The term neuralgia refers to a combination of two words "neuro" meaning relating to nerves and "algesia" meaning sensitivity to pain. Neuralgia therefore describes pain felt in one or more nerves. The pain sensation may arise without stimulation of pain receptors and instead as the result of abnormal function or structure of nerves.
There are four possible mechanisms by which pain due to neuralgia may occur and these include dysfunction of the ion channel gate; mechanically sensitive neuronal fibres generating an ectopic signal; the crossing of signals from touch fibres to pain fibres and dysfunction caused by damage to the central nervous system.
Neuralgia may result from nerve damage. Seddon's classification is used to classify or grade the severity of injury to the nerves. Under this classification, nerve injury can be classified as:
The level of pain is assessed using pain assessment scales such as the McGill Pain Questionnaire. It is important to qualify and quantify the pain before diagnosis is confirmed and in order to assess the efficacy of treatment. Qualitative senses testing is also done using the Quantitative sensory testing (QST) procedure.When a nerve is traumatised or injured, there is a short term increase in nervous impulse which is referred to as injury discharge. This can last for only a few minutes or may lead to the beginning of neuropathic pain.
Neuralgia is classified according to the stimulus that elicits a pain response. This could be different for different neuralgias. Sometimes pain may be stimulated by mechanical pressure and in other cases, heat or chemicals may stimulate a response.
There are different types of neuralgia including trigeminal neuralgia, atypical trigeminal neuralgia, occipital neuralgia and postherpetic neuralgia. The major symptoms seen in nearly all types of neuralgia include: