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Garcia-Larrea L. Non-invasive cortical stimulation for drug-resistant pain. Curr Opin Support Palliat Care 2023; 17:142-149. [PMID: 37339516 DOI: 10.1097/spc.0000000000000654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
PURPOSE OF REVIEW Neuromodulation techniques are being increasingly used to alleviate pain and enhance quality of life. Non-invasive cortical stimulation was originally intended to predict the efficacy of invasive (neurosurgical) techniques, but has now gained a place as an analgesic procedure in its own right. RECENT FINDINGS Repetitive transcranial magnetic stimulation (rTMS): Evidence from 14 randomised, placebo-controlled trials (~750 patients) supports a significant analgesic effect of high-frequency motor cortex rTMS in neuropathic pain. Dorsolateral frontal stimulation has not proven efficacious so far. The posterior operculo-insular cortex is an attractive target but evidence remains insufficient. Short-term efficacy can be achieved with NNT (numbers needed to treat) ~2-3, but long-lasting efficacy remains a challenge.Like rTMS, transcranial direct-current stimulation (tDCS) induces activity changes in distributed brain networks and can influence various aspects of pain. Lower cost relative to rTMS, few safety issues and availability of home-based protocols are practical advantages. The limited quality of many published reports lowers the level of evidence, which will remain uncertain until more prospective controlled studies are available. SUMMARY Both rTMS and tDCS act preferentially upon abnormal hyperexcitable states of pain, rather than acute or experimental pain. For both techniques, M1 appears to be the best target for chronic pain relief, and repeated sessions over relatively long periods of time may be required to obtain clinically significant benefits. Patients responsive to tDCS may differ from those improved by rTMS.
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Affiliation(s)
- Luis Garcia-Larrea
- Central Integration of Pain (NeuroPain) Lab, Lyon Centre for Neuroscience (CRNL), INSERM U1028, University Claude Bernard Lyon 1, Villeurbanne
- University Hospital Pain Centre (CETD), Neurological Hospital, Hospices Civils de Lyon, Lyon, France
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Lv T, You S, Qin R, Hu Z, Ke Z, Yao W, Zhao H, Xu Y, Bai F. Distinct reserve capacity impacts on default-mode network in response to left angular gyrus-navigated repetitive transcranial magnetic stimulation in the prodromal Alzheimer disease. Behav Brain Res 2023; 439:114226. [PMID: 36436729 DOI: 10.1016/j.bbr.2022.114226] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/01/2022] [Accepted: 11/23/2022] [Indexed: 11/25/2022]
Abstract
Default-mode network (DMN) may be the earliest affected network and is associated with cognitive decline in Alzheimer's disease (AD). Repetitive transcranial magnetic stimulation (rTMS) may help to modulate DMN plasticity. Still, stimulation effects substantially vary across studies and individuals. Global left frontal cortex (gLFC) connectivity, a substitute for reserve capacity, may contribute to the heterogeneous physiological effects of neuro-navigated rTMS. This study investigated the effects of left angular gyrus-navigated rTMS on DMN connectivity in different reserve capacity participants. gLFC connectivity, was computed through resting-state fMRI correlations. Thirty-one prodromal AD patients were divided into low connection group (LCG) and high connection group (HCG) by the median of gLFC connectivity. Distinct reserve capacity impacts on DMN in response to rTMS were identified in these two groups. Then, brain-behavior relationships were examined. gLFC connectivity within a certain range is directly proportional to cognitive reserve ability (i.e., LCG), and the effectiveness of functional connectivity beyond this range decreases (i.e, HCG). Moreover, LCG exhibited increased DMN connectivity and significantly positive memory improvements, while HCG showed a contrary connectivity decline and maintained or slightly improved their cognitive function after neuro-navigated rTMS treatment. The prodromal AD patients with the distinct reserve capacity may benefit differently from left angular gyrus-navigated rTMS, which may lead to increasing attention in defining personalized medicine approach of AD.
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Affiliation(s)
- Tingyu Lv
- Department of Neurology, Nanjing Drum Tower Hospital Clinical College of Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210008, China
| | - Shengqi You
- Department of Neurology, Nanjing Drum Tower Hospital Clinical College of Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210008, China
| | - Ruomeng Qin
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China; Jiangsu Province Stroke Center for Diagnosis and Therapy, Nanjing 210008, China; Nanjing Neuropsychiatry Clinic Medical Center, Nanjing 210008, China
| | - Zheqi Hu
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China
| | - Zhihong Ke
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China
| | - Weina Yao
- Department of Neurology, Nanjing Drum Tower Hospital Clinical College of Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210008, China
| | - Hui Zhao
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China; Jiangsu Province Stroke Center for Diagnosis and Therapy, Nanjing 210008, China; Nanjing Neuropsychiatry Clinic Medical Center, Nanjing 210008, China
| | - Yun Xu
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China; Jiangsu Province Stroke Center for Diagnosis and Therapy, Nanjing 210008, China; Nanjing Neuropsychiatry Clinic Medical Center, Nanjing 210008, China
| | - Feng Bai
- Department of Neurology, Nanjing Drum Tower Hospital of The Affiliated Hospital of Nanjing University Medical School, and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science, Nanjing University, Nanjing 210008, China; Jiangsu Province Stroke Center for Diagnosis and Therapy, Nanjing 210008, China; Nanjing Neuropsychiatry Clinic Medical Center, Nanjing 210008, China.
