Neural pathways in chronic pain.

The evidence for changes in function of the central nervous system in cases of chronic pain is persuasive. We are not dealing with a passively wired system but one which changes structure and function and even connectivity in response to incoming sensory information. Whether these changes are capable of reversal with time and treatment remains to be shown. An optimist would suggest that physiological changes without abnormalities are indeed capable of reversal given time and appropriate neural input that matches normal non-painful afferent stimulation. That this is feasible is suggested by strategies of management with successful outcomes in patients with chronic pain, especially when pain is due to intermittent or limited ongoing stimulation of nociceptors. Clinical experience suggests, however, that deafferentation pain syndromes where pain is a consequence of damage directly to the nervous system cannot be viewed in such an optimistic light. A great deal more knowledge is required of how both the peripheral and central nervous system react to damage before we will be in a position to manage this source of chronic pain successfully.