neurologic disorders
Chronic Pain
Introduction
Chronic pain is pain that persists or recurs for>3 months, persists>1 month after resolution of an acute tissue injury, or accompanies a nonhealing lesion. Causes include chronic disorders (eg, cancer, arthritis, diabetes), injuries (eg, herniated disk, torn ligament), and many primary pain disorders (eg, neuropathic pain, fibromyalgia, chronic headache). Various drugs and psychologic treatments are used. (See also Fibromyalgia and Unresolved, long-lasting disorders (eg, cancer, rheumatoid arthritis, herniated disk) that produce ongoing nociceptive stimuli may account completely for chronic pain. Alternatively, injury, even mild injury, may lead to long-lasting changes (sensitization) in the nervous system—from peripheral receptors to the cerebral cortex—that may produce persistent pain in the absence of ongoing nociceptive stimuli. With sensitization, discomfort that is due to a nearly resolved disorder and might otherwise be perceived as mild or trivial is instead perceived as significant pain. In some cases (eg, chronic back pain after injury), the original precipitant of pain is obvious; in others (eg, chronic headache, atypical facial pain, Chronic Abdominal Pain and Recurrent Abdominal Pain ), the precipitant is remote or occult. Psychologic factors may amplify persistent pain. Thus, chronic pain may appear out of proportion to identifiable physical processes. Chronic pain commonly leads to or exacerbates psychologic problems (eg, depression, anxiety). Distinguishing psychologic cause from effect is often difficult, but if pain, depression, and anxiety co-exist, they typically intensify the overall pain experience. Various factors in the patient’s environment (eg, family members, friends) may reinforce behaviors that perpetuate chronic pain. 