Complex regional pain syndrome (CRPS)

What is complex regional pain syndrome?

Complex regional pain syndrome (CRPS) is a painful and long-lasting condition. CRPS usually causes severe, constant, burning pain in the affected arm or leg.

The cause of CRPS remains unknown. However, this condition can be triggered by damage to nerve fibers in tissue that has been injured. Smoking is a risk factor for the condition. The cause may be autoimmune, as autoantibodies (antibodies directed against normal tissue) targeting nerve cells have been identified in people with CRPS. Experts believe that in CRPS, nerves become overly sensitive. Painful signals become more painful. And common stimuli, such as light touch and temperature changes, also are experienced as pain.

This condition usually starts after an injury or other event. Examples include trauma, fracture, infection, surgery, stroke or wearing a plaster cast.

Often, the injury that triggers CRPS is mild compared with the pain that follows it. However, the condition also can follow more severe injury or paralysis. The pain often is not limited to the area that was injured.

This condition can occur at any age. It is relatively rare.

CRPS has been called by many other names. These include reflex sympathetic dystrophy syndrome (RSDS), algodystrophy, causalgia, shoulder-hand syndrome, Sudeck's atrophy and transient osteoporosis. Although the name was officially changed from RSDS to CRPS, the name change has not been universally accepted.

There are two types of CRPS:

• Type I – there is no nerve damage present
• Type II – a nerve abnormality can be detected.

Symptoms of CRPS

Symptoms of CRPS can include:

• intense pain, throbbing, burning, and swelling, usually in the hand or foot
• shiny, thin skin around the affected area
• initially increased but later diminished hair over the affected area
• brittle, thickened nails
• dry and withered skin
• skin that feels warmer or cooler than usual
• skin that changes color
• increased sweating.

The condition can progress through three stages. However, not everyone goes through every stage.

In the earliest stage, days to weeks after an injury, the limb can become dry, hot, red and painful. Even the lightest touch or the slightest movement can cause excruciating pain. At this point, CRPS can be mistaken for other conditions. Your doctor may not be able to confirm the diagnosis of CRPS at this stage.

Over the next few weeks to months, the skin can become shiny, thin and cool. The limb becomes mottled and purplish. There is considerable swelling. Pain worsens. The nails become brittle and can grow faster or slower than normal. As the limb becomes difficult to move, you may have more pain further up the limb. This might be related to muscle stiffness and soreness.

Some people experience other movement problems, including weakness, spasm and tremor. An affected limb can become permanently flexed or bent (contractures). In some people, the skin can become tight, dry and shriveled. The bones can become brittle because they aren't being used. The skin, muscles and joints stiffen so that the affected area cannot be moved. Some patients have less pain at this point. Once the disease reaches this point, it is extremely difficult to treat.

Diagnosing CRPS

Your doctor will ask questions about your medical history. He or she will examine you.

CRPS is diagnosed when the following symptoms are present:

• burning, spontaneous pain
• hypersensitivity
• swelling
• temperature changes
• sweating.

In the earliest stages, before many of these features develop, diagnosis is difficult or impossible.

In later stages, X-rays sometimes show bone loss, especially around the joints. A bone scan can help to confirm the diagnosis. But the condition cannot be diagnosed with a bone scan alone.

Two tests that evaluate nerve function may be ordered. They look for nerve damage or another cause of your symptoms. These tests are called electromyography and nerve conduction studies.

Your doctor also may recommend a diagnostic sympathetic block. This is an injection in the neck or low back. If the block reduces or eliminates pain, this can help to confirm the diagnosis.

Some physicians use other specialized tests to help diagnose this condition. For example:

• Evaluation of the nerves that control sweating and skin temperature. This can be done by measuring sweat output and skin temperature.
• A thermogram maps the temperature in the skin at different sites in the body. This shows how well blood is flowing in different areas. Abnormal blood flow in the painful area is common in CRPS.

Expected duration of CRPS

Some people with CRPS improve without treatment. But getting early treatment improves your chances of pain relief.

About half of people with CRPS continue to experience pain six months after treatment was started.

Preventing CRPS

There is no way to prevent CRPS because the cause is not clear.

However, physical activity or physical therapy after stroke may prevent CRPS following stroke.

And there is limited evidence that vitamin C (500 milligrams daily) may prevent CRPS following wrist fracture.

As smoking is a risk factor for CRPS, smoking cessation may play a role in preventing the condition from developing.

Treating CRPS

It is important to get care from health care professionals who have expertise in the treatment of CRPS. These professionals include an anesthesiologist, pain specialist, vascular surgeon, physical therapist and/or occupational therapist.

Maintaining movement is an important goal of treatment. Your doctor will likely recommend physical or occupational therapy, together with supervised exercises. Once a reasonable degree of movement is restored, an exercise routine should be started. This will help to strengthen muscles and joints, and maintain functioning.

In many cases, psychological and behavioral therapy can be helpful.

Medications can help to manage pain. Corticosteroids and physical therapy can help to ease pain during an acute episode, but long-term results are mixed.

Medications that may help include:

• nonsteroidal anti-inflammatory drugs (NSAIDs) and other pain relievers
• topical medications such as capsaicin (a cream or ointment thought to interrupt pain signals) or lidocaine (a numbing medication)
• certain antidepressants and anticonvulsants used in nerve pain treatment such as amitriptyline (Elavil) or gabapentin (Neurontin)
• blood pressure medications that affect the sympathetic nervous system such as prazosin (Minipress)
• bisphosphonates, medications that reduce bone loss such as alendronate (Fosamax)
• calcitonin, by injection or nasal spray. It may slow bone loss and provide pain relief.
• trigger-point injections. A corticosteroid and a long-acting anesthetic medication are injected just beneath the skin in painful areas.
• baclofen may help relieve muscle spasms.

A transcutaneous electrical nerve stimulator (TENS) unit sometimes can help to relieve pain. This small, battery-operated device is thought to work by blocking nerve impulses. Biofeedback also can help to control pain, blood flow and skin temperature.

Simple measures such as applying heat or cold may help. Applying cold might relieve pain temporarily. But ice may worsen the symptoms of CRPS later on. The response to heat also varies.

For severe pain or pain that does not respond to other treatment, your doctor may recommend a nerve block. During this procedure, an injection of a numbing agent is administered near the affected nerves or alongside the spinal column to block the nerves of the sympathetic nervous system. It usually is done as a series of three to five injections over seven to 14 days. If the numbing is effective, a more permanent procedure called a sympathectomy may be done. In this procedure, the nerves are destroyed with chemicals or by surgery.

Newer treatments include:

• implanting a device that stimulates the spinal cord or nearby nerves
• injections of clonidine (Catapres) into the space near the spinal cord
• injections of ketamine intravenously.

These treatments do not always work and may be associated with complications. But for severe cases that have not responded to other treatments, the benefits of the "last resort" treatments may exceed the risks.

When to call a professional

Contact your physician if you experience the symptoms of CRPS.

Prognosis

The earlier the condition is diagnosed, the better the prognosis.

If treatment is started early, symptoms can disappear after as few as three months. Delayed treatment can lead to permanent bone and muscle changes.

The overall response to treatment is poor. In at least half of cases, people with CRPS are still in pain months and even years later.

Additional info

American Chronic Pain Association
http://www.theacpa.org/

National Institute of Neurological Disorders and Stroke
National Institutes of Health
http://www.ninds.nih.gov/