The early influence of COVID-19 pandemic-associated restrictions on pain, mood, and everyday life of patients with painful polyneuropathy

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Validated questionnaires revealed a shift of attention from chronic pain towards the COVID-19 pandemic in patients with chronic painful polyneuropathy.

Introduction:

The SARS-Cov-2 pandemic requires special attention on its psychological effects and the impact on patients with chronic pain.

Objectives:

This study aimed at examining the influence of the COVID-19 pandemic-associated regulations initiated by the German government on pain intensity and characteristics, emotional well-being, and everyday life of patients with painful polyneuropathy.

Methods:

Forty-three patients (well assessed with questionnaires before the pandemic and without change of their health status between baseline and current assessment) were investigated with validated, self-reported questionnaires and COVID-19-specific items 2 weeks after the regulations came into effect.

Results:

Pain intensity remained stable or even improved like the neuropathic pain symptom inventory total score (t0: 33.54 ± 20.48 vs t1: 27.38 ± 16.16, P = 0.008). Only 11.6% reported a pandemic-associated pain worsening. Rumination scores of the Pain Catastrophizing Scale were lower during t1 compared to before the pandemic regulations (t0: 7.81 ± 4.70, t1: 6.49 ± 4.39; P = 0.030). Interestingly, pain ratings for the last 7 days were higher in patients with a changed social life compared to those without (−1.63 ± 1.60 vs 0.31 ± 1.83; P = 0.01). Quality of life was decreased and helplessness increased in those with higher pain ratings.

Conclusion:

Results suggest a shift of attention from the chronic pain condition towards the imminent threat of a global pandemic. As the impacts of the pandemic are persistent and evolving, the development of the measured parameters in the forthcoming weeks will be of great interest.

Increased substance P-like immunoreactivities in parabrachial and amygdaloid nuclei in a rat model with masticatory myofascial pain

This study explores the involvement of substance P (SP) in the parabrachial nucleus (PBN) and central amygdaloid nucleus (CeA) in the nociception-emotion link and of rats with masticatory myofascial pain (MMP) induced by chronic tetanic eccentric muscle contraction. A total of 18 rats were randomly and equally assigned for MMP (MMP group) and sham-MMP induction (sMMP group). MMP was induced by electrical-stimulated repetitive tetanic eccentric contraction of the masseter muscle for 14 consecutive days. Myofascial trigger points in the masseter muscle were identified by palpable taut bands, increased prevalence of endplate noise (EPN), focal hypoechoic nodules on ultrasound and restricted jaw opening. All animals were killed for morphological and SP immunohistochemical analyses. Chronic tetanic eccentric contraction induced significantly thicker masseter muscle confirmed by hypoechogenicity, increased prevalence and amplitudes of EPN, and limited jaw opening. Immunohistochemically, the SP-like positive neurons increased significantly in PBN and CeA of the MMP group. Our results suggested that MMP increases the SP protein levels in PBN and CeA, which play important roles in MMP-mediated chronic pain processing as well as MMP-related emotional processes.

Motivations and expectations for using cannabis products to treat pain in humans and dogs: a mixed methods study

BACKGROUND

Social media and academic literature suggest that more people are using cannabis to treat their own or their dog's chronic pain. This study identifies the reasons people use cannabis products to treat their own pain or their dog's pain and explores whether these products have fulfilled their expectations.

METHODS

An anonymous, online survey was used to collect quantitative and qualitative self-report data on respondents' perceptions, motivations and expectations about their or their dog's chronic pain and cannabis use. The analyses are based on U.S. adults who reported using cannabis products to treat their own (N = 313) or their dog's (N = 204) chronic pain. Quantitative responses from the two groups were compared using Chi-Square tests and qualitative data were analyzed using a thematic analysis.

RESULTS

Human patients and dog owners reported similar motivations for using cannabis products to treat chronic pain, with the more popular reasons being that cannabis products are natural, are preferred over conventional medication, are believed to be the best treatment or good treatment option for pain. Similar proportions of human patients and dog owners reported that the use of cannabis products fulfilled their expectations (86% vs. 82% respectively, χ2 (1, 200) = .59, p = .32). The qualitative data revealed that their expectations were met by reducing pain, increasing relaxation, and improving sleep, coping, functionality and overall well being. Additionally, the qualitative data suggests that cannabis products offer a return to normalcy and a restored sense of self to human and dog patients.

CONCLUSIONS

The results suggest that people choose cannabis products because they are natural and a possible solution to managing chronic pain when conventional medicines have not been effective. Most people report that their expectations regarding pain management are fulfilled by these products. More accurate assessments are vital, however, for understanding both the objective biomedical and subjective socioemotional benefits of cannabis products for effective pain management for human and dog patients. In addition, objective factual information regarding cannabis products for effective pain management in humans and dogs is needed. It is recommended that both physicians and veterinarians work towards feeling more comfortable proactively broaching the subject of cannabis use with additional training and education.

