Sex Differences in Pain Sensitivity in a Dutch Cohort: Cross-Sectional and Web-Based Multidimensional Study.

BACKGROUND: Sex is an important factor influencing the development and treatment of chronic pain, but the extent of its influence is still unclear. Other demographic factors as well as nonpharmacological interventions might influence pain sensitivity differently in men and women. OBJECTIVE: In this study, we aimed to investigate the influence of sex and other demographic, lifestyle, behavioral, clinical, and environmental factors on pain sensitivity in the Dutch population. Different films were used to investigate how they would impact pain sensitivity and what influence sex and other variables have on the effect of this simple intervention. METHODS: We performed a study consisting of 2 parts: (1) a cross-sectional research to investigate pain sensitivity differences between men and women and the influence of other demographic variables on the pain sensitivity in a Dutch cohort and (2) an internet intervention study to determine whether a short film could skew pain sensitivity. RESULTS: All respondents filled in a web-based demographic questionnaire and were randomized into 4 groups. The control group filled in the Pain Sensitivity Questionnaire without watching a preliminary film. A cross-sectional analysis was performed in the control group (n=1746). The other 3 groups watched short films: one group watched a film with scenes of nature (n=2650), another group watched a film on laughing people (n=2735), and the last group watched a film on physically painful events (n=2708). Immediately after the film viewing, participants were directed to the Pain Sensitivity Questionnaire to measure their pain sensitivity. The Pain Sensitivity Questionnaire score was stated as a mean per question on the numeric rating scale from 0-1. The cross-sectional study revealed no significant differences between men and women but showed male-female differences in the Pain Sensitivity Questionnaire when specific background factors were present. Watching a short film had a positive impact on the pain sensitivity of the respondents who had chronic pain, with a higher effect observed in female respondents. CONCLUSIONS: Scientists performing pain research need to account for factors that can influence the outcome of their study and be aware that these factors can be sex-dependent, and pain sensitivity should be analyzed accordingly. Even relatively small interventions such as watching a film can impact pain sensitivity, especially in respondents with current chronic pain. This effect can vary as well when different background factors are present. Our findings warrant further explorations of the possibilities that simple interventions bring for patients in personalized medicine. TRIAL REGISTRATION: Landelijk Trial Register NTR-new NL8182; https://onderzoekmetmensen.nl/en/trial/29537.

The Predicted Outcome of Spinal Cord Stimulation in Patients With a Psychopathological Disorder and Persistent Spinal Pain Syndrome Type 2: A Systematic Review From 2009 to 2021.

OBJECTIVES: Psychologic screening is often included as a mandatory component of evaluation of the impact of psychopathology disorders on the predicted outcome of spinal cord stimulation (SCS) for patients with chronic pain due to persistent spinal pain syndrome type 2 (PSPS type 2). The conclusion of such screenings can influence the decision to offer SCS therapy to a patient. However, evidence on the impact of psychopathology on SCS outcomes is still scarce. MATERIALS AND METHODS: To address this knowledge gap, we systematically reviewed the literature from 2009 to 2021 to explore the correlation between the presence of a psychopathological disorder and the predicted outcome of SCS in patients with PSPS type 2. The literature search was conducted using various online data bases with "failed back surgery syndrome," "psychopathology," and "spinal cord stimulation" used as essential keywords. The identified studies were organized in a Rayyan AI data base, and the quality was analyzed with the Critical Appraisal Skills Program tool. RESULTS: Our search generated the identification of 468 original articles, of which two prospective and four retrospective studies met our inclusion criteria. These studies reported pain relief, a reduction of symptoms of anxiety and depression, and an improvement in rumination on the Pain Catastrophizing Scale in patients with PSPS type 2 after SCS therapy. The studies also found contradictory outcomes measured using the Oswestry Disability Index, and in terms of the impact of psychopathological disorder on the clinical outcome and revision rate of the SCS system. CONCLUSION: In this systematic review, we found no convincing evidence that the presence of a psychopathological disorder affects the predicted outcome of SCS therapy in patients with PSPS type 2.

Factors Predicting Clinically Relevant Pain Relief After Spinal Cord Stimulation for Patients With Chronic Low Back and/or Leg Pain: A Systematic Review With Meta-Analysis and Meta-Regression.

