parent proxy report. This study investigated the psychometric properties of the Pain Interference Index (PII), a six-item questionnaire originally developed in Swedish, in chronically ill youth.

METHODS

We adapted the PII for English-speaking participants and created a parallel parent proxy measure. Respondents indicate how much pain has interfered with the child's life in the past 2 weeks (0-6 scale); higher scores indicate more pain interference. Eligible participants included individuals 6-25 years with neurofibromatosis type 1 (NF1) and cancer. Internal consistency was assessed; validity was examined by correlating PII scores with existing measures of pain interference (Modified Brief Pain Inventory [MBPI]) and pain intensity (visual analogue scale [VAS]), and with measures of disease severity.

RESULTS

Among 60 participants (mean age 14.7 years, range 6-24) and their parents, PII internal consistency was 0.84 and 0.96, respectively. PII scores correlated with MBPI (r = 0.81, P < 0.0001) and VAS (r = 0.55, P < 0.0001) scores and differentiated between patients with mild vs moderate/severe NF1 disease severity (P < 0.05). The PII-Parent was significantly correlated with the mothers' and fathers' VAS rating of the child's pain intensity (Ps < 0.01).

CONCLUSIONS

Internal consistency of the English PII is high; validity is supported by the PII's correlations with other measures of pain interference and pain intensity, and with disease severity in patients with NF1. Preliminary data indicate that the English PII is a reliable, valid, feasible pain interference measure for youth with NF1 and cancer.

Oral administration of the p38α MAPK inhibitor, UR13870, inhibits affective pain behavior after spinal cord injury

The p38α mitogenous activated protein kinase (MAPK) cell signaling pathway is a key mechanism of microglia activation and has been studied as a target for neuropathic pain. The effect of UR13870, a p38α MAPK inhibitor, on microglia expression in the anterior cingulate cortex (ACC) and spinal dorsal horn was addressed after T9 contusion spinal cord injury (SCI) in the rat, in addition to behavioral testing of pain-related aversion and anxiety. Administration of intravenous UR13870 (1mg/kg i.v.) and pregabalin (30 mg/kg i.v.) reduced place escape avoidance paradigm (PEAP) but did not affect open-field anxiety behavior 42 days after SCI. PEAP behavior was also reduced in animals administered daily with oral UR13870 (10mg/kg p.o.) and preserved spinal tissue 28 days after SCI. Although UR13870 (10mg/kg p.o.) failed to reduce OX-42 and glial fibrillar acid protein immunoreactivity within the spinal dorsal horn, a reduction toward the control level was observed close to the SCI site. In the anterior cingulate cortex (ACC), a significant increase in OX-42 immunoreactivity was identified after SCI. UR13870 (10mg/kg p.o.) treatment significantly reduced OX-42, metabotropic glutamate type 5 receptor (mGluR5), and NMDA (N-methyl-d-aspartate) 2B subunit receptor (NR2B) expression in the ACC after SCI. To conclude, oral treatment with a p38α MAPK inhibitor reduces the affective behavioral component of pain after SCI in association with a reduction of microglia and specific glutamate receptors within the ACC. Nevertheless the role of neuroinflammatory processes within the vicinity of the SCI site in the development of affective neuropathic pain cannot be excluded.

Reactive oxygen species and lipid peroxidation inhibitors reduce mechanical sensitivity in a chronic neuropathic pain model of spinal cord injury in rats

Chronic neuropathic pain is a common consequence of spinal cord injury (SCI), develops over time and negatively impacts quality of life, often leading to substance abuse and suicide. Recent evidence has demonstrated that reactive oxygen species (ROS) play a role in contributing to neuropathic pain in SCI animal models. This investigation examines four compounds that reduce ROS and the downstream lipid peroxidation products, apocynin, 4-oxo-tempo, U-83836E, and tirilazad, and tests if these compounds can reduce nocioceptive behaviors in chronic SCI animals. Apocynin and 4-oxo-tempo significantly reduced abnormal mechanical hypersensitivity measured in forelimbs and hindlimbs in a model of chronic SCI-induced neuropathic pain. Thus, compounds that inhibit ROS or lipid peroxidation products can be used to ameliorate chronic neuropathic pain. We propose that the application of compounds that inhibit reactive oxygen species (ROS) and related downstream molecules will also reduce the behavioral measures of chronic neuropathic pain. Injury or trauma to nervous tissue leads to increased concentrations of ROS in the surviving tissue. Further damage from ROS molecules to dorsal lamina neurons leads to membrane excitability, the physiological correlate of chronic pain. Chronic pain is difficult to treat with current analgesics and this research will provide a novel therapy for this disease.