Unintended consequences of COVID-19 safety measures on patients with chronic knee pain forced to defer joint replacement surgery

COVID-19 crisis deferred elective arthroplasty leading to potential surgical backlog. Prolonged surgical waiting times may worsen physical and mental health of patients in chronic pain.

In recent months, with the emergence of the COVID-19 pandemic, the American College of Surgeons and the U.S. Centers for Disease Control and Prevention officially recommended the delay of nonemergency procedures until the public health crisis is resolved. Deferring elective joint replacement surgeries for an unknown period is likely to decrease the incidence of infection with SARS-CoV-2 but is likely to have detrimental effects in individuals suffering from chronic knee pain. These detrimental effects extend beyond the discomfort of osteoarthritis (OA) and the inconvenience of rescheduling surgery. Disabling pain is a driving factor for individuals to seek medical intervention, including pharmacological palliative treatment and surgical procedures. The need for surgical intervention due to chronic pain as for knee and hip replacement is now put on hold indefinitely because access to surgical care has been limited. Although a moderate delay in surgical intervention may not produce a significant progression of OA within the knee, it could lead to muscle wasting due to immobility and exacerbate comorbidities, making rehabilitation more challenging. Importantly, it will have an impact on comorbidities driven by OA severity, notably decreased quality of life and depression. These patients with unremitting pain become increasingly susceptible to substance use disorders including opioids, alcohol, as well as prescription and illegal drugs. Appreciation of this downstream crisis created by delayed surgical correction requires aggressive consideration of nonsurgical, nonopiate supported interventions to reduce the morbidity associated with these delays brought upon by the currently restricted access to joint repair.

The Efficacy of Radiofrequency Ablation for Pain Management in Patients with Pre-Existing Hardware at the Site of Ablation

INTRODUCTION

Radiofrequency ablation (RFA) is an interventional procedure that provides pain relief by using thermal energy to disrupt peripheral nerves carrying nociceptive signals back to the central nervous system. In the past, having implantable hardware at the planned site of RFA was considered to confer increased risk of adverse outcomes given the theoretical risk of heating of the hardware components. The present study examines patient outcomes to determine whether the efficacy of RFA was affected by the presence of implanted hardware directly at the site.

METHODS

This was a retrospective case-control study that included 52 patients who received RFA procedures in the presence of hardware at the site of RFA and a control group of 170 patients who received RFA procedures in the absence of hardware. Data were collected from electronic medical records entered into an Excel sheet and then analyzed using SPSS version 22. Outcomes tested included post procedure pain scores, percent, and duration of improvement, if any.

RESULTS

We found no statistically significant difference in measured outcomes between either group.

CONCLUSIONS

This study provides some evidence in support of the theory that RFA procedures performed on patients with pre-existing hardware have similar efficacy when compared to their hardware-free counterparts.

A protocol for chronic pain outcome measurement enhancement by linking PROMIS-29 scale to legacy measures and improving chronic pain stratification

BACKGROUND

Substantial investment has gone into research on the efficacy and effectiveness of pharmaceutical and nonpharmacologic interventions for chronic pain. However, synthesizing this extensive literature is challenging because of differences in the outcome measures used in studies of similar or competing interventions. The absence of a common metric makes it difficult to replicate findings, pool data from multiple studies, resolve conflicting conclusions, or reach consensus when interpreting findings.

METHODS

This study has a seven-member Advisory Council of chronic pain experts. Preliminary analyses will be performed on data from several large existing datasets; intermediate analyses will be performed using primary data collected from Amazon's Mechanical Turk (MTurk); and cross-validation will use primary data collected from a nationally-representative, probability-based panel. Target sample size for both primary datasets is 1500. The three study aims are as follows: Aim 1 will develop and evaluate links between the 29-item Patient-Reported Outcomes Measurement Information System (PROMIS®-29) and legacy measures used for chronic pain such as the Roland-Morris Disability Questionnaire (RMDQ) and the Oswestry Disability Index (ODI). We will assess the best method of score linking and create crosswalk tables. Aim 2 will evaluate and refine the Impact Stratification Score (ISS) based on 9 PROMIS-29 items and proposed by the NIH Research Task Force on chronic low back pain. We will evaluate the ISS in terms of other indicators of condition severity and patient prognosis and outcomes and identify cut-points to stratify chronic pain patients into subgroups. Aim 3 will evaluate the strengths and limitations of MTurk as a data collection platform for estimating chronic pain by comparing its data to other data sources.

DISCUSSION

The accomplishment of Aims 1 and 2 will allow direct comparison of results across past and future studies of chronic pain. These comparisons will help us to understand different results from seemingly similar studies, and to determine the relative effectiveness of all pharmaceutical and nonpharmacologic interventions for chronic pain across different trials. Aim 3 findings will provide valuable information to researchers about the pros and cons of using the MTurk platform for research-based data collection.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04426812 ; June 10, 2020.

