A new definition of neuropathic pain
TL;DR: A new definition of neuropathic pain is published which is defined as “pain caused by a lesion or disease of the somatosensory system” ( www.iasp-pain.org/resources/painDefinition).
Abstract: 1. IntroductionIASP has recently published a new definition of neuropathic pain according to which neuropathic pain is defined as “pain caused by a lesion or disease of the somatosensory system” (www.iasp-pain.org/resources/painDefinition). This definition replaces the 17-year old definition that ap
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Heidelberg University1, University of Marburg2, Queen Mary University of London3, University of Leeds4, Rutgers University5, University of New South Wales6, University of Münster7, Aarhus University8, Columbia University9, University of Chieti-Pescara10, Norwegian University of Science and Technology11, Karolinska Institutet12, Université catholique de Louvain13, University of Sydney14, University of Western Australia15, University of Dundee16, Maastricht University17, Katholieke Universiteit Leuven18, National Yang-Ming University19
TL;DR: The IASP Task Force, which comprises pain experts from across the globe, has developed a new and pragmatic classification of chronic pain for the upcoming 11th revision of the International Classification of Diseases, termed “multiple parenting.”
Abstract: Chronic pain has been recognized as pain that persists past normal healing time5 and hence lacks the acute warning function of physiological nociception.35 Usually pain is regarded as chronic when it lasts or recurs for more than 3 to 6 months.29 Chronic pain is a frequent condition, affecting an estimated 20% of people worldwide6,13,14,18 and accounting for 15% to 20% of physician visits.25,28 Chronic pain should receive greater attention as a global health priority because adequate pain treatment is a human right, and it is the duty of any health care system to provide it.4,13
The current version of the International Classification of Diseases (ICD) of the World Health Organization (WHO) includes some diagnostic codes for chronic pain conditions, but these diagnoses do not reflect the actual epidemiology of chronic pain, nor are they categorized in a systematic manner. The ICD is the preeminent tool for coding diagnoses and documenting investigations or therapeutic measures within the health care systems of many countries. In addition, ICD codes are commonly used to report target diseases and comorbidities of participants in clinical research. Consequently, the current lack of adequate coding in the ICD makes the acquisition of accurate epidemiological data related to chronic pain difficult, prevents adequate billing for health care expenses related to pain treatment, and hinders the development and implementation of new therapies.10,11,16,23,27,31,37
Responding to these shortcomings, the International Association for the Study of Pain (IASP) contacted the WHO and established a Task Force for the Classification of Chronic Pain. The IASP Task Force, which comprises pain experts from across the globe,19 has developed a new and pragmatic classification of chronic pain for the upcoming 11th revision of the ICD. The goal is to create a classification system that is applicable in primary care and in clinical settings for specialized pain management.
A major challenge in this process was finding a rational principle of classification that suits the different types of chronic pain and fits into the general ICD-11 framework. Pain categories are variably defined based on the perceived location (headache), etiology (cancer pain), or the primarily affected anatomical system (neuropathic pain). Some diagnoses of pain defy these classification principles (fibromyalgia).
This problem is not unique to the classification of pain, but exists throughout the ICD. The IASP Task Force decided to give first priority to pain etiology, followed by underlying pathophysiological mechanisms, and finally the body site. Developing this multilayered classification was greatly facilitated by a novel principle of assigning diagnostic codes in ICD-11, termed “multiple parenting.” Multiple parenting allows the same diagnosis to be subsumed under more than 1 category (for a glossary of ICD terms refer to Table Table1).1). Each diagnosis retains 1 category as primary parent, but is cross-referenced to other categories that function as secondary parents.
Table 1
Glossary of ICD-11 terms.
The new ICD category for “Chronic Pain” comprises the most common clinically relevant disorders. These disorders were divided into 7 groups (Fig. (Fig.1):1): (1) chronic primary pain, (2) chronic cancer pain, (3) chronic posttraumatic and postsurgical pain, (4) chronic neuropathic pain, (5) chronic headache and orofacial pain, (6) chronic visceral pain, and (7) chronic musculoskeletal pain. Experts assigned to each group are responsible for the definition of diagnostic criteria and the selection of the diagnoses to be included under these subcategories of chronic pain. Thanks to Bedirhan Ustun and Robert Jakob of the WHO, these pain diagnoses are now integrated in the beta version of ICD-11 (http://id.who.int/icd/entity/1581976053). The Task Force is generating content models for single entities to describe their clinical characteristics. After peer review overseen by the WHO Steering Committee,39 the classification of chronic pain will be voted into action by the World Health Assembly in 2017.