An open-label, long-term study examining the safety and tolerability of pregabalin in Japanese patients with central neuropathic pain

Purpose

Studies of pregabalin for the treatment of central neuropathic pain have been limited to double-blind trials of 4–17 weeks in duration. The purpose of this study was to assess the long-term safety and tolerability of pregabalin in Japanese patients with central neuropathic pain. The efficacy of pregabalin was also assessed as a secondary measure.

Patients and methods

This was a 53-week, multicenter, open-label trial of pregabalin (150–600 mg/day) in Japanese patients with central neuropathic pain due to spinal cord injury, multiple sclerosis, or cerebral stroke.

Results

A total of 103 patients received pregabalin (post-stroke =60; spinal cord injury =38; and multiple sclerosis =5). A majority of patients (87.4%) experienced one or more treatment-related adverse events, most commonly somnolence, weight gain, dizziness, or peripheral edema. The adverse event profile was similar to that seen in other indications of pregabalin. Most treatment-related adverse events were mild (89.1%) or moderate (9.2%) in intensity. Pregabalin treatment improved total score, sensory pain, affective pain, visual analog scale (VAS), and present pain intensity scores on the Short-Form McGill Pain Questionnaire (SF-MPQ) and ten-item modified Brief Pain Inventory (mBPI-10) total score at endpoint compared with baseline. Improvements in SF-MPQ VAS and mBPI-10 total scores were evident in all patient subpopulations. Mean changes from baseline in SF-MPQ VAS and mBPI-10 scores at endpoint were −20.1 and −1.4, respectively.

Conclusion

These findings demonstrate that pregabalin is generally well tolerated and provides sustained efficacy over a 53-week treatment period in patients with chronic central neuropathic pain.

Thermal hyperalgesia assessment for rats after spinal cord injury: developing a valid and useful pain index

BACKGROUND CONTEXT

Ongoing research to understand the mechanism behind pain is heavily dependent on animal testing. However, unlike humans, animal subjects cannot directly communicate with researchers to express the degree of pain they are experiencing. Therefore, measuring the presence of pain in animal studies is based on behavioral tests. The use of arbitrary values for determining the presence of pain in animal studies is an oversimplification of a complex and cortically dependent process.

PURPOSE

The purpose of the present study was to identify a statistically supported latency time indicator that can be used as an accurate index for hyperalgesia to thermal stimuli in Sprague-Dawley rats subjected to T9 contusive spinal cord injury (SCI).

STUDY DESIGN

A statistical analysis of latency of withdrawal from stimulus-mediated spinal reflex in 979 Sprague-Dawley rats that had been subjected to a T9 contusive SCI was performed.

METHODS

This is a retrospective review of a large research database derived from a series of studies performed evaluating thermal hyperalgesia in rats after SCI. Sprague-Dawley rats underwent a T9 contusive SCI and were tested for withdrawal latency from a heat stimulus. Assessment was done preinjury and on Postinjury Days 21, 28, 35, and 42 of the chronic phase of injury via a plantar withdrawal test.

RESULTS

The baseline test results of the 979 rats showed a significant resemblance to the normal distribution. The observed change in withdrawal showed mean latency drops of 0.42 second (standard error of the mean [SEM], 0.18; p=.026), 0.57 second (SEM, 0.19; p=.004), 0.63 second (SEM, 0.19; p=.002), and 0.69 second (SEM, 0.19; p=.0003). The standard deviation from the mean at all four postsurgical assessments was between 2.8 and 2.9 seconds.

CONCLUSIONS

Interpretation of withdrawal latency times as a marker for thermal hyperalgesia must be based on an appreciation for the normal distribution of pain scores. Recognizing that withdrawal latency is normally distributed both before and after injury allows for rational assignment of animals to groups designated as hyperalgesic and nonhyperalgesic. Two point nine seconds faster than the mean latency time is a statistically reliable indicator of thermal hyperalgesia in Sprague-Dawley rats subjected to contusive SCI. Repeated testing of animals to establish the presence or absence of thermal hyperalgesia beyond 21 days is not necessary in the absence of intervention.

