Current understanding of nociplastic pain

Abstract

Nociplastic pain by the "International Association for the Study of Pain" is defined as pain that arises from altered nociception despite no clear evidence of nociceptive or neuropathic pain. Augmented central nervous system pain and sensory processing with altered pain modulation are suggested to be the mechanism of nociplastic pain. Clinical criteria for possible nociplastic pain affecting somatic structures include chronic regional pain and evoked pain hypersensitivity including allodynia with after-sensation. In addition to possible nociplastic pain, clinical criteria for probable nociplastic pain are pain hypersensitivity in the region of pain to non-noxious stimuli and presence of comorbidity such as generalized symptoms with sleep disturbance, fatigue, or cognitive problems with hypersensitivity of special senses. Criteria for definitive nociplastic pain is not determined yet. Eight specific disorders related to central sensitization are suggested to be restless leg syndrome, chronic fatigue syndrome, fibromyalgia, temporomandibular disorder, migraine or tension headache, irritable bowel syndrome, multiple chemical sensitivities, and whiplash injury; non-specific emotional disorders related to central sensitization include anxiety or panic attack and depression. These central sensitization pain syndromes are overlapped to previous functional pain syndromes which are unlike organic pain syndromes and have emotional components. Therefore, nociplastic pain can be understood as chronic altered nociception related to central sensitization including both sensory components with nociceptive and/or neuropathic pain and emotional components. Nociplastic pain may be developed to explain unexplained chronic pain beyond tissue damage or pathology regardless of its origin from nociceptive, neuropathic, emotional, or mixed pain components.

Keywords: Central Nervous System Sensitization; Chronic Pain; Emotions; Hyperalgesia; Hypersensitivity; Neuralgia; Neuronal Plasticity; Nociception; Nociceptive Pain.

Fig. 1

Current concept of nociplastic pain. (A) Traditional pain consists of sensory (nociceptive and neuropathic pain) and emotional components (anxiety, depression, and pain panic), originating from actual and potential tissue damages, respectively. (B) Nociplastic pain is chronic pain with altered nociception, originating from entirely neither nociceptive nor neuropathic pain, along with emotional components. (C) According to the criteria of nociplastic pain, central sensitization (blue circle) becomes a basic mechanism for explanation of nociplastic pain. Functional pain syndrome (black circle) shows nociceptive pain (rather than neuropathic pain) based on emotional component. Psychogenic pain (orange circle) shows pain, depends on emotional status, and responds to antipsychotics, antidepressants, or anxiolytics.