Recent advances in the knowledge of mechanisms of intractable pain.

Chronic intractable pain can arise from damage at three separate sites, or a combination of these sites: (a) deep tissue, (b) peripheral nerves, and (c) dorsal roots. At each site there is a complex progression of local and distant effects which are produced by a variety of chemical mediators and neurophysiological events. Damage, no matter at which site, often brings changes far beyond the original lesion. It is only by an understanding of the complex mechanisms involved, and the effects that they cause, that new and rational treatments for pain will be found.