Electrophysiological properties of dorsal root ganglion neurons cultured on 3D silicon micro-pillar substrates.

BACKGROUND: Silicon-based micro-pillar substrates (MPS), as three-dimensional cell culture platforms with vertically aligned micro-patterned scaffolding structures, are known to facilitate high-quality growth and morphology of dorsal root ganglion (DRG) sensory neurons, promote neurite outgrowth and enhance neurite alignment. However, the electrophysiological aspects of DRG neurons cultured on silicon MPSs have not been thoroughly investigated, which is of greatest importance to ensure that such substrates do not disrupt neuronal homeostasis and function before their widespread adoption in diverse biomedical applications. NEW METHOD: We conducted whole-cell patch-clamp recordings to explore the electrophysiological properties of DRG neurons cultured on MPS arrays, utilizing a custom-made upright patch-clamp setup. RESULTS: Our findings revealed that DRG neurons exhibited similar electrophysiological responses on patterned MPS samples when compared to the control planar glass surfaces. Notably, there were no significant differences observed in the action potential parameters or firing patterns of action potentials between neurons grown on either substrate. COMPARISON WITH EXISTING METHODS: In the current study we for the first time confirmed that successful electrophysiological recordings can be obtained from the cells grown on MPS. CONCLUSION: Our results imply that, despite the potential alterations caused by the cumulative trauma of tissue harvest and cell dissociation, essential functional cell properties of DRG neurons appear to be relatively maintained on MPS surfaces. Therefore, vertically aligned silicon MPSs could be considered as a potentially effective three-dimensional system for supporting a controlled cellular environment in culture.

Conclusiveness, linguistic characteristics and readability of Cochrane plain language summaries of intervention reviews: a cross-sectional study.

BACKGROUND: One of the most important formats to disseminate the evidence in health to different populations are Cochrane Plain Language Summaries (PLSs). PLSs should be written in a simplified language, easily understandable and providing clear message for the consumer. The aim of this study was to examine the extent to which PLSs are customized for lay persons, specifically by providing conclusive, comprehensible, and readable messages. METHODS: The study analyzed Cochrane PLSs of interventional studies (N = 4360) in the English language published from 1995 to 2019. We categorized the conclusiveness into one of the following categories: "positive", "positive inconclusive", "no evidence", "no opinion", "negative", "negative inconclusive", "unclear", "equal", "equal inconclusive". Language characteristics were analyzed using Linguistic Inquiry and Word Count (LIWC) software. The level of readability was measured by SMOG (Simple Measure of Gobbledygook) index, indicating the number of years of education required to read the text. For each PLS, we also collected the following data: Cochrane Review Network, year of publication and number of authors. RESULTS: Most of the PLSs (80%) did not have a conclusive message. In 53% PLSs there was no concluding opinion about the studied intervention or the conclusion was unclear. The most frequent conclusiveness category was "no opinion" (30%), and its frequency increased over time. The conclusiveness categories were similarly dispersed across Cochrane Networks. PLSs were written in an objective style, with high levels of analytical tone and clout above neutral, but a lower relation to authenticity and tone. The median number of years of non-specific education needed to read the PLSs was 14.9 (IQR 13.8 to 16.1), indicating that the person needs almost 15 years of general education to read the content with ease. CONCLUSION: Most of the Cochrane PLSs provided no concluding opinion or unclear conclusion regarding the effects of analyzed intervention. Analysis of readability indicated that they may be difficult to read for the lay population without medical education. Our results indicate that PLSs may not be so plain, and that the writing of Cochrane PLSs requires more effort. Tools used in this study could improve PLSs and make them better suited for lay audiences.

Implantable, Programmable, and Wireless Device for Electrical Stimulation of the Dorsal Root Ganglion in Freely-Moving Rats: A Proof of Concept Study.

