CRPS is a disorder of the sympathetic nervous system, and it has no cure. It is extremely painful--medically rated as the worst form of chronic pain that exists today, and rated a 42 out of 50 on the McGill Pain Index--worse than unmedicated childbirth and amputation of a digit without anesthesia. Untreated, it can lead to atrophy and loss of use of the affected extremity.
CRPS can go into remissions. The remissions are completely unpredictable (however, you usually show an incline in improvement leading up to the remission).