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Multifocal tDCS Targeting the Motor Network Modulates Event-Related Cortical Responses During Prolonged Pain. THE JOURNAL OF PAIN 2023; 24:226-236. [PMID: 36162791 DOI: 10.1016/j.jpain.2022.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 09/08/2022] [Accepted: 09/13/2022] [Indexed: 02/07/2023]
Abstract
Multifocal transcranial direct current stimulation (tDCS) targeting several brain regions is promising for inducing cortical plasticity. It remains unknown whether multifocal tDCS aimed at the resting-state motor network (network-tDCS) can revert N2-P2 cortical responses otherwise attenuated during prolonged experimental pain. Thirty-eight healthy subjects participated in 2 sessions separated by 24 hours (Day1, Day2) of active (n = 19) or sham (n = 19) network-tDCS. Experimental pain induced by topical capsaicin was maintained for 24 hours and assessed using a numerical rating scale. Electrical detection and pain thresholds, and N2-P2 evoked potentials (electroencephalography) to noxious electrical stimulation were recorded before capsaicin-induced pain (Day1-baseline), after capsaicin application (Day1-post-cap), and after 2 sessions of network-tDCS (Day2). Capsaicin induced moderate pain at Day1-post-cap, which further increased at Day2 in both groups (P = .01). Electrical detection/pain thresholds did not change over time. N2-P2 responses were reduced on Day1-post-cap compared to Day1-baseline (P = .019). At Day2 compared with Day1-post-cap, N2-P2 responses were significantly higher in the Active network-tDCS group (P<.05), while the sham group remained inhibited. These results suggest that tDCS targeting regions associated with the motor network may modulate the late evoked brain responses to noxious peripheral stimulation otherwise initially inhibited by capsaicin-induced pain. PERSPECTIVE: This study extends the evidence of N2-P2 reduction due to capsaicin-induced pain from 30 minutes to 24 hrs. Moreover, 2 sessions of tDCS targeting the motor network in the early stage of nociceptive pain may revert the inhibition of N2-P2 associated with capsaicin-induced pain.
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Erdoğan ET, Küçük Z, Eskikurt G, Kurt A, Ermutlu N, Karamürsel S. Single Session Anodal Transcranial Direct Current Stimulation on Different Cortical Areas. J PSYCHOPHYSIOL 2022. [DOI: 10.1027/0269-8803/a000311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract. Transcranial direct current stimulation (tDCS) studies in healthy volunteers have shown conflicting results in terms of modulation in pain thresholds. The aim of this study was to investigate how single session anodal tDCS and modulated tDCS (mtDCS) of distinct cortical areas affected pain and perception thresholds in healthy participants. Five different stimulation conditions were applied at different cortical sites to 20 healthy volunteers to investigate the effects of tDCS and mtDCS (20 Hz) on pain and perception thresholds. TDCS over the motor cortex (M1), mtDCS over the motor cortex, tDCS over the dorsolateral prefrontal cortex (DLPFC), mtDCS of the DLPFC, and mtDCS over the occipital cortex were the stimulation conditions. All of the stimulations were anodal. The stimulations were given in a randomized order at 20-minute intervals. For comparison, electrical pain and perception thresholds were obtained from the right middle finger before and during the tDCS. After each measurement, participants were asked to give a score to their pain. In repeated measures analysis of variance (RM-ANOVA) test, the Condition × Time interaction showed no significant influence on changes in pain, perception thresholds, and pain scores ( p = .48, p = .89, and p = .50, respectively). However, regardless of the condition types, there was a significant difference in pain and perceptual thresholds during tDCS ( p = .01, p = .025, respectively). Our findings did not support difference in pain and perception modulation by a single session anodal tDCS over M1 and DLPFC compared to the occipital cortex in healthy volunteers. The increase in all thresholds during tDCS, irrespective of conditions, and peripheral sensations, including an active control group, taken together, suggest a placebo effect of active tDCS. Future studies about pain and perception in healthy subjects should consider the level of experimental pain and a strong placebo effect.
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Affiliation(s)
- Ezgi Tuna Erdoğan
- Department of Physiology, School of Medicine, Koç University, Istanbul, Turkey
| | - Zeynep Küçük
- Department of Psychology, Faculty of Science and Literature, Halic University, Istanbul, Turkey
| | - Gökçer Eskikurt
- Department of Physiology, Faculty of Medicine, Istinye University, Istanbul, Turkey
| | - Adnan Kurt
- Department of Physiology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Numan Ermutlu
- Department of Physiology, Faculty of Medicine, Istanbul Health and Technology University, Istanbul, Turkey
| | - Sacit Karamürsel
- Department of Physiology, School of Medicine, Koç University, Istanbul, Turkey
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Garcia-Larrea L, Quesada C. Cortical stimulation for chronic pain: from anecdote to evidence. Eur J Phys Rehabil Med 2022; 58:290-305. [PMID: 35343176 PMCID: PMC9980528 DOI: 10.23736/s1973-9087.22.07411-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Epidural stimulation of the motor cortex (eMCS) was devised in the 1990's, and has now largely supplanted thalamic stimulation for neuropathic pain relief. Its mechanisms of action involve activation of multiple cortico-subcortical areas initiated in the thalamus, with involvement of endogenous opioids and descending inhibition toward the spinal cord. Evidence for clinical efficacy is now supported by at least seven RCTs; benefits may persist up to 10 years, and can be reasonably predicted by preoperative use of non-invasive repetitive magnetic stimulation (rTMS). rTMS first developed as a means of predicting the efficacy of epidural procedures, then as an analgesic method on its own right. Reasonable evidence from at least six well-conducted RCTs favors a significant analgesic effect of high-frequency rTMS of the motor cortex in neuropathic pain (NP), and less consistently in widespread/fibromyalgic pain. Stimulation of the dorsolateral frontal cortex (DLPFC) has not proven efficacious for pain, so far. The posterior operculo-insular cortex is a new and attractive target but evidence remains inconsistent. Transcranial direct current stimulation (tDCS) is applied upon similar targets as rTMS and eMCS; it does not elicit action potentials but modulates the neuronal resting membrane state. tDCS presents practical advantages including low cost, few safety issues, and possibility of home-based protocols; however, the limited quality of most published reports entails a low level of evidence. Patients responsive to tDCS may differ from those improved by rTMS, and in both cases repeated sessions over a long time may be required to achieve clinically significant relief. Both invasive and non-invasive procedures exert their effects through multiple distributed brain networks influencing the sensory, affective and cognitive aspects of chronic pain. Their effects are mainly exerted upon abnormally sensitized pathways, rather than on acute physiological pain. Extending the duration of long-term benefits remains a challenge, for which different strategies are discussed in this review.
