Neurology (58)

Abstract

Peripheral neuropathic pain: from mechanisms to symptoms. (Christian‐Albrechts‐Univerität Kiel, Kiel, Germany) Clin J Pain 2000;16:S12–20.This review concentrates on the several independent pathophysiological mechanisms in both the peripheral and central nervous system that are responsible for sensory symptoms as well as spontaneous and evoked pains in peripheral neuropathies. These mechanisms can operate in concert in a single disease entity and also in a single patient. Distinct pathophysiological mechanisms lead to specific sensory symptoms, for example, dynamic mechanical allodynia and cold hyperalgesia. It is also possible that the pain‐generating mechanism and the symptoms change during the course of the disease. A thorough analysis of sensory symptoms may reveal the underlying mechanisms that are mainly active in a particular patient. The treatment of neuropathic pain is currently unsatisfactory. In the future, drugs will be developed that address specifically the relevant combination of mechanisms. Comment by Enrique Reig, MD.This is an excellent article, which will be a landmark in the approach to the treatment of neuropathic pain. There are several pathophysiological mechanisms, which can cause sensitive symptoms and spontaneous or evoked pain. Mechanical or thermal hyperalgesia is caused by peripheral sensitization. Pinprick hyperalgesia is correlated to the “wind‐up” phenomenon. Allodynia has multiple triggering factors: central sensitization, central reorganization and loss of inhibitory control. Paresthesia is explained by ectopic discharges due to the accumulation of Na+ channels, as with stabbing or paroxysmal pain. A hot or burning pain can be explained by peripheral sensitization and loss of inhibitory mechanisms. This explains why not all painful syndromes respond with the same efficacy to a given treatment. Neuropathic pain can occur in very different forms. For instance, a diabetic neuropathy can be associated with allodynia and hyperalgesia, or with burning and paroxysmal pain. A different treatment is required for each of these symptoms. From now on, we must use a different criterion to label painful neuropathic syndromes. Keeping to the above example, we shall distinguish between diabetic neuropathy with allodynia and diabetic neuropathy with burning pain.