RATIONALE: To optimize results with spinal cord stimulation (SCS) for chronic low back pain (CLBP) and/or leg pain, including persistent spinal pain syndrome (PSPS), careful patient selection based on proved predictive factors is essential. Unfortunately, the necessary selection process required to optimize outcomes of SCS remains challenging. OBJECTIVE: This review aimed to evaluate predictive factors of clinically relevant pain relief after SCS for patients with CLBP and/or radicular leg pain, including PSPS. MATERIALS AND METHODS: In August 2023, PubMed, Cinahl, Cochrane, and EMBASE were searched to identify studies published between January 2010 and August 2023. Studies reporting the percentage of patients with ≥50% pain relief after SCS in patients with CLBP and leg pain, including PSPS at 12 or 24 months, were included. Meta-analysis was conducted to pool results for back, leg, and general pain relief. Predictive factors for pain relief after 12 months were examined using univariable and multivariable meta-regression. RESULTS: A total of 27 studies (2220 patients) were included for further analysis. The mean percentages of patients with substantial pain relief were 68% for leg pain, 63% for back pain, and 73% for general pain at 12 months follow-up, and 63% for leg pain, 59% for back pain, and 71% for general pain at 24 months follow-up assessment. The implantation method and baseline Oswestry Disability Index made the multivariable meta-regression model for ≥50% back pain relief. Sex and pain duration made the final model for ≥50% leg pain relief. Variable stimulation and implantation method made the final model for general pain relief. CONCLUSIONS: This review supports SCS as an effective pain-relieving treatment for CLBP and/or leg pain, and models were developed to predict substantial back and leg pain relief. To provide high-grade evidence for predictive factors, SCS studies of high quality are needed in which standardized factors predictive of SCS success, based on in-patient improvements, are monitored and reported.

Are specialist-provided end-of-life scenarios key to initiation of advance care planning in primary care? A mixed-methods study.

OBJECTIVES: Specialist-provided end-of-life scenarios (SP-EOLS) may improve advance care planning (ACP) implementation in primary care by helping overcome barriers such as uncertain prognosis and poor interprofessional collaboration. We aimed to explore the current use and potential impact of SP-EOLS on ACP in Dutch primary care. METHODS: We performed a mixed-methods study. From patients discussed in a hospital-based academic palliative care multidisciplinary team meeting between 2016 and 2019 and died, we collected primary care electronic medical records data on SP-EOLS, actual EOLS, and ACP initiation and applied descriptive and comparative analyses. Subsequently, we interviewed general practitioners (GPs) and thematically analyzed the transcripts. RESULTS: In 69.7% of 66 reviewed patient files, SP-EOLS were found. In patients whose GP had received SP-EOLS, ACP conversations were more often reported (92.0 vs. 61.0%, p = 0.006). From 11 GP interviews, we identified 4 themes: (1) SP-EOLS guide GPs, patients, and relatives when dealing with an uncertain future perspective; (2) SP-EOLS provide continuity of care between primary and secondary/tertiary care; (3) SP-EOLS should be tailored to the individual patient; and (4) SP-EOLS need to be personalized and uniformly transferred to GPs. SIGNIFICANCE OF RESULTS: SP-EOLS may facilitate ACP conversations by GPs. They have the potential to help overcome existing barriers to ACP implementation by providing guidance and supporting interprofessional collaboration. Future research should focus on improving SP-EOLS and tailor them to the needs of all end users, focusing on improving their effect on ACP conversations.

Subcutaneous Stimulation as Add-on Therapy to Spinal Cord Stimulation in Patients With Persistent Spinal Pain Syndrome Significantly Increases the Total Electrical Charge per Second: Aspects on Stimulation Parameters and Energy Requirements of the Implanted Neurostimulators.

