Chronic nerve pain, or chronic neuropathic pain, is a medical condition that occurs when nerves become damaged or injured, causing pain that persists for a long time, according to WebMD. The condition is caused by diseases, such as diabetes and HIV, and toxins, such as those used in chemotherapy. Accidental or surgical trauma can also damage nerves, leading to long-term pain.
Some patients experience extreme sensitivity to a typically gentle stimulus, such as a light touch, a condition known as allodynia, explains American Family Physician. Others experience hyperalgesia, which is an exaggerated response to a mildly painful stimulus, such as a pin prick. Spontaneous pain that is not the result of any stimulus is common as well. Many patients have constant burning pain that greatly interferes with their quality of life.
Complex regional pain syndrome is an example of a chronic neuropathic pain syndrome, as Merck Manuals reports. Also known as reflex sympathetic dystrophy, this illness occurs in two forms. Type I follows an injury to an extremity or a systemic illness, such as a heart attack, cancer or a stroke. Type II usually occurs with no apparent underlying cause. Both forms of the illness cause allodynia, hyperalgesia, and severe, burning or aching pain that often limits motion in the extremity. Changes in blood flow cause color changes, such as red, mottled or blue-tinged skin. Swelling, sweating of the extremity and other skin changes are common as well.