ABSTRACT
With rare exceptions, clinical pain is a neurological phenomenon known universally to human patients. Pain becomes chronic only when this unpleasant sensory and emotional experience persists for much longer than expected relative to the severity or duration of the initial noxious stimulus. The regions of symptom onset, patterns of radiation or referral to other body sites, and any association with loss or excess of somatic sensation within the symptomatic regions have major relevance in the diagnosis of neuropathic pain. In patients who suffer from multiple pain types or regions, or in whom there coexists abnormal perception of different modes of sensory stimulation, documenting clinical data using only verbal descriptors can be overwhelming. Historically, large portions of the autonomic nervous system have been thought of as only being responsible for the creation of involuntary physiological responses to acute, stressful or noxious stimuli.
