Complex Regional Pain Syndrome (CRPS)

What complex regional pain syndrome is

CRPS is a disorder of how the nervous system processes pain after an injury. Normally pain fades as tissue heals. In CRPS, the nerves, spinal cord and brain stay in a heightened state, and the small blood vessels, sweat glands and immune system in the limb behave abnormally. The result is pain that is far worse, and lasts far longer, than the original injury would explain.

It usually affects one hand, wrist, foot or ankle. It is most common after a wrist fracture, but it can follow an ankle injury, surgery, a minor sprain, an injection, or sometimes a heart attack or stroke. In about 1 in 10 cases there is no clear trigger. Women are affected about three times as often as men, with a peak in middle age.

CRPS type 1 and type 2

CRPS symptoms

The hallmark is pain out of proportion to the injury. It is often described as burning, stinging, throbbing or crushing. Other symptoms fall into four groups:

• Sensory: extreme sensitivity to light touch, clothing or bedsheets (allodynia), and exaggerated pain from mild pressure (hyperalgesia).
• Blood vessel: the limb looks red, purple, mottled or pale, and feels hotter or colder than the other side. The difference often changes during the day.
• Swelling and sweating: puffy skin and more or less sweating than the other limb.
• Movement and tissue changes: stiffness, weakness, tremor or jerks, difficulty starting movements, and changes in hair growth, nail growth and shiny, thin skin.

Many people also describe the limb feeling foreign, bigger than it is, or "not part of me". This altered body perception is real and part of the condition. Poor sleep, low mood and anxiety commonly follow long-lasting pain.

Early CRPS tends to be warm, red and swollen. Long-standing CRPS more often becomes cold, stiff and thin, with muscle loss and bone thinning visible on X-ray. Not everyone goes through these stages in order.

Causes and risk factors

The exact cause is not fully understood. Several processes appear to combine:

• inflammation in the limb driven by nerve-released chemicals
• sensitization of nerves in the spinal cord and brain (central sensitization)
• changes in the brain map of the affected limb
• abnormal control of blood flow and sweating
• in some people, an autoimmune element

Risk factors include a cast that is too tight, long immobilization, high pain levels early after injury, and a history of migraine or asthma. CRPS is not caused by anxiety or "in the head", even though stress can make the pain worse.

How CRPS is diagnosed

There is no single test. Doctors use the Budapest criteria:

1. Continuing pain disproportionate to any inciting event.
2. At least one symptom reported in three of the four categories (sensory, vascular, sweating/swelling, motor/trophic).
3. At least one sign seen on examination in two or more of those categories.
4. No other diagnosis better explains the signs and symptoms.

Tests are mainly used to rule out other problems: blood tests for infection or inflammation, ultrasound for a blood clot, X-rays or MRI for an unhealed fracture, and nerve studies for nerve damage such as carpal tunnel syndrome. A three-phase bone scan or skin temperature measurement can support the diagnosis but are not required.

CRPS treatment

The best results come from starting treatment early and combining approaches. The aim is to restore use of the limb, because pain and disuse feed each other.

Physical and occupational therapy

This is the foundation of treatment:

• gentle, graded movement and strengthening, increased step by step
• desensitization: touching the skin with different textures, from soft to rough
• graded motor imagery and mirror therapy: retraining the brain's map of the limb, starting with recognizing left and right limbs in pictures, then imagining movement, then watching the healthy limb in a mirror
• edema control and help with everyday tasks

Medicines

No drug is approved specifically for CRPS in the US, and evidence is mixed. Doctors commonly try:

• nerve pain medicines such as gabapentin, pregabalin, amitriptyline or duloxetine
• a short course of oral steroids in early, inflamed CRPS
• bisphosphonates, which have some evidence in early CRPS
• NSAIDs for associated joint or tissue pain (follow the label dose, and take care with stomach or kidney problems)

Long-term opioids are generally not recommended because they work poorly for this type of pain and carry significant risks.

Psychological support

Pain psychology, cognitive behavioral therapy and pain management programs help people cope, pace activity, improve sleep and reduce fear of movement. This is standard care, not a suggestion that the pain is imagined.

Procedures

For people who do not improve, options at specialist pain centers include sympathetic nerve blocks, spinal cord stimulation, and dorsal root ganglion stimulation. Amputation is very rarely considered and often does not relieve pain.

Outlook

Many people, especially those diagnosed early after a fracture, improve a great deal within 6 to 12 months. A minority develop long-lasting CRPS with persistent pain and disability. CRPS can recur after a new injury or surgery on the same or another limb, so tell your surgeon if you have had it before. Rarely, it spreads beyond the original area.

Frequently asked questions

What is the difference between CRPS and RSD?

They are the same condition. Reflex sympathetic dystrophy (RSD) is the old name for what is now called CRPS type 1. The name changed because the sympathetic nervous system is not always involved and "dystrophy" did not fit every case.

Can CRPS go away on its own?

It can improve or resolve, particularly when caught early, but waiting without treatment is not advised. Keeping the limb moving with physical therapy and controlling pain early give the best chance of recovery. Long-standing CRPS is less likely to resolve fully.

Is CRPS a neurological disease?

Yes. It is classed as a neurological pain disorder involving the nerves, spinal cord and brain, together with inflammation and blood-flow changes in the affected limb. Neurologists, pain specialists and physical therapists usually manage it together.

Can CRPS spread to other parts of the body?

Usually it stays in one limb, but in a minority it spreads to a wider area of the same limb, the opposite limb or, rarely, elsewhere. Spread is more common in long-standing cases. New injuries can also trigger CRPS in another limb.

How can CRPS be prevented after a fracture?

Good pain control, avoiding a cast that is too tight, and moving the fingers or toes early all reduce risk. Some guidelines suggest vitamin C after a wrist fracture, though the evidence is mixed. Tell your doctor promptly about pain or swelling that is getting worse rather than better.