Figure 1
Organizational chart of Task Force, IASP, and WHO interactions. The IASP Task Force was created by the IASP council and its scope defined in direct consultation of the chairs (R.D.T. and W.R.) with WHO representatives in 2012. The Task Force reports to ...
2. Classification of chronic pain
Chronic pain was defined as persistent or recurrent pain lasting longer than 3 months. This definition according to pain duration has the advantage that it is clear and operationalized.
Optional specifiers for each diagnosis record evidence of psychosocial factors and the severity of the pain. Pain severity can be graded based on pain intensity, pain-related distress, and functional impairment.
2.1. Chronic primary pain
Chronic primary pain is pain in 1 or more anatomic regions that persists or recurs for longer than 3 months and is associated with significant emotional distress or significant functional disability (interference with activities of daily life and participation in social roles) and that cannot be better explained by another chronic pain condition. This is a new phenomenological definition, created because the etiology is unknown for many forms of chronic pain. Common conditions such as, eg, back pain that is neither identified as musculoskeletal or neuropathic pain, chronic widespread pain, fibromyalgia, and irritable bowel syndrome will be found in this section and biological findings contributing to the pain problem may or may not be present. The term “primary pain” was chosen in close liaison with the ICD-11 revision committee, who felt this was the most widely acceptable term, in particular, from a nonspecialist perspective.
1,627 citations
Cites background from "A new definition of neuropathic pai..."
...Chronic neuropathic pain is caused by a lesion or disease of the somatosensory nervous system.(20,22) The somatosensory nervous system provides information about the body including skin, musculoskeletal, and visceral organs....
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...The diagnosis of neuropathic pain requires a history of nervous system injury, for example, by a stroke, nerve trauma, or diabetic neuropathy, and a neuroanatomically plausible distribution of the pain.(22) For the identification of definite neuropathic pain, it is necessary to demonstrate the lesion or disease involving the nervous system, for example, by imaging, biopsy, neurophysiological, or laboratory tests....
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Johns Hopkins University School of Medicine1, Tufts University2, University of New South Wales3, Aarhus University Hospital4, Aarhus University5, Heidelberg University6, University of Melbourne7, Duke University8, McGill University9, University of Iowa10, Southern University of Science and Technology11, University of Toronto12, University of Washington13, Dalhousie University14, Aichi Medical University15, Queen's University16
TL;DR: This review provides a synopsis of the critical concepts, the analysis of comments from the IASP membership and public, and the committee's final recommendations for revisions to the definition and notes, which were discussed over a 2-year period.
Abstract: The current International Association for the Study of Pain (IASP) definition of pain as "An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage" was recommended by the Subcommittee on Taxonomy and adopted by the IASP Council in 1979. This definition has become accepted widely by health care professionals and researchers in the pain field and adopted by several professional, governmental, and nongovernmental organizations, including the World Health Organization. In recent years, some in the field have reasoned that advances in our understanding of pain warrant a reevaluation of the definition and have proposed modifications. Therefore, in 2018, the IASP formed a 14-member, multinational Presidential Task Force comprising individuals with broad expertise in clinical and basic science related to pain, to evaluate the current definition and accompanying note and recommend whether they should be retained or changed. This review provides a synopsis of the critical concepts, the analysis of comments from the IASP membership and public, and the committee's final recommendations for revisions to the definition and notes, which were discussed over a 2-year period. The task force ultimately recommended that the definition of pain be revised to "An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage," and that the accompanying notes be updated to a bulleted list that included the etymology. The revised definition and notes were unanimously accepted by the IASP Council early this year.
1,432 citations
Cites background from "A new definition of neuropathic pai..."
...The definition should be valid for acute and chronic pain and apply to all pain conditions, regardless of their pathophysiology (eg, nociceptive, neuropathic, and nociplastic).(20,22) Second, the definition of pain should be applicable to humans and nonhuman animals....
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Heidelberg University1, University of Marburg2, Queen Mary University of London3, University of Leeds4, Rutgers University5, University of New South Wales6, University of Münster7, Aarhus University8, Columbia University9, University of Chieti-Pescara10, University of Oslo11, Karolinska Institutet12, Université catholique de Louvain13, University of Sydney14, Paris Descartes University15, University of Western Australia16, Royal Perth Hospital17, University of Dundee18, Maastricht University19, Katholieke Universiteit Leuven20, National Yang-Ming University21, Taipei Veterans General Hospital22
TL;DR: In conditions such as fibromyalgia or nonspecific low-back pain, chronic pain may be conceived as a disease in its own right; in this proposal, this subgroup is called “chronic primary pain,” and in 6 other subgroups, pain is secondary to an underlying disease.
