[Assessment of neuropathic pain]

Abstract

Neuropathic pain is underdiagnosed and, in consequence, not properly treated. Neuropathic pain is defined as pain initiated or caused by a primary lesion or dysfunction in the nervous system. The term dysfunction is not clearly defined and is suggested not used. The prevalence of neuropathic pain is unknown, but a few detailed studies show that neuropathic pain is more common than previously assumed. Some common causes of neuropathic pain are entrapment/injuries to peripheral nerves, painful neuropathies, infections in the nervous system (i.e. postherpetic neuralgia), spinal cord injuries, multiple sclerosis and cerebral infarcts. Evaluation of neuropathic pain is performed on the basis of a thorough clinical examination which includes detailed questioning of different types of pain. Both spontaneous (ongoing and paroxysmal) as well as evoked pain may occur. The ongoing pain may be described by a large number of adjectives such as burning, aching, throbbing, sore, cutting, but there is no pain descriptor which is diagnostic for neuropathic pain. Pain may usually be evoked by lightly touching the skin or by exposure to cold. A clinical neurological examination is necessary in the evaluation of the level of injury, possibly also electromyography/neurography in case of peripheral nerve lesions or CT/MR in case of central lesions. Neuropathic pain is almost always characterised by changes in sensibility, usually involving the thin-fibre system (peripheral nerve fibres or central projections). Special emphasis is put on the examination of sensory dysfunction.