OBJECTIVE: This was a proof of concept study, based on systematic reviews of the efficacy and safety of the dorsal root ganglion (DRG) stimulation. The main objective was to develop an implantable, programmable, and wireless device for electrical stimulation of DRG and a methodology that can be used in translational research, especially to understand the mechanism of neuromodulation and to test new treatment modalities in animal models of pain. METHODS: We developed and tested a stimulator that uses a battery-powered microelectronic circuit, to generate constant current square biphasic or monophasic pulsed waveform of variable amplitudes and duration. It is controlled by software and an external controller that allows radio frequency communication with the stimulator. The stimulator was implanted in Sprague-Dawley (SD) rats. The lead was positioned at the L5 DRG level, while the stimulator was placed in the skin pocket at the ipsilateral side. Forty-five animals were used and divided into six groups: spinal nerve ligation (SNL), chronic compression injury of the DRG (CCD), SNL + active DRG stimulation, intact control group, group with the implanted sham stimulator, and sham lead. Behavioral testing was performed on the day preceding surgery and three times postoperatively (1st, 3rd, and 7th day). RESULTS: In animals with SNL, neurostimulation reduced pain-related behavior, tested with pinprick hyperalgesia, pinprick withdrawal test, and cold test, while the leads per se did not cause DRG compression. The rats well tolerated the stimulator. It did not hinder animal movement, and it enabled the animals to be housed under regular conditions. CONCLUSION: A proof-of-concept experiment with our stimulator verified the usability of the device. The stimulator enables a wide range of research applications from adjusting stimulation parameters for different pain conditions, studying new stimulation methods with different frequencies and waveforms to obtain knowledge about analgesic mechanisms of DRG stimulation.

Reasons and factors associated with inconclusiveness of systematic reviews about interventions for neuropathic pain.

Aim: Systematic reviews (SRs) are frequently inconclusive. The aim of this study was to analyze factors associated with conclusiveness of SRs about efficacy and safety of interventions for neuropathic pain (NeuP). Materials & methods: The study protocol was registered in the PROSPERO database (No. CRD42015025831). Five electronic databases (Medical Literature Analysis and Retrieval System Online, Cochrane Database of Systematic Reviews, Cumulative Index for Nursing and Allied Health Literature, Database of Abstracts of Reviews of Effects and Psychological Information Database) were searched until July 2018 for SRs about NeuP management. Conclusion statements for efficacy and safety, and characteristics of SRs were analyzed. Conclusiveness was defined as explicit statement by the SR authors that one intervention is better/similar to the other in terms of efficacy and safety. Methodological quality of SRs was assessed with the AMSTAR (A MeaSurement Tool to Assess systematic Reviews) tool. Results: Of 160 SRs, 37 (23%) were conclusive for efficacy and/or safety. In the SRs, conclusions about safety were missing in half of the analyzed abstracts, and a third of the full texts. Conclusive SRs included significantly more trials and participants, searched more databases, had more authors, conducted meta-analysis, analyzed quality of evidence, and had lower methodological quality than inconclusive SRs. The most common reasons for the lack of conclusiveness indicated by the SR authors were the small number of participants and trials, and the high heterogeneity of included studies. Conclusion: Most SRs about NeuP treatment were inconclusive. Sources of inconclusiveness of NeuP reviews need to be further studied, and SR authors need to provide conclusions about both safety and efficacy of interventions.

Adequacy of risk of bias assessment in surgical vs non-surgical trials in Cochrane reviews: a methodological study.

BACKGROUND: Bias in randomized controlled trials (RCTs) can lead to underestimation or overestimation of the true effects of interventions. Surgical RCTs may suffer from the risk of bias (RoB) that is avoidable in trials of other interventions, and vice versa. We aimed to compare the adequacy of RoB assessments in surgical versus non-surgical RCTs included in Cochrane reviews and to assess the most common differences in those RoB assessments. Due to specificities of surgical trials, i.e. difficulties associated with blinding of surgical interventions, we hypothesized that assessments of surgical trials may be more adequate, compared to RCTs of non-surgical interventions. METHODS: This was a methodological study, analyzing methods of published Cochrane systematic reviews. Data were extracted from RoB tables in Cochrane reviews (judgments and accompanying explanatory comment) for the following four RoB domains used in the 2011 Cochrane RoB tool: randomization, allocation concealment, blinding of participants and personnel, and blinding of outcome assessors. We defined adequate assessments as those that were in line with instructions from the Cochrane Handbook for Systematic Reviews of Interventions. The prevalence of adequate assessments was compared in surgical versus non-surgical trials. The most common differences in both groups of reviews were presented. RESULTS: In 729 analyzed Cochrane reviews, there were 10,537 included trials. The prevalence of adequate RoB judgments made by Cochrane authors ranged from 87.9, 95%CI (87.3 to 88.6%) for randomization to 70.7, 95%CI (69.8 to 71.5%) for blinding of participants and personnel. For all analyzed RoB domains, the prevalence of adequate RoB domains was higher in surgical trials than in non-surgical trials. For two RoB domains assessing blinding, this difference between surgical and non-surgical trials was statistically significant (P < 0.001), while the difference was not significant for the RoB domain regarding randomization (P = 0.124) and allocation concealment (P = 0.039, ß < 0.8). CONCLUSIONS: RoB judgments were more in line with instructions from the Cochrane Handbook when Cochrane reviews assessed surgical trials, compared to those that analyzed non-surgical interventions. However, further steps are warranted to scrutinize RoB assessment in trials of both surgical and non-surgical interventions.

