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Limerick G, Christo DK, Tram J, Moheimani R, Manor J, Chakravarthy K, Karri J, Christo PJ. Complex Regional Pain Syndrome: Evidence-Based Advances in Concepts and Treatments. Curr Pain Headache Rep 2023; 27:269-298. [PMID: 37421541 DOI: 10.1007/s11916-023-01130-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2023] [Indexed: 07/10/2023]
Abstract
PURPOSE OF REVIEW This review presents the most current information about the epidemiology of complex regional pain syndrome (CRPS), classification and diagnostic criteria, childhood CRPS, subtypes, pathophysiology, conventional and less conventional treatments, and preventive strategies. RECENT FINDINGS CRPS is a painful disorder with multifactorial pathophysiology. The data describe sensitization of the central and peripheral nervous systems, inflammation, possible genetic factors, sympatho-afferent coupling, autoimmunity, and mental health factors as contributors to the syndrome. In addition to conventional subtypes (type I and type II), cluster analyses have uncovered other proposed subtypes. Prevalence of CRPS is approximately 1.2%, female gender is consistently associated with a higher risk of development, and substantial physical, emotional, and financial costs can result from the syndrome. Children with CRPS seem to benefit from multifaceted physical therapy leading to a high percentage of symptom-free patients. The best available evidence along with standard clinical practice supports pharmacological agents, physical and occupational therapy, sympathetic blocks for engaging physical restoration, steroids for acute CRPS, neuromodulation, ketamine, and intrathecal baclofen as therapeutic approaches. There are many emerging treatments that can be considered as a part of individualized, patient-centered care. Vitamin C may be preventive. CRPS can lead to progressively painful sensory and vascular changes, edema, limb weakness, and trophic disturbances, all of which substantially erode healthy living. Despite some progress in research, more comprehensive basic science investigation is needed to clarify the molecular mechanisms of the disease so that targeted treatments can be developed for better outcomes. Incorporating a variety of standard therapies with different modes of action may offer the most effective analgesia. Introducing less conventional approaches may also be helpful when traditional treatments fail to provide sufficient improvement.
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Affiliation(s)
- Gerard Limerick
- Division of Pain Medicine, Department of Anesthesiology & Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, USA
- Department of Physical Medicine & Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, USA
| | - Dana K Christo
- Division of General Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, USA
| | - Jennifer Tram
- Department of Anesthesiology, University of California, San Diego, CA, USA
| | | | - John Manor
- Department of Physical Medicine & Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, USA
| | | | - Jay Karri
- Division of Pain Medicine, Department of Anesthesiology & Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, USA
- Department of Orthopedic Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Paul J Christo
- Division of Pain Medicine, Department of Anesthesiology & Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, USA.
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Huck NA, Donovan LJ, Shen H, Jordan CE, Muwanga GP, Bridges CM, Forman TE, Cordonnier SA, Haight ES, Dale-Huang F, Takemura Y, Tawfik VL. Sex-distinct microglial activation and myeloid cell infiltration in the spinal cord after painful peripheral injury. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2022; 12:100106. [PMID: 36531615 PMCID: PMC9755061 DOI: 10.1016/j.ynpai.2022.100106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 09/30/2022] [Accepted: 10/10/2022] [Indexed: 05/26/2023]
Abstract
Chronic pain is a common and often debilitating problem that affects 100 million Americans. A better understanding of pain's molecular mechanisms is necessary for developing safe and effective therapeutics. Microglial activation has been implicated as a mediator of chronic pain in numerous preclinical studies; unfortunately, translational efforts using known glial modulators have largely failed, perhaps at least in part due to poor specificity of the compounds pursued, or an incomplete understanding of microglial reactivity. In order to achieve a more granular understanding of the role of microglia in chronic pain as a means of optimizing translational efforts, we utilized a clinically-informed mouse model of complex regional pain syndrome (CRPS), and monitored microglial activation throughout pain progression. We discovered that while both males and females exhibit spinal cord microglial activation as evidenced by increases in Iba1, activation is attenuated and delayed in females. We further evaluated the expression of the newly identified microglia-specific marker, TMEM119, and identified two distinct populations in the spinal cord parenchyma after peripheral injury: TMEM119+ microglia and TMEM119- infiltrating myeloid lineage cells, which are comprised of Ly6G + neutrophils and Ly6G- macrophages/monocytes. Neurons are sensitized by inflammatory mediators released in the CNS after injury; however, the cellular source of these cytokines remains somewhat unclear. Using multiplex in situ hybridization in combination with immunohistochemistry, we demonstrate that spinal cord TMEM119+ microglia are the cellular source of cytokines IL6 and IL1β after peripheral injury. Taken together, these data have important implications for translational studies: 1) microglia remain a viable analgesic target for males and females, so long as duration after injury is considered; 2) the analgesic properties of microglial modulators are likely at least in part related to their suppression of microglial-released cytokines, and 3) a limited number of neutrophils and macrophages/monocytes infiltrate the spinal cord after peripheral injury but have unknown impact on pain persistence or resolution. Further studies to uncover glial-targeted therapeutic interventions will need to consider sex, timing after injury, and the exact target population of interest to have the specificity necessary for translation.
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Affiliation(s)
- Nolan A. Huck
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Lauren J. Donovan
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Huaishuang Shen
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
- Department of Orthopedic Surgery, First Affiliated Hospital of Soochow University, Suzhou 215000, China
| | - Claire E. Jordan
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Gabriella P.B. Muwanga
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
- Neurosciences Graduate Program, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Caldwell M. Bridges
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Thomas E. Forman
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Stephanie A. Cordonnier
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Elena S. Haight
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Fiona Dale-Huang
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
| | - Yoshinori Takemura
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
- Department of Anesthesiology, University of Toyama, Toyama 930-0194, Japan
| | - Vivianne L. Tawfik
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA 94305, USA
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