What Is Complex Regional Pain Syndrome (CRPS)? What Causes Complex Regional Pain Syndrome?

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Main Category: Pain / Anesthetics
Also Included In: Neurology / Neuroscience
Article Date: 02 Apr 2010 - 0:00 PST

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Complex regional pain syndrome, also known as CRPS is a rare, chronic (long-term) and progressive condition characterized by severe pain, inflammation and changes in the skin. Patients commonly describe the pain as a burning sensation, which affects one of the arms, legs, hands or feet.

CRPS used to be known as reflex sympathetic dystrophy - however, when possible causes of CRPS were later discovered, the name was changed.

Experts are not sure what the cause of CRPS is. We know that injury or surgery may have occurred before the onset of symptoms. However, in many cases no previous injury took place and there is no evidence of neurological or physical damage to the affected area.

According to the National Health Service (NHS), UK, and the International Association for the Study of Pain, there are two types of CRPS:

• CRPS Type 1 - used to be known as reflex sympathetic dystrophy, Sudeck's atrophy, reflex neurovascular dystrophy, or algoneurodystrophy. No damage has occurred. It is triggered by an apparent trivial injury, such as a fractured or sprained ankle.
• CRPS Type 2 - used to be known as causalgia. This is triggered by a more serious injury, such as a broken bone or some surgical operation. It may also be caused by a serious infection. In all cases there is clear evidence that nerve damage has occurred.

Treatment for CRPS, which usually includes a combination of physical therapy (physiotherapy) and medications, is much more effective if it starts soon after the onset of symptoms.

As the condition is very difficult to diagnose, it is not possible to make reliable estimates of the number of people affected. A significant number of patients never tell their GP (general practitioner, primary care physician) or doctor if their symptoms are mild. The National Health Service (NHS), UK, believes that approximately 1 in every 2,000 accidents or incidents of trauma probably result in CRPS.

Although CRPS can affect people of any age, first symptoms tend to become noticeable in patients aged between 40 and 60 years. Experts say that more females are affected than males.

The severity of symptoms and frequency of episodes of CRPS vary enormously. Some individuals have repeated CRPS episodes throughout their life, while others have symptoms which go away forever after a few months.

According to Medilexicon's medical dictionary:

Complex regional pain syndrome type I is "diffuse persistent pain usually in an extremity often associated with vasomotor disturbances, trophic changes, and limitation or immobility of joints; frequently follows some local injury."

What are the signs and symptoms of complex regional pain syndrome (CRPS)?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.

The predominant symptom of CRPS is pain:

• Pain - the pain is severe and continuous. Patients describe it as a burning pain. Some have said it feels like a combination of burning and electrical shocks. Part or all of a limb may be affected, such as an arm, leg, hand or foot. The pain is triggered by an injury and is much worse than one would expect. For example, a patient who sprained an ankle may experience an unbearable burning sensation.
  
  The affected limb, or part of the limb can become hypersensitive. If touched, bumped on, or exposed to temperature changes the pain can be severe.
  
  If symptoms are severe there may eventually be muscle atrophy (wasting) in the affected limb. This is because the patient does not use the limb due of the pain.

Other possible signs and symptoms include:

• Changes in skin temperature - the skin may be sweaty on some occasions, and cold and clammy in others.
• Changes in skin color - there may be blotches or streaks on the skin. It may range in color from very pale to pink. Sometimes the affected area of skin may take on a blue tinge.
• Skin texture - the skin may sometimes seem thin and shiny.
• Nails and hair - hair and nails may grow at unusual speeds (too slow or too fast).
• Joints - the affected joint(s) may be painful, stiff and inflamed.
• Mobility - the patient may find it harder to move the affected limb or part of limb.

CRPS generally progress in 3 stages. Not everyone will experience all three stages. Some people may have symptoms in different stages.

• Stage 1 of CRPS - typically lasts from 1 to 3 months. There is a severe, burning pain in one of the limbs. There may be muscle spasms (involuntary muscle contractions), joint stiffness and fast-growing hair and nails. Skin color and temperature may also change as blood vessels in the area are affected.
• Stage 2 of CRPS - usually lasts for 3 to 6 months. Pain in the affected limb, hand or foot may get worse, as may alterations in skin texture and color. Muscle tone may weaken. Inflammation and stiffness may worsen.
• Stage 3 of CRPS - changes that have occurred so far are usually irreversible at this stage. There will be significant loss of muscle tone in the affected limb, bones may have become contorted, while the joints have become stiffer. The patient will likely find it very hard to use the affected limb. Patients who receive prompt treatment for CRPS early on are very unlikely to ever reach this stage.