Efficacy and Safety of Pulsed Radiofrequency as a Method of Dorsal Root Ganglia Stimulation in Patients with Neuropathic Pain: A Systematic Review.

OBJECTIVE: Pulsed radiofrequency (PRF) is a nonablative pain treatment that uses radiofrequency current in short high-voltage bursts, resulting in interruption of nociceptive afferent pathways. We conducted a systematic review with the aim to create a synthesis of evidence about the efficacy and safety of PRF applied to the dorsal root ganglion (DRG) for the treatment of neuropathic pain. METHODS: We searched MEDLINE, CINAHL, Embase, and PsycINFO through January 8, 2019, as well as ClinicalTrials.gov and the clinical trial register of the World Health Organization. All study designs were eligible. We assessed risk of bias using the Cochrane tool for randomized controlled trials and the Risk Of Bias In Non-Randomized Studies of Interventions (ROBINS-I). We assessed level of evidence using the Oxford tool and quality of evidence with GRADE. RESULTS: We included 28 studies with participants suffering from lumbosacral, cervical, or thoracic radicular pain, post-herpetic neuralgia, neuropathicbone pain in cancer patients, or carpal tunnel syndrome. Only five studies were randomized controlled trials (RCTs), while others were of nonrandomized designs, predominantly before and after comparisons. A total of 991 participants were included, with a median number (range) of 31 (1-101) participants. Only 204 participants were included in the RCTs, with a median number (range) of 38 (23-62) participants. The overall quality of evidence was low, as the majority of the included studies were rated as evidence level 4 or 5. The quality of evidence was very low. CONCLUSIONS: Evidence about the efficacy and safety of PRF of the DRG for the treatment of neuropathic pain is based mainly on results from very small studies with low evidence quality. Current research results about the benefits of PRF of the DRG for the treatment of neuropathic pain should be considered preliminary and confirmed in high-quality RCTs with sufficient numbers of participants.

Efficacy and safety of pulsed radiofrequency as a method of dorsal root ganglia stimulation for treatment of non-neuropathic pain: a systematic review.

BACKGROUND: We systematically reviewed the evidence on the efficacy and safety of dorsal root ganglion (DRG) targeted pulsed radiofrequency (PRF) versus any comparator for treatment of non-neuropathic pain. METHODS: We searched MEDLINE, CINAHL, Embase, PsycINFO, clinicaltrials.gov and WHO clinical trial register until January 8, 2019. All study designs were eligible. Two authors independently conducted literature screening. Primary outcomes were pain intensity and serious adverse events (SAEs). Secondary outcomes were any other pain-related outcome and any other safety outcome that was reported. We assessed the risk of bias using the Cochrane tool and Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I). We conducted narrative evidence synthesis and assessed the conclusiveness of included studies regarding efficacy and safety. RESULTS: We included 17 studies with 599 participants, which analyzed various pain syndromes. Two studies were randomized controlled trials; both included participants with low back pain (LBP). Non-randomized studies included patients with the following indications: LBP, postsurgical pain, pain associated with herpes zoster, cervicogenic headache, complex regional pain syndrome type 1, intractable vertebral metastatic pain, chronic scrotal and inguinal pain, occipital radiating pain in rheumatoid arthritis and chronic migraine. In these studies, the PRF was usually initiated after other treatments have failed. Eleven studies had positive conclusive statements (11/17) about efficacy; the remaining had positive inconclusive statements. Only three studies provided conclusiveness of evidence statements regarding safety - two indicated that the evidence was positive conclusive, and one positive inconclusive. The risk of bias was predominantly unclear in randomized and serious in non-randomized studies. CONCLUSION: Poor quality and few participants characterize evidence about benefits and harms of DRG PRF in patients with non-neuropathic pain. Results from available studies should only be considered preliminary. Not all studies have reported data regarding the safety of the intervention, but those that did, indicate that the intervention is relatively safe. As the procedure is non-destructive and early results are promising, further comparative studies about PRF in non-neuropathic pain syndromes would be welcomed.

Overall bias methods and their use in sensitivity analysis of Cochrane reviews were not consistent.