A physical activity program versus usual care in the management of quality of life for pre-frail older adults with chronic pain: randomized controlled trial

BACKGROUND

Exercise has shown being effective for managing chronic pain and preventing frailty status in older adults but the effect of an exercise program in the quality of life of pre-frail older adults with chronic pain remains unclear. Our objective was to evaluate the effectiveness of multicomponent structured physical exercise program for pre-frail adults aged 65 years or more with chronic pain to improve their perceived health related quality of life, compared with usual care.

METHODS

Open label randomized controlled trial. Participants were community-dwelling pre-frail older adults aged 65 years or older with chronic pain and non-dependent for basic activities of daily living attending a Primary Healthcare Centre. Forty-four participants were randomly allocated to a control group (n = 20) that received usual care or an intervention group (n = 24) that received an 8-week physical activity and education program. Frailty status (SHARE Frailty Index), quality of life (EuroQol-5D-5L), pain intensity (Visual Analogue Scale), physical performance (Short Physical Performance Battery) and depression (Yessavage) were assessed at baseline, after the intervention and after 3 months follow-up. The effect of the intervention was analysed by mean differences between the intervention and control groups.

RESULTS

The follow-up period (3 months) was completed by 32 patients (73%), 17 in the control group and 15 in the intervention group. Most participants were women (78.1%) with a mean age (standard deviation) of 77.2 (5.9) years and a mean pain intensity of 48.1 (24.4) mm. No relevant differences were found between groups at baseline. After the intervention, mean differences in the EuroQol Index Value between control and intervention groups were significant (- 0.19 95% CI(- 0.33- -0.04)) and remained after 3 months follow-up (- 0.21 95% CI(- 0.37- -0.05)). Participants in the exercise group showed better results in pain intensity and frailty after the intervention, and an improvement in physical performance after the intervention and after 3 months.

CONCLUSIONS

An eight-week physical activity and education program for pre-frail older adults with chronic pain, compared with usual care, could be effective to improve quality of life after the intervention and after three-months follow-up.

STUDY REGISTRATION DETAILS

This study was retrospectively registered in ClinicalTrials.gov with the identifier NCT04045535 .

The Physiology and Maintenance of Respiration: A Narrative Review

Chronic pain is one of the most common reasons adults seek medical care and is often managed with opioid analgesics; however, opioids may cause respiratory depression by suppressing various components of respiration. Respiration is the physiological process that facilitates gas exchange and is mediated through the proper function of and communication among central neural control (respiratory drive), sensory input systems, the lungs, and the muscles involved in respiration. Normal respiratory function can be dampened with the use of central nervous system (CNS) depressants and/or underlying health conditions. Patients with chronic pain are often exposed to CNS depressants other than opioids, including benzodiazepines, barbiturates, nonbenzodiazepine sedative-hypnotics, and ethanol, which can function synergistically with opioids to increase the risk of respiratory depression. Some patients may also have underlying health issues, such as obstructive sleep apnea, that can be exacerbated with the use of opioids and other CNS depressants and further contribute to respiratory depression. Clinicians should have a thorough understanding of respiration, recognize how various CNS depressants suppress it, and take necessary steps to mitigate the risk of opioid-induced respiratory depression by collaborating with a multidisciplinary team (i.e., sleep and pain specialists), choosing appropriate medications, and educating patients on the proper use and storage of opioids.

Multicenter Retrospective Analysis of Dorsal Root Ganglion Stimulator Placement Using Intraoperative Neuromonitoring in Asleep Patients During Early Periods of Adoption

OBJECTIVES

Intraoperative neuromonitoring (IONM) has been used in the implantation of spinal cord stimulation for both safety and confirmation of lead placement. It is less well defined in its use for dorsal root ganglion (DRG) stimulator placement.

MATERIALS AND METHODS

This is a retrospective analysis of 304 leads placed in 93 patients undergoing DRG stimulation therapy with its placement utilizing IONM in asleep patients by four implanting physicians in four separate centers. The first year, or early adoption period, of placements for each site was chosen as the included cases to evaluate.

RESULTS

There were a total of 14 IONM alerts across the 304 lead placements. There were two complications, no permanent or severe adverse events, and no revisions. All alerts led to a change in approach as a corrective action. The two complications were a patient requiring a blood patch for an undetected CSF leak, while the other was a generator site seroma that resolved with conservative care. A single patient experienced transient calf paresthesia's in the post-operative period.

CONCLUSION

This retrospective series demonstrates the utility and accuracy of IONM in not only confirming proper dorsal placement of a DRG electrode but also in maintaining a low adverse event profile. It further demonstrates that its utility in the real world with new users can be safe and accurate with an ease of integration.

Explantation Rates of High Frequency Spinal Cord Stimulation in Two Outpatient Clinics

OBJECTIVES

To report the explantation rates of high frequency 10 kHz spinal cord stimulation (SCS) in a real-world setting.

MATERIALS AND METHODS

This is a retrospective review of patients implanted with high frequency spinal cord stimulators over a 4-year period in two outpatient private practice clinics, from July 2015 through June 2019, using the Kaplan-Meier product-limit method to estimate probabilities of implant survival over time.