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Affiliation(s)
- Luis Garcia-Larrea
- Central Integration of Pain (NeuroPain) Lab, Lyon Center for Neuroscience (CRNL), INSERM U1028, University Claude Bernard Lyon 1, Villeurbanne, France - .,University Hospital Pain Center (CETD), Neurological Hospital, Hospices Civils de Lyon, Lyon, France -
| | - Charles Quesada
- Central Integration of Pain (NeuroPain) Lab, Lyon Center for Neuroscience (CRNL), INSERM U1028, University Claude Bernard Lyon 1, Villeurbanne, France.,Department of Physiotherapy, Sciences of Rehabilitation Institute (ISTR), University Claude Bernard Lyon 1, Villeurbanne, France
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Ramos-Fresnedo A, Perez-Vega C, Domingo RA, Cheshire WP, Middlebrooks EH, Grewal SS. Motor Cortex Stimulation for Pain: A Narrative Review of Indications, Techniques, and Outcomes. Neuromodulation 2022; 25:211-221. [DOI: 10.1016/j.neurom.2021.10.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 10/19/2022]
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Mehesz E, Karoui H, Strutton PH, Hughes SW. Exposure to an Immersive Virtual Reality Environment can Modulate Perceptual Correlates of Endogenous Analgesia and Central Sensitization in Healthy Volunteers. THE JOURNAL OF PAIN 2021; 22:707-714. [PMID: 33465506 DOI: 10.1016/j.jpain.2020.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 12/14/2020] [Accepted: 12/29/2020] [Indexed: 11/26/2022]
Abstract
Virtual reality (VR) has been shown to produce analgesic effects during different experimental and clinical pain states. Despite this, the top-down mechanisms are still poorly understood. In this study, we examined the influence of both a real and sham (ie, the same images in 2D) immersive arctic VR environment on conditioned pain modulation (CPM) and in a human surrogate model of central sensitization in 38 healthy volunteers. CPM and acute heat pain thresholds were assessed before and during VR/sham exposure in the absence of any sensitization. In a follow-on study, we used the cutaneous high frequency stimulation model of central sensitization and measured changes in mechanical pain sensitivity in an area of heterotopic sensitization before and during VR/sham exposure. There was an increase in CPM efficiency during the VR condition compared to baseline (P < .01). In the sham condition, there was a decrease in CPM efficiency compared to baseline (P < .01) and the real VR condition (P < .001). Neither real nor sham VR had any effect on pain ratings reported during the conditioning period or on heat pain threshold. There was also an attenuation of mechanical pain sensitivity during the VR condition indicating a lower sensitivity compared to sham (P < .05). We conclude that exposure to an immersive VR environment has no effect over acute pain thresholds but can modulate dynamic CPM responses and mechanical hypersensitivity in healthy volunteers. PERSPECTIVE: This study has demonstrated that exposure to an immersive virtual reality environment can modulate perceptual correlates of endogenous pain modulation and secondary hyperalgesia in a human surrogate pain model. These results suggest that virtual reality could provide a novel mechanism-driven analgesic strategy in patients with altered central pain processing.
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Affiliation(s)
- Erzsebet Mehesz
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Hajer Karoui
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Paul H Strutton
- The Nick Davey Laboratory, Department of Surgery and Cancer, Imperial College London, London, UK
| | - Sam W Hughes
- The Pain Neuroplasticity and Modulation Laboratory, Brain Research and Imaging Centre (BRIC), School of Psychology, Faculty of Health, University of Plymouth, Plymouth, UK.
