Physiology of pain
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
It should be stated at the outset that the biological response to a noxious stimulus is not pain. The International Association for the Study of Pain has defined pain in the following way:Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. It must always be remembered that the perception of pain is a complex interaction that involves sensory, emotional and behavioural factors. A person’s emotional and behavioural responses must always be considered as an important component in the perception and expression of pain. The person in pain must always be seen in the context of interactions between biological and psychosocial processes. Any attempts to manage pain that fail to take these interactions into account will, inevitably, lead to frustration and failure. The biological processes involved in our perception of pain are no longer viewed as a simple ‘hardwired’ system with a pure ‘stimulus–response’ relationship. The more recent conceptualization of pain seeks to take into account the changes that occur within the nervous system following any prolonged, noxious stimulus. Trauma to any part of the body – and nerve damage in particular – can lead to changes within other regions of the nervous system, which influence subsequent responses to sensory input. Long-term changes occur within the peripheral and central nervous system following noxious input. This ‘plasticity’ of the nervous system then alters the body’s response to further peripheral sensory input. Pain can be divided into two entities: ‘physiological’ and ‘pathophysiological’ (or ‘clinical’).
Overview of Pain: Classification and Concepts
Mark V. Boswell, B. Eliot Cole in Weiner's Pain Management, 2005
The human body possesses antipain (antinociception) systems including endorphins, enkephalins, etc. that are utilized as natural pain killers and neural feedback modulation to reduce perception of pain and the quantity of pain signals arriving at the “perceptron.”In normal function, the human body releases these painkillers to modulate or mollify pain. At the very least, if these chemicals are not released or do not arrive at the affected receptors, the perceptrons will appreciate pain or greater pain, in the presence of pain signals (Craig, 2002). Pain experts have also recognized that pain is nociceptive and/or neuropathic (Abrams, 2000), which are commonly thought to be equivalent to “acute” and “chronic,” respectively. The difficulty is that most acute and chronic pain conditions are a combination of both nociceptive and neuropathic pain, which can and do change over time. An acutely damaged nerve can result in acute neuropathic pain, and chronic arthritis can result in a chronic recurrent nociceptive pain. Antinociceptive dysfunction (Brookoff, 2000) occurs in the perceptron (brain and/or spinal cord) and can worsen both nociceptive and neuropathic pains; antinociceptive pain, in other words, is dysfunction of the natural pain modulation system (Heinricher, 2002). Then, externally delivered painkillers are antinociceptive, as well. Then, there are natural pain modulations that can malfunction resulting in more pain (hyperalgesia) or even pain without a noxious stimulus (allodynia). In this physiological manner, pain can be better understood. Each possible mechanism is dynamic in anatomical location, along pain pathways, and over time; each mechanism is individual and unique according to the underlying pain condition.
Acute neuropathic and persistent postacute pain
Pamela E. Macintyre, Stephan A. Schug in Acute Pain Management, 2014
Pain can be broadly classified into two main types—nociceptive and neuropathic—see Chapter 3. Nociceptive pain is the most common type of pain seen in the acute clinical setting and its treatment is therefore the primary focus of this book. Neuropathic pain is defined as “pain caused by injury or disease of the somato-sensory nervous system” (Jensen et al., 2011). It is also referred to as neurogenic pain, deafferentation pain, neuralgia, neuralgic pain, and nerve pain. It is the pathophysiological consequence of multiple changes in the peripheral and central nervous systems that occur after nerve injury (Cohen and Mao, 2014) (see Table 12.1). In the periphery, such lesions lead to structural and functional changes in the damaged neuron. Increased expression of ion channels (in particular,voltage-gated sodium channels) and upregulated receptors reduce the threshold for inducing action potentials and lead to increased numbers of action potentials described as “ectopic discharges”—that is, spontaneous firing of nerve impulses (Baron et al., 2010). Other peripheral changes are related to alterations in the microneuroanatomy (e.g., touch fibers become pain fibers). At a central level, central sensitization develops as a result of ectopic activity in the periphery. This results in increased release of excitatory amino acids (e.g., glutamate) and neuropeptides (e.g., substance P) in the dorsal horn of the spinal cord, where they lead to functional changes of second-order neurons. These changes are referred to as neuroplasticity and manifest as hyperexcitability leading to hyperalgesia and allodynia.