RESULTS

The estimated median time to explantation was 3.5 years (95% confidence interval [CI] = 3.1-3.7) [Correction added on 15 October 2020, after first online publication: The preceeding sentence was amended to reflect the estimated median time.]. The estimated probabilities of implant survival beyond 1, 2, and 3 years postimplantation were 88.4% (95% CI = 81.3-93.0%), 76.5% (95% CI = 67.8-83.2%), and 60.7% (95% CI = 50.2-69.6%), respectively. The minimum (i.e., known) cumulative percentages of patients explanted by 1, 2, and 3 years postimplantation were 11.1% (14/126), 22.2% (28/126), and 32.5% (41/126), respectively. 65.9% of patients in this study had prior neurostimulation.

CONCLUSIONS

Recently, high frequency SCS technology has been demonstrated as more effective in treatment of lower- and leg-pain, compared to conventional low frequency SCS, in a 12-month randomized controlled trial (SENZA-RCT). Longer term results have yet to be published. In this study, we found that the explantation rate was much higher than expected, based on the prior studies demonstrating its efficacy. As the use of neuromodulation continues to grow, longitudinal data will be critical in understanding its long-term effects on treated patients.

Adolescents' experiences of fluctuating pain in musculoskeletal disorders: a qualitative systematic review and thematic synthesis

BACKGROUND

Adolescents with chronic musculoskeletal pain experience daily fluctuations in pain. Although not all fluctuations are bothersome, pain flares are a distinct type of symptom fluctuation with greater impact. Since literature on the experience of pain flares is non-existent, the aim of this review was to (i) synthesise the qualitative literature on adolescents' experiences of fluctuating pain in musculoskeletal disorders in order to (ii) identify knowledge gaps to inform future research on pain flares.

METHODS

Electronic databases (CINAHL, MEDLINE, EMBASE, PsycINFO), grey literature and reference lists were searched from inception to June 2018 for qualitative studies reporting adolescents' experiences of pain. Comprehensiveness of reporting was assessed using the Consolidated Criteria for Reporting Qualitative Health Research. Studies were analysed using thematic synthesis.

RESULTS

Of the 3787 records identified, 32 studies (n = 536) were included. Principal findings were synthesised under three key themes: 1) symptom experience, 2) disruption and loss, and 3) regaining control. The first theme (symptom experience) describes adolescent's perception and interpretation of pain fluctuations. The second theme (disruption and loss) describes the physical, social and emotional constraints faced as a result of changes in pain. The third theme (regaining control) describes coping strategies used to resist and accommodate unpredictable phases of pain. Each theme was experienced differently depending on adolescents' characteristics such as their developmental status, pain condition, and the duration of the pain experience.

CONCLUSIONS

Adolescents with chronic musculoskeletal pain live with a daily background level of symptoms which frequently fluctuate and are associated with functional and emotional difficulties. It was not clear whether these symptoms and challenges were experienced as part of 'typical' fluctuations in pain, or whether they reflect symptom exacerbations classified as 'flares'. Further research is needed to explore the frequency and characteristics of pain flares, and how they differ from their typical fluctuations in pain. The review also highlights areas relating to the pain experience, symptom management and health service provision that require further exploration to support more personalised, tailored care for adolescents with chronic musculoskeletal pain.

A pilot study in the association between Waddell Non-organic Signs and Central Sensitization

STUDY DESIGN

A cross-sectional observational multicenter pilot-study was performed within care as usual in three rehabilitation centers in the Netherlands.

OBJECTIVE

To explore the relationship between Waddell Non-organic Signs (NOS) and Central Sensitization (CS) in patients with chronic back pain.

SUMMARY OF BACKGROUND DATA

A possible relationship between NOS and CS is theoretically plausible, but it has never been tested.

METHODS

A cross-sectional observational multicenter pilot-study was performed in three rehabilitation centers in the Netherlands. Patients with chronic back pain were included. Main measures were Waddell's NOS, a battery of eight clinical tests performed during a physical examination, and Central Sensitization Inventory (CSI), a questionnaire measuring symptoms originating from CS. Analyses included Spearman correlation and univariate multiple regression analysis with NOS as dependent variable, CSI as independent, and controlled for confounders (psychosocial variables).

RESULTS

Data of n = 56 patients (59% female, mean age 42.6 years) were obtained. Correlation between NOS and CSI was rs = 0.34 (p = 0.01). After controlling for confounders, CSI did not independently predict NOS.

CONCLUSION

In this pilot study, CS was moderately related to NOS, but CS did not independently contribute to NOS after controlling for confounders. The results suggest that NOS may not exclusively be non-organic tests, although questions remain. The results of this pilot study can help to develop larger studies to allow replication and more detailed analyses.