OBJECTIVE: In our previous multicenter randomized controlled trial, we demonstrated the clinical effectiveness of peripheral nerve field stimulation (PNFS) as add-on therapy to spinal cord stimulation (SCS) for the treatment of chronic back pain in patients with persistent spinal pain syndrome (PSPS) or failed back surgery syndrome (FBSS). To our knowledge, no previous study has investigated the effect of PNFS as an add-on to SCS on the energy consumption of the implanted neurostimulators. Therefore, in this study, we compared the specific stimulation parameters and energy requirements of a previously unreported group of patients with only SCS with those of a group of patients with SCS and add-on PNFS. We also investigated differences that might explain the need for PNFS in the treatment of chronic low back pain. MATERIALS AND METHODS: We analyzed 75 patients with complete sets of stimulation parameters, with 21 patients in the SCS-only group and 54 patients in the SCS + PNFS group. Outcome measures were average visual analog scale score, SCS parameters (voltage, frequency, and pulse width), SCS charge per second, and total charge per second. We analyzed baseline characteristics and differences between and within groups over time. RESULTS: Both groups had comparable patient characteristics at baseline and showed a significant decrease in back and leg pain. SCS charge per second did not significantly differ between the groups at baseline or at 12 months. The total charge per second was significantly higher in the active SCS + PNFS group than in the SCS-only group at baseline; in the SCS + PNFS group, this persisted for up to 12 months, and the SCS charge per second and total charge per second increased significantly over time. CONCLUSIONS: Our results show that add-on PNFS increases the total charge per second compared with SCS alone, as expected. However, further research is needed because our results do not directly explain why some patients require add-on PNFS to treat low back pain.

Spinal Cord Stimulation With Additional Peripheral Nerve/Field Stimulation Versus Spinal Cord Stimulation Alone on Back Pain and Quality of Life in Patients With Persistent Spinal Pain Syndrome.

INTRODUCTION: Persistent spinal pain syndrome (PSPS) or failed back surgery syndrome (FBSS) refers to new or persistent pain following spinal surgery for back or leg pain in a subset of patients. Spinal cord stimulation (SCS) is a neuromodulation technique that can be considered in patients with predominant leg pain refractory to conservative treatment. Patients with predominant low back pain benefit less from SCS. Another neuromodulation technique for treatment of chronic low back pain is subcutaneous stimulation or peripheral nerve field stimulation (PNFS). We investigated the effect of SCS with additional PNFS on pain and quality of life of patients with PSPS compared with that of SCS alone after 12 months. MATERIALS AND METHODS: This is a comparative study of patients with PSPS who responded to treatment with either SCS + PNFS or SCS only following a multicenter randomized clinical trial protocol. In total, 75 patients completed the 12-month follow-up: 21 in the SCS-only group and 54 in the SCS + PNFS group. Outcome measures were pain (visual analog scale), quality of life (36-Item Short Form Survey [SF-36]), anxiety and depression (Hospital Anxiety and Depression Scale [HADS]), overall health (EuroQol Five-Dimension [EQ-5D]), disability (Oswestry Disability Index [ODI]), and pain assessed by the McGill questionnaire. RESULTS: There were no significant differences in baseline characteristics between the two groups. Both groups showed a significant reduction in back and leg pain at 12 months compared with baseline measurements. No significant differences were found between the groups in effect on both primary (pain) and secondary parameters (SF-36, HADS, EQ-5D, ODI, and McGill pain). CONCLUSION: In a subgroup of patients with chronic back and leg pain, SCS alone provided similar long-term pain relief and quality-of-life improvement as PNFS in addition to SCS. In patients with refractory low back pain not responding to SCS alone, adding PNFS should be recommended. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT01776749.

Are psychedelics the answer to chronic pain: A review of current literature.

AIMS: We aim to provide an evidence-based overview of the use of psychedelics in chronic pain, specifically LSD and psilocybin. CONTENT: Chronic pain is a common and complex problem, with an unknown etiology. Psychedelics like lysergic acid diethylamide (LSD) and psilocybin, may play a role in the management of chronic pain. Through activation of the serotonin-2A (5-HT2A) receptor, several neurophysiological responses result in the disruption of functional connections in brain regions associated with chronic pain. Healthy reconnections can be made through neuroplastic effects, resulting in sustained pain relief. However, this process is not fully understood, and evidence of efficacy is limited and of low quality. In cancer and palliative related pain, the analgesic potential of psychedelics was established decades ago, and the current literature shows promising results on efficacy and safety in patients with cancer-related psychological distress. In other areas, patients suffering from severe headache disorders like migraine and cluster headache who have self-medicated with psychedelics report both acute and prophylactic efficacy of LSD and psilocybin. Randomized control trials are now being conducted to study the effects in cluster headache Furthermore, psychedelics have a generally favorable safety profile especially when compared to other analgesics like opioids. In addition, psychedelics do not have the addictive potential of opioids. IMPLICATIONS: Given the current epidemic use of opioids, and that patients are in desperate need of an alternative treatment, it is important that further research is conducted on the efficacy of psychedelics in chronic pain conditions.