Moving towards multiple site outcomes in spinal cord injury pain clinical trials: An issue of clustered observations in trial design and analysis

INTRODUCTION

Pain remains a problem for many with spinal cord injury (SCI), and there is a need for sound, randomized clinical trials examining the efficacy of existing and novel therapeutics. SCI-related pain is complex, as more than one type of pain is often experienced. The purpose of this report is to (i) demonstrate how to design and power calculation of a clinical trial of SCI pain using multiple pain sites per individual; (ii) discuss consequences of failing to adjust for this; and (iii) provide intraclass correlation (ICC) estimates for common pain outcome measures that may be used to power future clinical trials in SCI pain.

METHOD

Using an existing dataset from a past SCI pain clinical trial, the ICC was calculated for common pain outcome measures to illustrate appropriate corrections for powering, analyzing and interpreting results from multiple pain sites per individual. The problem associated with not accounting for multiple pain sites per individual and the effect on the Type I error rate is also shown.

RESULTS AND DISCUSSION

Not accounting for the ICC can lead to (1) incorrect power estimates in the design of a trial, and (2) an inflated Type I error rate with a higher likelihood of misinterpretation of outcomes.

CONCLUSIONS

Powering for future SCI pain trials and statistical analysis of trial outcomes may be substantially compromised if methods do not account for the intra-individual associations between pain sites, ultimately affecting study interpretations and evidence-based practice. We present ICC estimates based on SCI pain data for purposes of estimating power for future trials.

Effects of chronic pain on function, depression, and sleep among patients with traumatic spinal cord injury

BACKGROUND AND OBJECTIVES

The main objectives of this cross-sectional study were (1) to examine chronic pain using the Multidimensional Pain Inventory-Spinal Cord Injury (MPI-SCI) version and (2) to assess the relationship between chronic pain and functional status, depression, and sleep quality among patients with SCI.

DESIGN AND SETTINGS

This was a cross-sectional study of all eligible patients admitted to the Ministry of Health Ankara Diskapi Yildirim Beyazit Education and Research Hospital Physical Therapy and Rehabilitation Clinic between January 2007 and July 2010.

METHODS

Forty-four patients (33 male, 11 female) with traumatic SCI, aged >=18 years, who had pain continuing for >=6 months and were hospitalized in the physical therapy and rehabilitation clinic were included in this cross-sectional study. Chronic pain intensity, functional status, depression, and sleep quality were assessed according to the MPI-SCI, Functional Independence Measure (FIM), Hamilton Rating Scale for Depression (HAM-D), and Pittsburg Sleep Quality Index (PSQI), respectively.

RESULTS

A positive correlation was observed between "Pain Severity" (one of the subscales of the MPI-SCI) and HAM-D (r=0.487, P=.001) and PSQI (r=0.312, P=.039). "Pain Severity" was significantly higher in the "impaired sleep" group (P < .05) than in the "normal sleep" group and in the "depression" group (P < .05) than in the "no depression" group.

CONCLUSION

We identified a strong interrelationship between SCI-related "Pain Severity" and both depression and sleep quality. Hence, a comprehensive pain examination and management strategies including psychosocial interventions should be given particular consideration to address the critical issue of chronic pain in individuals with SCI.

Validation of the Short Form of the Brief Pain Inventory (BPI-SF) in Spanish Patients with Non-Cancer-Related Pain

The Brief Pain Inventory (BPI) is a widely used pain measurement tool. There are 2 versions, the BPI Long Form (BPI-LF) and Short Form (BPI-SF), which share 2 core scales measuring pain severity and pain interference but which use different recall periods (24 hours vs. 1 week). To date, the BPI-SF has not been validated for use in Spain. This study investigated the psychometric properties of the BPI-SF Spanish version and compared results on the core scales between BPI-LF and BPI-SF. The data came from a 3-month observational study of 3,029 nononcologic patients managed in Spanish pain units. The BPI-SF's reliability, validity, and responsiveness were assessed. The effect of different recall periods was investigated by using intraclass correlation coefficients (ICCs) to determine the strength of correlation between BPI-LF and BPI-SF. The BPI-SF showed good reliability, with Cronbach's alphas of 0.931 for the severity and interference scales, which also discriminated well between patients reporting different levels of quality of life on EuroQol-5D dimensions (between group effect sizes [ESs] over 0.8). Substantial improvements were seen on both subscales after 3 months of treatment (ES of 1.76 for pain severity and 1.51 for pain interference). Recall period did not noticeably affect scores; ICCs (95% CI) between the long and short versions were 0.946 (0.938 to 0.954) and 0.929 (0.919 to 0.939) for the severity and interference subscales, respectively. The Spanish version of the BPI-SF is a valid and reliable instrument to measure pain severity and interference.