Patient Satisfaction Following Intrathecal Targeted Drug Delivery for Benign Chronic Pain: Results of a Single-Center Survey Study

OBJECTIVES

Targeted Drug Delivery (TDD) is commonly used for the management of patients with intractable pain. Past studies have proven efficacy in pain relief and reduction in opioid use and cost-effectiveness in long-term pain management. There are few studies investigating satisfaction among patients with implanted pain pumps that are managed with targeted intrathecal medications.

MATERIAL AND METHODS

Patients in a single medical practice implanted with pain pumps for relief of intractable pain were identified and extracted from the electronic health record (EHR). Six hundred and ten active TDD patients were identified and an anonymous 18-question survey was administered to determine satisfaction with TDD therapy. During an 18-month period from May 2018 to August 2019, patients were invited to take a satisfaction survey. Both primary and secondary outcomes were reported as proportions; P < 0.05 was considered significant.

RESULTS

Four hundred and forty-three patients (74% of the active pump population) completed the survey. The majority of patients reported improvement in pain, improvement of physical function, improvement in quality of life and reduction in opioid use. Complete discontinuation of oral opioid intake was reported in 38.9% of patients. The majority of patients had a 40 cc reservoir implanted in an upper buttock pocket site and overall, 91% of patients were happy with pump pocket location.

CONCLUSION

Intrathecal TDD therapy can relieve pain and improve quality of life in patients with intractable pain and offers a reasonable alternative to long-term oral or skin patch opioid management. Patients utilizing TDD therapy reported high degrees of satisfaction.

Episodic future thinking reduces chronic pain severity: A proof of concept study

BACKGROUND

Chronic pain is a major public health challenge in the United States and around the world. Current treatments including opioid analgesics and cognitive behavioral therapy possess harmful side effects or limited efficacy, respectively. Chronic pain is associated with a variety of unhealthy behaviors including opioid misuse. Moreover, individuals who suffer from chronic pain exhibit excessive discounting of delayed rewards, suggesting a constricted temporal window of valuation. Reductions in the excessive discounting of delayed rewards has been achieved with Episodic Future Thinking (EFT; vividly imagining realistic future events). EFT has also been associated with reductions in a variety of unhealthy behaviors. In this study, the effects of EFT on delay discounting and levels of pain were investigated in individuals reporting chronic pain.

METHODS

Individuals reporting chronic pain (N = 250; 42.4 % female) were recruited through the Amazon Mechanical Turk platform. Measures of delay discounting and pain were collected at baseline and again after randomization to EFT (N = 128) or Control Episodic Thinking (CET) (N = 122).

RESULTS

EFT significantly reduced delay discounting relative to baseline (p < 0.001) and EFT reduced pain scores in a baseline dependent manner (p = 0.001) when compared to CET; that is, those with the greatest reports of pain experienced the greatest reduction. Furthermore the reduction in delay discounting fully mediated the reduction in pain.

CONCLUSIONS

These findings suggest that Episodic Future Thinking, by widening the temporal window, may reduce pain in those reporting chronic pain and therefore represents a potential novel therapeutic.

A registry-based 2-year follow-up comparative study of two meshes used in transinguinal preperitoneal (TIPP) groin hernia repair

PURPOSE

Onflex™ mesh has replaced Polysoft™ patch on the market, without being clinically evaluated thus far in the transinguinal preperitoneal (TIPP) technique.

METHODS

All consecutive TIPP registered in our registry during the overlap period of availability of both meshes were included and studied with the chronic postoperative inguinal pain (CPIP) as primary endpoint, assessed with a verbal rating scale (VRS), and included in a patient-related outcome measurement (PROM) phone questionnaire.

RESULTS

A total of 181 Onflex cases vs 182 Polysoft cases were studied with a 2-year follow-up rate of 92% vs 88%. The overall rate of pain or discomfort was not statistically different in the 2 studied subgroups (16.5% vs 17.6%; p = 0.71), while moderate or severe pain were significantly more frequent in the Polysoft subgroup (5.5% vs 11.6%; p = 0.01). These symptoms did not interfere with the patient daily life in 16% vs 16.5% of cases, and they were self-assessed as more bothersome than the hernia in only 0.5% vs 0.5% of cases, suggesting an overestimation of the pain by the VRS. Patients assessed the result of their hernia repair as excellent or good in 97.8% vs 96.7% and medium or bad in 2.2% vs 3.3% (p = 0.53). The cumulative recurrence rate was 0% vs 2.2%. Two reoperations (one for early and one for late recurrence) were reported in the Polysoft subgroup (1%), none related to the non-absorbable memory ring.

CONCLUSIONS

These results suggest that TIPP with Onflex provides results at least similar than those with Polysoft.

Do Bisphosphonates Alleviate Pain in Children? A Systematic Review

PURPOSE OF REVIEW

The goal of this systematic review is to analyze the effectiveness of bisphosphonates (BPs) to treat bone pain in children and adolescents who have diseases with skeletal involvement.