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Quesada C, Kostenko A, Ho I, Leone C, Nochi Z, Stouffs A, Wittayer M, Caspani O, Brix Finnerup N, Mouraux A, Pickering G, Tracey I, Truini A, Treede RD, Garcia-Larrea L. Human surrogate models of central sensitization: A critical review and practical guide. Eur J Pain 2021; 25:1389-1428. [PMID: 33759294 PMCID: PMC8360051 DOI: 10.1002/ejp.1768] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 03/17/2021] [Accepted: 03/21/2021] [Indexed: 12/11/2022]
Abstract
Background As in other fields of medicine, development of new medications for management of neuropathic pain has been difficult since preclinical rodent models do not necessarily translate to the clinics. Aside from ongoing pain with burning or shock‐like qualities, neuropathic pain is often characterized by pain hypersensitivity (hyperalgesia and allodynia), most often towards mechanical stimuli, reflecting sensitization of neural transmission. Data treatment We therefore performed a systematic literature review (PubMed‐Medline, Cochrane, WoS, ClinicalTrials) and semi‐quantitative meta‐analysis of human pain models that aim to induce central sensitization, and generate hyperalgesia surrounding a real or simulated injury. Results From an initial set of 1569 reports, we identified and analysed 269 studies using more than a dozen human models of sensitization. Five of these models (intradermal or topical capsaicin, low‐ or high‐frequency electrical stimulation, thermode‐induced heat‐injury) were found to reliably induce secondary hyperalgesia to pinprick and have been implemented in multiple laboratories. The ability of these models to induce dynamic mechanical allodynia was however substantially lower. The proportion of subjects who developed hypersensitivity was rarely provided, giving rise to significant reporting bias. In four of these models pharmacological profiles allowed to verify similarity to some clinical conditions, and therefore may inform basic research for new drug development. Conclusions While there is no single “optimal” model of central sensitization, the range of validated and easy‐to‐use procedures in humans should be able to inform preclinical researchers on helpful potential biomarkers, thereby narrowing the translation gap between basic and clinical data. Significance Being able to mimic aspects of pathological pain directly in humans has a huge potential to understand pathophysiology and provide animal research with translatable biomarkers for drug development. One group of human surrogate models has proven to have excellent predictive validity: they respond to clinically active medications and do not respond to clinically inactive medications, including some that worked in animals but failed in the clinics. They should therefore inform basic research for new drug development.
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Affiliation(s)
- Charles Quesada
- NeuroPain lab, Lyon Centre for Neuroscience Inserm U1028, Lyon, France.,Pain Center Neurological Hospital (CETD), Hospices Civils de Lyon, Lyon, France
| | - Anna Kostenko
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Idy Ho
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Caterina Leone
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Zahra Nochi
- Danish Pain Research Center, Dept of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Alexandre Stouffs
- Institute of Neuroscience (IoNS), Université Catholique de Louvain (UCLouvain), Ottignies-Louvain-la-Neuve, Belgium
| | - Matthias Wittayer
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Ombretta Caspani
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Nanna Brix Finnerup
- Danish Pain Research Center, Dept of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - André Mouraux
- Institute of Neuroscience (IoNS), Université Catholique de Louvain (UCLouvain), Ottignies-Louvain-la-Neuve, Belgium
| | | | - Irene Tracey
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Andrea Truini
- Department of Human Neuroscience, Sapienza University, Rome, Italy
| | - Rolf-Detlef Treede
- Department of Neurophysiology, Mannheim center for Translational Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Luis Garcia-Larrea
- NeuroPain lab, Lyon Centre for Neuroscience Inserm U1028, Lyon, France.,Pain Center Neurological Hospital (CETD), Hospices Civils de Lyon, Lyon, France
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Gregoret L, Zamorano AM, Graven‐Nielsen T. Effects of multifocal transcranial direct current stimulation targeting the motor network during prolonged experimental pain. Eur J Pain 2021; 25:1241-1253. [DOI: 10.1002/ejp.1743] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Luisina Gregoret
- Center for Neuroplasticity and Pain (CNAP) Department of Health Science and Technology Faculty of Medicine Aalborg University Aalborg Denmark
| | - Anna M. Zamorano
- Center for Neuroplasticity and Pain (CNAP) Department of Health Science and Technology Faculty of Medicine Aalborg University Aalborg Denmark
| | - Thomas Graven‐Nielsen
- Center for Neuroplasticity and Pain (CNAP) Department of Health Science and Technology Faculty of Medicine Aalborg University Aalborg Denmark
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Hughes SW, Ward G, Strutton PH. Anodal transcranial direct current stimulation over the primary motor cortex attenuates capsaicin‐induced dynamic mechanical allodynia and mechanical pain sensitivity in humans. Eur J Pain 2020; 24:1130-1137. [DOI: 10.1002/ejp.1557] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/20/2020] [Accepted: 03/04/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Sam W. Hughes
- The Nick Davey Laboratory Faculty of Medicine Imperial College London London UK
| | - Grace Ward
- The Nick Davey Laboratory Faculty of Medicine Imperial College London London UK
| | - Paul H. Strutton
- The Nick Davey Laboratory Faculty of Medicine Imperial College London London UK
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Hagiwara K, Perchet C, Frot M, Bastuji H, Garcia-Larrea L. Cortical modulation of nociception by galvanic vestibular stimulation: A potential clinical tool? Brain Stimul 2019; 13:60-68. [PMID: 31636023 DOI: 10.1016/j.brs.2019.10.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 09/27/2019] [Accepted: 10/09/2019] [Indexed: 01/03/2023] Open
Abstract
OBJECTIVE Vestibular afferents converge with nociceptive ones within the posterior insula, and can therefore modulate nociception. Consistent with this hypothesis, caloric vestibular stimulation (CVS) has been shown to reduce experimental and clinical pain. Since CVS can induce undesirable effects in a proportion of patients, here we explored an alternative means to activate non-invasively the vestibular pathways using innocuous bi-mastoid galvanic stimulation (GVS), and assessed its effects on experimental pain. METHODS Sixteen healthy volunteers participated in this study. Experimental pain was induced by noxious laser-heat stimuli to the left hand while recording pain ratings and related brain potentials (LEPs). We evaluated changes of these indices during left- or right-anodal GVS (cathode on contralateral mastoid), and contrasted them with those during sham GVS, optokinetic vestibular stimulation (OKS) using virtual reality, and attentional distraction to ascertain the vestibular-specific analgesic effects of GVS. RESULTS GVS elicited brief sensations of head/trunk deviation, inoffensive to all participants. Both active GVS conditions showed analgesic effects, greater for the right anodal stimulation. OKS was helpful to attain significant LEP reductions during the left-anodal stimulation. Neither sham-GVS nor the distraction task were able to modulate significantly pain ratings or LEPs. CONCLUSIONS GVS appeared as a well-tolerated and powerful procedure for the relief of experimental pain, probably through physiological interaction within insular nociceptive networks. Either isolated or in combination with other types of vestibular activation (e.g., optokinetic stimuli), GVS deserves being tested in clinical settings.