Cervical dystonia and pain: characteristics and treatment patterns from CD PROBE (Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy)

To compare profiles of subjects with and without cervical dystonia (CD)-associated pain, to evaluate the contribution of pain and the motor component of CD on quality of life, and to compare the initial botulinum toxin treatment paradigm between pain groups, baseline data were used from the CD Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE), a multicenter, prospective, observational registry designed to capture real-world practices and outcomes for onabotulinumtoxinA CD treatment. Subjects were divided into no/mild pain [Pain Numeric Rating Scale (PNRS) score 0–3] and moderate/severe pain groups (PNRS score 4–10). Descriptive and differential statistics were utilized to compare groups. 1,037 subjects completed the first treatment session, reported baseline botulinum toxin status, and completed baseline PNRS. Those with no/mild pain were significantly older at baseline. Those subjects with moderate/severe pain had higher Toronto Western Spasmodic Torticollis Rating Scale Severity (17.7 ± 5.1 vs. 16.2 ± 5.6, p < 0.0001) and Disability (12.7 ± 6.1 vs. 7.5 ± 5.6, p < 0.0001). CD subjects with moderate/severe pain received a higher mean dose (177.3 ± 82.9 vs. 158.0 ± 67.1 U, p = 0.0001) of onabotulinumtoxinA and were injected in more muscles (4.1 ± 1.4 vs. 3.7 ± 1.2, p < 0.0001) at initial treatment. CD PROBE clearly demonstrates the frequency of pain in CD and substantiates its importance when determining an optimal treatment paradigm. Future analyses of CD PROBE will further our understanding of the treatment patterns and outcomes related to onabotulinumtoxinA therapy for this disabling condition.

Depression, pain intensity, and interference in acute spinal cord injury

BACKGROUND

The high prevalence of pain and depression in persons with spinal cord injury (SCI) is well known. However the link between pain intensity, interference, and depression, particularly in the acute period of injury, has not received sufficient attention in the literature.

OBJECTIVE

To investigate the relationship of depression, pain intensity, and pain interference in individuals undergoing acute inpatient rehabilitation for traumatic SCI.

METHODS

Participants completed a survey that included measures of depression (PHQ-9), pain intensity ("right now"), and pain interference (Brief Pain Inventory: general activity, mood, mobility, relations with others, sleep, and enjoyment of life). Demographic and injury characteristics and information about current use of antidepressants and pre-injury binge drinking also were collected. Hierarchical multiple regression was used to test depression models in 3 steps: (1) age, gender, days since injury, injury level, antidepressant use, and pre-injury binge drinking (controlling variables); (2) pain intensity; and (3) pain interference (each tested separately).

RESULTS

With one exception, pain interference was the only statistically significant independent variable in each of the final models. Although pain intensity accounted for only 0.2% to 1.2% of the depression variance, pain interference accounted for 13% to 26% of the variance in depression.

CONCLUSION

Our results suggest that pain intensity alone is insufficient for understanding the relationship of pain and depression in acute SCI. Instead, the ways in which pain interferes with daily life appear to have a much greater bearing on depression than pain intensity alone in the acute setting.

Anticonvulsant medication use for the management of pain following spinal cord injury: systematic review and effectiveness analysis

STUDY DESIGN

Systematic review and effectiveness analysis.

OBJECTIVES

Assess the effectiveness of anticonvulsants for the management of post spinal cord injury (SCI) neuropathic pain.

SETTING

Studies from multiple countries were included.

