Nociplastic pain: controversy of the concept

Classically, pain can be of a nociceptive or neuropathic nature, which refers to non-neural or neural tissue lesions, respectively. Chronic pain in conditions such as migraine, fibromyalgia, and complex regional pain syndrome (CRPS), is thought to perpetuate without a noxious input. Pain in such patients can be assigned neither to the nociceptive nor neuropathic category. Therefore, a third pain descriptor, named "nociplastic pain", has been adopted by the International Association for the Study of Pain. The current controversy-focused narrative review updates littledebated aspects of the new pain concept. The most disputable feature of nociplastic pain is its autonomous persistence, i.e., existence without causative tissue damage, presumably because of a malfunction of pain pathways and processing. This contradicts the fact that nociplastic pain is accompanied by persistent central sensitization that has been shown to require a continuing noxious input, e.g ., nerve injury. Even if sensitization occurs without a lesion, e.g ., in psychogenic and emotional pain, peripheral stimulus is necessary to produce pain. A logical weakness of the concept is that the word "plastic" in biology refers to adaptation rather than to maladaptation. The pathophysiologic mechanism of nociplastic pain may, in fact, be associated with background conditions that elude diagnosis because of the limitations of current diagnostic means. Misapplication of the nociplastic pain category may weaken diagnostic alertness toward occult causes of pain. Possible diagnostic errors could be avoided by understanding that nociplastic pain is a mechanism of pain rather than a diagnosis. Clinical use of this pain descriptor deserves a wider critical discussion.