International Association for the Study of Pain®

The autonomic nervous system (ANS) is an extensive neural network whose main role is to regulate the milieu intérieur by controlling homeostasis and visceral functions. Although most functions regulated by the ANS are out of conscious control, emotions and somatosensory inputs profoundly influence the ANS. Observing the marked vasomotor and sudomotor changes after traumatic nerve injury, it became apparent long ago that the ANS plays an important role in pain modulation and perception. Despite the debate on whether the role of the sympathetic nervous system in generating and sustaining certain pain syndromes is significant, specialists in pain management have sought tools for investigating the ANS.