METHODS

CINAHL, Cochrane, EMBASE and MEDLINE were searched up to April 2013. Quality assessment was conducted using the Jadad and the Downs and Black tools. Effect sizes and odds ratios were calculated for primary and secondary outcome in the included studies.

RESULTS

Gabapentinoids, valproate, lamotrigine, levetiracetam and carbamazepine were examined in the 13 included studies, ten of which are randomized controlled trials. Large effect size (0.873-3.362) for improvement of pain relief was found in 4 of the 6 studies examining the effectiveness of gabapentin. Pregabalin was shown to have a moderate to large effect (0.695-3.805) on improving neuropathic pain post SCI in 3 studies. Valproate and levetiracetam were not effective in improving neuropathic pain post SCI, while lamotrigine was effective in reducing neuropathic pain amongst persons with incomplete lesions and carbamazepine was found effective for relief of moderate to intense pain.

CONCLUSION

Gabapentin and pregabalin are the two anticonvulsants which have been shown to have some benefit in reducing neuropathic pain.

Efficacy and safety of pregabalin in patients with spinal cord injury: a pooled analysis

OBJECTIVE

To summarize the efficacy and examine the safety and tolerability of pregabalin in patients with central neuropathic pain due to spinal cord injury (SCI).

RESEARCH DESIGN AND METHODS

Data were pooled from two 12 to 16 week, placebo-controlled trials of pregabalin in patients with neuropathic pain due to SCI. Pain diaries were used to rate pain from 0 = no pain to 10 = worst possible pain. Efficacy measures included: mean change in pain from baseline to endpoint; duration adjusted average change (DAAC) in pain; the percentage of patients with ≥30% or ≥50% reductions in pain score from baseline to endpoint; and Patient Global Impression of Change (PGIC) score at endpoint. Adverse events (AEs) were also compared between treatment groups.

RESULTS

In total 174 patients received placebo and 182 received pregabalin. Mean change in pain from baseline to endpoint was improved in the pregabalin group compared with placebo (placebo-adjusted difference = -0.79; 95% CI = -1.15, -0.43; p < 0.001; baseline-observation-carried-forward). DAAC in pain was improved in patients receiving pregabalin compared with placebo (p < 0.001). The percentage of patients achieving ≥30% and ≥50% reductions in pain from baseline to endpoint was greater in the pregabalin arm compared with placebo (placebo: 30% = 22.5%, 50% = 11.6: pregabalin 30% = 35.6%, 50% = 22.4%) (all p < 0.01). PGIC scores at endpoint were significantly better in the pregabalin arm compared with placebo (p < 0.05). Treatment-related AEs, most commonly somnolence, dizziness, dry mouth, fatigue, edema, blurred vision, and constipation occurred more frequently in patients treated with pregabalin than placebo. The majority of AEs were mild to moderate in severity.

CONCLUSIONS

Pregabalin reduced neuropathic pain due to SCI over a 12 to 16 week treatment period. Treatment-related AEs were mostly mild to moderate in severity and are consistent with the known safety profile of pregabalin. These findings should not be extrapolated to longer durations of treatment or other patient populations.

The association of age, pain, and fatigue with physical functioning and depressive symptoms in persons with spinal cord injury

CONTEXT/OBJECTIVE

To describe the relationship of pain and fatigue with physical and psychological functioning in adults with spinal cord injury (SCI).

DESIGN

Cross-sectional survey.

SETTING

Community-based survey.

PARTICIPANTS

Convenience sample of individuals with SCI.

INTERVENTION

Not applicable.

OUTCOME MEASURES

Physical functioning (Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Functioning item bank items), depression (Patient Health Questionnaire-9 (PHQ-9)), pain severity (0-10 Numerical Rating Scale (NRS)), and fatigue (0-10 NRS).

RESULTS

Pain and fatigue were independently associated with depression, but only pain was associated with physical functioning. Additionally, depression was more severe among middle-aged participants relative to younger or older participants. Physical functioning declined with increasing age, as well as with higher level of injury.

CONCLUSIONS

The findings support the need for continued development of effective treatments for both pain and fatigue in order to prevent and mitigate the negative effects these symptoms can have on functioning.

Effects of nicotine on spinal cord injury pain: a randomized, double-blind, placebo controlled crossover trial

BACKGROUND

One factor affecting spinal cord injury (SCI)-related pain may be nicotine. Case reports have described a worsening of neuropathic pain from smoking and relief from abstinence. Neurobiological correlates also implicate the potential effect of nicotine on SCI-related pain.