Monitoring Opioids in Europe: The Need for Shared Definitions and Measuring Drivers of Opioid Use and Related Harms.

The past 20 years, the USA is facing a serious opioid crisis initiated by an increase in prescription opioid use. Europe has also seen an increase in prescription opioid use, but the extent of related harm is still largely unknown. Given the impact of the US opioid epidemic, it is important to closely monitor signs of emerging opioid-related problems to guarantee early warnings and timely actions. Shared and meaningful definitions for opioid use and related harms, and relevant information about specific drivers for opioid use and related problems are needed for an adequate policy response. In this commentary, we discuss these definitions, the need to know more about the specific drivers for increased opioid use, its related harm, and proposals for strategies to move forward. Policy recommendations include making a distinction between licit and illicit opioids when monitoring and reporting on opioid-related harm, and using oral morphine equivalents to quantify prescription opioid use in a clinically relevant and comparable manner. A major topic of further research is exploring unique and universal drivers of prescription opioid (mis)use across Europe, in particular the role of opioid diversion.

Surgical Paddle Electrode Implantation as a Rescue Therapy to Failed Percutaneous Leads in Failed Back Surgery Syndrome Patients.

INTRODUCTION: Spinal cord stimulation (SCS) to treat failed back surgery syndrome (FBSS) can be provided with either percutaneously or surgically implanted electrodes. Percutaneous electrodes are considered the first choice in many pain practices, but surgical paddle electrodes can also be indicated if a percutaneous electrode fails to retain sufficient pain relief or if percutaneous implantation is considered unachievable. Although the current efficacy of surgical paddle electrodes has been based mainly upon pain intensity scores, the evidence on surgical paddle electrodes as a rescue to failed percutaneous electrodes remains even more scarce. OBJECTIVE: This study aimed to evaluate the safety and clinical effectiveness of rescue surgical paddle electrodes in FBSS patients, multidimensionally. MATERIALS AND METHODS: The occurrence of complications, pain intensity scores, psychosocial-related questionnaires, and medication intake were collected. Subsequently, a Quality-of-Life Index (QLI) was calculated. A clinically relevant effect was obtained if the minimal clinically important difference regarding pain intensity was reached. RESULTS: A total of 25 patients were included in the study. The pain intensity scores were significantly reduced (p < 0.001), and clinically relevant reductions occurred during short-term (0-6 months), mid-term (1-3 years), and long-term follow-up (≥4 years). The structural morphine usage and QLI were significantly decreased at short-term follow-up (p = 0.038 and p = 0.036, respectively). Six complications occurred in five patients, of which, four concerned hardware-related problems and two were of biological origin. CONCLUSION: SCS utilizing a surgical paddle electrode as a salvage treatment to failed conventional percutaneous cylindrical lead SCS can be practiced safely and effectively to treat FBSS. Because of potentially improved clinical effectiveness and cost-effectiveness resulting from fewer reoperations, a SCS treatment algorithm may benefit from expediting surgical paddle electrodes.

Experiences From the Patient Perspective on Spinal Cord Stimulation for Failed Back Surgery Syndrome: A Qualitatively Driven Mixed Method Analysis.

INTRODUCTION: When neither pharmacological therapies nor alternative interventions provide sufficient pain relief, spinal cord stimulation (SCS) can be used to treat Failed Back Surgery Syndrome (FBSS). Although it seems reasonable that quality of life (QoL)- and psychosocial-related factors contribute to the outcome of SCS since pain is a multidimensional experience, few qualitative studies have explored the expectations of SCS and experiences on SCS to treat FBSS from the patient perspective. OBJECTIVES: The aim of this study was to qualitatively and quantitatively map the FBSS patients' experiences with SCS and the effects of SCS on low back pain caused by FBSS. MATERIALS AND METHODS: A qualitative study with in-depth semi-structured interviews, assisted by the Brief Pain Inventory (BPI)-questionnaire. RESULTS: Seven themes regarding patients' experiences, subdivided into 15 categories, were identified, including an understudied theme within this field of research, Spiritual Well-Being. "Acceptance" and "coping" emerged as pre-eminent motifs throughout these themes. Moreover, the realization of patients' expectations were variable throughout the presented themes. According to the BPI Questionnaire, four out of 13 patients (31%) had significant pain relief (≥50%). Seven out of 13 (54%) reported a ≥50% increase regarding enjoyment of life. CONCLUSION: Multiple QoL- and psychosocial-related themes are related to SCS-outcomes. In order to improve SCS-outcomes for both short- and long-term, these themes should be implemented as a multidimensional approach, both prior to implantation as during follow-up.