What are the causes of complex regional pain syndrome (CRPS)?

• Type 1 - occurs after an injury or illness that did not directly damage nerves in the affected area. Approximately 90% of CRPS cases are Type 1.
• Type 2 - follows an evident nerve injury.

Many CRPS cases occur after a forceful trauma to a limb, such as shrapnel blast or gunshot wound. Surgery, heart attacks, infections, sprained ankles and fractures may also trigger CRPS.

Experts do not know exactly why such injuries or medical events trigger CRPS, even though the condition has been recognized by the medical profession for over 150 years. Specialists mostly agree that there is probably more than one single cause. Some argue that CRPS is a combination of different conditions with the same symptoms - they say it is not a single medical condition.

The psychological theory

Sigmund Freud, (1856-1939), an Austrian neurologist who founded the psychoanalytic school of psychiatry put forward the idea that CRPS might be mainly a psychological condition, caused by some unknown underlying psychological difficulty or trauma which make patients feel pain. As subsequent research has demonstrated that CRPS patients undergo real physical changes in their nervous system, this theory has been largely discarded. Other studies have shown that CRPS patients do not have a history of mental illness prior to the onset of symptoms.

Sympathetic nervous system malfunction theory

The sympathetic nervous system (SNS) is one of the 3 parts of the autonomic nervous system (that regulate heart rate, digestion, respiration rate, salivation, perspiration), along with the enteric and parasympathetic systems. The SNS's general action is to mobilize our body's resources under stress - to trigger the flight-or-fight response.

If we find ourselves in danger, for example, if a huge drunken man walks in your direction in a dark street at night, your sympathetic nervous system will start to accelerate your heart rate, breathing rate, blood pressure, as well as the level of certain hormones (adrenalin) - you are being prepared for a sudden, short-term release of energy, so that you can either fight better or run away faster (flight-or-fight response).

Some people believe that a physical injury, for example, may cause the SNS to release catecholamines. Catecholamines are 'fight-or-flight' hormones. Due to an unknown underlying problem, catecholamines are thought to activate pain receptors. Pain receptors are nerve endings which send pain signals to the brain (which makes you feel pain). They say that is why the post-injury pain experienced by CRPS patients is much greater than one would expect from that injury.

In other words, it is not the injury that causes the intense pain, but rather the way the body has responded to it.

The sympathetic nervous system has other functions too, such as regulating the blood vessels of the skin. A sympathetic nervous system malfunction might result in changes of skin color and temperature; one of the signs linked to CRPS.

Some cases of CRPS, however, have no evidence at all of any sympathetic nervous system malfunction.

Immune system malfunction theory

Some believe that Type 2 CRPS is caused by a problem with the immune system. When the body has an injury its immune system makes that area inflamed (swollen) as it attempts to stop infection from spreading. For some reason not yet known to us, theorists say, inflammation continues well after the injury has healed. The persistent inflammation irritates the nerves in that area, resulting in pain.

Diagnosing complex regional pain syndrome (CRPS)

There is no single test that can determine the presence of CRPS. Diagnosis is based on a physical exam, looking out for swollen joints, and changes to skin temperature and appearance, and the patient's medical history. The doctor may order the following diagnostic tests to help make a diagnosis:

• Bone scan - a radioactive liquid is injected into a vein, allowing the bones to be viewed with a special camera. Increased circulation to the joints in the affected area may be detected.
• Sympathetic nervous system tests - the aim is to identify possible anomalies in the patient's sympathetic nervous system.
  
  
  • Sweat test - the amount of sweat produced by the affected limb is compared to sweat production of the unaffected limb. If there is a big difference, the likelihood of CRPS is greater.
  • Thermography - an infrared thermometer measures skin temperature of specific parts of the body, including the affected area. If skin temperature in the affected area is too high or too low, it could indicate CRPS.
  • Electrodiagnostic testing - wires are attached to the skin and the electrical activity of nerves is measured. If readings are abnormal it could mean there is nerve damage, indicating possible presence of type 2 CRPS.
• X-ray - in later stages of CRPS, X-rays may detect levels of mineral loss in the bones. The doctor may order X-ray to rule out problems with joints and bones.
• MRI (magnetic resonance imaging) scan - an MRI machine uses a magnetic field and radio waves to create detailed images of the inside of the body. The doctor may order an MRI scan to rule out underlying problems with bones or tissue.
• Blood tests - these may be ordered to rule out underlying infection, or rheumatoid arthritis.
• A biopsy - a small sample of tissue from the affected area is removed and checked for cancerous cells.

