Browsing by Author "Madden, Victoria J"

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    Open Access
    A systematic review of experimental methods to manipulate secondary hyperalgesia in humans: protocol
    (2019-08-19) Madden, Victoria J; Bedwell, Gillian J; Chikezie, Prince C; Rice, Andrew S C; Kamerman, Peter R
    Abstract Background Neuropathic pain affects 7–10% of people, but responds poorly to pharmacotherapy, indicating a need for better treatments. Mechanistic research on neuropathic pain frequently uses human surrogate models of the secondary hyperalgesia that is a common feature of neuropathic pain. Experimentally induced secondary hyperalgesia has been manipulated with pharmacological and non-pharmacological methods to clarify the relative contributions of different mechanisms to secondary hyperalgesia. However, this literature has not been systematically synthesised. The aim of this systematic review is to identify, describe, and compare methods that have been used to manipulate experimentally induced secondary hyperalgesia in healthy humans. Methods A systematic search strategy will be supplemented by reference list checks and direct contact with identified laboratories to maximise the identification of data reporting the experimental manipulation of experimentally induced secondary hyperalgesia in healthy humans. Duplicated screening, risk of bias assessment, and data extraction procedures will be used. Authors will be asked to provide data as necessary. Data will be pooled and meta-analyses conducted where possible, with subgrouping according to manipulation method. Manipulation methods will be ranked for potency and risk. Discussion The results of this review will provide a useful reference for researchers interested in using experimental methods to manipulate secondary hyperalgesia in humans and will help to clarify the relative contributions of different mechanisms to secondary hyperalgesia. Systematic review registration This protocol will be registered on PROSPERO before the review begins. Review records will be updated on PROSPERO once the review is complete. This review is intended for publication in a peer-reviewed journal. Analyses and scripts will be made publicly available.
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    The prevalence and risk factors for phantom limb pain in people with amputations: A systematic review and meta-analysis
    (2020-10-14) Limakatso, Katleho; Bedwell, Gillian J; Madden, Victoria J; Parker, Romy
    Background: Phantom limb pain (PLP)-pain felt in the amputated limb-is often accompanied by significant suffering. Estimates of the burden of PLP have provided conflicting data. To obtain a robust estimate of the burden of PLP, we gathered and critically appraised the literature on the prevalence and risk factors associated with PLP in people with limb amputations. Methods: Articles published between 1980 and July 2019 were identified through a systematic search of the following electronic databases: MEDLINE/PubMed, PsycINFO, PsycArticles, Cumulative Index to Nursing and Allied Health Literature, Africa-Wide Information, Health Source: Nursing/Academic Edition, SCOPUS, Web of Science and Academic Search Premier. Grey literature was searched on databases for preprints. Two reviewers independently conducted the screening of articles, data extraction and risk of bias assessment. The meta-analyses were conducted using the random effects model. A statistically significant level for the analyses was set at p<0.05. Results: The pooling of all studies demonstrated a prevalence estimate of 64% [95% CI: 60.01-68.05] with high heterogeneity [I2 = 95.95% (95% CI: 95.10-96.60)]. The prevalence of PLP was significantly lower in developing countries compared to developed countries [53.98% vs 66.55%; p = 0.03]. Persistent pre-operative pain, proximal site of amputation, stump pain, lower limb amputation and phantom sensations were identified as risk factors for PLP. Conclusion: This systematic review and meta-analysis estimates that six of every 10 people with an amputation report PLP-a high and important prevalence of PLP. Healthcare professionals ought to be aware of the high rates of PLP and implement strategies to reduce PLP by addressing known risk factors, specifically those identified by the current study.
