Complex Regional Pain Syndrome (or CRPS) refers to a classification of disorders, which can occur even after minor injury to a limb and which is a major cause of disability and characterized by pain out of proportion to physical findings.

In the past, it was called Reflex sympathetic dystrophy causalgia, Sudeck atrophy, or Leriche posttraumatic syndrome. In 1994, complex regional pain syndromes term was established by the International Association for the Study of Pain.

The incidence of CRPS is:

  • 1–2 % after various fractures
  • 2–5 % after peripheral nerve injury,
  • 7–35 % in Colles fracture.

Complex regional pain syndrome occurs most commonly in elderly patients and those with psychological or psychiatric conditions and has been reported in 8% to 35% of patients with distal radial fractures.

CRPS Etiology

There is no well-defined or complete system for explaining the etiology for CRPS. Many theories have been introduced:

  1. Mitchell, Morehouse, and Keen in 1867 after median neural injury occurring during the Civil War aided in defining certain characteristics, such as burning, dysesthesia, and vasomotor instability after injury.
  2. Sudeck delineated other features of osseous and vascular changes.
  3. Evans described the sympathetic instability.

More clearly explanation was that there is a local injury consequences to sensory nerves, resulting in altered vasomotor responses and aberrant afferent neural transmission, and internuncial transmission dysregulation. This alteration results in sympathetic hyperactivity.

CRPS frequently does not limit itself exclusively to well-delineated dermatomes, myotomes, or sclerotomes.

Adults can present with CRPS after a fracture or trauma with immobilization. With children, it occurs most often in athletic girls (1:6, boys to girls) with an average age of 12 years.

reflex sympathetic dystrophy

CRPS Types

There are two types of Complex Regional Pain Syndrome that are recognized by the International Association for the Study of Pain:

CRPS Type 1:

CRPS Type 1 refers to the pain syndrome, previously termed Reflex sympathetic dystrophy RSD, which involves a pain syndrome triggered by a noxious event that is not limited to a single peripheral nerve.

CRPS Type 2:

CRPS Type 2 refers to the pain syndrome, previously termed causalgia, which involves a pain syndrome that involves direct partial or complete injury to a nerve or one of its major branches.

More recently, it has been suggested that a third type may exist. This type is characterized by irreversible changes in the skin and bones, marked muscle atrophy, unyielding pain, and severely limited mobility of the affected area.

CRPS Symptoms

The signs and symptoms for both types include:

  1. Pain,
  2. Edema,
  3. Stiffness,
  4. Skin temperature changes,
  5. Sweating.

The pain of type I CRPS is classified as sympathetically maintained pain or sympathetically independent pain, where sympathetically maintained pain is characterized by an abnormal reaction of the sympathetic nervous system.

Pain is not necessarily located in an area corresponding to the cutaneous distribution of the nerve. Another characteristic of the pain, particularly in major causalgia, is accentuation by stimuli to such emotions as surprise and anger and by other disturbances in the patients’ environment.

The edema, which can be pitting or nonpitting, is often present throughout all stages of CRPS and may be the result of vasomotor instability coupled with a lack of motion.

The stiffness is one of the components of type 1 that increases with time and is due to increased fibrosis in the ligamentous structures and adhesion formation around the tendons.

The diagnosis of CRPS is made from the physical examination and the patient’s medical history, which may include past events of trauma, persistent pain, hyperalgesia, allodynia (perception of a nonpainful stimulus as painful), edema, and diminished function of the area.

The type of pain and its duration are perhaps the most important diagnostic signs. The pain is typically burning in nature and is of a much longer duration than would be expected from the injury.

Complex Regional Pain Syndrome symptoms
CRPS Symptoms

CRPS Clinical Phases

CRPS 1 has been subdivided into three clinical phases:

1. Acute inflammatory phase:

An acute inflammatory phase that can last from 10 days to 2–3 months. The acute stage of CRPS lasts from 1 to 3 months. This stage is reversible if the patient is treated. The affected limb becomes flushed, warm, and dry because regional blood vessels are relaxed, and stimulation of the sweat glands is reduced. The pain is diffuse, severe, and constant with a burning, throbbing, or aching quality. Edema and increased hair and nail growth can also occur. By the end of this stage, the limb turns cold, sweaty, and cyanotic from vasoconstriction caused by paradoxical
sympathetic stimulation.

2. Vasomotor Instability phase:

A phase of vasomotor instability that can last for several months. This is the dystrophic stage, which lasts another 3–6 months. Constricted blood vessels can cool limb temperature by nearly 10 degrees. The area will be pale, mottled, edematous, and sweaty. Pain remains continuous, burning, or throbbing but is more severe. Nails may crack or become brittle and heavily grooved. Limb movement is limited by muscle wasting and joint stiffness. Osteoporosis and contractures can develop.

