ABSTRACT
Acute pain, a phenomenon with which we are all familiar, is an experience with sensory
and affective components that serves to warn the individual about potentially harmful
stimuli in the environment. The sensory component of pain allows the individual to
localize the sensation to a site on the body and identify to some extent the nature of the
inciting insult. The affective component of pain, mediated by structures in the brainstem
and limbic lobes of the brain, lends pain the unpleasant emotional content that is so
important in making individuals withdraw from and avoid painful stimuli. Chronic pain is
defined as pain persisting more than one month beyond the resolution of an acute tissue
injury, or pain that persists or recurs for more than three months associated with a tissue
injury that is expected to continue or progress. Unlike acute pain, chronic pain has few
redeeming features. Chronic pain has been estimated to affect more than 60 million people
in the United States, and the cost, to individuals in terms of suffering and lost income, and
the cost to society in terms of lost productivity and requirement of care is enormous.
