Complex regional pain syndrome is a rare, chronic, and sometimes progressive condition. It involves spontaneous or evoked pain in a region, or area of the body.
It usually affects one of the arms, legs, hands, or feet after an injury, but complications can impact the whole body, including the internal organs.
It appears to be an autoimmune condition, in which the body responds in an unusual way to a perceived threat. As the immune system fights to defend the body, inflammation occurs.
Symptoms that distinguish the pain of chronic regional pain syndrome (CRPS) from that of other types of pain are autonomic and inflammatory signs such as changes in skin color, temperature, or sweating.
A person who develops CRPS after experiencing an injury may find that they have pain that is more severe than they would normally have expected with such an injury.
CRPS can affect people of any age, but it usually appears between the ages of 40 and 70 years, and it is more common among females.
Severity ranges from self-limiting and mild to severe and debilitating.
CPRS involves a burning pain, and the joints may be inflamed.
The severity and frequency of symptoms vary widely. Some people have repeated episodes, while others find that symptoms disappear forever after a few months.
There are two types of CRPS:
Type 1: An apparently trivial injury, such as a fractured or sprained ankle, has occurred, but with no confirmed nerve damage. This type was previously known as reflex sympathetic dystrophy.
Type 2: This may emerge after breaking a bone, having surgery, or after a serious infection. There is clear evidence of nerve damage. This type was previously known as causalgia.
However, debate about the classification of these types is ongoing. Since nerve injury is sometimes found in people with type 1, the National Institute of Neurological Disorders and Stroke (NINDS) notes that the distinction between the two categories may be removed at some point.
Some experts suggest that type 1 is not CRPS at all, but that is it either a normal reaction or the result of treatment received after a trauma.
Pain may radiate up the arm from an injury in the hand.
If CRPS happens after an injury, the pain of the injury may be unusually severe. For example, an ankle sprain may trigger an unbearable burning sensation. The pain may not be limited to the area where the injury occurred.
Damage to a toe or finger, for example, may lead to pain in the whole limb, or even pain in the opposite extremity.
The affected part can become hypersensitive. Touching, bumping, or exposing the limb to temperature changes may cause severe pain.
Muscle atrophy, or wasting, can result, if the patient stops using the limb because of the pain.
There may also be:
changes in skin temperature
fluid retention (edema) and sweating
changes in skin color, causing blotches or streaks, ranging from very pale to pink, and perhaps with a blue tinge
changes to finger and toenails
thin and shiny skin texture
unusually fast or slow nail and hair growth
painful, stiff, and inflamed joints
difficulty co-ordinating muscle movement
unusual movement in the limb
The limb may be fixed in an abnormal position or may experience movements such as jerking or tremors.
Mobility can be reduced, as it becomes difficult to move the affected part.
As mentioned above, CRPS may develop following an injury or surgery. The exact cause is not clear, but multiple mechanisms may be involved.
Research published in 2005 lists the likely mechanisms as:
trauma-related release of cytokines, substances produced by the immune system
exaggerated inflammation in the nervous system
changes to the nervous system that cause the pain to continue
Some people may have an existing abnormality in the peripheral nerves that make them more sensitive if damage occurs. If the individual experiences an injury, they may react to it in a different way than most people do.
Some theories propose that inflammation and changes in the brain and sympathetic, peripheral, and spinal nervous systems, aggravated by immobility, may contribute.