According to the National Health Service (NHS), UK, experts have created a diagnostic checklist to help GPs (general practitioners, primary care physicians), as well as other healthcare professionals. If ALL of the following signs and symptoms are present, a CRPS diagnosis can be made:

• The patient has recently suffered an injury or some kind of trauma.
• There is persistent pain in a limb that is disproportionate to the original trauma or injury.
• Swelling and changes to skin temperature and appearance are evident.
• No other diagnosis could explain the signs and symptoms better than CRPS.

What are the treatment options for complex regional pain syndrome (CRPS)?

Treatment is most effective if carried out as soon as possible after the first signs and symptoms appear. In some cases even remission (total disappearance of signs and symptoms) is possible.

CRPS treatment strategy is usually multi-disciplinary, with the use of different types of medications combined with specific physical therapies.

A multi-disciplinary approach (a number of different specialists):

• Neurologist - this is a doctor who is specialized in treating nervous system illnesses and conditions.
• Physical therapist - physical therapy is a branch of rehabilitative health that uses specially targeted exercises and devices to help people improve or regain their physical abilities. For CRPS patients this may include regaining their range of movement and coordination, as well as preventing muscle wastage and contortion of the bones.
  
  Physical therapy is the key factor in successfully treating CRPS.
  
  Some patients may find physical therapy initially painful. Studies have shown that for those who persist with their physical therapy, symptoms of pain generally improve dramatically.
• Occupational therapist - trained to evaluate patients with certain conditions and diseases, including CRPS, to determine the impact of their condition on activities and daily living. They can design and prescribe assistive devices which can help with the activities of daily living.
• Psychologist - the patient may require help in coping with living with a chronic, painful condition.
• Social worker - in most developed nations a social worker will provide the patient with information about services that are available.
• Pain relief specialist - this is generally a doctor with specialist training in relieving pain.

Medications and electrical stimulation

• NDSAIDs (nonsteroidal anti-inflammatory drugs) - OTC (over-the-counter, no prescription required) NSAIDs such as ibuprofen, naproxen sodium or aspirin may relieve pain and inflammation.
• Antidepressants - such as amitriptyline may be prescribed for neuropathic pain (pain caused by a damaged nerve). Should not be taken by those with a history of heart disease. Side effects may include drowsiness, dry mouth, blurred vision, constipation and problems urinating. Individuals who feel drowsy should not drive or operate heavy machinery.
• Anticonvulsants - these were originally designed for epilepsy treatment. However, they are also useful in treating nerve pain. Gabapentin is the most commonly prescribed anticonvulsant for CRPS. As side effects may include loss of coordination, drowsiness, dizziness and fatigue, patients may have to refrain from driving or operating heavy machinery.
• Corticosteroids - such as prednisone may reduce inflammation.
• Bone-loss medications - such as alendronate (Fosamax) and calcitonin (Miacalcin) may also be prescribed.
• Opioid medications (opiates) - Opioids (opiates) are a class of drugs that are commonly prescribed for their analgesic or pain-killing, properties. They include substances such as morphine, codeine, oxycodone, and methadone. Opioids are not suitable if the patient has a history of substance abuse or lung disease. Codeine and diamorphine can bring short-term pain relief in severe CRPS cases. Opiates should not be used long-term because of their potential side effects. Long-term use also carries a risk of addiction. Side effects may include drowsiness (improves) and constipation. Individuals who feel drowsy should not drive or operate heave machinery.
• Sympathetic nerve-blocking drugs - an anesthetic may be injected, blocking the nerve fibers in the affected nerves.
• Topical analgesics - topical means "applied onto the skin". Several types of creams, such a lidocaine, or a combination of ketamine, clonidine and amitriptyline may reduce hypersensitivity.
• Heat and cold therapy - sweating and inflammation may respond well to the application of cold. If the affected area is too cold, heat therapy may help.
• TENS (transcutaneous electrical nerve stimulation) - electrical impulses are applied to nerve endings, often providing pain relief.
• Spinal cord stimulation - tiny electrodes are inserted into the spinal cord. This is done by a doctor. Spinal cord stimulation can provide effective pain relief for many patients.

What are the possible complications of complex regional pain syndrome (CRPS)?

If complications do occur, they are nearly always because the condition remained untreated, or treatment started late.

• Muscle atrophy (muscle withers) - if a limb is not used for any reason, which in this case would be pain, the muscles begin to waste.
• Contracture - the hand, fingers or foot, depending on which area is affected, may contract into a fixed position as the muscles gradually tighten.
• CRPS may spread - CRPS symptoms may spread to the opposite limb, hand or foot (mirror-image type), to a distant part of the body (independent type), or to a nearby site (continuity type).

Written by Christian Nordqvist


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