Qualitative Evaluation of the Influence of Acute Oxaliplatin-Induced Peripheral Neuropathy on Quality of Life and Activities of Daily Life.

INTRODUCTION/AIMS: Oxaliplatin often causes acute or chronic peripheral neuropathy in patients with an intestinal or pancreatic tumor, but in-depth insights in its influence on quality of life (QoL) are lacking. We explored the influence of acute oxaliplatin-induced peripheral neuropathy (OIPN) on daily QoL in these patients. METHODS: We performed semistructured interviews with a purposive sample of patients receiving oxaliplatin and possibly experiencing acute OIPN. Interviews were audio-recorded, transcribed verbatim, and coded by two researchers. Data were analyzed by using the constant comparative method for content analysis with ATLAS.ti software. RESULTS: After nine patients, saturation took place. In total, 11 patients were interviewed. Four themes were extracted from the data: (1) adverse effects, (2) physical (un)well-being, (3) emotional aspects, and (4) treatment aspects. All participants were suffering from acute OIPN to a certain extent, leading to restrictions in daily activities such as household chores, but also to a decrease in mobility and independency. Other adverse effects such as general malaise and gastrointestinal side effects also influenced the participants' well-being, as did the diagnosis and prognosis of their disease. CONCLUSION: Acute OIPN, together with other side effects of chemotherapeutic treatment and the difficulties that come with the diagnosis of cancer and its prognosis, largely influences patients' daily QoL. Managing expectations (by patient education) seems important.

Decreased costs and retained QoL due to the 'PACE Steps to Success' intervention in LTCFs: cost-effectiveness analysis of a randomized controlled trial.

BACKGROUND: The number of residents in long-term care facilities (LTCFs) in need of palliative care is growing in the Western world. Therefore, it is foreseen that significantly higher percentages of budgets will be spent on palliative care. However, cost-effectiveness analyses of palliative care interventions in these settings are lacking. Therefore, the objective of this paper was to assess the cost-effectiveness of the 'PACE Steps to Success' intervention. PACE (Palliative Care for Older People) is a 1-year palliative care programme aiming at integrating general palliative care into day-to-day routines in LTCFs, throughout seven EU countries. METHODS: A cluster RCT was conducted. LTCFs were randomly assigned to intervention or usual care. LTCFs reported deaths of residents, about whom questionnaires were filled in retrospectively about resource use and quality of the last month of life. A health care perspective was adopted. Direct medical costs, QALYs based on the EQ-5D-5L and costs per quality increase measured with the QOD-LTC were outcome measures. RESULTS: Although outcomes on the EQ-5D-5L remained the same, a significant increase on the QOD-LTC (3.19 points, p value 0.00) and significant cost-savings were achieved in the intervention group (€983.28, p value 0.020). The cost reduction mainly resulted from decreased hospitalization-related costs (€919.51, p value 0.018). CONCLUSIONS: Costs decreased and QoL was retained due to the PACE Steps to Success intervention. Significant cost savings and improvement in quality of end of life (care) as measured with the QOD-LTC were achieved. A clinically relevant difference of almost 3 nights shorter hospitalizations in favour of the intervention group was found. This indicates that timely palliative care in the LTCF setting can prevent lengthy hospitalizations while retaining QoL. In line with earlier findings, we conclude that integrating general palliative care into daily routine in LTCFs can be cost-effective. TRIAL REGISTRATION: ISRCTN14741671 .

Invasive Motor Cortex Stimulation Influences Intracerebral Structures in Patients With Neuropathic Pain: An Activation Likelihood Estimation Meta-Analysis of Imaging Data.