OBJECTIVE: The objective of the study was to analyze methods of assessing "overall bias" in Cochrane reviews of interventions published in the Cochrane Database of Systematic Reviews and sensitivity analyses related to overall risk of bias (RoB). STUDY DESIGN AND SETTING: From Cochrane reviews published within 3 years, from July 2015 to June 2018, we extracted data regarding methods of judging overall bias for a single trial, as well as details regarding methods used in frequency of RoB in sensitivity analyses. RESULTS: Of the 1,452 analyzed Cochrane reviews, 409 mentioned assessment of overall RoB on a study level. In 107 reviews, authors clearly specified key domains that determined the overall RoB, whereas in the remaining reviews, assessment of overall bias was not in line with the Cochrane Handbook. Among 268 Cochrane reviews that had any RoB-related sensitivity analysis, in 56 (21%) reviews, the authors reported a significant change for at least one outcome compared with the initial analysis. CONCLUSION: Highly heterogeneous approaches to summarizing overall RoB on a study level and using RoB for sensitivity analyses may yield inconsistent and incomparable results across Cochrane reviews.

Risk of bias judgments for random sequence generation in Cochrane systematic reviews were frequently not in line with Cochrane Handbook.

BACKGROUND: Assessing the risk of bias (RoB) in included studies is one of the key methodological aspects of systematic reviews. Cochrane systematic reviews appraise RoB of randomised controlled trials (RCTs) with the Cochrane RoB tool. Detailed instructions for using the Cochrane RoB tool are provided in the Cochrane Handbook for Systematic Reviews of Interventions (The Cochrane Handbook). The purpose of this study was to analyse whether Cochrane authors use adequate judgments about the RoB for random sequence generation of RCTs included in Cochrane reviews. METHODS: We extracted authors' judgments (high, low or unclear RoB) and supports for judgments (comments accompanying judgments which explain the rationale for a judgment) for random sequence generation of included RCTs from RoB tables of Cochrane reviews using automated data scraping. We categorised all supporting comments, analysed the number and type of various supporting comments and assessed adequacy of RoB judgment for randomisation in line with recommendations from the Cochrane Handbook. RESULTS: We analysed 10,103 RCTs that were included in 704 Cochrane reviews. For 5,706 RCTs, randomisation was not described, but for the remaining RCTs, it was indicated that randomisation was performed using computer/software/internet (N = 2,850), random number table (N = 883), mechanical method (N = 359) or it was incomplete/inappropriate (N = 305). Overall, 1,220/10,103 trials (12%) did not have a RoB judgment in line with Cochrane Handbook guidance about randomisation. The highest proportion of misjudgements was found for trials with high RoB (28%), followed by those with low (20%) or unclear (3%). Therefore, one in eight judgments for the analysed domain in Cochrane reviews was not in line with Cochrane Handbook, and one in four if the judgment was "high risk". CONCLUSION: Authors of Cochrane reviews often make judgments about the RoB related to random sequence generation that are not in line with instructions given in the Cochrane Handbook, which compromises the reliability of the systematic reviews. Our results can help authors of both Cochrane and non-Cochrane reviews which use Cochrane RoB tool to avoid making common mistakes when assessing RoB in included trials.

Assessments of attrition bias in Cochrane systematic reviews are highly inconsistent and thus hindering trial comparability.

BACKGROUND: An important part of the systematic review methodology is appraisal of the risk of bias in included studies. Cochrane systematic reviews are considered golden standard regarding systematic review methodology, but Cochrane's instructions for assessing risk of attrition bias are vague, which may lead to inconsistencies in authors' assessments. The aim of this study was to analyze consistency of judgments and support for judgments of attrition bias in Cochrane reviews of interventions published in the Cochrane Database of Systematic Reviews (CDSR). METHODS: We analyzed Cochrane reviews published from July 2015 to June 2016 in the CDSR. We extracted data on number of included trials, judgment of attrition risk of bias for each included trial (low, unclear or high) and accompanying support for the judgment (supporting explanation). We also assessed how many Cochrane reviews had different judgments for the same supporting explanations. RESULTS: In the main analysis we included 10,292 judgments and supporting explanations for attrition bias from 729 Cochrane reviews. We categorized supporting explanations for those judgments into four categories and we found that most of the supporting explanations were unclear. Numerical indicators for percent of attrition, as well as statistics related to attrition were judged very differently. One third of Cochrane review authors had more than one category of supporting explanation; some had up to four different categories. Inconsistencies were found even with the number of judgments, names of risk of bias domains and different judgments for the same supporting explanations in the same Cochrane review. CONCLUSION: We found very high inconsistency in methods of appraising risk of attrition bias in recent Cochrane reviews. Systematic review authors need clear guidance about different categories they should assess and judgments for those explanations. Clear instructions about appraising risk of attrition bias will improve reliability of the Cochrane's risk of bias tool, help authors in making decisions about risk of bias and help in making reliable decisions in healthcare.

