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 complex 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.
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.
Symptoms include severe and continuous pain, often in part or all of a limb. It has been described as “burning” or a combination of burning and electrical shocks.
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.
CPRS does not always result from an obvious injury. It may happen because of damage that has occurred internally, such as a blood vessel problem.
If CPRS occurs in members of the same family, it may be more severe, suggesting that genetic factors may play a role or make some people more susceptible.
If a patient seeks medical help, and they may have CRPS, the doctor will ask about their medical history and will look for swollen joints and changes in skin temperature and appearance.
The diagnosis is based on clinical findings that exclude other possible causes.
A number of diagnostic tests can help eliminate other causes and confirm a diagnosis.
Blood tests can help exclude infection or inflammation in the joints as a possible cause of symptoms.
Thermography measures skin temperature of specific parts of the body. High or low skin temperature in the affected area could indicate CRPS.
Electrodiagnostic testing, or nerve conduction studies, involve attaching wires to the skin and measuring the electrical activity of nerves. Abnormal readings could indicate nerve damage, and possible type 2 CRPS.
X-rays can detect mineral loss in the bones at later stages.
An MRI scan, a blood test or a biopsy can rule out underlying problems with bones or tissue.
There is little definitive treatment for CRPS, and the course is best determined by the doctor who treats it. Early treatment is most effective, and it is best for a specialty pain clinic to assess and determine a plan.
Treatment may involve a neurologist, a physical therapist, and other specialists.
Physical therapy: This can help patients improve blood flow, regain their range of movement and coordination and help prevent muscle wastage and contortion of bones.
Medication: No single medication has been approved to treat CPRS, but the following may help:
- non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen
- anticonvulsants, such as gabapentin, to manage nerve pain.
- topical creams and patches to reduce the pain, for example, 5-percent lidocaine patches. A combination of ketamine, clonidine, and amitriptyline may reduce hypersensitivity.
- corticosteroids for inflammation, such as prednisolone, but these should be used sparingly, because they can have severe adverse effects
- bisphosphonates, for example alendronate or pamidronate, which prevent bone reabsorption, but these are not recommended for routine practice
- botulinum toxin (botox) injections
- opioids, for example, oxycodone, morphine, codeine, to be used strictly under medical supervision, due to the risk of addiction
- N-methyl-D-aspartate (NMDA) receptor antagonists, for example, dextromethorphan
Medications are most likely to be effective if they are prescribed early. Each person is different, and a different combination of treatments may be needed.
Treatments that remain controversial are:
- Sympathetic nerve-blocking drugs, such as an anesthetic, may be injected to block the nerve fibers in the affected nerves.
- Surgical sympathectomy, where a surgeon cuts or clamps a nerve chain, to prevent the transmission of pain messages
- Spinal cord stimulation, involves tiny electrodes being inserted into the spinal cord
Other types of neural stimulation that might help include repetitive Transcranial Magnetic Stimulation, (rTMS) and deep brain stimulation. These are less invasive than some other treatments, but the effects do not last, and they need to be applied regularly.
An occupational therapist can determine how CRPS is likely to impact a patient’s daily life, and they can prescribe assistive devices. A psychologist can help the patient to cope with living with a chronic, painful condition.
Alternative or complementary therapies that may help include:
- relaxation techniques, including biofeedback
- chiropractic therapy
- heat and cold therapy
- transcutaneous electrical nerve stimulation (TENS), which provides pain relief by applying electrical impulses to nerve endings
Experimental therapies include:
- intravenous immunoglobulin, which may relieve pain for up to 5 weeks
- the use of 5 to 10 percent capsaicin, but this may worsen the pain
- amputation, but this is only recommended if there is an infection
- topical dimethylsulfoxide (DMSO 50%), N-acetylcysteine (NAC), free-radical scavengers that may help some patients in the early stages
As CPRS affects the nervous system, it can lead to a wide range of complications throughout the body.
Issues that have been linked to CRPS include:
- chest pain
- changes to the way the body perceives and manages pain
- problems with thinking and memory
- lethargy, fatigue, and weakness
- rapid pulse and heart palpitations
- breathing problems
- fluid retention
- muscle weakness, bone loss, and other musculoskeletal problems
- rashes, mottling, and other skin problems
- urological problems such as difficulty urinating or incontinence
- gastrointestinal problems, including nausea, vomiting, diarrhea, and symptoms of irritable bowel syndrome (IBS)
- gastroesophageal reflux
- low cortisol levels and hypothyroidism
If the condition remains untreated or treatment starts late, there may be muscle wasting and contracting of the hand, fingers or foot, as the muscles tighten.