RECENT FINDINGS

We included 24 studies (2 randomized controlled trials, 3 non-randomized controlled trials, 10 non-randomized open-label uncontrolled studies, 8 retrospective studies, and 1 study with design not specified). The majority of included studies assessed pain from a unidimensional approach, with pain intensity the most frequently evaluated dimension. Only 38% of studies used validated tools; visual analogue scale was the most frequently employed. BPs were used to alleviate bone pain in a wide variety of pediatrics conditions such as osteogenesis imperfecta, secondary osteoporosis, osteonecrosis related to chemotherapy, chronic non-bacterial osteitis, idiopathic juvenile osteoporosis, unresectable benign bone tumor, and cancer-related pain. Twenty of the 24 studies reported a positive effect of BPs for alleviating pain in different pathologies, but 58% of the studies were categorized as having high risk of bias. Intravenous BPs are helpful in alleviating bone pain in children and adolescents. It is advised that our results be interpreted with caution due to the heterogeneity of the doses used, duration of treatments, and types of pathologies included. In addition, this review shows the paucity of high-quality evidence in the available literature and further research is needed.

TRIAL REGISTRATION

Before the completion of this review, the protocol was registered to PROSPERO (International prospective register of systematic reviews), PROSPERO 2020 ID # CRD42020158316. Available from: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020158316.

Transient receptor potential V1 (TRPV1) modulates the therapeutic effects for comorbidity of pain and depression: The common molecular implication for electroacupuncture and omega-3 polyunsaturated fatty acids

Chronic pain and depression are conditions that are highly comorbid and present with overlapping clinical presentations and common pathological biological pathways in neuroinflammation, both of which can be reversed by the use of electroacupuncture (EA) and omega-3 polyunsaturated fatty acids (PUFAs). Transient receptor potential V1 (TRPV1), a Ca²⁺ permeable ion channel that can be activated by inflammation, is reported to be involved in the development of chronic pain and depression. Here, we investigated the role of TRPV1 and its related pathways in the murine models of cold stress-induced nociception and depression. Female C57BL/6 wild type and TRPV1 knockout mice were subjected to intermittent cold-stress (ICS) to initiate depressive-like and chronic pain behaviors, respectively. The Bio-Plex ELISA technique was utilized to analyze inflammatory mediators in mice plasma. The western blot and immunostaining techniques were used to analyze the presence of TRPV1 and related molecules in the medial prefrontal cortex (mPFC), hippocampus, periaqueductal gray (PAG), and amygdala. The ICS model significantly induced chronic pain (mechanical: 2.55 ± 0.31 g; thermal: 8.12 ± 0.87 s) and depressive-like behaviors (10.95 ± 0.95% in the center zone; 53.14 ± 4.01% in immobility). The treatment efficacy of EA, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) were observed in both nociceptive and depression test results. Inflammatory mediators were increased after ICS induction and further reversed by the use of EA, EPA and DHA. A majority of TRPV1 proteins and related molecules were significantly decreased in the mPFC, hippocampus and PAG of mice. This decrease can be reversed by the use of EA, EPA and DHA. In contrast, these molecules were increased in the mice's amygdala, and were attenuated by the use of EA, EPA and DHA. Our findings indicate that these inflammatory mediators can regulate the TRPV1 signaling pathway and initiate new potential therapeutic targets for chronic pain and depression treatment.

Brain TNF drives post-inflammation depression-like behavior and persistent pain in experimental arthritis

Patients with rheumatoid arthritis experience chronic pain, depression and fatigue, even when inflammation of the joints is well controlled. To study the relationship between arthritis, depression, and sustained pain when articular inflammation is no longer observed, we tested the hypothesis that brain TNF drives post-inflammation depression-like behavior and persistent pain in experimental arthritis. The murine model of antigen-induced arthritis (AIA) was used to evaluate the effects of knee inflammation on sustained pain and depression-like behavior. We measured joint pain using an automated dynamic plantar algesiometer and depression-like behavior with the tail suspension test. Cytokines were measured by Luminex assay and ELISA. TNF in the brain was blocked by intracerebroventricular injection of anti-TNF antibodies. Histological damage and elevated levels of cytokines were observed in the knee 24 h after antigen treatment, but not at 13 days. Reduced pain thresholds were seen 24 h and 13 days after treatment. Depression-like behavior was observed on day 13. Treatment with the antidepressant imipramine reduced both depression-like behavior and persistent pain. However, blocking joint pain with the analgesic dipyrone did not alter depression-like behavior. Elevated levels of TNF, CCL2, and CXCL-1 were observed in the hippocampus 24 h after treatment, with TNF remaining elevated at day 13. Intracerebroventricular infusion of an anti-TNF antibody blocked depression-like behavior and reduced persistent pain. We have demonstrated that depression-like behavior and pain is sustained in AIA mice after the resolution of inflammation. These changes are associated with elevated levels of TNF in the hippocampus and are dependent upon brain TNF. The findings reveal an important mechanistic link between the expression of chronic pain and depression in experimental arthritis. Furthermore, they suggest treating depression in rheumatoid arthritis may positively impact other debilitating features of this condition.

