PAINFUL PERIPHERAL NEUROPATHIES - ROLE OF NOCICEPTIVE C-AFFERENTS

Peripheral neuropathies are often associated with chronic and therapy resistant pain syndromes. The pathophysiological mechanisms underlying these disorders are unknown. All hypotheses that had been put forward until now have focussed pathological changes in the activity of nociceptive unmyelinated C-fibers as the major process in initiation and maintenance of neuropathic pain. Novel studies including animal models with mechanical peripheral nerve lesions and research on neuropathic pain patients do not support these concepts and claim, that the role of the nociceptive C-fibers has to be reconsidered or even discarded. The results of these studies indicate that in some chronic types of painful peripheral neuropathies all unmyelinated nociceptive C-fibers of the affected nerves are completely degenerated. Changes in the CNS synaptic processing depending on nociceptive C-fiber degeneration may occur that strengthen the synaptic ties between central pain signaling pathways and low-threshold mechanoreceptors with AP-fibers that are still intact. These possible central mechanisms will require new therapy concepts.