Complex Regional Pain Syndrome

CRPS of the left hand

What is complex regional pain syndrome?

Complex regional pain syndrome (CRPS) is a chronic pain condition that lasts more than 6 months, and affects a hand or foot after an injury, although other body parts may rarely be involved as well. It is thought to occur as a result of damage to the nerves in the periphery or more centrally i.e. around the spinal cord. is a chronic (lasting greater than six months) pain condition that most often affects one limb (arm, leg, hand, or foot) usually after an injury.

What are the features of complex regional pain syndrome?

People with CRPS typically have extreme pain along with skin color and temperature changes as well as swelling over the affected area. is characterized by prolonged or excessive pain and changes in skin color, temperature, and/or swelling in the affected area.

Some may experience pain that is neuropathic and described as “burning”, “pins and needles”. Others may experience sharp or electrical sort of pain. The pain may spread to other nearby parts like the arm or leg even though previously only the finger or toe is involved, with the opposite limb being involved in some cases. There is increased sensitivity so much so that even contact with clothing or having the wind blow on the affected part can be experienced as pain.

The circulation over the affected part becomes abnormal and the temperature over the limb can be warmer or colder than the opposite limb, and the color can be red or pale or even blue, with some affected limbs becoming blotchy in some cases.

There may be loss of hair over the affected limb, and the skin may look unusually shiny or thin, with unhealthy nails that may appear brittle at times. There may be difficulty moving the limb as the muscles become abnormal, with some limbs developing tremors or jerks or becoming uncoordinated with the rest of the body.

There are 2 types of CRPS. In type 1, patients have no confirmed nerve injury whereas in type 2, there is some form of confirmed nerve injury. Regardless, the treatment and management is mostly similar. Although some cases are self-limiting and may resolve on its own after months or years, many cases do not recover without treatment and can result in long term disability.

Who is at risk of CRPS?

This condition affects more women than men, and can happen at any age, with a peak at the age of 40. But it is rarely seen in the elderly and in children under the age of 10.

What is the cause of CRPS?

It is still not certain why some people develop CRPS after a trivial injury whereas other people who had severe injuries do not get CRPS even if there was nerve damage. In most cases (90%), there is usually a clear triggering event like an injury such as a fracture, sprain, burns, cuts, surgery or having a limb placed in a plaster cast. The cause is likely to be a complex interaction between genes, environment and the injury.

It is thought that nerve damage causes something caused “neurogenic inflammation” which results in the end of the nerve fibers secreting chemicals that induce pain, swelling, and redness. This sets up a vicious cycle whereby the nerve fiber is activated by the chemicals released which cause changes in the spinal cord and brain, which then sends signals for even more chemicals to be released by the nerve endings at the receptor level. The immune system also becomes involved, with is the immune cells release lots of inflammatory chemicals which only increases the pain and swelling. CRPS has be reported to be more common in people with asthma and other autoimmune conditions, which lends support for this theory.

CRPS is likely to have a genetic basis as there have been families where CRPS is common, occurs earlier and is more severe, with more than one body part being affected. Limited data suggest that CRPS also may be influenced by genetics.  

At other times, CRPS can occur for no observable rhyme or reason, and can be understandably disturbing for those who are affected.

Are there any special tests required for diagnosis?

There is no specific test that can confirm CRPS. The diagnosis is made based on the medical history provided and by looking for certain features during a physical examination. Tests like MRI and bone scans may show areas of bone resorption which may be suggestive of CRPS, but can also be seen in other conditions as well.

Will someone with CRPS get better?

It really depends. Young people like children and teenagers have better outcomes. Although many old people have good outcomes, there are some who have to suffer with the pain and disability that accompanies CRPS for the rest of their lives. Some research has suggest that early treatment of the condition is better in limiting the pain and suffering of those involved.

What are the treatment options available?

The treatment for this condition is multi-modal and involves a mixture of physiotherapy and exercise, medications, psychotherapy, and pain interventions. Lastly, there are surgical options.

Physiotherapy and exercise is important and can prevent the stiffness and contractures that may accompany prolonged disuse. It can also prevent the brain and spinal cord changes that is associated with this chronic pain condition. Occupational therapy is important as well to enable the patient to cope with the condition and live life as normally as possible.

Psychotherapy is important to manage the depression, anxiety and catastrophization that may often accompany CPRS and which make it harder for them to recover from the condition. Sometimes, post-traumatic stress has to be dealt with in order for them to overcome pain behaviours that may impede rehabilitation.

Medications can be tried and there is a whole range of them. But different people respond to different medications to different extents. Drugs that can be tried include anti-depressants that have been shown to work on neuropathic pain conditions like CRPS including amitriptyline and nortriptyline and duloxetine, anti-epileptics including gabapentin and pregabalin, topical medication like lignocaine patch and capsaicin, and N-methyl-D-aspartate (NMDA) receptor antagonists such as ketamine, and non-steroidal anti-inflammatory drugs like ibuprofen and COX II inhibitors like Arcoxia and Celecoxib. Bisphosphonates and corticosteroids can be tried as well. Opioids can be effective in the short term, but fail to show convincing improvement in pain scores or function in the longer term. Finally botox injections can be tried in some cases.

Unfortunately most of the medications only provide a limited degree of pain relief, and there is often side effects like drowsiness, forgetfulness and mood changes. Some can also be contraindicated in people with heart conditions or prostate symptoms.

Sympathetic blocks can be tried, and some have reported good pain relief for limited duration. This involves injected local anaesthetic next to the cell bodies of the sympathetic nerves. The results vary, but it can be extremely effective and life-changing for some, with a low risk of serious side effects. It can also be repeated if needed if it is effective but does not last long enough. Permanent destruction of the sympathetic nerves can be a contentious issue , but can certainly be considered if the sympathetic nerve block has been proven to be effective but does not last long enough.

Neuromodulation techniques involving stimulating the spinal cord that receives the nerve transmission from the affected area. This can be done with a spinal cord stimulator lead which places certain electrodes next to the spine to provide a tingling or buzzing sensation. A trial is done first and if it is effective, a permanent stimulator with battery and electrodes is placed under the skin. Up to a quarter to half of all patients may need to have another surgery to fix the technical issues that will arise. Other stimulators that can be used include peripheral nerve stimulators that target the injured nerve downstream, deep brain stimulation, and transcranial magnetic stimulation, although these are not as established. Pulsed radiofrequency stimulation of the dorsal root ganglion can also be tried. This is a procedure that is done as a day procedure with thin needles under sedation and the patient can go back home on the same day if necessary. It aims to ‘reset’ the damage nerve to decrease nerve sensitivity. Sometimes the procedure will need to be repeated several times before the desired effect is achieved.

Intrathecal pumps can be trialled as well especially in cases where there is a response to opioids but doses cannot be increased further because of side effects. The medication is delivered straight next to the fluid surrounding the spinal cord so that less of the medication such as an opioid or baclofen is required, thus limiting their side effects. Unlike neuromodulation techniques, there are less studies showing the benefit of intrathecal pump for CRPS.

Other techniques that some are trying include immune modulation with intravenous immunoglobulin, ketamine infusions, and graded motor imagery which includes mirror-box therapy. Acupuncture, relaxation techniques and chiropractic treatment has also been tried with differing success rates.