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Affiliation(s)
- Koichi Hagiwara
- Central Integration of Pain (NeuroPain), Lab-Lyon Neuroscience Research Center, INSERM U1028, CNRS, UMR5292, Université Claude Bernard, Bron, F-69677, France.
| | - Caroline Perchet
- Central Integration of Pain (NeuroPain), Lab-Lyon Neuroscience Research Center, INSERM U1028, CNRS, UMR5292, Université Claude Bernard, Bron, F-69677, France
| | - Maud Frot
- Central Integration of Pain (NeuroPain), Lab-Lyon Neuroscience Research Center, INSERM U1028, CNRS, UMR5292, Université Claude Bernard, Bron, F-69677, France
| | - Hélène Bastuji
- Central Integration of Pain (NeuroPain), Lab-Lyon Neuroscience Research Center, INSERM U1028, CNRS, UMR5292, Université Claude Bernard, Bron, F-69677, France; Service de Neurologie Fonctionnelle et D'Épileptologie et Centre Du Sommeil, Hospices Civils de Lyon, Bron, F-69677, France
| | - Luis Garcia-Larrea
- Central Integration of Pain (NeuroPain), Lab-Lyon Neuroscience Research Center, INSERM U1028, CNRS, UMR5292, Université Claude Bernard, Bron, F-69677, France; Centre D'évaluation et de Traitement de La Douleur, Hôpital Neurologique, Lyon, F-69000, France
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12
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Effects of continuous theta-burst stimulation of the primary motor and secondary somatosensory areas on the central processing and the perception of trigeminal nociceptive input in healthy volunteers. Pain 2019; 160:172-186. [PMID: 30204647 PMCID: PMC6344075 DOI: 10.1097/j.pain.0000000000001393] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Supplemental Digital Content is Available in the Text. Inactivating paired continuous theta-burst stimulation of the primary motor cortex but not on the secondary somatosensory area flattened the relationship between brain activation and stimulus strength while not impacting on the subjective perceptions. Noninvasive modulation of the activity of pain-related brain regions by means of transcranial magnetic stimulation promises an innovative approach at analgesic treatments. However, heterogeneous successes in pain modulation by setting reversible “virtual lesions” at different brain areas point at unresolved problems including the optimum stimulation site. The secondary somatosensory cortex (S2) has been previously identified to be involved in the perception of pain-intensity differences. Therefore, impeding its activity should impede the coding of the sensory component of pain intensity, resulting in a flattening of the relationship between pain intensity and physical stimulus strength. This was assessed using inactivating spaced continuous theta-burst stimulation (cTBS) in 18 healthy volunteers. In addition, cTBS was applied on the primary motor cortex (M1) shown previously to yield moderate and variable analgesic effects, whereas sham stimulation at both sites served as placebo condition. Continuous theta-burst stimulation flattened the relationship between brain activation and stimulus strength, mainly at S2, the insular cortex, and the postcentral gyrus (16 subjects analyzed). However, these effects were observed after inactivation of M1 while this effect was not observed after inactivation of S2. Nevertheless, both the M1 and the S2-spaced cTBS treatment were not reflected in the ratings of the nociceptive stimuli of different strengths (17 subjects analyzed), contrasting with the clear coding of stimulus strength by these data. Hence, while modulating the central processing of nociceptive input, cTBS failed to produce subjectively relevant changes in pain perception, indicating that the method in the present implementation is still unsuitable for clinical application.
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Abstract
Clinical neurophysiologic investigation of pain pathways in humans is based on specific techniques and approaches, since conventional methods of nerve conduction studies and somatosensory evoked potentials do not explore these pathways. The proposed techniques use various types of painful stimuli (thermal, laser, mechanical, or electrical) and various types of assessments (measurement of sensory thresholds, study of nerve fiber excitability, or recording of electromyographic reflexes or cortical potentials). The two main tests used in clinical practice are quantitative sensory testing and pain-related evoked potentials (PREPs). In particular, PREPs offer the possibility of an objective assessment of nociceptive pathways. Three types of PREPs can be distinguished depending on the type of stimulation used to evoke pain: laser-evoked potentials, contact heat evoked potentials, and intraepidermal electrical stimulation evoked potentials (IEEPs). These three techniques investigate both small-diameter peripheral nociceptive afferents (mainly Aδ nerve fibers) and spinothalamic tracts without theoretically being able to differentiate the level of lesion in the case of abnormal results. In routine clinical practice, PREP recording is a reliable method of investigation for objectifying the existence of a peripheral or central lesion or loss of function concerning the nociceptive pathways, but not the existence of pain. Other methods, such as nerve fiber excitability studies using microneurography, more directly reflect the activities of nociceptive axons in response to provoked pain, but without detecting or quantifying the presence of spontaneous pain. These methods are more often used in research or experimental study design. Thus, it should be kept in mind that most of the results of neurophysiologic investigation performed in clinical practice assess small fiber or spinothalamic tract lesions rather than the neuronal mechanisms directly at the origin of pain and they do not provide objective quantification of pain.