OBJECTIVE: Invasive motor cortex stimulation (iMCS) has been proposed as a treatment for intractable neuropathic pain syndromes. Although the mechanisms underlying the analgesic effect of iMCS remain largely elusive, several studies found iMCS-related changes in regional cerebral blood flow (rCBF) in neuropathic pain patients. The aim of this study was to meta-analyze the findings of neuroimaging studies on rCBF changes to iMCS. METHODS: PubMed, Embase, MEDLINE, Google Scholar, and the Cochrane Library were systematically searched for retrieval of relevant scientific papers. After initial assessment of relevancy by screening title and abstract by two investigators, independently, predefined inclusion and exclusion criteria were used for final inclusion of papers. Descriptive results were statistically assessed, whereas coordinates were pooled and meta-analyzed in accordance with the activation likelihood estimation (ALE) methodology. RESULTS: Six studies were included in the systematic narrative analysis, suggesting rCBF increases in the cingulate gyrus, thalamus, insula, and putamen after switching the MCS device "ON" as compared to the "OFF" situation. Decreases in rCBF were found in for example the precentral gyrus and different occipital regions. Two studies did not report stereotactic coordinates and were excluded from further analysis. ALE meta-analysis showed that, after switching the iMCS electrode "ON," increased rCBF occurred in the (1) anterior cingulate gyrus; (2) putamen; (3) cerebral peduncle; (4) precentral gyrus; (5) superior frontal gyrus; (6) red nucleus; (7) internal part of the globus pallidus; (8) ventral lateral nucleus of the thalamus; (9) medial frontal gyrus; (10) inferior frontal gyrus; and (11) claustrum, as compared to the "OFF" situation. Reductions in rCBF were found in the posterior cingulate gyrus when the iMCS electrode was turned "OFF." CONCLUSIONS: These findings suggested that iMCS induces changes in principal components of the default mode-, the salience-, and sensorimotor network.

Cost-Effectiveness Analysis of Peripheral Nerve Field Stimulation as Add-On Therapy to Spinal Cord Stimulation in the Treatment of Chronic Low Back Pain in Failed Back Surgery Syndrome Patients.

OBJECTIVE: Presently, there is only limited evidence about the cost-effectiveness of peripheral nerve field stimulation (PNFS) and no evidence to date on the cost-effectiveness of PNFS as an add-on therapy to spinal cord stimulation (SCS). In a multicenter randomized controlled trial, PNFS as add-on therapy to SCS demonstrated clinical effectiveness in treating chronic low back pain in failed back surgery syndrome (FBSS) patients. We report here the cost-effectiveness of PNFS as additional therapy. MATERIALS AND METHODS: Cost-effectiveness analysis was performed from a health-care perspective using the general principles of cost-utility analysis, using empirical data from our multicenter randomized controlled trial on the effectiveness of hybrid SCS + PNFS on low back pain in FBSS patients, who were back pain non-responders to initial SCS-therapy, over a time-horizon of three months. Outcome measures were costs and quality-adjusted life-years (QALYs). Cost and QALYs were integrated using the net monetary benefit (NMB). Differences in costs, effects, and NMB were analyzed using multilevel regression. Uncertainty surrounding the NMB was presented by cost-effectiveness acceptability curves. RESULTS: A total of 52 patients implanted with both SCS and PNFS, randomly assigned to a group with PNFS either activated or inactive, completed the controlled part of the study. With mean total costs for the SCS + active PNFS group of €1813.86 (SD €109.78) versus €1103.64 (SD €123.43) for the SCS + inactive PNFS group at three months, we found an incremental cost-utility ratio of €25.311 per QALY gained and a probability being cost-effective of more than 80% given a willingness to pay for a QALY of about €40.000. CONCLUSIONS: From a Dutch national health-care context, when the willingness to pay threshold is up to 60.000 Euros per QALY, PNFS as an add-on therapy to SCS for the treatment of low back pain in FBSS patients has a high probability of being cost-effective.

Peripheral Nerve Field Stimulation for Chronic Back Pain: Therapy Outcome Predictive Factors.

OBJECTIVE: To identify variables that influence pain reduction following peripheral nerve field stimulation (PNFS) in order to identify a potential responder profile. METHODS: Exploratory univariate and multivariate (random forest) analyses were performed separately on 2 randomized controlled trials and a registry; all included patients with chronic back pain, mainly failed back surgery syndrome. An international expert panel judged the clinical relevance of variables to identify responders by consensus. RESULTS: Variables identified that may help predict PNFS success in patients with back pain include patient and pain characteristics (age, time since onset of pain and spinal surgery, pain medication history, position and size of pain area, pain severity, mixed nociceptive/neuropathic pain, health-related quality of life, depression, functional disability, and leg pain status), implant procedure variables (the number and position of leads, paresthesia coverage, and amount of pain relief during the trial), and programming (number of programs, cathodes, and anodes; pulse rate; pulse width; and percentage of device usage). CONCLUSIONS: While these analyses are exploratory and restricted to a limited sample size, they suggest variables that may play a role in predicting a therapeutic response. These results, however, are informative only and should be cautiously interpreted. Future research to validate the variables in a clinical study is needed.

