What Is Reflex Sympathetic Dystrophy?

Reflex sympathetic dystrophy is an older name for a chronic pain condition now called complex regional pain syndrome, or CRPS. It usually begins after an injury, surgery, or illness and causes severe pain that is out of proportion to the original trigger. The pain is often joined by swelling, skin color changes, and temperature differences in the affected limb. The name changed because the “sympathetic” part turned out to be misleading, and the older term is no longer used in clinical diagnosis.

What Is Reflex Sympathetic Dystrophy?

Reflex sympathetic dystrophy (RSD) was the name used for decades to describe a specific pattern of chronic pain that typically affects an arm, leg, hand, or foot. In 1994, an international consensus conference replaced the term with complex regional pain syndrome to better reflect what is actually happening in the body.

The shift mattered. The old name assumed the sympathetic nervous system was the main driver of the pain. That assumption turned out to be wrong, or at least incomplete, for most people with the condition. The new name drops the assumption and describes what clinicians actually observe: complex pain, regional in distribution, occurring as a syndrome.

Two types are recognized. Type I, which is what RSD usually referred to, occurs without a detectable nerve injury. Type II involves confirmed damage to a specific nerve. Both produce similar symptoms and are managed similarly.

What Causes Complex Regional Pain Syndrome?

The trigger is usually a physical event. Common ones include fractures, sprains, surgery, crush injuries, and even minor procedures like blood draws. In some cases no clear trigger is identified.

What happens after the trigger is not fully understood. Several mechanisms appear to be involved at once, which is part of why the condition is difficult to treat.

• Inflammation. After injury, the body releases inflammatory chemicals. In CRPS, this response appears to persist or become dysregulated rather than resolving normally.
• Nervous system changes. The central nervous system can become sensitized, meaning pain signals are amplified. This is sometimes described as the nervous system turning up its own volume.
• Autonomic dysfunction. The autonomic nervous system, which controls blood flow and sweat, behaves abnormally in the affected limb. This explains the color and temperature changes.
• Brain changes. Imaging studies have found changes in how the brain represents the affected body part. Whether these changes cause symptoms or result from them is still debated.
• Genetic and immune factors. Some evidence points to genetic susceptibility and immune involvement, but no single gene or antibody has been confirmed as the cause.

Not everyone who has an injury develops CRPS. Why some people do and others do not remains an open question. No reliable way to predict who will develop it currently exists.

What Are the Symptoms of Reflex Sympathetic Dystrophy?

The defining symptom is pain that is far more severe than expected from the original injury. The pain is often described as burning, throbbing, or shooting. It can be constant or triggered by things that normally do not hurt, like a light touch or cool air.

Other symptoms typically appear in the affected limb:

• Swelling
• Skin color changes, ranging from red to pale to bluish
• Skin temperature differences, either warmer or cooler than the other side
• Abnormal sweating
• Changes in hair and nail growth
• Stiffness and reduced range of motion
• Muscle weakness or tremor
• Decreased ability to move the limb normally

Symptoms usually begin in one limb, most often after an injury to that limb. They can spread, though this is less common. The condition is sometimes described in stages, but research has not confirmed that everyone follows the same progression. Many clinicians now avoid staging because it does not reliably predict outcomes.

How Is It Diagnosed?

There is no single test that confirms CRPS. Diagnosis is clinical, meaning it is based on the person’s history and a physical exam.

The most widely used criteria come from the International Association for the Study of Pain. They require:

• Continuing pain that is disproportionate to any inciting event
• At least one symptom in three of four categories: sensory, vasomotor, sudomotor/edema, or motor/trophic
• At least one sign at the time of evaluation in two or more of those categories
• No other diagnosis that better explains the symptoms

Because the criteria require ruling out other conditions, diagnosis can take time. Conditions that can look similar include nerve compression, infection, blood clots, and other pain disorders. Imaging and nerve studies may be used to rule these out, but they do not confirm CRPS itself.

Early recognition matters. Some evidence suggests that treatment started earlier may lead to better outcomes, though this has not been proven in large controlled trials.

How Is Reflex Sympathetic Dystrophy Treated?

Treatment aims to reduce pain and restore function. There is no cure, and no single treatment works for everyone. Most clinicians combine several approaches.

Physical and occupational therapy is considered a cornerstone. The goal is to keep the limb moving and prevent stiffness and muscle loss. This can be difficult because movement often hurts, so therapy is usually gradual.

Medications may include:

• NSAIDs for pain and inflammation
• Certain antidepressants and anticonvulsants that are used for nerve pain
• Corticosteroids, sometimes used early
• Bisphosphonates, which some studies suggest may help, though results vary
• Topical medications like lidocaine or capsaicin

Opioids are generally avoided for long-term use because of limited evidence of benefit and risk of dependence.

Nerve blocks that target the sympathetic nervous system are sometimes used. Evidence for their effectiveness is mixed, and they are typically considered a trial rather than a guaranteed treatment.

Spinal cord stimulation involves implanting a device that delivers electrical signals to the spinal cord. Some studies suggest it may reduce pain in certain people, but it is usually reserved for cases that have not responded to other treatments.

Psychological support can help people cope with chronic pain, though it does not treat the underlying condition. Cognitive behavioral therapy and pain management programs are common.

Response to treatment varies widely. Some people improve significantly, while others continue to have symptoms for years. There is currently no way to predict which path a person will take.

What Is the Outlook for People With CRPS?

The course of CRPS is unpredictable. Some people recover fully, some improve but have lingering symptoms, and some continue to experience significant pain and disability.

Research on long-term outcomes is limited. Studies that follow people over time report a range of results, and it is difficult to compare them because diagnostic criteria and treatments have changed. What is clear is that early treatment and keeping the limb active are generally associated with better outcomes.

CRPS is not life-threatening, but it can affect quality of life, sleep, and mental health. Depression and anxiety are common in people with chronic pain, and addressing these is part of comprehensive care.