Patients with chronic musculoskeletal pain present low level of the knowledge about the neurophysiology of pain
Published in European Journal of Physiotherapy, 2021
Paula S. Ferreira, Leticia A. Corrêa, Juliana V. Bittencourt, Felipe J. J. Reis, Ney Meziat-Filho, Leandro A. C. Nogueira
Objective Identify the level of knowledge of the neurophysiology of pain in patients with chronic musculoskeletal pain and compare the level of knowledge of pain according to the type of musculoskeletal pain classification. Methods A cross-sectional study was conducted with 83 patients with chronic musculoskeletal pain. The classification of the pain mechanism was defined using clinical indicators, which uses a combination of patient self-report pain characteristics and physical examination. The level of neurophysiological pain knowledge was evaluated by the Brazilian version of the Neurophysiology of Pain Questionnaire, and the results were compared among musculoskeletal pain groups. Results In general, patients with chronic musculoskeletal pain presented low levels of knowledge about the neurophysiology of pain (31.1%). Thirty-six patients presented nociceptive pain, 21 of peripheral neuropathic pain, and 26 of central sensitisation. The level of neurophysiological knowledge of pain did not show a significant difference between the groups (central sensitisation: 33.7%; nociceptive pain: 32.2%; peripheral neuropathic pain: 25.9%; p = .153). Conclusions Patients with chronic musculoskeletal pain presented low levels of neurophysiological pain knowledge, regardless of their classification of pain based on its mechanism. Practical implications Patients with chronic musculoskeletal pain showed a low pain knowledge. Educational programmes are needed for musculoskeletal practice.
PERSONALITY TRAITS IN CHRONIC PAIN PATIENTS ARE ASSOCIATED WITH LOW ACCEPTANCE AND CATASTROPHIZING ABOUT PAIN
Published in Acta Clinica Belgica, 2011
C Poppe, G Crombez, J Devulder, I Hanoulle, D Vogelaers, M Petrovic
Objective: Pain acceptance is considered important for mental well-being with better functional outcomes for chronic pain patients. The present study explored whether pain-related variables (pain severity, pain interference, pain duration, and pain catastrophizing) and non-pain-related variables (personality traits) influence acceptance and additionally examined the interrelationship between the influencing variables and acceptance. Methods: One hundred patients with chronic pain from a multidisciplinary pain centre completed selfreport questionnaires on acceptance, pain severity, interference of life, pain duration, pain catastrophizing, and personality. Results: Pain severity, pain interference, and pain duration had no significant correlations with acceptance. Pain catastrophizing and most personality traits were significantly and negatively related to acceptance. Regression analyses revealed that of all personality traits, the avoidant personality trait explains most variance of acceptance. Subsequent mediation analysis indicated that catastrophizing about pain mediated the relationship between the avoidant personality trait and acceptance. Conclusion: The findings indicate that acceptance is influenced by catastrophizing and avoidant personality traits. The clinical implication might be that acceptanceoriented treatments may prove less successful in chronic pain patients with more pronounced avoidant personality traits. Extra focus on a reduction of the frequency of pain catastrophizing might be helpful.
Parent chronic pain and mental health symptoms impact responses to children’s pain
Published in Canadian Journal of Pain, 2018
Lauren M. Fussner, Cathleen Schild, Amy Lewandowski Holley, Anna C. Wilson
ABSTRACT Background Chronic pain is a prevalent health condition associated with parenting difficulties. Pain-specific parenting, such as protectiveness and catastrophizing, may contribute to chronic pain in children. Additional work is needed to test predictors of pain-specific parenting. Aim The current study tested parent mental health symptoms as predictors of protectiveness and catastrophizing about child pain and whether comorbid pain and mental health symptoms exacerbate risk for problematic responses to children’s pain. Methods Parents with chronic pain (n = 62) and parents without chronic pain (n = 80) completed self-report questionnaires assessing pain characteristics, mental health symptoms, and pain-specific parenting responses. Results Results indicated significantly higher rates of depression, anxiety, and somatization in parents with chronic pain. Depression predicted protectiveness and catastrophizing over and above chronic pain status. Chronic pain status moderated the association between increased anxiety and greater catastrophizing about child pain. Conclusions Findings highlight the potential impact of mental health symptoms on pain-specific parenting even when accounting for chronic pain status.
Related Knowledge Centers
- Ulnar Nerve
- Rheumatoid Arthritis
- Etiology
- Peripheral Neuropathy
- International Association For The Study of Pain