Relationship Between Postoperative Pain and Overall 30-Day Complications in a Broad Surgical Population: An Observational Study.

OBJECTIVE: The aim of this study was to establish the relationship between postoperative pain and 30-day postoperative complications. BACKGROUND: Only scarce data are available on the association between postoperative pain and a broad range of postoperative complications in a large heterogeneous surgical population. METHODS: Having postoperative pain was assessed in 2 ways: the movement-evoked pain score on the Numerical Rating Scale (NRS-MEP) and the patients' opinion whether the pain was acceptable or not. Outcome was the presence of a complication within 30 days after surgery. We used binary logistic regression for the total population and homogeneous subgroups to control for case complexity. Results for homogeneous subgroups were summarized in a meta-analysis using inverse variance weighting. RESULTS: In 1014 patients, 55% experienced moderate-to-severe pain on the first postoperative day. The overall complication rate was 34%. The proportion of patients experiencing postoperative complications increased from 0.25 [95% confidence interval (CI) = 0.21-0.31] for NRS-MEP = 0 to 0.45 (95% CI = 0.36-0.55) for NRS-MEP = 10. Patients who found their pain unacceptable had more complications (adjusted odds ratio = 2.17 (95% CI = 1.51-3.10; P < 0.001)). Summary effect sizes obtained with homogeneous groups were similar to those obtained from the total population who underwent very different types of surgery. CONCLUSIONS: Higher actual postoperative pain scores and unacceptable pain, even on the first postoperative day, are associated with more postoperative complications. Our findings provide important support for the centrality of personalized analgesia in modern perioperative care.

Unpredictable Injectate Spread of the Erector Spinae Plane Block in Human Cadavers.

We performed bilateral ultrasound-guided erector spinae plane blocks at the second and eighth thoracic vertebrae in 11 fresh frozen cadavers. Methylene blue dye spread variably and extensively deep to the erector spinae muscles fascia with involvement of the spinal rami and paravertebral space in 1 of 11 cadavers when injected at the eighth thoracic vertebra, and in 4 of 11 cadavers at the second thoracic vertebra, with crossover to the contralateral side of the spine. Our study demonstrates that in cadavers, an erector spinae plane block follows the fascial planes with unpredictable spread, which might explain its varying clinical efficacy.

Long-Term Effect of Peripheral Nerve Field Stimulation as Add-On Therapy to Spinal Cord Stimulation to Treat Low Back Pain in Failed Back Surgery Syndrome Patients: A 12-Month Follow-Up of a Randomized Controlled Study.

OBJECTIVE: Different approaches in neuromodulation have been used to treat chronic low back pain in failed back surgery syndrome (FBSS) patients. We previously randomized 52 FBSS patients to be treated with spinal cord stimulation (SCS) and additional peripheral nerve field stimulation (PNFS) or SCS alone. At three months, we found a significant reduction of back pain in the PNFS-SCS group compared to the SCS group. In the subsequent open phase part of the study, all patients received optimal SCS and PNFS simultaneously. Here, we present the 12-month follow-up data on back and leg pain. MATERIALS AND METHODS: Data regarding back and leg pain, function, quality of life, patient satisfaction, anxiety and depression, and use of medication were collected by analyzing patients' questionnaires at 12 months and compared with data collected at baseline. Data were analyzed using multilevel regression models. RESULTS: A combined group of 50 subjects completed the 12-month follow-up. Back pain, measured on a 100-mm visual analog scale (VAS), significantly decreased over this period by 30.0 mm (95% CI: [-37.7/-22.4]; p < 0.001), while leg pain decreased by 43.7 mm (95% CI: [-51.5/-36.2]; p < 0.001). We observed statistically significant improvement in almost all secondary outcome measurements. CONCLUSIONS: At 12-month follow-up, PNFS in addition to SCS continues to provide a statistically significant and clinically relevant relief of low back pain in FBSS patients in whom SCS alone is effective for relief of leg pain only.

Avoiding Catch-22: validating the PainDETECT in a in a population of patients with chronic pain.

