Has basic research contributed to chronic pain treatment?

Our understanding of nociceptive processing and of plastic changes after pe rsistent noxious input has increased immensely within the last two decades. It is now clear that long-lasting noxious stimulation or damage to the ner vous system give rise to a neuronal hyperexcitability and that this sensiti sation of the nervous system plays an important role for development and ma intenance of chronic pain. The manifestations of such hyperexcitability are numerous and include among others: increased neuronal response to a suprat hreshold stimulus, expansion of the peripheral areas from where a central n eurone can be activated and the recruitment of previous non-responding noci ceptive neurones. Furthermore, it has been possible to modulate this neuron al hyperexcitability by the discovery of molecular targets for pain, by seq uencing DNA of ion channels and receptors and by development of new molecul es that exert their effects on these molecular targets. The changes in resp onsiveness appear to be partly time and intensity dependent and partly depe ndent on the cause of injury. Whereas relatively short-lasting and moderate noxious input leads to reversible plastic changes, more intense and long-l asting noxious stimulation implies a risk for persistent and more profound alterations in transmitters, receptors, ion channels and in neuronal connec tivity. Despite the explosion of new knowledge in pain processing and in mo lecular background for neuroplasticity, this progress has unfortunately not resulted in a corresponding improvement of our ability to treat chronic pa in. The number of patients with chronic unrelieved pain is still high and n ewer types of treatment have so far not resulted in a substantially better treatment. Nevertheless, there is now an ongoing systematic research in whi ch chronic pain conditions are assessed in a fashion so that mechanisms und erlying pain can be dissected. Moreover, controlled clinical trials togethe r with systematic reviews are carried out which in the future should permit formulation of treatment algorithms for chronic pain. Finally, it is likel y that the development of new specific types of treatment will show efficac y if they are evaluated and analysed not on the global pain experience, but more specifically on those targets and elements of the pain experience the y are aimed to deal with.