Clinical Effectiveness and Mechanism of Action of Spinal Cord Stimulation for Treating Chronic Low Back and Lower Extremity Pain: a Systematic Review

PURPOSE OF REVIEW

The purpose of the present systematic review is to provide a current understanding of the mechanism of action and the evidence available to support clinical decision-making. The focus is to summarize randomized controlled trials (RCTs) and nonrandomized or observational studies of spinal cord stimulation in chronic pain to understand clinical effectiveness and the mechanism of action.

RECENT FINDINGS

Several recent studies have demonstrated the benefit of spinal cord stimulation in managing chronic pain. Until recently, the mechanism of action was founded on a central paradigm derived from gate control theory, which is the need to stimulate the dorsal column of the spinal cord to generate paresthesia. The recent development of new therapies that do not rely on paresthesia has left the field without a clear mechanism of action that could serve as a strong foundation to further improve clinical outcomes. Consequently, multiple theories have emerged to explain how electrical pulse applied to the spinal cord could alleviate pain, including activation of specific supraspinal pathways, and segmental modulation of the neurological interaction. Recent systematic reviews also have shown the clinical effectiveness of spinal cord stimulation in managing chronic spinal pain, phantom limb pain, complex regional pain syndrome, and other chronic painful conditions. Spinal cord stimulation for the treatment of chronic pain is rapidly evolving with technology at its forefront. This comprehensive focused review evaluated 11 RCTs and 7 nonrandomized/observational studies which provided levels of evidence ranging from I to II.

A network approach to investigating the key microbes and stability of gut microbial communities in a mouse neuropathic pain model

Background

Neuropathic pain is an abnormally increased sensitivity to pain, especially from mechanical or thermal stimuli. To date, the current pharmacological treatments for neuropathic pain are still unsatisfactory. The gut microbiota reportedly plays important roles in inducing neuropathic pain, so probiotics have also been used to treat it. However, the underlying questions around the interactions in and stability of the gut microbiota in a spared nerve injury-induced neuropathic pain model and the key microbes (i.e., the microbes that play critical roles) involved have not been answered. We collected 66 fecal samples over 2 weeks (three mice and 11 time points in spared nerve injury-induced neuropathic pain and Sham groups). The 16S rRNA gene was polymerase chain reaction amplified, sequenced on a MiSeq platform, and analyzed using a MOTHUR- UPARSE pipeline.

Results

Here we show that spared nerve injury-induced neuropathic pain alters gut microbial diversity in mice. We successfully constructed reliable microbial interaction networks using the Metagenomic Microbial Interaction Simulator (MetaMIS) and analyzed these networks based on 177,147 simulations. Interestingly, at a higher resolution, our results showed that spared nerve injury-induced neuropathic pain altered both the stability of the microbial community and the key microbes in a gut micro-ecosystem. Oscillospira, which was classified as a low-abundance and core microbe, was identified as the key microbe in the Sham group, whereas Staphylococcus, classified as a rare and non-core microbe, was identified as the key microbe in the spared nerve injury-induced neuropathic pain group.

Conclusions

In summary, our results provide novel experimental evidence that spared nerve injury-induced neuropathic pain reshapes gut microbial diversity, and alters the stability and key microbes in the gut.

Exploring the use of extended release opioids at shortened dosing intervals in people with chronic pain and high risk medication or substance use

Background Critical attention to rational opioid prescribing has emerged from the opioid epidemic in North America. Individuals with chronic pain are prescribed extended release opioids in an effort to maintain stable drug levels and for more convenient dosing, though evidence to support improvements in pain or function is lacking. It has been observed that extended release opioid products are used at intervals shorter than recommended by product monographs. The need for shortened intervals has been linked with potential inter-patient variability in pharmacokinetics, among other rationale. Implications of shortened dosing intervals for extended release opioids have not been systematically studied. Objective The aim of this study was to characterize the use of extended release opioid formulations at shortened dosing intervals in a population of patients with chronic pain and high risk for opioid-related harms. Setting This study took place in the Interprofessional Pain and Addiction Recovery Clinic, a specialty ambulatory clinic at the Centre for Addiction and Mental Health in Toronto, Canada for adults with chronic pain and a diagnosis or suspicion of substance use disorder. Method This was a retrospective cross-sectional study. Data were collected from records of patients with assessments completed in the years 2012-2017 (n = 210). Main outcome measure Proportion of patients using extended release opioids at shortened intervals. Results Sixty-one percent of individuals using extended release opioids (n = 78) were using them at shortened intervals. This use was associated with a higher daily morphine equivalent dose (533 mg vs 236 mg, p < 0.01), use of oxycodone extended release products (50% vs. 27%, p < 0.01), a longer duration of opioid therapy (8.9 vs. 6.8 years, p = 0.03) and a diagnosis of chronic neuropathic pain (63% vs. 39%, p < 0.01), with no differences in reported pain intensities, compared with use at standard intervals. Conclusion The use of extended release opioids at shortened intervals was associated with increased daily morphine equivalent doses, thus an increased risk of opioid-related mortality. It is unlikely that of those using extended release opioids, the high proportion of use at shortened intervals is the result of inter-patient differences in metabolism alone. Further study is warranted to explore the underlying drivers and implications for people with chronic pain.

