Denervation causes hypersensitivity resulting in increased pain and increased norepinephrine release causes the sympathetic findings. Onset in the majority is within 24 hours of injury. The median, ulnar and sciatic nerves are the most commonly involved. Almost any sensory stimulation worsens the pain. The initial step in diagnosis is a thorough history and physical examination.
Physical examination is difficult to perform secondary to pain.
The diagnostic procedure of choice is proof of complete or partial relief with a sympathetic block. Medical therapy is usually ineffective. These procedures lead to sympathetic denervation of the head, neck and upper extremity, the lower extremity, and the abdominal region, respectively. Techniques used include anterior thoracic, thoracic endoscopy, percutaneous radiofrequency and supraclavicular. Similar results have been obtained with reflex sympathetic dystrophy.