Causalgia is an old name for complex regional pain syndrome.
Related to trauma
The condition is very uncommon but usually has a relationship to trauma in patients who are particularly susceptible. The over-riding symptom is pain that is markedly out of proportion to the original insult. This is accompanied by skin changes, such as blueness or mottling. Eventually there may be wasting of the limb, and actual muscle loss. The condition really needs expert management by pain specialists.