Medical cannabis use in the United States: a retrospective database study

Introduction

Growing interest in the medicinal properties of cannabis has led to an increase in its use to treat medical conditions, and the establishment of state-specific medical cannabis programs. Despite medical cannabis being legal in 33 states and the District of Colombia, there remains a paucity of data characterizing the patients accessing medical cannabis programs.

Methods

We retrospectively reviewed a registry with data from 33 medical cannabis evaluation clinics in the United States, owned and operated by CB2 Insights. Data were collected primarily by face-to-face interviews for patients seeking medical cannabis certification between November 18, 2018 and March 18, 2020. Patients were removed from the analysis if they did not have a valid date of birth, were less than 18, or did not have a primary medical condition reported; a total of 61,379 patients were included in the analysis. Data were summarized using descriptive statistics expressed as a mean (standard deviation (SD)) or median (interquartile range (IQR)) as appropriate for continuous variables, and number (percent) for categorical variables. Statistical tests performed across groups included t-tests, chi-squared tests and regression.

Results

The average age of patients was 45.5, 54.8% were male and the majority were Caucasian (87.5%). Female patients were significantly older than males (47.0 compared to 44.6). Most patients reported cannabis experience prior to seeking medical certification (66.9%). The top three mutually exclusive primary medical conditions reported were unspecified chronic pain (38.8%), anxiety (13.5%) and post-traumatic stress disorder (PTSD) (8.4%). The average number of comorbid conditions reported was 2.7, of which anxiety was the most common (28.3%). Females reported significantly more comorbid conditions than males (3.1 compared to 2.3).

Conclusion

This retrospective study highlighted the range and number of conditions for which patients in the US seek medical cannabis. Rigorous clinical trials investigating the use of medical cannabis to treat pain conditions, anxiety, insomnia, depression and PTSD would benefit a large number of patients, many of whom use medical cannabis to treat multiple conditions.

Functional Medicine: A View from Physical Medicine and Rehabilitation

Using the functional medicine rubric in physical medicine and rehabilitation (PM&R), a physiatrist can capitalize on addressing the root causes and downstream effects in patients with chronic diseases. Similar to the International Classification of Function model in rehabilitation, the functional medicine model uses biopsychosocial understanding with a systems biology approach to find fulcrum points to create the biggest impact on health care. Given the position of rehabilitation medicine with the type and location of patients, both functional medicine and PM&R would benefit from a mutual partnership.

Chronic groin pain following open inguinal hernia repair: has consenting practice improved?

INTRODUCTION

Chronic groin pain following inguinal hernia surgery is a common and potentially debilitating complication, and yet patients are infrequently informed of this risk. This leaves surgeons open to negligence claims, especially given recent changes to case law, which for the first time highlighted the need for a more patient-centred approach to risk disclosure. We investigated how these changes have influenced our consenting practice with respect to the disclosure of this risk.

METHODS

We compared how often surgeons discussed the risk of chronic groin pain with adults undergoing elective open unilateral inguinal hernia mesh repairs in 2019 and 2009. The first 50 patients in each of these two years were retrospectively compared. Discussions during the initial consultation and on the day of surgery were assessed by reviewing clinic letters, medical notes and consent forms.

FINDINGS

The risk of chronic pain was discussed with significantly more patients in 2019 than in 2009 (96% v 54%, p<0.0001). Most of these discussions occurred on the day of surgery (92% v 54%, p<0.0001). Only a few patients had these discussions during their initial consultation (18% v 4%, p<0.025).

CONCLUSIONS

Discussing the risk of chronic groin pain has improved significantly over the past 10 years. However, these discussions occur mostly on the day of surgery, which gives patients very little time to weigh up the risk. This potentially invalidates the consent they give for surgery. Patients should be given an opportunity to discuss their operative risks in advance of their operation.

The Quest for More Effective Analgesics with Reduced Abuse Liability and Fewer Adverse Effects: Promises, Pitfalls, and Future Perspectives of Biased Agonists at Opioid Receptors

Chronic pain is a relevant health condition affecting one out of five individuals that is often not adequately treated by currently available analgesics. This, together with the dramatic increase in addicted people within the dramatic "opioid epidemics," significantly spurs the quest for innovative analgesics provided with increased efficacy, reduced abuse liability, and fewer adverse effects.Within this frame, biased agonists at opioid receptors have attracted increasing interest in the last decade as they have emerged as more effective and safer candidate analgesics.In this chapter, promises, pitfalls, and future perspective of biased agonists at mu (MOR) and kappa (KOR) opioid receptors are discussed. Moreover, methodological insights are provided with regard to the most appropriate experimental settings to be employed aiming at developing novel biased KOR agonists.