BACKGROUND: Neuropathic pain is defined as pain caused by a lesion or disease of the somatosensory nervous system and is a major therapeutic challenge. Several screening tools have been developed to help physicians detect patients with neuropathic pain. These have typically been validated in populations pre-stratified for neuropathic pain, leading to a so called "Catch-22 situation:" "a problematic situation for which the only solution is denied by a circumstance inherent in the problem or by a rule". The validity of screening tools needs to be proven in patients with pain who were not pre-stratified on basis of the target outcome: neuropathic pain or non-neuropathic pain. This study aims to assess the validity of the Dutch PainDETECT (PainDETECT-Dlv) in a large population of patients with chronic pain. METHODS: A cross-sectional multicentre design was used to assess PainDETECT-Dlv validity. Included where patients with low back pain radiating into the leg(s), patients with neck-shoulder-arm pain and patients with pain due to a suspected peripheral nerve damage. Patients' pain was classified as having a neuropathic pain component (yes/no) by two experienced physicians ("gold standard"). Physician opinion based on the Grading System was a secondary comparison. RESULTS: In total, 291 patients were included. Primary analysis was done on patients where both physicians agreed upon the pain classification (n = 228). Compared to the physician's classification, PainDETECT-Dlv had a sensitivity of 80% and specificity of 55%, versus the Grading System it achieved 74 and 46%. CONCLUSION: Despite its internal consistency and test-retest reliability the PainDETECT-Dlv is not an effective screening tool for a neuropathic pain component in a population of patients with chronic pain because of its moderate sensitivity and low specificity. Moreover, the indiscriminate use of the PainDETECT-Dlv as a surrogate for clinical assessment should be avoided in daily clinical practice as well as in (clinical-) research. Catch-22 situations in the validation of screening tools can be prevented by not pre-stratifying the patients on basis of the target outcome before inclusion in a validation study for screening instruments. TRIAL REGISTRATION: The protocol was registered prospectively in the Dutch National Trial Register: NTR 3030 .

Tetrahydrocannabinol Does Not Reduce Pain in Patients With Chronic Abdominal Pain in a Phase 2 Placebo-controlled Study.

BACKGROUND & AIMS: Delta-9-tetrahydrocannabinol (THC) is the most abundant cannabinoid from the plant Cannabis sativa. There is only equivocal evidence that THC has analgesic effects. We performed a phase 2 controlled trial to evaluate the analgesic efficacy, pharmacokinetics, safety, and tolerability of an oral tablet containing purified THC in patients with chronic abdominal pain. METHODS: Sixty-five patients with chronic abdominal pain for 3 months or more (numeric rating scale scores of 3 or more) after surgery or because of chronic pancreatitis were randomly assigned to groups given the THC tablet or identical matching placebos for 50-52 days. Subjects in the THC group were given the tablet first in a step-up phase (3 mg 3 times daily for 5 days and then 5 mg 3 times daily for 5 days), followed by a stable dose phase (8 mg 3 times daily until days 50-52). Preceding and during the entire study period, patients were asked to continue taking their medications (including analgesics) according to prescription. Patients reported any additional pain medications in a diary. Efficacy and safety assessments were conducted preceding medication intake (day 1), after 15 days, and at 50-52 days. Plasma samples were collected on study days 1, 15, and 50-52; mean plasma concentration curves of THC and 11-OH-THC were plotted. The primary end point was pain relief, which was measured by a visual analogue scale (VAS) of the mean pain (VAS mean scores) on the basis of information from patient diaries. Secondary end points included pain and quality of life (determined from patient questionnaires), pharmacokinetics, and safety. RESULTS: At days 50-52, VAS mean scores did not differ significantly between the THC and placebo groups (F1,46 = 0.016; P = .901). Between the start and end of the study, VAS mean scores decreased by 1.6 points (40%) in the THC group compared with 1.9 points (37%) in the placebo group. No differences were observed in secondary outcomes. Oral THC was generally well-absorbed. Seven patients in the THC group stopped taking the tablets because of adverse events, compared with 2 patients in the placebo group. All (possibly) related adverse events were mild or moderate. CONCLUSIONS: In a phase 2 study, we found no difference between a THC tablet and a placebo tablet in reducing pain measures in patients with chronic abdominal pain. THC, administered 3 times daily, was safe and well-tolerated during a 50-day to 52-day treatment period. ClinicalTrials.gov number: NCT01562483 and NCT01551511.