If the pain is continuous for a long period, parts of the intact body may become sensitized, so that touching them evokes pain in the phantom limb. It is often described as shooting, crushing, burning or cramping. Some amputees experience continuous pain that varies in intensity or quality others experience several bouts of pain per day, or it may reoccur less often. One study found that eight days after amputation, 72% of patients had phantom limb pain, and six months later, 67% reported it. The prevalence of phantom pain in upper limb amputees is nearly 82%, and in lower limb amputees is 54%. Phantom pain is pain felt in a part of the body that has been amputated, or from which the brain no longer receives signals. It has no biological function and is classified by stimuli into dynamic mechanical, punctate and static. Chronic pain may be classified as " cancer-related" or "benign." AllodyniaĪllodynia is pain experienced in response to a normally painless stimulus. A popular alternative definition of "chronic pain", involving no arbitrarily fixed duration, is "pain that extends beyond the expected period of healing". : 93 Others apply "acute" to pain that lasts less than 30 days, "chronic" to pain of more than six months' duration, and "subacute" to pain that lasts from one to six months. Traditionally, the distinction between acute and chronic pain has relied upon an arbitrary interval of time between onset and resolution the two most commonly used markers being 3 months and 6 months since the onset of pain, though some theorists and researchers have placed the transition from acute to chronic pain at 12 months.
Pain that lasts a long time is called " chronic" or "persistent", and pain that resolves quickly is called " acute". Pain is usually transitory, lasting only until the noxious stimulus is removed or the underlying damage or pathology has healed, but some painful conditions, such as rheumatoid arthritis, peripheral neuropathy, cancer and idiopathic pain, may persist for years.
Pain motivates the individual to withdraw from damaging situations, to protect a damaged body part while it heals, and to avoid similar experiences in the future.
The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." In medical diagnosis, pain is regarded as a symptom of an underlying condition. Pain is a distressing feeling often caused by intense or damaging stimuli.