Pain is a concept difficult to define and derived from “poena” in Latin (punishment, revenge, torture. According to the definition of International Association for the Study of Pain (IASP), “ pain is a sensorial unpleasant feeling and behavior that originates from a certain region of the body, that is can be dependent on tissue damage or not, and is accociated with previous experiences of the person ”. Pain is complex sensation with neurophysiological, biochemical, psychological, ethnic, cultural, religious, cognitive and environmental dimensions .
Neuropathic pain is defined by IASP as pain initiated or caused by primary lesion or dysfunction of nervous system. Patients with neuropathic pain account for 30-50% of subjects presenting to pain clinics . Pain is always subjective. Each individual gains this experience as a consequence of painful conditions he/she has encountered throughout life. Many people state that they experience pain without tissue damage and physiopathological changes. This pain is perceived as a sensation deriving from any place in the body; it also has emotional components. It is impossible to discriminate this sensation from that associated with tissue damage. If a patient defines a sensation as pain, physican should accept is as pain. Nociception, is activity formed via receptors called nociceptors against painful stimulants and stimulants that will cause pain if they are prolonged. Pain is a nociception sensation and like other perceptions, it is determined by the interaction between neurosensorial activity and organic and psychological factors .