Complex Regional Pain Syndrome (CRPS): Types, Causes, Risk Factors, Signs, Symptoms, Treatment

Complex regional pain syndrome or CRPS is a chronic pain condition that is believed to be caused due to dysfunction of the central or peripheral nervous system. Typical features of Complex Regional Pain Syndrome (CRPS) are dramatic changes in the temperature and color of the skin over the affected area along with intense burning pain, sweating, skin sensitivity, and swelling.

Some of the older terms used for Complex Regional Pain Syndrome (CRPS) are reflex sympathetic dystrophy syndrome and causalgia, which was first used during the Civil War.

CRPS can affect an individual at any age. It affects both men and women, although it is believed young women are more prone to it.

• CRPS Type I: This was formerly known as reflex sympathetic dystrophy syndrome. The most common cause for this is soft tissue injury such as sprains, strains, tears, burns, bursitis, tendonitis, etc. There is no definite definable nerve injury as the underlying cause. This is generally caused following a minor nerve injury owing to a simple trauma from a fall or sprain, injury from a bullet or knife, fracture especially of wrist and ankle, surgery, spinal injuries, heart problems, infections, repetitive stress injuries, carpal tunnel syndrome, tarsal tunnel syndrome, injections, and some partial paralysis injury.
• CRPS Type II: This was formerly known as Causalgia. The cause for this is a definable major nerve injury. Serious injuries such as broken bones or some major surgeries are the main cause for this. Other causes may include serious infection. There is clear-cut evidence of nerve damage in all the cases.

There are millions of men, women, and children across the country affected with CRPS. It is estimated that United States alone has between 1.5 and 3 million individuals affected with Complex Regional Pain Syndrome (CRPS). Women are seen to be affected more than men. It is estimated that approximately 75% of victims are women. Majority of the individuals develop the disease in the age groups of 30’s and 40’s but it can affect all age groups. It is seen that in recent years more and more individuals in their teens seem to be developing this disease.

The pathophysiology of Complex Regional Pain Syndrome (CRPS) may be multifactorial, but it is exactly not known. The mixed peripheral nerves have pain-sensing nociceptive nerve fibers. Any sort of dysfunction in these fibers results in increased responsiveness to peripheral stimuli, decreased pain thresholds, and CNS changes which intensify and extend the symptoms, also called central sensitization. Central sensitization results in increased responsiveness to generally very mild mechanical stimulus and spreading of pain in areas that are not involved. Though type 1 CRPS has no identifiable nerve injury as its cause, small-fiber abnormalities in “A Delta” and “C fibers” have been detected in biopsies. However, it is different from type 2 CRPS in which case the nerve injury occurs to a specific defined nerve.

Both peripheral and central autonomic nerve dysfunctions are thought to have underlying pseudomotor, vasomotor, and trophic changes which vary over hours to days. Presence of increased skin temperature along with erythema and edema during the first six months is common with gradual decline thereafter along with cyanosis and thinning of skin.

Some of these features can be secondary to neurogenic inflammation. Nociceptor activation results in release of neuropeptides in the edges. This gives rise to neurogenic inflammation and subsequent protein extravasation, vasodilation, and edema.

There can be other central nervous system changes which may occur. This explains motor findings, cutaneous sympathetic dysfunction, hyperreflexia, and therapeutic potential of motor cortex stimulation. The motor cortex has been shown to be involved in pathophysiology of chronic pain.

There is no known cause for Complex Regional Pain Syndrome (CRPS). The sympathetic nervous system plays an important role in retaining the pain in some of the cases. More recent theories suggest that pain receptors in the affected part of the body become responsive to a family of nervous system messengers known as catecholamines. It is believed that the importance of the sympathetic nervous system depends on the stage of the disease.

Another theory proposed is that CRPS II is caused by immune response trigger, which leads to the characteristic inflammatory symptoms of warmth, redness, and swelling in the affected area. Hence, CRPS may represent a disruption of the healing process. Complex Regional Pain Syndrome (CRPS) does not have a single cause, but is rather multifactorial that produces similar symptoms.

