The clinical picture of neuropathic pain.

Neuropathic pains refer to a heterogeneous group of pain conditions characterised by lesion or dysfunction of the normal sensory pathways. Clinical characteristics include: delayed onset of pain after nervous system lesion, pain in area of sensory loss, spontaneous and different evoked types of pains. It has so far only been possible to classify these pains on basis of underlying cause or on anatomical location. The mechanisms underlying neuropathic pain are not yet clear, but neuronal hyperexcitability in those neurons that have lost their normal patterned input seems to be a common denominator for many, if not all types, of neuropathic pains. Along these lines, a mechanism-based classification has recently been proposed, which is an attractive approach because it provides a frame for a rationally based therapy of neuropathic pains. The clinical manifestations of neuronal hyperexcitability due to nervous system lesions is described.