Abstract: 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.
1,311 citations
Aarhus University1, Washington University in St. Louis2, University of the Witwatersrand3, University of Oxford4, Sapienza University of Rome5, Harvard University6, Karolinska Institutet7, Walton Centre8, Johns Hopkins University9, Imperial College London10, Chelsea and Westminster Hospital NHS Foundation Trust11, University of Dundee12, Heidelberg University13
TL;DR: A revised grading system of possible, probable, and definite neuropathic pain from 2008 is presented with an adjusted order, better reflecting clinical practice, improvements in the specifications, and a word of caution that even the “definite” level of neuropathicPain does not always indicate causality.
Abstract: 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.
745 citations
TL;DR: The pain phenotype can serve as a window on underlying pathophysiological neural mechanisms and as a guide for developing personalized pain medicine.
680 citations
Cites background from "A new definition of neuropathic pai..."
...By definition, neuropathic pain involves damage to the nervous system (Jensen et al., 2011)....
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TL;DR: A grading system of definite, probable, and possible neuropathic pain is proposed, which includes the grade possible, which can only be regarded as a working hypothesis, and the grades probable and definite, which require confirmatory evidence from a neurologic examination.
Abstract: Pain usually results from activation of nociceptive afferents by actually or potentially tissue-damaging stimuli. Pain may also arise by activity generated within the nervous system without adequate stimulation of its peripheral sensory endings. For this type of pain, the International Association for the Study of Pain introduced the term neuropathic pain, defined as "pain initiated or caused by a primary lesion or dysfunction in the nervous system." While this definition has been useful in distinguishing some characteristics of neuropathic and nociceptive types of pain, it lacks defined boundaries. Since the sensitivity of the nociceptive system is modulated by its adequate activation (e.g., by central sensitization), it has been difficult to distinguish neuropathic dysfunction from physiologic neuroplasticity. We present a more precise definition developed by a group of experts from the neurologic and pain community: pain arising as a direct consequence of a lesion or disease affecting the somatosensory system. This revised definition fits into the nosology of neurologic disorders. The reference to the somatosensory system was derived from a wide range of neuropathic pain conditions ranging from painful neuropathy to central poststroke pain. Because of the lack of a specific diagnostic tool for neuropathic pain, a grading system of definite, probable, and possible neuropathic pain is proposed. The grade possible can only be regarded as a working hypothesis, which does not exclude but does not diagnose neuropathic pain. The grades probable and definite require confirmatory evidence from a neurologic examination. This grading system is proposed for clinical and research purposes.
2,342 citations
TL;DR: Large‐scale drug trials that aim to identify possible subgroups of patients who are likely to respond to specific drugs are needed to test the hypothesis that a mechanism‐based classification may help improve treatment of the individual patients.
Abstract: Randomized, double-blind, placebo-controlled trials on neuropathic pain treatment are accumulating, so an updated review of the available evidence is needed. Studies were identified using MEDLINE and EMBASE searches. Numbers needed to treat (NNT) and numbers needed to harm (NNH) values were used to compare the efficacy and safety of different treatments for a number of neuropathic pain conditions. One hundred and seventy-four studies were included, representing a 66% increase in published randomized, placebo-controlled trials in the last 5 years. Painful poly-neuropathy (most often due to diabetes) was examined in 69 studies, postherpetic neuralgia in 23, while peripheral nerve injury, central pain, HIV neuropathy, and trigeminal neuralgia were less often studied. Tricyclic antidepressants, serotonin noradrenaline reuptake inhibitors, the anticonvulsants gabapentin and pregabalin, and opioids are the drug classes for which there is the best evidence for a clinical relevant effect. Despite a 66% increase in published trials only a limited improvement of neuropathic pain treatment has been obtained. A large proportion of neuropathic pain patients are left with insufficient pain relief. This fact calls for other treatment options to target chronic neuropathic pain. Large-scale drug trials that aim to identify possible subgroups of patients who are likely to respond to specific drugs are needed to test the hypothesis that a mechanism-based classification may help improve treatment of the individual patients.