The main symptom of Complex Regional Pain Syndrome (CRPS) is continuous, intense pain that is out of proportion to the severity of the injury occurred, which continues to get worse rather than better over a period of time.

Complex Regional Pain Syndrome (CRPS) most often affects one of the extremities arms, legs, hands, or feet and is accompanied by the following symptoms:

• Burning pain.
• Changes in skin temperature.
• Changes in skin color.
• Increased sensitivity.
• Changes in skin texture, sometimes excessively sweaty.
• Changes in nail and hair growth patterns.
• Stiffness and swelling in affected joints.
• Motor disability or decreased ability to move the affected body part.
• Pain that spreads to include the entire arm or leg even though the initial injury may be only to a finger or toe. Pain can sometimes travel to the opposite extremity. Emotional stress too can increase the pain.

The symptoms of Complex Regional Pain Syndrome (CRPS) can vary in length and severity. It is believed that there are three stages associated with CRPS, marked by progressive changes in the skin, muscles, ligaments, bones, and joints of the affected area.

Stage one generally lasts from anywhere between one to three months and is characterized by severe, burning pain, along with joint stiffness, muscle spasm, rapid hair growth, and alterations in the blood vessels that cause the skin to change temperature and color.

Stage two lasts from anywhere between three to six months and is characterized by swelling, intensifying pain, decreased hair growth, brittle, grooved, cracked, or spotty nails, stiff joints, softened bones, and weak muscle tone.

With stage three, the syndrome progresses to the point where bone and skin changes become irreversible. Pain becomes uncompromising and may involve the entire limb or affected area. There may be severely limited mobility, marked muscle atrophy, and involuntary contractions of the muscles and tendons that flex the joints. Affected limb may be contorted.

Treatment is primarily aimed at relieving painful symptoms as there is no cure for Complex Regional Pain Syndrome (CRPS).

• Physical Therapy (PT): A gradually increasing exercise program to keep the painful limb or body part moving may help restore some range of motion and function.
• Psychotherapy: CRPS most of the times has a profound psychological effect on individuals and their families. CRPS victims may suffer from anxiety, depression, or posttraumatic stress disorder which all heighten the perception of pain and lead to difficulties with rehabilitation efforts.
• Sympathetic Nerve Block: Sympathetic nerve blocks provide significant pain relief to some victims. Sympathetic blocks can be done in different ways. One of the techniques involves intravenous administration of phentolamine that blocks sympathetic receptors. Another technique involves placing an anesthetic just next to the spine to block the sympathetic nerves directly.
• Medications: Many different medications are used including topical analgesic drugs that act locally on painful nerves, muscles and skin, antidepressants, antiepileptic drugs, opioids and corticosteroids. However, no single drug or combination of drugs can produce long-lasting improvement in symptoms.
• Surgical Sympathectomy: Surgical sympathectomy is a technique that destroys the nerves involved in CRPS, but this is controversial. It is believed that surgical sympathectomy can in fact make CRPS worse, but some report a favorable outcome. Sympathectomy should be used only in patients whose pain is dramatically relieved though temporarily by selective sympathetic blocks.
• Spinal Cord Stimulation: Stimulating electrodes are placed next to the spinal cord to provide a pleasant tingling sensation in the painful area. This helps many patients with the pain.
• Intrathecal Drug Pumps: Intrathecal pumps administer drugs directly into the spinal fluid so that local anesthetic agents and opioids can be delivered to pain-signaling targets in the spinal cord. This is dosed far lower than those of for oral administration. This technique decreases side effects and increases drug effectiveness.

It can be difficult to make a firm diagnosis of CRPS early in the course of the disorder because many other conditions have similar symptoms. Diagnosis can be further complicated because some individuals tend to gradually improve over time without any treatment.

Despite all this, CRPS can only be diagnosed through careful observation of the signs and symptoms.

Because of absence of any specific diagnostic test for CRPS, the only option left out is by ruling out other conditions. Sometimes triple-phase bone scans are used to identify changes in the bone and in blood circulation.