METHOD

The current study employed a randomized, placebo-controlled crossover design to examine the effect of nicotine exposure on subtypes of SCI-related pain among smokers and nonsmokers.

RESULTS

Whereas nonsmokers with SCI showed a reduction in mixed forms of pain following nicotine exposure, smokers with SCI showed a converse increase in pain with regard to both mixed and neuropathic forms of pain. The exacerbation of pain in chronic nicotine or tobacco users may not only elucidate possible pain mechanisms but may also be of use in smoking cessation counseling among those with SCI.

Patients' perspectives on pain

Nociceptive and neuropathic pain (NP) are common consequences following spinal cord injury (SCI), with large impact on sleep, mood, work, and quality of life. NP affects 40% to 50% of individuals with SCI and is sometimes considered the major problem following SCI. Current treatment recommendations for SCI-NP primarily focus on pharmacological strategies suggesting the use of anticonvulsant and antidepressant drugs, followed by tramadol and opioid medications. Unfortunately, these are only partly successful in relieving pain. Qualitative studies report that individuals with SCI-related long-lasting pain seek alternatives to medication due to the limited efficacy, unwanted side effects, and perceived risk of dependency. They spend time and money searching for additional treatments. Many have learned coping strategies on their own, including various forms of warmth, relaxation, massage, stretching, distraction, and physical activity. Studies indicate that many individuals with SCI are dissatisfied with their pain management and with the information given to them about their pain, and they want to know more about causes and strategies to manage pain. They express a desire to improve communication with their physicians and learn about reliable alternative sources for obtaining information about their pain and pain management. The discrepancy between treatment algorithms and patient expectations is significant. Clinicians will benefit from hearing the patient´s voice.

Is Pain Intensity Really That Important to Assess in Chronic Pain Patients? A Study Based on the Swedish Quality Registry for Pain Rehabilitation (SQRP)

BACKGROUND

Incorporating the patient's view on care and treatment has become increasingly important for health care. Patients describe the variety of consequences of their chronic pain conditions as significant pain intensity, depression, and anxiety. We hypothesised that intensities of common symptoms in chronic pain conditions carry important information that can be used to identify clinically relevant subgroups. This study has three aims: 1) to determine the importance of different symptoms with respect to participation and ill-health; 2) to identify subgroups based on data concerning important symptoms; and 3) to determine the secondary consequences for the identified subgroups with respect to participation and health factors.

METHODS AND SUBJECTS

This study is based on a cohort of patients referred to a multidisciplinary pain centre at a university hospital (n = 4645, participation rate 88%) in Sweden. The patients answered a number of questionnaires concerning symptoms, participation, and health aspects as a part of the Swedish Quality Registry for Pain Rehabilitation (SQRP).

RESULTS

Common symptoms (such as pain intensity, depression, and anxiety) in patients with chronic pain showed great variability across subjects and 60% of the cohort had normal values with respect to depressive and anxiety symptoms. Pain intensity more than psychological symptoms showed stronger relationships with participation and health. It was possible to identify subgroups based on pain intensity, depression, and anxiety. With respect to participation and health, high depressive symptomatology had greater negative consequences than high anxiety.

CONCLUSIONS

Common symptoms (such as pain intensity and depressive and anxiety symptoms) in chronic pain conditions carry important information that can be used to identify clinically relevant subgroups.

Neuropathic pain post spinal cord injury part 2: systematic review of dorsal root entry zone procedure

BACKGROUND

Pharmacotherapy may not sufficiently reduce neuropathic pain in many individuals post spinal cord injury (SCI). The use of alternative therapies such as surgery may be effective in reducing neuropathic pain in these individuals. However, because of the invasive nature of surgery, it is important to examine the evidence for use of this treatment.

OBJECTIVE

The purpose of this study was to conduct a systematic review of published literature on the surgical treatment of neuropathic pain after SCI.