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    The effect of stimulus threat on experimentally induced secondary hyperalgesia
    (2020) Bedwell, Gillian Jennifer; Madden, Victoria J; Parker, Romy
    Background Neuropathic pain affects 7 – 10% of people and responds poorly to pharmacotherapy. Numbers needed to treat for first line drugs range from 4 – 8. Therefore, there is an obvious need for improved understanding of the mechanisms of neuropathic pain to inform improved treatments. Mechanistic research on neuropathic pain frequently uses a human surrogate model of secondary hyperalgesia that is a common feature of neuropathic pain. The value of experimentally inducing secondary hyperalgesia is that one can then test the influence of different pharmacological and nonpharmacological interventions. This may shed some light on the physiological mechanisms within the spinal cord, which possibly also translates to the effects of the interventions on other pathways that are involved in processing signals that may be related to pain. Additionally, pain is known to be influenced by the threat value of the situation. Many South Africans live under constant threat: less than a third of South Africans feel safe walking alone at night. This constant threat may be perpetuating the pain problem in South Arica. However, the mechanism by which threat achieves this influence on pain is unclear. This project is focused on one possible mechanistic hypothesis: that threat influences pain by affecting central physiological changes within the dorsal horn of the spinal cord. These central changes often present clinically as secondary hyperalgesia. A thorough understanding of these mechanisms will inform improved treatment strategies. Methods Phase one: systematic review and meta-analysis The aim of this systematic review was to identify, describe, and compare methods that have been used to manipulate experimentally induced secondary hyperalgesia in healthy humans. A systematic search strategy (conducted on 01 October 2019) was supplemented by reference list checks and direct contact with identified laboratories to maximise the identification of data reporting the experimental manipulation of experimentally induced secondary hyperalgesia in humans. Studies were only included if they were published and in-press or accepted records for which the title, abstract, and full-text versions were available in English. Duplicate screening, risk of bias assessment, and data extraction procedures were used. Risk of bias was appraised for the following domains: selection, performance, detection, attrition, measurement, reporting, and other sources of bias. Data were extracted using a standardised data extraction form. This form was piloted and refined beforehand. Authors were asked to provide data were necessary. Data were pooled by method of v manipulation and outcome (intensity of secondary hyperalgesia, area of secondary hyperalgesia, or both). Phase two: experimental paradigm An experimental study was developed and conducted to investigate the effect of a stimulus threat on secondary hyperalgesia. The aim of this study was to investigate the effect of a manipulation of the threat value of a stimulus on experimentally induced secondary hyperalgesia in healthy human volunteers. All participants underwent a sham skin examination (the threat stimulus) at both the experimental and control sites. Through this sham skin examination, participants were informed that their skin integrity was fragile at the experimental site and robust at the control site. Secondary hyperalgesia was induced with high-frequency electrical stimulation at both the experimental and control site. Sensory testing was conducted at the experimental and control site, providing a withinsubject comparison of the intensity and area of secondary hyperalgesia at each site. It was hypothesised that greater threat will be associated with (hypothesis 1) greater intensity and (hypothesis 2) greater surface area of induced secondary hyperalgesia. Results Phase one: systematic review Twenty-one studies with non-pharmacological manipulations were included. Nine (out of 21) studies assessed intensity of secondary hyperalgesia after manipulation. Nicotine deprivation and negative expectations about the induction increased the intensity of secondary hyperalgesia. Three studies using attentional modulation and cognitive loading reported conflicting results with two studies having no effect and the other reporting a decrease in the intensity of secondary hyperalgesia. Emotional disclosure decreased the intensity of secondary hyperalgesia at four days and at one month after the manipulation. Hot/cold application, and verbal suggestion had no effect on the intensity of secondary hyperalgesia. Seventeen (out of 21) studies assessed area of secondary hyperalgesia after manipulation. Nicotine deprivation and sleep deprivation increased the area of secondary hyperalgesia. Hyperbaric oxygen therapy, cognitive behavioural therapy, emotional disclosure, spinal manipulation, transcranial direct current stimulation, and placebo analgesia decreased the area of secondary hyperalgesia. Interestingly, the effects of emotional disclosure and hyperbaric oxygen therapy were evident one month after manipulation. Acupuncture had no significant effect on the area of secondary hyperalgesia. Four studies assessed the effect of hot/cold application. Three studies reported no effect and one study reported an increase in the area of secondary hyperalgesia after cold application.
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    The prevalence of phantom limb pain and associated risk factors in people with amputations: a systematic review protocol
    (2019-01-10) Limakatso, Katleho; Bedwell, Gillian J; Madden, Victoria J; Parker, Romy
    Background The prevalence of phantom limb pain (PLP) in people with amputations is unclear because of the conflicting reports across the literature. It is proposed that the conflicting reports on the prevalence of PLP are a consequence of variations in the time period during which the studies were undertaken, countries in which the studies were conducted and recruitment processes implemented during collection of epidemiological data. In consideration of these factors, we aim to gather and critically appraise relevant literature to determine the prevalence estimate of and risk factors for PLP in people with amputations. Methods We will use a customised search strategy containing relevant words and terms to search the following databases: MEDLINE/PubMed (via EBSCOhost), PsycINFO (via EBSCOhost), PsycArticles, Cumulative Index to Nursing and Allied Health Literature (CINAHL) (via EBSCOhost), Africa-Wide Information (via EBSCOhost), Health Source: Nursing/Academic Edition (via EBSCOhost) SCOPUS, Web of Science and Academic Search Premier (via EBSCOhost). The risk of bias assessment will be conducted using a risk of bias assessment tool for prevalence studies, and data will be extracted using a piloted customised data extraction sheet. Data extracted from individual studies will be entered into Review Manager 5 and assessed for clinical and statistical heterogeneity. Studies will be pooled for meta-analysis using the random-effects model to determine a summary estimate of the prevalence of PLP across included studies. A statistically significant level will be set at p < 0.05. Discussion As far as we know, a systematic review and meta-analysis on the prevalence of, and risk factors for PLP in people with amputations has not been conducted. Given the varying reports in the literature, it is necessary to determine an estimate of the prevalence of PLP to generate an informed conclusion on this subject. The results of this review will be published in an internationally accredited journal and used to inform researchers, clinicians, policy-makers and the public about the burden of, and risk factors for PLP. This will be done with a further aim to improve the quality of pain management in society. Systematic review registration PROSPERO CRD42018094821