Complex regional pain syndrome (CRPS): symptoms, causes and treatment

The NHS describes complex regional pain syndrome (CRPS) as a poorly understood condition in which a person has persistent, severe and debilitating pain. Although most cases are triggered by an injury, the resulting pain is much more severe and long-lasting than would be expected.

The NHS says the pain usually affects only 1 limb, though it can sometimes spread to other parts of the body. It is thought to be fairly uncommon, but difficult to estimate exactly because many cases may go undiagnosed or be misdiagnosed. CRPS can affect people of any age, including children, and tends to be more common in women than men.

The main symptom is pain. The NHS says it can sometimes be severe, continuous and debilitating, and may feel like a mix of burning, stabbing or stinging, with tingling and numbness. You may have flare-ups lasting a few days or weeks when the pain gets worse, and stress in particular can lead to flare-ups.

Skin in the affected area can become very sensitive, so even the slightest touch, bump or change in temperature causes intense pain. The NHS names two medical terms for this: hyperalgesia (feeling more pain than usual from something painful) and allodynia (feeling pain from something that does not usually cause pain, such as a light touch).

• Strange sensations in the limb, such as feeling it does not belong to the rest of your body or feels bigger or smaller than the other limb.

• Alternating skin changes: sometimes hot, red and dry, other times cold, blue and sweaty (colour changes may be harder to see on brown and black skin).

• Hair and nail changes: growing unusually slowly or quickly, with nails that may become brittle or grooved.

• Joint stiffness and swelling (oedema) in the affected limb.

• Tremors and muscle spasms (dystonia), and difficulty moving the affected body part.

• Difficulty sleeping, and small patches of fragile bones in the limb, although the NHS says there is no evidence this could lead to fractures.

The NHS says the cause of CRPS is unknown, but for many people it is thought to be the result of the body reacting abnormally to an injury. The pain is usually triggered by an injury, but is much more severe and long-lasting than would normally be expected.

The NHS also says there is currently no way to predict who will improve and when.

The NHS says diagnosing CRPS can be difficult because it involves having tests to rule out other possible causes of the symptoms. It is best to get help as soon as possible because early treatment may help reduce painful symptoms.

The NHS says it is difficult to estimate how common CRPS is because many cases may go undiagnosed or be misdiagnosed. Its treatment guidance says your pain specialist will be able to discuss the medicines that may help.

The NHS says there is no known cure, but a combination of physical treatments, medicine and psychological support can help manage the symptoms. A number of different healthcare professionals will usually be involved in your care.

The NHS says your treatment team will try lower-strength painkillers first and will only use stronger painkillers if necessary. None of the medicines used to treat CRPS is licensed for this use in the UK. They are licensed for another condition and have undergone clinical trials for it, and doctors may choose to use them if they think they will be effective and the benefits outweigh the risks.

NSAIDs such as ibuprofen are often used first, but the NHS says they are unlikely to directly reduce CRPS pain, though they can help with associated pains. Anticonvulsants, mainly gabapentin and pregabalin, and tricyclic antidepressants, mainly amitriptyline and nortriptyline, are used for nerve pain. Opioids such as codeine and morphine can sometimes provide relief in severe pain, but the NHS says they are often not very effective for CRPS and long-term high doses are generally not recommended.

If medicines do not reduce pain, the NHS says spinal cord stimulation may be recommended, which involves a device placed under the skin attached to a lead close to the nerves in the spine. Do not stop anticonvulsants or tricyclic antidepressants suddenly, as withdrawal effects can occur; your GP will reduce the dose gradually.

The NHS says the aim of rehabilitation is to gradually increase your activities and function without making the pain worse. This can be difficult because any movement or stimulation of the limb will increase pain or other symptoms, such as swelling, colour changes and sweating. Too much or too vigorous exercise can aggravate the condition, so therapy should be supported by a therapist with experience of CRPS.

Exercises can range from simple stretches to hydrotherapy or weight-bearing exercises. Desensitisation usually involves touching an unaffected body part close to the affected area with materials of different textures, such as wool and silk, and concentrating on how it feels, then gradually applying the same materials to the painful area. It is likely to be uncomfortable at first but may eventually reduce sensitivity.

Mirror visual feedback and graded motor imagery aim to improve movement by retraining the brain, because information the brain needs to perform movements is often missing or confused in CRPS.

The NHS says CRPS often gradually improves over time, but some people experience pain for many years. It estimates that around 85% of people with CRPS slowly experience a reduction in their pain and some of their symptoms in the first 2 years, but some experience continuous pain despite treatment. In rare cases further problems may develop, such as muscle wastage in the affected limb.

The NHS lists rare complications including skin infections and open sores, muscle atrophy (wasting) and muscle contractures, in which muscles shorten and lose their normal range of movement.

The NHS says the emotional strain of living with chronic pain can sometimes lead to depression and anxiety, and that during periods of extreme pain some people may have suicidal thoughts. It advises seeing a GP as soon as possible if you have been experiencing depression or have had suicidal thoughts, or calling the Samaritans on 116 123, which is available 24 hours a day.

Psychological support is one of the four main parts of CRPS treatment, and techniques such as relaxation and mindfulness are described by the NHS as an important part of treating flare-ups triggered by stress.

On the NHS, CRPS is usually diagnosed and managed through a GP referral to a pain service, often with physiotherapy, occupational therapy and psychology. Some people also see a private pain specialist for assessment or procedures such as spinal cord stimulation. As the NHS says that a number of professionals are usually involved, a coordinated plan, and clarity about who leads your care, helps in either setting.