Complex regional pain syndrome

The term "complex regional pain syndrome" (CRPS) refers to a syndrome manifested by severe chronic pain in the limb in combination with local vegetative disorders and trophic disorders, which occurs, as a rule, after various peripheral traumas. Symptoms of a complex regional pain syndrome are familiar to almost every doctor, but at the same time, the issues of terminology, classification, pathogenesis and treatment of this syndrome remain largely controversial.

In 1855, N.I. Pirogov described intense burning pains in the extremities, accompanied by vegetative and trophic disturbances, which arise in the soldiers some time after the injury. These disorders, he called "post-traumatic hyperesthesia." After 10 years, S. Mitchell et al. (Mitchell S., Morehouse G., Keen W.) described a similar clinical picture of soldiers affected by the civil war in the United States. These states S. Mitchell initially designated as "erythromelalgia", and then, in 1867, proposed the term "causalgia". In 1900, P.G. Zudek described such manifestations in combination with osteoporosis and called them "dystrophy." In the future, different authors described similar clinical conditions, invariably offering their own terms ("acute bone atrophy", "algoneurodystrophy", "acute trophic neurosis", "posttraumatic osteoporosis", "posttraumatic sympathy", etc.). In 1947, O. Steinbrocker described shoulder-brush syndrome (pain, edema, trophic disorders in the hand that occur after myocardial infarction, strokes, trauma and inflammatory diseases). In the same year, Evans J. Proposed the term "reflex sympathetic dystrophy," which until recently was generally accepted. In 1994, to denote local pain syndromes, combined with vegetative and trophic disorders, a new term was proposed - "complex regional pain syndrome".

Classification of complex regional pain syndrome

There are 2 types of complex regional pain syndrome. With lesions that are not accompanied by defeat of peripheral nerves, type I CRPS is formed. CRRS II type is diagnosed with the development of the syndrome after peripheral nerve damage and is considered as a variant of neuropathic pain.

[1], [2], [3], [4], [5]

Causes and pathogenesis of complex regional pain syndrome

The causes of complex regional pain syndrome type I can be trauma of soft tissues of the limb, fractures, dislocations, distension, fasciitis, bursitis, ligamentitis, vein and arterial thrombosis, vasculitis, herpetic infection. CRRS II type develops with nerve damage due to compression, with tunnel syndromes, radiculopathies, plexopathies, etc.

The pathogenesis of complex regional pain syndrome is not well understood. In the origin of complex regional pain syndrome type II, the possible role of aberrant regeneration between afferent (sensory) and efferent (vegetative) fibers is discussed. Postulate that prolonged pain can be fixed in memory, causing a higher sensitivity to repeated pain stimuli. There is a view that nerve damage sites become ectopic pacemakers with a dramatically increased number of alpha-adrenergic receptors, which are excited spontaneously and under the action of circulating or released from sympathetic endings of noradrenaline. According to another concept, in the complex regional pain syndrome, activation of spinal neurons of a wide range participating in the transfer of nociceptive information is of particular importance. It is believed that, after trauma, intense stimulation of these neurons occurs, leading to their sensitization. In the future, even weak afferent stimuli, acting on these neurons, cause a powerful nociceptive flow.

Due to disorders of microcirculation, leading to the development of hypoxia, acidosis and the accumulation of acidic metabolic products in the blood, there is an increased disintegration of phosphoric calcium bone compounds with the development of osteoporosis. "Spotted" osteoporosis, usually observed at the first stages of the disease, is associated with the dominance of lacunar resorption of bone tissue. An important factor in the development of osteoporosis is immobilization. In some cases, it is caused by severe pain, in others it is associated with the underlying disease (for example, paresis or plegy after a stroke) or with therapeutic manipulations (immobilization after fractures). In all cases, a decrease in physical activity, prolonged immobility lead to bone demineralization and the development of osteoporosis.

[6], [7], [8], [9], [10]

Symptoms of complex regional pain syndrome

Among the patients, women predominate (4: 1). The disease can occur at almost any age (from 4 to 80 years). CRPS on the lower limbs is noted in 58%, on the upper - in 42% of cases. Involvement of several zones is observed in 69% of patients. Cases of complex regional pain syndrome on the face are described.

Clinical manifestations of complex regional pain syndrome of all types are identical and consist of 3 groups of symptoms: pain, vegetative vaso- and sudomotor disorders, dystrophic changes in the skin, subcutaneous tissue, muscles, ligaments, bones.

