FWD:Complex Regional Pain Syndrome

Complex Regional Pain Syndrome
Steven J Parrillo, DO, FACEP, FACOEP, Associate Professor, Emergency Medicine, Jefferson Medical College and Philadelphia College of Osteopathic Medicine; Medical Director, Department of Emergency Medicine, Einstein Elkins Park; Chair, Emergency Management Committee, Albert Einstein Healthcare Network; Medical Director, Disaster Medicine and Management Masters Program, Philadelphia University
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Updated: Apr 3, 2008

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Overview
Differential Diagnoses & Workup
Treatment & Medication
Follow-up
References
Keywords
Introduction
Background
Reflex sympathetic dystrophy syndrome (RSDS) has been recognized since the Civil War when it was called causalgia, a name chosen to describe intense, burning extremity pain after an injury. Since then, RSDS has had a number of name changes. Bonica coined the term reflex sympathetic dystrophy in 1953. The American Association of Hand Surgery proposed changing the name to sympathetic maintained pain syndrome. A consensus expert panel recommended a change to complex regional pain syndrome (CRPS). However, although many clinicians still use the term RSDS, the terms currently in favor are complex regional pain syndrome I (the equivalent of RSD) and complex regional pain syndrome II, also known as causalgia.

CRPS/RSDS has readily identifiable signs and symptoms and is treatable if recognized early; however, the syndrome may become disabling if unrecognized. Emergency physicians are frequently in a position to identify the problem and may play a significant role in minimizing impact of this common entity.


Pathophysiology
No single hypothesis explains all features of RSDS. Schwartzmann stated that a common mechanism may be injury to central or peripheral neural tissue.1 Roberts proposed that sympathetic pain results from tonic activity in myelinated mechanoreceptor afferents.2 Input causes tonic firing in neurons that are part of a nociceptive pathway. Campbell et al propose a hypothesis that places the primary abnormality in the peripheral nervous system.3

Most agree that CRPS is a neurologic disorder affecting central and peripheral nervous systems.

Two new etiologic possibilities have been suggested. German research has noted the association between elevated levels of soluble tumor necrosis factor receptor 1 (sTNF-R1) and enhanced tumor necrosis factor-alpha activity in patients with polyneuropathy with allodynia.4 Other German researchers have described autoantibodies in patients with CRPS, especially CRPS type 2.5

All agree that, regardless of the mechanism, the patient experiences intense, burning pain in one or more extremities.

Frequency
United States
RSDS occurs in approximately 1-15% of peripheral nerve injury cases. Schwartzmann states that CRPS usually occurs secondary to fractures, sprains, and trivial soft tissue injury.1 The incidence after fractures and contusions ranges from 10-30%. While some cases are associated with an identifiable nerve injury, many are not. Even "microtrauma" as might occur with an immunization may be responsible. The upper extremities are more likely to be involved than the lower. Entities that have led to RSDS include the following:



Head injury
Stroke
Polio
Amyotrophic lateral sclerosis (ALS)
Myocardial infarction
Polymyalgia rheumatica
Operative procedures (eg, carpal tunnel release)
Brachial plexopathy
Cast/splint immobilization
Minor extremity injury
Prolonged bedrest

Mortality/Morbidity
In and of itself, the disease is not fatal. Morbidity of RSDS is associated with disease progress through a series of stages (see Physical).

Race
No racial predilection is noted.

Sex
Stanton-Hicks6 and others note that women predominate in a range of 60-80% of cases.

Age
Persons of all ages are affected; however, CRPS is treated most effectively in pediatric patients.

Clinical
History
The International Association for the Study of Pain (IASP) lists the diagnostic criteria for complex regional pain syndrome I (CRPS I) (RSDS) as follows:

The presence of an initiating noxious event or a cause of immobilization
Continuing pain, allodynia (perception of pain from a nonpainful stimulus), or hyperalgesia disproportionate to the inciting event
Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the area of pain
The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction.
According to the IASP, CRPS II (also known as causalgia) is diagnosed as follows:

The presence of continuing pain, allodynia, or hyperalgesia after a nerve injury, not necessarily limited to the distribution of the injured nerve
Evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain
The diagnosis is excluded by the existence of any condition that would otherwise account for the degree of pain and dysfunction.
Note that the primary difference between type I and type II is the identification of a definable nerve injury.

