Neuropathic pain and injured nerve: peripheral mechanisms.

Injury to sensory axons often has the paradoxical effect of inducing positive sensory disturbances; paraesthesias and chronic neuropathic pain. Such symptoms can be at least partially understood in terms of pathophysiological changes that occur in the electrical excitability of the injured sensory neuron. These changes result in the generation of an abnormal ongoing and evoked discharge, originating, alternatively, at various ectopic neural pacemaker sites. Many of the most effective therapeutic modalities recommended for neuropathic pain act by reducing this ectopic neural discharge.