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A-Z Medical Terms

Glossary of Terms - Complex Regional Pain Syndrome (CRPS)

This CRPS glossary of terms A-Z is aimed at giving patients, their families and loved ones a helping hand in understanding the various terms and phrases used in conjunction with Complex Regional Pain Syndrome (CRPS).

This is not a definitive list as there are many words and phrases used by doctors and others in the medical profession, but those listed here are the most commonly used.

CRPS GLOSSARY (A to Z of terms)

  • ACUTE PAIN – Pain that occurs immediately after an injury and can usually be treated.
  • ALLODYNIA – The perception of pain due to a touch of something that does not usually cause pain, e.g. clothing, light breeze.
  • ATROPHIC STAGE – The phase where there is distinct degeneration of the muscle, bone or limb.
  • ATROPHY – Waste away; wastage
  • BLOOD VESSELS – These structures carry blood through the tissues and organs. They can be veins, capillaries or arteries
  • CATECHOLAMINES – These are hormones mostly made by adrenal glands which are usually as a reaction to stress
  • CAUSALGIA – Now called CRPS Type II
  • CENTRAL NERVOUS SYSTEM – This is the main complex system of nerve tissues that controls the body’s activities. It comprises of the brain and spinal cord
  • CENTRAL SENSITISATION – The increased excitability of nociceptive neurons in the spinal cord, triggered from constant or extremely noxious input related to tissue or nerve damage. 
  • CHRONIC PAIN – Pain that lasts longer than three (3) months, or goes beyond the time of expected healing. It is quite often unaffected by treatments.
  • CHRONIC PRIMARY PAIN – pain that persists for longer than three months and is associated with significant emotional distress or functional disability and that cannot be explained by another chronic condition. Typical examples of chronic primary pain conditions are Fibromyalgia, Complex Regional Pain Syndrome and non-specific low back pain.
  • CONTIGUOUS – This is where the original CRPS site will gradually enlarge and grow bigger
  • CONTRACTURE – Tendons and muscles become permanently shortened.
  • CONTRALATERAL (spreading of CRPS) – This is also known as Mirror Image Spread 
  • CRPS – Complex Regional Pain Syndrome | What is CRPS?
  • CYANOSIS – This is where the limb or extremity looks blue-ish in colour which is because of the lack of circulation or poor oxygen in the blood.
  • DIAGNONAL – This is where the CRPS symptoms spread or occur on the diagonally opposite part of the body
  • DORSAL ROOT GANGLION (DRG) –  The DRG is a cluster of nerve cell bodies (a ganglion) in a dorsal root of a spinal nerve
  • DORSAL ROOT GANGLION STIMULATOR – The DRG stimulator is a CRPS treatment option stimulator to the Spinal Cord Stimulator. Please read our Complete Guide to the DRG Stimulator for CRPS Blog
  • DROPSY – This is now called oedema (spelt EDEMA in USA English) See OEDEMA below
  • DYSTONIA – This is where a muscle spasm will last which causes strange positions of the body or twisting actions.
  • DYSTROPHIC – This is caused by or concerning dystrophy (see below).
  • DYSTROPHY – Weakness of the limb / extremity or evidence of muscle wasting. This is mainly due to the lack of use of the muscle or affected limb / extremity.
  • EDEMA – See OEDEMA below
  • EMG – Electromyography – This is a test to measure the response of electrical activity in a muscle after the nerve is stimulated. A small needle would be inserted through the skin into a muscle and the results are shown on a special monitor.
  • EXTREMITY – A limb of the body i.e. – hand or foot.
  • HYPERALGESIA / HYPERSENSITIVITY – Increased sensitivity, and/or heightened sense of pain
  • HYPERPATHIA – This is where the limb or extremity is touched with something and you still feel a huge response to where it was touched even well after the touch has ended 
  • IMMUNE SYSTEM – This is the main system where the organs and processes of the body provide resistance against toxins and infections
  • INDEPENDENT SPREAD – This is where new CRPS symptoms appear in a different area of the body away from the original CRPS area
  • IPSILATERAL (spread of CRPS) – This is where the CRPS symptoms occur or spread on the same side of the body as the original CRPS are
  • MRI – Magnetic Resonance Imaging
  • MUSCLE ATROPHY – Muscle wastage
  • NERVE CONDUCTION STUDY / STUDIES – also known as Nerve Conduction Velocity Test. The doctor sends an electrical impulse, using an electrode pad stuck on your skin, through a nerve in your body where they believe the problem is and the study / test will measure the speed of it by measuring the time it takes for the electrical impulse to reach the electrodes. The nerves are stimulated start being stimulated by a low electrical impulse and it is raised gradually. They can also tell whether there is any damage to the nerve or not
  • NERVOUS SYSTEM – This is the body’s network of nerve cells and and fibers that transmit nerve impulses between the different parts of the body
  • NEURON – This is a specialised cell that transmits nerve impulses. It is also called a nerve cell
  • NEUROPLASTICITY – Neuroplasticity allows the neurons (nerve cells) in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment. Neuroplasticity is also called brain plasticity or brain malleability. (See Complete Guide to Graded Motor Imagery for CRPS)
  • NOCICEPTOR – A nerve cell that senses pain and sends a pain signal.
  • NOXIOUS STIMULUS – is actually, or potentially, damaging to body tissues and is likely to cause pain, but does not actually do so.
  • OEDEMA (EDEMA in USA English) – It used to be known as DROPSY. This is basically a condition that is caused by excess fluid in the spaces between cells or body tissues. The fluid then will leak out of any cells that are damaged. The fluid cannot normally be drained by needle and doesn’t normally improve if you are prescribed ‘water pills’ (diuretics). Another simple definition would be simply swelling.
  • OSTEOPENIA – Reduction in bone mass.
  • OSTEOPOROSIS – This is a condition that happened when there is a loss of minerals and proteins in bones, therefore there is a decrease of bone strength so they will become easily broken.
  • PERIPHERAL NERVOUS SYSTEM – This is the nervous system outside the brain and spinal cord
  • RSD – Reflex Sympathetic Dystrophy (previous name of CRPS) | This is now called CRPS Type I
  • SCS – Spinal Cord Stimulator
  • SPINAL CORD STIMULATOR – This is a device that is implanted into the body in the spinal cord usually with an internal battery that sends electrical impulses to the spinal cord to control chronic pain or CRPS. It is a treatment for CRPS | Learn more about CRPS Type II 
  • STIMULUS – Something that causes a reaction
  • SYMPATHETIC NERVOUS SYSTEM – The sympathetic nervous system (SNS) is part of the autonomic nervous system (ANS), which also includes the parasympathetic nervous system (PNS). The sympathetic nervous system activates what is often termed the fight or flight response
  • VELOCITY – Speed


This A-Z glossary for Complex Regional Pain Syndrome (CRPS) is not a definitive list and doesn’t give you every word or phrase that is used in connection with CRPS. It is instead to be used as a guide to help you understand and learn about CRPS and the various problems sufferers and their families and loved ones cope with.



Dictionaries Used
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