Quantitative sensory testing (QST) is a formal variant of a time-honoured clinical examination technique in neurology, the sensory examination. Prototypical QST profiles have been found in human ...surrogate models of peripheral sensitization, central sensitization, and deafferentation. Probabilistic sorting of individual patients to any combination of these profiles has been developed, and there is emerging evidence for the predictive value of such sensory profiles for treatment efficacy. This way, QST aids in diagnostics of individual patients and may help guide their care in the future. Deficits in "dynamic" QST have been proposed as predictors of chronic pain (impaired descending inhibition and delayed recovery from central sensitization). Several psychological factors had previously been found to be predictors of pain chronicity (catastrophizing, self-efficacy, and neuroticism). The relative importance of psychological vs sensory testing predictors has not been evaluated. It is likely that both will have differential roles in clinical practice.
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GEOZS, IJS, IMTLJ, KILJ, OILJ, SBCE, SBJE, UL, UPUK
Milton Cohen, John Quintner, and Simon van Rysewyk proposed a revision of the IASP definition of pain of 1979. This commentary summarizes, why this proposal is useful for guiding assessment of pain, ...but not its definition.
The "gate control theory of pain" of 1965 became famous for integrating clinical observations and the understanding of spinal dorsal horn circuitry at that time into a testable model. Although it ...became rapidly clear that spinal circuitry is much more complex than that proposed by Melzack and Wall, their prediction of the clinical efficacy of transcutaneous electrical nerve stimulation and spinal cord stimulation has left an important clinical legacy also 50 years later. In the meantime, it has been recognized that the sensitivity of the nociceptive system can be decreased or increased and that this "gain control" can occur at peripheral, spinal, and supraspinal levels. The resulting changes in pain sensitivity can be rapidly reversible or persistent, highly localized or widespread. Profiling of spatio-temporal characteristics of altered pain sensitivity (evoked pain to mechanical and/or heat stimuli) allows implications on the mechanisms likely active in a given patient, including peripheral or central sensitization, intraspinal or descending inhibition. This hypothesis generation in the diagnostic process is an essential step towards a mechanism-based treatment of pain. The challenge now is to generate the rational basis of multimodal pain therapy algorithms by including profile-based stratification of patients into studies on efficacy of pharmacological and nonpharmacological treatment modalities. This review outlines the current evidence base for this approach.
Chronic pain is a major source of suffering. It interferes with daily functioning and often is accompanied by distress. Yet, in the International Classification of Diseases, chronic pain diagnoses ...are not represented systematically. The lack of appropriate codes renders accurate epidemiological investigations difficult and impedes health policy decisions regarding chronic pain such as adequate financing of access to multimodal pain management. In cooperation with the WHO, an IASP Working Group has developed a classification system that is applicable in a wide range of contexts, including pain medicine, primary care, and low-resource environments. Chronic pain is defined as pain that persists or recurs for more than 3 months. In chronic pain syndromes, pain can be the sole or a leading complaint and requires special treatment and care. In conditions such as fibromyalgia or nonspecific low-back pain, chronic pain may be conceived as a disease in its own right; in our proposal, we call this subgroup "chronic primary pain." In 6 other subgroups, pain is secondary to an underlying disease: chronic cancer-related pain, chronic neuropathic pain, chronic secondary visceral pain, chronic posttraumatic and postsurgical pain, chronic secondary headache and orofacial pain, and chronic secondary musculoskeletal pain. These conditions are summarized as "chronic secondary pain" where pain may at least initially be conceived as a symptom. Implementation of these codes in the upcoming 11th edition of International Classification of Diseases will lead to improved classification and diagnostic coding, thereby advancing the recognition of chronic pain as a health condition in its own right.
Chronic pain after tissue trauma is frequent and may have a lasting impact on the functioning and quality of life of the affected person. Despite this, chronic postsurgical and posttraumatic pain is ...underrecognised and, consequently, undertreated. It is not represented in the current International Classification of Diseases (ICD-10). This article describes the new classification of chronic postsurgical and posttraumatic pain for ICD-11. Chronic postsurgical or posttraumatic pain is defined as chronic pain that develops or increases in intensity after a surgical procedure or a tissue injury and persists beyond the healing process, ie, at least 3 months after the surgery or tissue trauma. In the classification, it is distinguished between tissue trauma arising from a controlled procedure in the delivery of health care (surgery) and forms of uncontrolled accidental damage (other traumas). In both sections, the most frequent conditions are included. This provides diagnostic codes for chronic pain conditions that persist after the initial tissue trauma has healed and that require specific treatment and management. It is expected that the representation of chronic postsurgical and posttraumatic pain in ICD-11 furthers identification, diagnosis, and treatment of these pain states. Even more importantly, it will make the diagnosis of chronic posttraumatic or postsurgical pain statistically visible and, it is hoped, stimulate research into these pain syndromes.
