Pain syndromes and their treatment.

Neurogenic pain (encompassing all types of neuropathic and central pain) is discussed. Experimental work is presented in a model in which the rat sciatic nerve is loosely ligatured. In painful human neuropathies, tricyclic antidepressants have been found to be effective in proportion to the degree they facilitate monoaminergic activity. Several papers also stress the importance of early treatment with amitriptyline or desipramine, and the ineffectiveness of analgesics, including narcotics. In nociceptive pain, recent findings in humans emphasize the importance of both the retroinsular (SII) and the anterior cingulate cortices in the conscious appreciation of pain. Opioid studies have revealed individual differences in the metabolism of morphine to its 3- and 6-glucuronosides; patients with nociceptive pain who respond poorly to morphine or diamorphine probably have a high 3:6 ratio. It has been pointed out that methadone may be useful in such cases, as it is not broken down to glucuronosides.