Neuropathic pain disorders are defined as persistent pain disorders that are a direct result of a lesion or a disease because of the parts of the nervous system that usually signal pain. They are varied conditions that cannot be explained by a single cause or specific lesion. According to the most widely accepted definition, neuropathic pain is "initiated or caused by a primary lesion or dysfunction in the nervous system."
Neuropathic pain may result from peripheral (near the surface) disorders of the nervous system or the central nervous system (brain and spinal cord). Therefore, neuropathic pain may be separated into the following categories:
Central neuropathic pain can occur as a result of a spinal cord injury, multiple sclerosis, and some strokes. Fibromyalgia, a condition characterized by chronic widespread pain, is most likely a central pain disorder and is responsive to medications that are effective for neuropathic pain.
Other than diabetes (see Diabetic neuropathy) and other metabolic conditions, the common causes of painful peripheral neuropathies are herpes zoster infection, HIV-related neuropathies, nutritional deficiencies, toxins, remote manifestations of malignancies, genetic, and immune mediated disorders.
Neuropathic pain is also common in cancer patients as a direct result of cancer on their peripheral nerves, as a side effect of some chemotherapy drugs, and as a result of radiation injury.
Common traits exist with neuropathic pain. They include burning or coldness, "pins and needles" sensations, numbness and itching. "Ordinary" pain is a consequence of stimulation of pain fibers, while neuropathic pain is frequently caused by the firing of both pain and non-pain (touch, warm, cool) sensory nerve fibers serving the same area.