Les douleurs neuropathiques en rhumatologie

Abstract

Neuropathic pain is a common symptom in rheumatology patients and often occurs in combination with pain related to excessive nociception. A neuropathic mechanism can explain why some patients experience difficulties in describing their pain and fail to respond to conventional analgesic therapy. Identification of a neuropathic component in a patient with a complex pain syndrome requires careful history taking, guided by appropriate questionnaires, a thorough physical evaluation including specific tests, and diagnostic investigations. The examining physician must be familiar with the various abnormalities characteristic of neuropathic pain, such as allodynia, hyperalgesia, and hyperpathia. In the field of rheumatology, neuropathic pain occurs mainly in patients with chronic and postoperative sciatica, autoimmune or inflammatory disease, entrapment syndromes, disease related to alcohol or other toxic substances, diabetes, drug-induced syndromes, and type 1 or 2 complex regional pain syndromes. The pathophysiology of neuropathic pain involves peripheral mechanisms (abnormal ectopic activities, nociceptor downregulation, and abnormal fiber cross-talk), which are often exacerbated by the sympathetic system. Central mechanisms play a role also, particularly in chronic forms (central downregulation, alteration in nociceptive message modulation, central plasticity). These mechanisms explain the effectiveness of the treatments commonly used in neuropathic pain, most are which are not conventional analgesics. In conclusion, to evaluate acute and chronic pain, rheumatologists must become familiar with neuropathic syndromes. In difficult cases, neuropathic pain should be considered and looked for with the goal of initiating a treatment program adapted to the underlying pathophysiological mechanism.