Complex Regional Pain Syndrome, often referred to simply as 'CRPS', describes a type of pain suffered after either an injury or, more rarely, after a stroke or heart attack, after surgery or after a limb has been placed in a cast for a long period. It typically affects either an arm or a leg.
CRPS pain is generally of a level much higher than the injury or condition would normally cause, and is often accompanied by a range of other symptoms. It can be acute (ie short-lasting) or chronic (long-lasting ie 6 months or longer).
CRPS may be the result of a specific nerve injury (CRPS-2) or not (CRPS-1).
Medical science does not fully understand what causes CRPS, but it is believed that it is related to malfunction of, or injury to the peripheral nervous system. This then has a knock- on effect on the central nervous system – the spinal cord and the brain.
Current thinking is that injury to the affected limb causes damage to sensory and autonomic nerve fibres (also referred to as 'small fibres') that transmit pain signals and other sensory information and control smaller blood vessels. They are more prone to damage and malfunction as these nerve fibres, unlike other nerve fibres, do not have myelin coatings, which would to a degree protect them from damage.
Certain things, referred to as 'disease mechanisms', are believed to be risk factors for developing the condition. These are…
- Immune-related conditions, for example asthma.
- Hereditary factors – CRPS can run in some families.
- Gender – women are more prone to develop CRPS than men.
- Age – CRPS is more common in people 30-50 years of age; it is uncommon in older people and in young children.
- Smoking – as it affects good blood circulation.
- Inflammatory response after an injury.
Apart from severe pain (much in excess of the original injury/cause), symptoms of CRPS can include one or more of the following…
- Burning sensation on the skin.
- Pins and needles.
- Hypersensitivity of the skin in the affected area ('allodynia') or specific increased pain from mild stimulus e.g. a pin prick ('hyperalgesia').
- 'Mirror pain' – pain at the same location on the opposite limb.
- Changes in skin temperature, texture or colouration.
- Swelling or stiffness in the affected limb.
- Abnormal sweating ('hyperhydrosis') in affected limb.
- Abnormal hair/nail growth rates in affected limb (either slower or faster than normal).
- Abnormal bone growth rates in affected limb (either slower or faster than normal) .
- Spasms or tremors.
- Difficulty with fine motor control.
Tests / Diagnosis
Diagnosis of CRPS generally involves an examination by a specialist (for example a neurologist) and identification of pain points and any other symptoms in order to identify the affected nerve/s. Specific tests are not needed to confirm a diagnosis of CRPS, but may be useful to diagnose other similar conditions.
Bone scans may be recommended (to identify any absorption of bone into the body which may indicate CRPS).