Neuromodulation with electrical field stimulation of dorsal root ganglion in various pain syndromes: a systematic review with focus on participant selection.

OBJECTIVE: We conducted a systematic review about patient selection, efficacy, and safety of neuromodulation with electrical field stimulation (EFS) of dorsal root ganglion (DRG) in various painful conditions. We also analyzed conclusion statements as well as conflict of interest and financing of the included studies. METHODS: All study designs were eligible for inclusion. We searched MEDLINE, CINAHL, Embase, PsycINFO, and clinical trial registries until September 7, 2018. We assessed risk of bias by using Cochrane tool for randomized controlled trials (RCTs). RESULTS: Among the 29 included studies, only one was RCT, majority being case series and case reports. The evidence is based on studies with small number of participants (median: 6, range 1-152) with various painful conditions. Neuromodulation with EFS of DRG was mostly performed in participants who have failed other treatment modalities. Most of the authors of the included studies reported positive, but inconclusive, evidence regarding efficacy of neuro-modulation with EFS of DRG. Meta-analysis was not possible since only one RCT was included. CONCLUSION: Available evidence suggest that neuromodulation with EFS of DRG may help highly selected participants with various pain syndromes, who have failed to achieve adequate pain relief with other pharmacological and nonpharmacological interventions. However, these findings should be confirmed in high-quality RCTs with sufficient numbers of participants.

In Cochrane reviews, risk of bias assessments for allocation concealment were frequently not in line with Cochrane's Handbook guidance.

OBJECTIVES: The aim of the article was to analyze whether the risk of bias (RoB) judgments for allocation concealment in Cochrane systematic reviews (CSRs) were in line with recommendations from the Cochrane Handbook. STUDY DESIGN AND SETTING: From CSR, we extracted data about judgments and supporting comments about allocation concealment for each included randomized controlled trial (RCT). We compared whether judgments for supporting comments were in line with Cochrane Handbook recommendations. RESULTS: We analyzed judgments and comments of 721 CSRs in which 10,280 RCTs were included. By following the Cochrane Handbook guidance, we found that judgments for allocation concealment were discrepant for 2,928 trials (29%). Most discrepancies were made for trials where RoB was judged as low (2,693 trials; 92%). Cochrane authors used 66 categories of comments describing envelopes as a method of allocation concealment. In 66 envelope-related categories, describing RoB assessments from 1,529 (15%) of the analyzed RCTs, most of the judgments were low RoB, although only one of those categories is associated with low RoB according to the Cochrane Handbook. Twenty categories of supporting comments, including 642 trials, were related to randomization, not allocation concealment. CONCLUSION: One-third of RoB judgments about allocation concealment in Cochrane reviews were discrepant from the Cochrane Handbook recommendations.

Electrical Stimulation of Dorsal Root Ganglion in the Context of Pain: A Systematic Review of In Vitro and In Vivo Animal Model Studies.

OBJECTIVE: Dorsal root ganglion (DRG) has recently emerged as an attractive target for neuromodulation therapy since primary sensory neurons and their soma in DRGs are important sites for pathophysiologic changes that lead to neuropathic pain. Our aim was to create evidence synthesis about the effects of electrical stimulation of DRG in the context of pain from in vitro and in vivo animal models, analyze methodology and quality of studies in the field. METHODS: For conducting systematic review we searched three data bases: MEDLINE, Embase and Web of Science. The quality of included studies was assessed with the Systematic Review Centre for Laboratory Animal Experimentation risk of bias tool for animal studies. The study was registered in the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies data base. RESULTS: We included six in vitro and eight in vivo animal studies. All included in vitro studies combined neurostimulation with substances or drugs and reported an improvement in pain-related parameters due to neurostimulation. Among in vivo studies, six used pulsed radiofrequency, while two used electrical field stimulation. All in vivo studies reported improvement in pain-related behavior following stimulation. Meta-analysis was not possible because of heterogeneity and missing data. The quality of included studies was suboptimal since all had an unclear risk of bias in multiple domains. CONCLUSIONS: Limited data from in vitro and in vivo animal studies indicate that electrical stimulation of DRG has a positive therapeutic effect in the context of pain-related outcomes. Further studies with a standardized methodological approach and outcomes will provide useful information about electrical stimulation of DRG in animal models.