Older literature records cardinal and secondary signs. They are worth noting not because they are in common use as primary and secondary but rather because they expand on the constellation of signs and symptoms the ED physician may see in patients.

Cardinal signs include pain, edema, stiffness, and discoloration.
Pain that is intense and burning, out of proportion to the injury, and affects the entire extremity occurs with RSDS.
Hyperpathia refers to pain that persists after the stimulus has been removed.
Allodynia refers to pain with light touch.
Movement frequently aggravates pain.
Patients describe exacerbations with cold. Many patients feel worse when a low-pressure weather front is arriving. Airplane ascent and descent can be painful.
Edema is usually one of the earliest findings.
Stiffness may occur.
Discoloration may vary from intensely erythematous to cyanotic, pale, purple, or gray.
Lankford's secondary characteristics include the following:7
Demineralization and osteoporosis are among the most classic (late) findings.
Sudomotor changes vary from hyperhidrosis to dryness.
Temperature difference between affected and unaffected extremities may be marked but is usually measurable at some point in time.
Vasomotor instability most commonly is manifested as decreased capillary refill.
Erythema may be a sign of increased capillary refill and should be compared with refill in unaffected extremity.
Skin may develop a glossy shiny appearance. In late stages, trophic changes may involve a decrease in subcutaneous tissue.
In RSDS of the hand, nodules and thickening of the palmar fascia may develop.
Much RSDS literature notes a predisposing personality of depression. However, many other studies have demonstrated that, while most patients are depressed, they are depressed because of their pain.
Many patients with CRPS/RSDS will exhibit some type of movement disorder ranging from strength reduction (78%) to tremor (25-60%) to myoclonus and dystonia. Although some authors believe these are pain-induced findings, others believe they are primary abnormalities.
Physical
Three stages have been classified. Although the consensus panel recommended that staging be eliminated, it is important for the emergency physician to have awareness of potential disease progress. Disease progress is very variable.


Stage I or early RSDS: Pain is more severe than would be expected from the injury, and it has a burning or aching quality. It may be increased by dependency of the limb, physical contact, or emotional upset. The affected area becomes edematous, may be hyperthermic or hypothermic, and shows increased nail and hair growth. Radiographs may show early bony changes. Duration is usually 3 months from onset of symptoms. Some patients remain in one stage or another for many months or even years. They may never progress or they may progress quickly to late stage. Remember that physical findings may be minimal, especially in those who remain in stage I or progress slowly.
Stage II or established RSDS: Edematous tissue becomes indurated. Skin becomes cool and hyperhidrotic with livedo reticularis or cyanosis. Hair may be lost, and nails become ridged, cracked, and brittle. Hand dryness becomes prominent, and atrophy of skin and subcutaneous tissues becomes noticeable. Pain remains the dominant feature. It usually is constant and is increased by any stimulus to the affected area. Stiffness develops at this stage. Radiographs may show diffuse osteoporosis. The 3-phase bone scan is usually positive. Duration is 3-12 months from onset.
Stage III or late RSDS: Pain spreads proximally. Although it may diminish in intensity, pain remains a prominent feature. Flare-ups may occur spontaneously. Irreversible tissue damage occurs. Skin is thin and shiny. Edema is absent. Contractures may occur. Radiographs indicate marked demineralization.
Causes
Some authors believe that development of RSDS requires the following triad of conditions: an injury, an abnormal sympathetic response, and a predisposing personality. Others, however, dispute the need for an underlying personality disorder. In August 2000, Schwartzman stated, "There is no evidence that affected patients have a personality disorder, but the severity of pain and the disruption of the patient's life can lead to anxiety and depression."8