3. Cold End Phase:

The atrophic stage is characterized by irreversible damage to muscles and joints. Over the next 2–3 months the bones atrophy and the joints become weak, stiff, or even ankylosed. The pain lessens and may become spasmodic or breakthrough but is no longer mediated by the sympathetic nervous system. The skin is cool and looks glossy and pale or cyanotic.

A prospective study of 829 patients indicated that the following:

  • In its early phase, CRPS is characterized by regional inflammation and not of a disturbance of the sympathetic nervous system. The regional inflammation increases after muscular exercise.
  • Tremor was found in 49 percent and muscular incoordination in 54 percent of patients.
  • Sympathetic signs such as hyperhidrosis are infrequent. These data support the concept of an exaggerated regional inflammatory response to injury or operation in CRPS.

Laboratory & Imaging Study

There are no laboratory studies that are diagnostic for CRPS.

The use of quantitative sensory and autonomic testing, quantitative sudomotor axonal reflex testing, thermography, and bone scans has been described.

Mackinnon and Holder showed that a three-phase radionuclide bone scan can aid in the early diagnosis of reflex sympathetic dystrophy. A diffusely increased uptake in the delayed images was found to be diagnostic of reflex sympathetic dystrophy with a sensitivity of 96% and a specificity of 98%. A bone scan may be helpful if positive in a nontraumatic patient.

MRI changes have been described in early CRPS phases, with muscle edema, interstitial edema, and hyperpermeability, but again this modality is not considered consistently a definitive resource.

Thus, CRPS diagnosis remains clinical.

CRPS Differential Diagnosis

A number of other conditions need to be ruled out before establishing a diagnosis of CRPS type 1, and these include, but are not limited to the following:

  1. Rheumatoid and septic arthritis
  2. Gout
  3. Disk herniation
  4. Peripheral neuropathy
  5. Peripheral nerve entrapment
  6. Peripheral vascular disease.

CRPS Treatment

No regimen has been completely satisfactory in treating Complex Regional Pain Syndrome.

Comprehensive multidisciplinary approach is optimal with help from specialists in neurology, physical or occupational therapy, physical medicine, pain management, and psychology as required.

Medications used in CRPS Treatment include:

  1. anti-inflammatory medication,
  2. analgesics (oral or topical),
  3. tricyclic antidepressants,
  4. selective serotonin reuptake inhibitors,
  5. anticonvulsants,
  6. antidepressants.

Interventional options used in CRPS treatment include:

  1. selective peripheral neural blocks,
  2. trigger point injections,
  3. sympathetic blocks (single or indwelling),
  4. dorsal column stimulators,
  5. and rarely sympathectomies (chemical or surgical).

A randomized, controlled, multicenter study involving 416 patients with 427 distal radial fractures determined that vitamin C (500 mg daily) can reduce the prevalence of CRPS, and this was listed as having “adequate evidence to support a moderately strong endorsement” in the recent AAOS clinical practice guidelines for distal radial fractures.

Complex Regional Pain Syndrome Physical Therapy

Physical therapy is the first line of intervention, whether it be the sole intervention or performed immediately following a nerve block.

The most important rule is to minimize pain while employing physical therapy. When excessive pain is created, sympathetically mediated pain may worsen.339 It is vital to not reinjure the region or aggravate the problem with aggressive physical rehabilitation.

Therapy should be directed not only to all the joints of the involved extremity but also include more generalized movement patterns.

The patient’s involved limb must be elevated as often as possible to counteract the vascular stasis and actively mobilized several times per day.

Recovery from muscle dysfunction, swelling, and joint stiffness requires appropriate physical activity and exercise, and pressure and motion are necessary to maintain joint movement and prevent stiffening. The progression should occur slowly and gently with strengthening, active assisted range-of-motion, and AROM exercises.

Weight-bearing exercises and active stress loading exercises should also be incorporated. Active stress loading exercises include scrubbing and carrying. Scrubbing is a form of closed kinetic chain exercise for the upper or lower extremity in which the patient in a variety of positions performs a scrubbing action on a firm surface. As its name suggests, carrying exercises for the upper extremity involve having the patient carry small objects in the hand on the affected side and gradually increasing the weight of the object. For the lower extremity stress loading can be achieved through weight bearing.

Sensory threshold techniques can be used. These include fluidotherapy, vibration desensitization, transcutaneous electrical nerve stimulation, contrast baths, and desensitization using light and heavy pressure of various textures over the sensitive area.

References

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