Complex regional pain syndrome - Causes of complex regional pain syndrome

Although complex regional pain syndrome (CRPS) has been a recognised medical condition for more than 150 years, its exact cause is still unclear.

Previous injury

The condition usually seems to develop within a month of an injury, either minor or more serious. These can include:

bone fractures
sprains and strains
burns
cuts

Most people will recover from these injuries without experiencing any significant long-term effects, but people with CPRS develop pain that is much more severe and long-lasting than usual.

The pain can spread beyond the site of the original injury, usually affecting an entire limb. For example, CRPS may affect your whole arm after an injury to your finger or hand. In some cases, more than one area of the body can be affected.

CRPS has also been known to occur after surgery to a limb or after part of a limb has been immobilised (for example, in a plaster cast).

Why does CRPS develop after an injury?

It is not known why some people develop CRPS after an injury. Due to the complex nature of the symptoms, it is unlikely the condition has a single, simple cause.

Some people even believe CRPS shouldn't be regarded as a single medical condition, because the symptoms could be the result of several different ones.

One of the main theories suggests that CRPS is the result of a widespread abnormal response to an injury that causes several of the body's systems to malfunction, including:

the central nervous system – the brain and spinal cord
the peripheral nervous system – the nerves that lie outside the central nervous system
the immune system – the body's natural defence against illness and infection
the blood vessels – the series of arteries and veins that transport blood around the body

These systems are responsible for many body functions that are often affected in people with CRPS, such as detecting pain and transmitting pain signals, triggering inflammation (swelling), and controlling temperature and movement.

It has also been suggested that some people may be more susceptible to CRPS because of genetic factors, although this is not clear and it is very unlikely other members of your family will be affected if you have CRPS.

In the past, some people believed CRPS may be a psychological condition that makes people think they are experiencing pain. However, this theory has been largely discredited.

Blood vessels: Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
Free radicals: Oxygen free radicals are a toxic waste product that is produced as a natural by-product of cell activity.
Genetic: Genetic is a term that refers to genes. Genes are the characteristics inherited from a family member.
Hormones: Hormones are groups of powerful chemicals that are produced by the body and have a wide range of effects.
Immune system: The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.
Inflammation: Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Nervous system: The brain, spinal cord and nerves.
Periphery nerves: The periphery nerves are a network of nerves that run from the brain and spinal cord and carry impulses to and from the rest of the body, such as the limbs and organs. They are responsible for the body’s senses and movements.