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Affiliation(s)
- Jean-Pascal Lefaucheur
- Excitabilité Nerveuse et Thérapeutique, Faculté de Médecine de Créteil, Université Paris-Est-Créteil, Hôpital Henri Mondor, Créteil, France; Service de Physiologie-Explorations Fonctionnelles, Hôpital Henri Mondor, Créteil, France.
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14
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Pazzaglia C, Vollono C, Testani E, Coraci D, Granata G, Padua L, Valeriani M. Low-Frequency rTMS of the Primary Motor Area Does Not Modify the Response of the Cerebral Cortex to Phasic Nociceptive Stimuli. Front Neurosci 2018; 12:878. [PMID: 30555294 PMCID: PMC6281959 DOI: 10.3389/fnins.2018.00878] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 11/12/2018] [Indexed: 01/12/2023] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique of cortical stimulation. Although the exact mechanism of action is not clearly understood, it has been postulated that rTMS action on pain depends most on stimulation sites and stimulation parameters. Most studies concern high-frequency rTMS of the primary motor cortex (M1). High-frequency rTMS over motor cortex seems to induce an analgesic effect while contrasting results were reported after low-frequency rTMS. The aim of the current study was to investigate the effects of 1 Hz rTMS stimulation over the left primary motor cortex on subjective laser pain rating and laser evoked potential (LEP) amplitudes in healthy subjects. Subjects underwent two different sessions (real and sham rTMS) according to a cross-sectional design. In each session, LEPs and laser-pain rating to stimulation of both right and left hand dorsum were collected before 1 Hz rTMS over the left M1 area (baseline), which lasted 20 min. Then, LEPs and laser-pain rating were measured immediately after rTMS (T0), after 20 min from T0 (T0+20), and after 40 min from T0 (T0+40). We could not find any modification of both laser-pain rating and LEP parameters (latencies and amplitudes) following 1 Hz rTMS. Therefore, our results show that the low-frequency rTMS of the M1 area does not change the response of the cerebral cortex to pain.
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Affiliation(s)
- Costanza Pazzaglia
- Unit of High Intensity Neurorehabilitation, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Catello Vollono
- Department of Geriatrics, Neuroscience and Orthopedics, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Elisa Testani
- Department of Neurological and Neurosensory Sciences, University Hospital of Siena, Siena, Italy
| | | | - Giuseppe Granata
- Department of Geriatrics, Neuroscience and Orthopedics, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Luca Padua
- IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy.,Department of Geriatrics, Neurosciences and Orthopedics, Catholic University of the Sacred Heart, Rome, Italy
| | - Massimiliano Valeriani
- Department of Neuroscience, Pediatric Hospital Bambino Gesù, Rome, Italy.,Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark
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15
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Hughes S, Grimsey S, Strutton PH. Primary Motor Cortex Transcranial Direct Current Stimulation Modulates Temporal Summation of the Nociceptive Withdrawal Reflex in Healthy Subjects. PAIN MEDICINE 2018; 20:1156-1165. [DOI: 10.1093/pm/pny200] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Sam Hughes
- The Nick Davey Laboratory, Faculty of Medicine, Imperial College London, London, UK
| | - Sybil Grimsey
- The Nick Davey Laboratory, Faculty of Medicine, Imperial College London, London, UK
| | - Paul H Strutton
- The Nick Davey Laboratory, Faculty of Medicine, Imperial College London, London, UK
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16
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Hughes SW, Ali M, Sharma P, Insan N, Strutton PH. Frequency-dependent top-down modulation of temporal summation by anodal transcranial direct-current stimulation of the primary motor cortex in healthy adults. Eur J Pain 2018; 22:1494-1501. [PMID: 29704875 DOI: 10.1002/ejp.1238] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2018] [Indexed: 02/28/2024]
Abstract
BACKGROUND Transcranial direct-current stimulation (tDCS) applied over the primary motor cortex has been shown to be effective in the treatment of a number of chronic pain conditions. However, there is a lack of understanding of the top-down analgesic mechanisms involved. METHOD In this study, we investigated the effects of tDCS on the facilitation of subjective sensory and pain scores using a transcutaneous electrically evoked measure of temporal summation. In this randomized, blinded, cross-over study healthy subjects received a single stimulus given at 0.9× pain threshold (pTh) over the L5 dermatome on the lateral aspect of the right leg, followed by a train of 5 stimuli given at 0.5, 1, 5 and 20 Hz before and after 20 min of sham or anodal tDCS (2 mA) applied over the primary motor cortex. Ratings of sensation and pain intensity were scored on a visual analogue scale (VAS). RESULTS Temporal summation leading to pain only occurred at higher frequencies (5 and 20 Hz). Sham or real tDCS had no effect over temporal summation evoked at 5 Hz; however, there was a significant analgesic effect at 20 Hz. Sham or real tDCS had no effect over acute, single stimuli-evoked responses. CONCLUSION These results indicate that anodal tDCS applied to the primary motor cortex preferentially modulates temporal summation induced by high-frequency electrical stimulation-induced pain. The inhibitory effects of tDCS appear to be dynamic and dependent on the degree of spinal cord excitability and may explain the higher analgesic efficacy in patients with moderate to severe chronic pain symptoms. SIGNIFICANCE The analgesic effects of tDCS are dependent on spinal cord excitability. This work provides insight into top-down modulation during acute pain and temporal summation. This knowledge may explain why tDCS has a higher analgesic efficacy in chronic pain patients.
