Integrating nociplastic pain into neuropathic pain framework: a proposal for a revised classification.

From an etiological perspective, the International Association for the Study of Pain (IASP) classifies pain into three categories: nociceptive pain (NcP), neuropathic pain (NeP), and nociplastic pain (NpP). In clinical practice, distinguishing between NpP and NeP can be particularly challenging. They share many clinical characteristics, including pain hypersensitivity and spontaneous pain. Currently, no evidence-based diagnostic method has been established for NpP, as defined by the IASP. Questionnaires had been developed before the IASP officially adopted NpP in 2017. Therefore, they cannot reliably distinguish between NpP and NeP. There is a previously unrecognized academic ambiguity arising from the coexistence of the unified concept of NeP including NpP and the separate concept of NeP excluding NpP. Moreover, NpP diagnosed using different criteria can coexist. There is currently no established guideline for either the pharmacological or the non-pharmacological treatment of NpP. The treatment of fibromyalgia, a typical NpP, closely resembles that of NeP. The theoretical concept of NpP has generated substantial uncertainty not only in pain research but also in clinical practice, particularly regarding diagnosis and treatment. To simplify diagnosis and treatment, resolve scholarly uncertainty, and improve the care of patients with pain, four provisional plans are proposed until an evidence-based method for diagnosing NpP has been established. (1) Integrate NpP into NeP and use the term NeP. (2) Classify NpP as a subcategory of NeP and use the term NeP. (3) Integrate NpP into NeP and use the term new NeP (nNeP). (4) Classify NpP as a subcategory of NeP and use the term nNeP. The recommended plan is (1). It is hoped that these four proposals will serve as constructive contributions toward advancing both the conceptual understanding of pain and its treatment.