CRPS I and II
CRPS, also known as complex regional pain syndrome, is a very vague term with a broad definition globally describing prolonged pain, inflammation, and excessive unpleasant sensation that follows an injury to an extremity, either the legs or the arms. The older term for CRPS was reflex sympathetic dystrophy and causalgia.
Classically disorders of the sympathetic system originally referred to as RSD, reflex sympathetic dystrophy, have been renamed complex-mediated pain syndrome, or CRPS type I and CRPS type II. This was done in 1994 by the International Association for the study of pain.
CRPS is generally caused by an imbalance of small peripheral C5 nerves that carry sensations of pain from the source to the brain. When these nerves fire excessively, this triggers an inflammatory response that is designed normally to assist in healing and rejuvenation after injury.
Overactivation of the system, however, results in pathology that can be acute, lasting less than six months, or chronic when it lasts more than six months. CRPS is divided into type I and type II. Type I, the etiology is often unknown. It may be something as subtle as an intravenous needle placement on a skin condition for a minor injury.
CRPS type II, however, is often associated very clearly with injury to one of the larger nerves, such as may happen with a crush injury or surgery of an extremity.
Typical symptoms of CRPS are an increase in painful sensation after a normal or nonpainful touch. We call this hyperalgesia.
The skin may exhibit changes in skin color, swelling of the affected extremity, and temperature changes either cooler or sometimes warmer than the corresponding normal limb.
Discoloration of the skin can include various shades of purple paleness, redness, or even a blotchy color. This is due to abnormal fluctuations in blood flow that is normally regulated by the smile type C nerve fibers.
The underlying bone may begin to be depleted of minerals and waste away along with the corresponding muscles. Decreased strength and prolonged cases become apparent.
Changes in sweating and malformation of nail and hair growth can also be seen.
It is unclear why some people with identical trauma develop CPRS and others do not. The most common and obvious causes are fractures, surgery, extensive sprains, burns, cuts, or prolonged extremity or joint mobilization from typecasting. Treatment of CRPS depends on first identifying and the extent of the injury and obtaining a thorough and detailed history and physical, bloodwork, and imaging including bone scans, as well as tissue biopsies in certain cases. Triple phase bone scans can occasionally show excess bone resorption.
Pharmacological remedies include nonsteroidal anti-inflammatory medication, topical analgesics, and lidocaine creams, antiepileptics such as gabapentin and pregabalin, oral lidocaine compounds such as mexiletine, certain opioid formulations, like methadone, and even low dose antidepressants. Botox injections have so been used in severe cases, especially when there is muscle contracture. Biphosphonates can slow down and reduce bony changes.
Physical therapy, acupuncture, and behavioral therapy are essential. Desensitization of the affected skin and nerves are important to recondition the central response.
These treatment options very closely resemble those for sympathetically maintained pain.
Interventional options include neuraxial steroid injections, sympathetic blocks and radiofrequency ablation of sympathetic ganglia, and peripheral and central or spinal cord stimulation. Intrathecal medication pumps have also been used in refractory cases.
Complementary therapies are gaining traction, including medical marijuana, relaxation techniques using guided imagery, and biofeedback.
Rarely is nerve transection or amputation required and represents a drastic option.
Research continues to understand this debilitating condition and explore the biomolecular etiologies so that better treatment options and preventative options can be made.