METHODS

MEDLINE, CINAHL, EMBASE, and PsycINFO databases were searched for articles in which surgical treatment of pain after SCI was examined. Articles were restricted to the English language. Article selection was conducted by 2 independent reviewers with the following inclusion criteria: the subjects participated in a surgical intervention for neuropathic pain; at least 50% of the subjects had an SCI; at least 3 subjects had an SCI; and a definable intervention involving the dorsal root entry zone (DREZ) procedure was used to reduce pain. Data extracted included study design, study type, subject demographics, inclusion and exclusion criteria, sample size, outcome measures, and study results. Randomized controlled trials (RCTs) were assessed for quality using the Physiotherapy Evidence Database (PEDro) assessment scale. Levels of evidence were assigned to each intervention using a modified Sackett scale.

RESULTS

Eleven studies met the inclusion criteria. One study provided level 2 evidence, and the rest provided level 4 evidence. The DREZ procedure was shown to be more effective for segmental pain than for diffuse pain after SCI. Further, individuals with conus medullaris level injury were found to have a higher level of neuropathic pain relief than those with cervical, thoracic, or cauda equina injury.

CONCLUSIONS

The studies demonstrated that the DREZ procedure may be effective in reducing segmental pain. Hence, DREZ may be important in treatment of neuropathic pain in individuals resistant to less invasive treatments. Because the studies lacked control conditions and examination of long-term effects, there is a need for larger trials with more stringent conditions.

The association of opioid use with incident lower extremity fractures in spinal cord injury

OBJECTIVE

To determine the association between opioid use and lower extremity fracture risk in men with spinal cord injury (SCI).

DESIGN

Retrospective cohort study.

SETTING

Veterans Affairs Healthcare System.

PARTICIPANTS

In total, 7447 male Veterans with a history of a traumatic SCI identified from the Veterans Affairs (VA) Spinal Cord Dysfunction Registry (SCD) from September 2002 through October 2007 and followed through October 2010.

OUTCOME MEASURES

Incident lower extremity fractures by use of opioids.

RESULTS

In individuals identified from the VA SCD Registry 2002-2007, opioid use was quite common, with approximately 70% of the cohort having received a prescription for an opioid. Overall, there were 892 incident lower extremity fractures over the time period of this study (597 fractures in the opioid users and 295 fractures in the non-opioid users). After adjusting for covariates, there was a statistically significant relationship between opioid use and increased risk for lower extremity fractures (hazard ratio 1.82 (95% confidence interval 1.59-2.09)). Shorter duration of use (<6 months) and higher doses were positively related to fracture risk (P < 0.0001).

CONCLUSIONS

Opioid use is quite common in SCI and is associated with an increased risk for lower extremity fractures. Careful attention to fracture prevention is warranted in patients with SCI, particularly upon initiation of an opioid prescription and when higher doses are used.

A randomized trial of pregabalin in patients with neuropathic pain due to spinal cord injury

OBJECTIVE

To assess the efficacy and tolerability of pregabalin for the treatment of central neuropathic pain after spinal cord injury (SCI).

METHODS

Patients with chronic, below-level, neuropathic pain due to SCI were randomized to receive 150 to 600 mg/d pregabalin (n = 108) or matching placebo (n = 112) for 17 weeks. Pain was classified in relation to the neurologic level of injury, defined as the most caudal spinal cord segment with normal sensory and motor function, as above, at, or below level. The primary outcome measure was duration-adjusted average change in pain. Key secondary outcome measures included the change in mean pain score from baseline to end point, the percentage of patients with ≥30% reduction in mean pain score at end point, patient global impression of change scores at end point, and the change in mean pain-related sleep interference score from baseline to end point. Additional outcome measures included the medical outcomes study-sleep scale and the Hospital anxiety and depression scale.

RESULTS

Pregabalin treatment resulted in statistically significant improvements over placebo for all primary and key secondary outcome measures. Significant pain improvement was evident as early as week 1 and was sustained throughout the treatment period. Adverse events were consistent with the known safety profile of pregabalin and were mostly mild to moderate in severity. Somnolence and dizziness were most frequently reported.

CONCLUSIONS

This study demonstrates that pregabalin is effective and well tolerated in patients with neuropathic pain due to SCI.

CLASSIFICATION OF EVIDENCE

This study provides class I evidence that pregabalin, 150 to 600 mg/d, is effective in reducing duration-adjusted average change in pain compared with baseline in patients with SCI over a 16-week period (p = 0.003, 95% confidence interval = -0.98, -0.20).