• For a complex regional pain syndrome, spontaneous intense burning, stitching, pulsating pains are typical. The phenomenon of allodynia is very characteristic. As a rule, the zone of pain goes beyond the innervation of any nerve. Often the intensity of pain is much greater than the severity of the injury. Increased pain is noted with emotional stress, movement.
• Vegetative disorders in a complex regional pain syndrome include vaso- and sudomotor disorders. The first include edema, the severity of which can vary, as well as violations of peripheral circulation (vasoconstrictive and vasodilation reactions) and skin temperature, changes in skin color. Sudomotor disorders are manifested by symptoms of local hyperhidrosis or decreased sweating (hypohidrosis).
• Dystrophic changes in complex regional pain syndrome can cover almost all limb tissues. There is a decrease in skin elasticity, hyperkeratosis, changes in the hairline (local hypertrichosis) and nail growth, atrophy of the subcutaneous tissue and muscles, muscle contractures, stiffness of the joints. The demineralization of bones and the development of osteoporosis are characteristic for complex regional pain syndrome. CRRS I type is characterized by constant pain in a certain part of the limb after an injury that does not affect the large nerve trunks. Pain is usually observed in the distal limb, adjacent to the injured area, as well as in the knee and hip, in the I-II fingers or feet. Burning persistent pain, usually occurs a few weeks after the initial injury, intensified by movement, skin stimulation and stress.

Stages of development of complex regional pain syndrome of type I

Stage	Clinical Characteristics
1 (0-3 months)	Burning pain and distal edema of the limb. The limb is warm, edematous and painful, especially in the area of the joints. Local sweating and hair growth are increasing. A light touch can cause pain (applause), which persists even after the cessation of exposure. Joints become stiff, pain is present both with active and passive movements in the joint
II (after 3-6 months)	The skin becomes thin, shiny and cold. All other symptoms of Stage 1 persist and worsen
III (6-12 months)	The skin becomes atrophic and dry. Contractures of muscles with deformities of hands and feet

CRRS II type is accompanied by burning pain, allodynia and hyperpathy in the corresponding arm or foot. Usually, pain occurs immediately after the injury of the nerve, but may appear even several months after the injury. Initially, spontaneous pain is localized in the innervation zone of the damaged nerve, and then can cover larger areas.

The main manifestations of complex regional pain syndrome type II

Symptom	Description
Characteristics of pain	Constant burning, intensifies with light touch, stress and emotions, changes in outside temperature or movements in the affected limb, visual and auditory stimuli (bright light, sudden loud sound). Allodynia / hyperalgesia is not limited to the zone of innervation of the damaged nerve
Other manifestations	Changes in skin temperature and color. The presence of edema. Disturbance of motor functions

Additional research

With the help of thermography, it is possible to detect changes in skin temperature on the affected extremity, reflecting peripheral vaso- and sudomotor disturbances. X-ray examination of bones is mandatory for all patients with complex regional pain syndrome. In the early stages of the disease, spotted osteoplastic osteoporosis is found, as the disease progresses, it becomes diffuse.

Treatment of complex regional pain syndrome

Therapy in complex regional pain syndrome is aimed at eliminating pain, normalizing vegetative sympathetic functions. It is also important to treat a background disease or a disorder that caused CRPS.

To eliminate pain, repeated regional blockade of sympathetic ganglia with local anesthetics is used. When the pain is eliminated, the autonomic functions also normalize. Various local anesthetics are also used (for example, ointments, creams and lidocaine plates). The application of dimethylsulfoxide, which has an analgesic effect, has a good effect. More pronounced analgesic effect is achieved with the application of dimethylsulfoxide with novocaine. Traditionally, acupuncture, percutaneous electroneurostimulation, ultrasound therapy and other types of physiotherapy are used to reduce pain. Effective hyperbaric oxygenation. Good results are obtained with the appointment of prednisolone (100-120 mg / day) for 2 weeks. To reduce sympathetic hyperactivity, beta-blockers (anaprilin at a dose of 80 mg / day) are used. Also used are calcium channel blockers (nifedipine at a dose of 30-90 mg / day), drugs that improve venous outflow (troxevasin, tribenozide). Taking into account the pathogenetic role of the central mechanisms of pain, the appointment of psychotropic drugs (antidepressants, anticonvulsants - gabapentin, pregabalin) and psychotherapy is recommended. Bisphosphonates are used to treat and prevent osteoporosis.

In conclusion, it should be noted that CRPS remains an insufficiently studied syndrome and the effectiveness of the applied methods of treatment has yet to be studied in careful controlled studies consistent with the principles of evidence-based medicine.