This article describes a proposal for the new diagnosis of chronic primary pain (CPP) in ICD-11. Chronic primary pain is chosen when pain has persisted for more than 3 months and is associated with ...significant emotional distress and/or functional disability, and the pain is not better accounted for by another condition. As with all pain, the article assumes a biopsychosocial framework for understanding CPP, which means all subtypes of the diagnosis are considered to be multifactorial in nature, with biological, psychological, and social factors contributing to each. Unlike the perspectives found in DSM-5 and ICD-10, the diagnosis of CPP is considered to be appropriate independently of identified biological or psychological contributors, unless another diagnosis would better account for the presenting symptoms. Such other diagnoses are called "chronic secondary pain" where pain may at least initially be conceived as a symptom secondary to an underlying disease. The goal here is to create a classification that is useful in both primary care and specialized pain management settings for the development of individualized management plans, and to assist both clinicians and researchers by providing a more accurate description of each diagnostic category.
Chronic musculoskeletal pain is defined as chronic pain arising from musculoskeletal structures such as bones or joints. Although comprising the most prevalent set of chronic pain conditions, it was ...not represented appropriately in the 10th edition of the International Classification of Diseases (ICD-10), which was organized mainly according to anatomical sites, was strongly focused on musculoskeletal disease or local damage, and did not consider the underlying mechanisms of pain. The new ICD-11 classification introduces the concept of chronic primary and secondary musculoskeletal pain, and integrates the biomedical axis with the psychological and social axes that comprise the complex experience of chronic musculoskeletal pain. Chronic primary musculoskeletal pain is a condition in its own right, not better accounted for by a specific classified disease. Chronic secondary musculoskeletal pain is a symptom that arises from an underlying disease classified elsewhere. Such secondary musculoskeletal pain originates in persistent nociception in musculoskeletal structures from local or systemic etiologies, or it may be related to deep somatic lesions. It can be caused by inflammation, by structural changes, or by biomechanical consequences of diseases of the nervous system. It is intended that this new classification will facilitate access to patient-centered multimodal pain management and promote research through more accurate epidemiological analyses.
Julius' laboratory discovered an ion channel that is gated by the pungent chemical capsaicin and also responds to noxious heat.1 This channel, initially named vanilloid receptor 1, is a member of the ...large family of transmembrane proteins called transient receptor potential (TRP) channels, and the heat-sensitive and capsaicin-sensitive channel was renamed TRPV1. Reports have shown that these effects on core body temperature are mediated via sensory input to the CNS rather than through peripheral actions on the vasculature,2 suggesting that novel TRPV1 antagonists with purely peripheral actions might diminish inflammatory pain without affecting core body temperature.2 To facilitate the development of analgesic drugs, many laboratories have attempted to derive nociceptor-like cells from cutaneous human stem cells; appropriate culture conditions were identified in 2022 by exploiting the responsiveness of these nociceptor-like cells to stimuli, such as capsaicin, heat, and inflammatory mediators, and the expression of TRPV1 by these cells.3 In chronic inflammation, pain is a symptom, but several disorders are defined by the presence of chronic pain (ie, chronic primary pain).4 TRPV1 is suggested to contribute to at least one such condition: chronic primary low-back pain, which is promoted by repeated, mild muscle injuries and chronic stress. In animal models of chronic primary low-back pain, TRPV1 activity is controlled by another TRP channel, TRP subfamily M member 3, via mitochondrial-signalling pathways.5 Patapoutian's team was one of many that were searching for the elusive ion channel that transduces noxious mechanical stimuli into the depolarisation of nociceptive primary afferents.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The redefinition of neuropathic pain as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system," which was suggested by the International Association for the ...Study of Pain (IASP) Special Interest Group on Neuropathic Pain (NeuPSIG) in 2008, has been widely accepted. In contrast, the proposed grading system of possible, probable, and definite neuropathic pain from 2008 has been used to a lesser extent. Here, we report a citation analysis of the original NeuPSIG grading paper of 2008, followed by an analysis of its use by an expert panel and recommendations for an improved grading system. As of February, 2015, 608 eligible articles in Scopus cited the paper, 414 of which cited the neuropathic pain definition. Of 220 clinical studies citing the paper, 56 had used the grading system. The percentage using the grading system increased from 5% in 2009 to 30% in 2014. Obstacles to a wider use of the grading system were identified, including (1) questions about the relative significance of confirmatory tests, (2) the role of screening tools, and (3) uncertainties about what is considered a neuroanatomically plausible pain distribution. Here, we present a revised grading system with an adjusted order, better reflecting clinical practice, improvements in the specifications, and a word of caution that even the "definite" level of neuropathic pain does not always indicate causality. In addition, we add a table illustrating the area of pain and sensory abnormalities in common neuropathic pain conditions and propose areas for further research.
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