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Affiliation(s)
- S W Hughes
- Faculty of Medicine, The Nick Davey Laboratory, Imperial College London, London, UK
| | - M Ali
- Faculty of Medicine, The Nick Davey Laboratory, Imperial College London, London, UK
| | - P Sharma
- Faculty of Medicine, The Nick Davey Laboratory, Imperial College London, London, UK
| | - N Insan
- Faculty of Medicine, The Nick Davey Laboratory, Imperial College London, London, UK
| | - P H Strutton
- Faculty of Medicine, The Nick Davey Laboratory, Imperial College London, London, UK
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17
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Kisler LB, Gurion I, Granovsky Y, Sinai A, Sprecher E, Shamay-Tsoory S, Weissman-Fogel I. Can a single pulse transcranial magnetic stimulation targeted to the motor cortex interrupt pain processing? PLoS One 2018; 13:e0195739. [PMID: 29630681 PMCID: PMC5891059 DOI: 10.1371/journal.pone.0195739] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 03/28/2018] [Indexed: 01/06/2023] Open
Abstract
The modulatory role of the primary motor cortex (M1), reflected by an inhibitory effect of M1-stimulation on clinical pain, motivated us to deepen our understanding of M1’s role in pain modulation. We used Transcranial Magnetic Stimulation (TMS)-induced virtual lesion (VL) to interrupt with M1 activity during noxious heat pain. We hypothesized that TMS-VL will effect experimental pain ratings. Three VL protocols were applied consisting of single-pulse TMS to transiently interfere with right M1 activity: (1) VLM1- TMS applied to 11 subjects, 20 msec before the individual’s first pain-related M1 peak activation, as determined by source analysis (sLORETA), (2) VL-50 (N = 16; TMS applied 50 ms prior to noxious stimulus onset), and (3) VL+150 (N = 16; TMS applied 150 ms after noxious stimulus onset). Each protocol included 3 conditions ('pain-alone', ' TMS-VL', and ‘SHAM-VL’), each consisted of 30 noxious heat stimuli. Pain ratings were compared, in each protocol, for TMS-VL vs. SHAM-VL and vs. pain-alone conditions. Repeated measures analysis of variance, corrected for multiple comparisons revealed no significant differences in the pain ratings between the different conditions within each protocol. Therefore, our results from this exploratory study suggest that a single pulse TMS-induced VL that is targeted to M1 failed to interrupt experimental pain processing in the specific three stimulation timing examined here.
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Affiliation(s)
- Lee-Bareket Kisler
- Department of Psychology, University of Haifa, Haifa, Israel
- Laboratory of Clinical Neurophysiology, Technion Faculty of Medicine, Haifa, Israel
| | - Ilan Gurion
- Department of Psychology, University of Haifa, Haifa, Israel
| | - Yelena Granovsky
- Laboratory of Clinical Neurophysiology, Technion Faculty of Medicine, Haifa, Israel
- Department of Neurology, Rambam Health Care Campus, Haifa, Israel
| | - Alon Sinai
- Department of Neurology, Rambam Health Care Campus, Haifa, Israel
- Department of Neurosurgery, Rambam Health Care Campus, Haifa, Israel
| | - Elliot Sprecher
- Department of Neurology, Rambam Health Care Campus, Haifa, Israel
| | | | - Irit Weissman-Fogel
- Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Israel
- * E-mail:
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18
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Bradley C, Bastuji H, Garcia-Larrea L. Evidence-based source modeling of nociceptive cortical responses: A direct comparison of scalp and intracranial activity in humans. Hum Brain Mapp 2017; 38:6083-6095. [PMID: 28925006 DOI: 10.1002/hbm.23812] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 08/27/2017] [Accepted: 09/05/2017] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Source modeling of EEG traditionally relies on interplay between physiological hypotheses and mathematical estimates. We propose to optimize the process by using evidence gathered from brain imaging and intracortical recordings. METHODS We recorded laser-evoked potentials in 18 healthy participants, using high-density EEG. Brain sources were modeled during the first second poststimulus, constraining their initial position to regions where nociceptive-related activity has been ascertained by intracranial EEG. These comprised the two posterior operculo-insular regions, primary sensorimotor, posterior parietal, anterior cingulate/supplementary motor (ACC/SMA), bilateral frontal/anterior insular, and posterior cingulate (PCC) cortices. RESULTS The model yielded an average goodness of fit of 91% for individual and 95.8% for grand-average data. When compared with intracranial recordings from 27 human subjects, no significant difference in peak latencies was observed between modeled and intracranial data for 5 of the 6 assessable regions. Morphological match was excellent for operculo-insular, frontal, ACC/SMA and PCC regions (cross-correlation > 0.7) and fair for sensori-motor and posterior parietal cortex (c-c ∼ 0.5). CONCLUSIONS Multiple overlapping activities evoked by nociceptive input can be disentangled from high-density scalp EEG guided by intracranial data. Modeled sources accurately described the timing and morphology of most activities recorded with intracranial electrodes, including those coinciding with the emergence of stimulus awareness. Hum Brain Mapp 38:6083-6095, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Claire Bradley
- NEUROPAIN lab, Centre de Recherche en Neurosciences de Lyon, Inserm U1028 - CNRS UMR5292, Université Claude Bernard Lyon 1, Lyon, France