935 citations
University of Helsinki1, French Institute of Health and Medical Research2, University of Wisconsin-Madison3, Lancaster University4, Sapienza University of Rome5, Karolinska University Hospital6, Johns Hopkins University7, University College London8, Aarhus University Hospital9, University of Liverpool10, Imperial College London11, University of California, San Francisco12, University of Würzburg13, University of Aberdeen14, Heidelberg University15
TL;DR: Screening questionnaires are suitable for identifying potential patients with neuropathic pain, but further validation of them is needed for epidemiological purposes and quantitative sensory testing is recommended for selected cases in clinic, including the diagnosis of small fiber neuropathies and for research purposes.
Abstract: This is a revision of guidelines, originally published in 2004, for the assessment of patients with neuropathic pain. Neuropathic pain is defined as pain arising as a direct consequence of a lesion or disease affecting the somatosensory system either at peripheral or central level. Screening questionnaires are suitable for identifying potential patients with neuropathic pain, but further validation of them is needed for epidemiological purposes. Clinical examination, including accurate sensory examination, is the basis of neuropathic pain diagnosis. For more accurate sensory profiling, quantitative sensory testing is recommended for selected cases in clinic, including the diagnosis of small fiber neuropathies and for research purposes. Measurement of trigeminal reflexes mediated by A-beta fibers can be used to differentiate symptomatic trigeminal neuralgia from classical trigeminal neuralgia. Measurement of laser-evoked potentials is useful for assessing function of the A-delta fiber pathways in patients with neuropathic pain. Functional brain imaging is not currently useful for individual patients in clinical practice, but is an interesting research tool. Skin biopsy to measure the intraepidermal nerve fiber density should be performed in patients with clinical signs of small fiber dysfunction. The intensity of pain and treatment effect (both in clinic and trials) should be assessed with numerical rating scale or visual analog scale. For future neuropathic pain trials, pain relief scales, patient and clinician global impression of change, the proportion of responders (50% and 30% pain relief), validated neuropathic pain quality measures and assessment of sleep, mood, functional capacity and quality of life are recommended.
909 citations
TL;DR: Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles and most of the new studies focused on small fiber neuropathy (SFN).
Abstract: Background: Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles. Most of the new studies focused on small fiber neuropathy (SFN), a subtype of neuropathy for which the diagnosis was first developed through skin biopsy examination. This revision focuses on the use of this technique to diagnose SFN.
Methods: Task force members searched the Medline database from 2005, the year of the publication of the first EFNS guideline, to June 30th, 2009. All pertinent articles were rated according to the EFNS and PNS guidance. After a consensus meeting, the task force members created a manuscript that was subsequently revised by two experts (JML and JVS) in the field of peripheral neuropathy and clinical neurophysiology, who were not previously involved in the use of skin biopsy.
Results and Conclusions: Distal leg skin biopsy with quantification of the linear density of intraepidermal nerve fibers (IENF), using generally agreed upon counting rules, is a reliable and efficient technique to assess the diagnosis of SFN (Recommendation Level A). Normative reference values are available for bright-field immunohistochemistry (Recommendation Level A) but not yet for confocal immunofluorescence or the blister technique. The morphometric analysis of IENF density, either performed with bright-field or immunofluorescence microscopy, should always refer to normative values matched for age (Recommendation Level A). Newly established laboratories should undergo adequate training in a well-established skin biopsy laboratory and provide their own stratified for age and gender normative values, intra- and interobserver reliability, and interlaboratory agreement. Quality control of the procedure at all levels is mandatory (Good Practice Point). Procedures to quantify subepidermal nerve fibers and autonomic innervated structures, including erector pili muscles, and skin vessels, are under development but need to be confirmed by further studies. Sweat gland innervation can be examined using an unbiased stereologic technique recently proposed (Recommendation Level B).A reduced IENF density is associated with the risk of developing neuropathic pain (Recommendation Level B), but it does not correlate with its intensity. Serial skin biopsies might be useful for detecting early changes of IENF density, which predict the progression of neuropathy, and to assess degeneration and regeneration of IENF (Recommendation Level C). However, further studies are warranted to confirm its potential usefulness as an outcome measure in clinical practice and research. Skin biopsy has not so far been useful for identifying the etiology of SFN. Finally, we emphasize that 3-mm skin biopsy at the ankle is a safe procedure based on the experience of 10 laboratories reporting absence of serious side effects in approximately 35 000 biopsies and a mere 0.19% incidence of non-serious side effects in about 15 years of practice (Good Practice Point).
704 citations