Causalgia: A complex regional pain syndrome characterized by burning pain and marked sensitivity to touch (HYPERESTHESIA) in the distribution of an injured peripheral nerve. Autonomic dysfunction in the form of sudomotor (i.e., sympathetic innervation to sweat glands), vasomotor, and trophic skin changes may also occur. (Adams et al., Principles of Neurology, 6th ed, p1359)Sympathectomy: The removal or interruption of some part of the sympathetic nervous system for therapeutic or research purposes.Reflex Sympathetic Dystrophy: A syndrome characterized by severe burning pain in an extremity accompanied by sudomotor, vasomotor, and trophic changes in bone without an associated specific nerve injury. This condition is most often precipitated by trauma to soft tissue or nerve complexes. The skin over the affected region is usually erythematous and demonstrates hypersensitivity to tactile stimuli and erythema. (Adams et al., Principles of Neurology, 6th ed, p1360; Pain 1995 Oct;63(1):127-33)Neuralgia: Intense or aching pain that occurs along the course or distribution of a peripheral or cranial nerve.