الفهرس 
Classification of PainOnly 14 pages are availabe for public view
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Abstract
The international association for the study of pain (ISAP) defines pain as unpleasant sensory and emotional experience associated with actual or potential tissue damage.The International Association for the Study of Pain (ISAP) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage” (Jonathan and Theodore, 2011). It is the most common reason for physician consultation in the united state and can significantly interfere with a person’s quality of life and general functioning (Breivik et al., 2008).
Pain is divided into two major groups: physiological pain and pathological pain (Zhuo, 2007). Physiological pain is important for animals to avoid potential injury, while pathological pain is unpleasant, lasts for an extended period of time after injury (Zhuo et al., 2011).
chronic pain can be classified into inflammatory pain and neuropathic pain by the underlying mechanism (Li et al., 2011).
Neuropathic pain is a progressive disease resulted from injury or disease of the nervous system, including the peripheral nerve, dorsal root ganglion (DRG), spinal cord or brain (Li et al., 2011; Zhuo et al., 2011).
It is often caused by nerve injury or diseases such as diabetes, acquired immunodeficiency syndrome or cancer (Koichi and Masamichi, 2011).
It is often associated with a continuous burning character together with the presence of abnormal sensory symptoms, such as hyperalgesia (an increased response to a stimulus which is normally painful; patients with hyperalgesia perceive pain spontaneously) and allodynia (pain as a result of a stimulus which does not provoke pain) (Siniscalco et al., 2011).
The neurophysiological and neurochemical changes are poorly understood. Previous studies showed that nerve injury can result in changes in gene expression, protein synthesis and intracellular signaling in nociceptive pathways, all of which contribute to neuronal membrane remodeling and hyperexcitability associated with neuropathic pain (Jonathan and Theodore, 2011).
Aim of the Work:
The aim of this review is to understand the pathophysiology of the neuropathic pain.