| | - Hélène Bastuji
- NEUROPAIN lab, Centre de Recherche en Neurosciences de Lyon, Inserm U1028 - CNRS UMR5292, Université Claude Bernard Lyon 1, Lyon, France
| | - Luis Garcia-Larrea
- NEUROPAIN lab, Centre de Recherche en Neurosciences de Lyon, Inserm U1028 - CNRS UMR5292, Université Claude Bernard Lyon 1, Lyon, France
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19
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Lamusuo S, Hirvonen J, Lindholm P, Martikainen IK, Hagelberg N, Parkkola R, Taiminen T, Hietala J, Helin S, Virtanen A, Pertovaara A, Jääskeläinen S. Neurotransmitters behind pain relief with transcranial magnetic stimulation - positron emission tomography evidence for release of endogenous opioids. Eur J Pain 2017; 21:1505-1515. [DOI: 10.1002/ejp.1052] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2017] [Indexed: 01/28/2023]
Affiliation(s)
- S. Lamusuo
- Department of Neurology; Turku University Hospital; Finland
- Division of Clinical Neuroscience; University of Turku; Finland
- Turku PET Centre; University of Turku; Finland
| | - J. Hirvonen
- Turku PET Centre; University of Turku; Finland
| | - P. Lindholm
- Department of Neurology; Turku University Hospital; Finland
- Department of Clinical Neurophysiology; Turku University Hospital and University of Turku; Finland
| | - I. K. Martikainen
- Department of Physiology; Turku University Hospital and University of Turku; Finland
| | - N. Hagelberg
- Pain Clinic; Turku University Hospital and University of Turku; Finland
| | - R. Parkkola
- Turku PET Centre; University of Turku; Finland
- Department of Radiology; Turku University Hospital and University of Turku; Finland
| | - T. Taiminen
- Department of Psychiatry; Turku University Hospital and University of Turku; Finland
| | - J. Hietala
- Turku PET Centre; University of Turku; Finland
- Department of Psychiatry; Turku University Hospital and University of Turku; Finland
| | - S. Helin
- Turku PET Centre; University of Turku; Finland
| | - A. Virtanen
- Department of Clinical Neurophysiology; Turku University Hospital and University of Turku; Finland
| | - A. Pertovaara
- Department of Physiology; Faculty of Medicine; University of Helsinki; Finland
| | - S.K. Jääskeläinen
- Department of Clinical Neurophysiology; Turku University Hospital and University of Turku; Finland
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20
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Okkerse P, Alvarez-Jimenez R, Hay JL, Tehim A, Kumar R, de Kam ML, Groeneveld GJ. No evidence of potentiation of buprenorphine by milnacipran in healthy subjects using a nociceptive test battery. Eur J Pain 2016; 21:494-506. [PMID: 27651026 DOI: 10.1002/ejp.943] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2016] [Indexed: 01/10/2023]
Abstract
BACKGROUND Serotonin-norepinephrine reuptake inhibitors inhibit the reuptake of serotonin and noradrenalin and are used in the treatment of neuropathic pain. Animal studies suggest that milnacipran co-administered with opioids may potentiate the analgesic effect of μ-opioid receptor agonists. This study hypothesized that co-administration of milnacipran and buprenorphine would have a synergistic effect in evoked pain models in healthy subjects. METHODS This was a randomized double-blinded, placebo-controlled, four-way cross-over, multiple dose clinical trial to investigate the analgesic effects of buprenorphine (placebo, 0.5, 1 and 3 μg/kg) in combination with milnacipran (placebo, 25 and 50 mg) in healthy subjects. RESULTS 11 healthy men were enrolled in the study. Buprenorphine alone showed a dose-response relationship indicative of anti-nociception in the pain tests. Following milnacipran administration, no changes were seen in the pharmacodynamic measurements for pain, psychomotor function, body stability or eye movements. For the electrical tests, cold pressor test and pressure pain test, buprenorphine alone was superior when compared with buprenorphine plus milnacipran. No differences in pharmacodynamic variables, besides an increase in pupil/iris ratio, were observed after repeated administration of milnacipran 50 mg. Single and multiple doses of 25 or 50 mg milnacipran did not further potentiate the anti-nociceptive effects of buprenorphine. CONCLUSIONS Buprenorphine showed dose-dependent effects consistent with its pharmacological profile. Milnacipran alone did not affect any of the pain variables. The combination of both buprenorphine and milnacipran did not potentiate or show a synergistic effect on the pain models used in this study. SIGNIFICANCE Buprenorphine is known to be a potent opioid agonist. Animal studies suggest that milnacipran co-administered with opioids may potentiate the analgesic effect of μ-opioid receptor agonists. Here, we found that buprenorphine showed a dose-dependent analgesic effect, but that no potentiation or synergy on a battery of evoked pain tasks could be observed after co-administration of both milnacipran and buprenorphine.
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Affiliation(s)
- P Okkerse
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | | | - J L Hay
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - A Tehim
- Dr. Reddy's Laboratories, Hyderabad, India
| | - R Kumar
- Dr. Reddy's Laboratories, Hyderabad, India
| | - M L de Kam
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
| | - G J Groeneveld
- Centre for Human Drug Research (CHDR), Leiden, The Netherlands
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