Type 1—previously termed reflex sympathetic dystrophy (RSD)—includes the clinical manifestations of pain, functional impairment, autonomic dysfunction, and/or dystrophic changes without an identifiable nerve lesion.

Type 2—previously termed Causalgia—is defined by pain, functional impairment, autonomic dysfunction, dystrophic changes with an identifiable nerve lesion.

Type 3—are other pain dysfunction problems and are not discussed in this chapter except as part of the differential diagnosis.

CRPS types I and II may be sympathetically maintained or sympathetically independent, as defined by pain relief from a sympatholytic intervention such as intravenous phentolamine of a stellate ganglion block. Many oral medications have a sympatholytic effect.

Nociceptive pain originates from a mechanical source. A nociceptive origin or component of CRPS is common.

Neuropathic pain emanates from an injury or malfunction of a peripheral nerve. CRPS is one manifestation of neuropathic pain. For example, pain from a neuroma or a neuroma-in-continuity that is localized to the injured nerve or phantom-limb pain is neuropathic but not CRPS.

Sympathetically maintained pain (SMP) is defined as pain, which is ameliorated by blocking sympathetic receptors. Drugs, which have this property are termed sympatholytic.

Unknown in most locals.

In Olmsted County, the incidence was reported as 5.5 per 100,000 and the prevalence as 20.7 per 100,000 in 2003.

The incidence after fracture of the distal radius varies from 4% to 39% in prospective series.

Smoking is a significant risk factor.

Algodystrophy

RSD

Causalgia

Major causalgia

Minor causalgia

Minor traumatic dystrophy

Major traumatic dystrophy

Shoulder-hand syndrome

Sympathetic-maintained pain syndrome (SMPS)

Peripheral abnormalities include alterations in vasomotor tone with enhanced nociceptor activity; abnormal sympathetic activity; abnormal stimulation of somatic sensory axons following partial nerve injury; increased sensory afferent impulses; local demyelination with “sprout” outgrowth resulting in increased nociceptor sensitivity; damage to peripheral nerve; damage to mixed motor/sensory nerves; peripheral microvascular shunting and secondary to abnormal sympathetic tone

Central neurologic dysfunction

These include abnormalities of the “internuncial pool”; increased activity within the substantia gelatinosa; abnormal modulation of widedynamic-range neurons; abnormal modulation of afferent signals in higher cortical centers of the brain; and/or cortical adaptations and changes.

True pathophysiology is probably a combination of peripheral and central mechanisms.

CRPS is conceptually an exaggeration or abnormal prolongation of the “normal” pathophysiologic events following injury.

It may either represent multiple pathophysiologic subgroups or have a common etiology; however, the exact pathophysiologic cause is not defined.

A transient dystrophic response (abnormal physiology) to injury or trauma is a normal phenomenon. Abnormal prolongation of this response and inability of the patient to modulate or control the pain cycle appears to be the best explanation of RSD. A cascade of reversible and irreversible events then ensues.

The natural history is poorly defined and is altered by treatment.

CRPS is not a psychogenic condition, and the emotional suffering is the result, and not the cause of CRPS.

In general, diagnosis and initiation of treatment within 6 to 12 months of onset result in significant improvement.

However, patients with CRPS and fracture of the distal radius have a poorer prognosis; stiffness, and “poor finger function” at 3 months correlate with 10 year morbidity

Some patients in spite of early and appropriate treatment do poorly with long-term functional impairment, chronic pain, deformity, or any combination thereof.

CRPS may result in irreversible end-organ dysfunction, including loss of normal arteriovenous (AV) shunt mechanism and permanent alterations in central neurologic responses.

Swelling occurs early, and stiffness and atrophy are present in later stages; pain at any stage is associated with AV shunting and nutritional deprivation (relative ischemia).

Eighty percent of those treated within 1 year of injury show subjective improvement; only 50% of those treated after one year improve.

The most effective aspect of treatment of RSD is early recognition—best results occur if diagnosis and active management are initiated before 6 months.

Pain is unremitting, “out of proportion to the injury” and does not depend on the magnitude of the inciting effect; often described as “tearing”, “burning”. Some CRPS patients may fearfully withdraw the limb from the examiner and develop avoidance patterns. Pain on exposure to cold is frequent. Pain is not significantly improved with the use of narcotic analgesics, but it will frequently respond to sympatholytic medications. Difficulty sleeping, restlessness, and anxiety are common complaints. Pain may be assessed using standardized and/or validated instruments (e.g., visual analog scale, Short-Form 36, self-administered questionnaires). Cold sensitivity may be assessed using the McCabe scale.

Pain includes

Stiffness of fingers, wrist, and shoulder is common.

Functional deficit is secondary to pain swelling and stiffness.

Trophic changes (autonomic dysfunction) include sudomotor dysfunction, temperature, swelling, diffuse osteopenia, and skin alterations.

Plain x-rays may be normal but often show osteoporosis with subchondral resorption. Classic CRPS roentgenograms demonstrate osteopenia with periarticular and subchondral resorption (Sudeck atrophy), but changes appear late and therefore radiographs are not a useful screening tool. As many as 30% of patients have no x-ray abnormalities.

Bone scans may be characteristic and confirmatory for CRPS, but are not pathognomonic. Three phase scans are utilized but are insufficiently sensitive. First and second phase bone scans may demonstrate asymmetry of flow dynamics and quantify vasomotor instability and abnormal autonomic flow. Third phase scans—when positive—demonstrate increased periarticular uptakes in involved and uninvolved joints.

A positive third phase bone scan adds credence to the clinical diagnosis; identifies a recognizable subgroup of CRPS; has no prognostic significance; and does not correlate with thermoregulatory or vasomotor states.

Thermoregulatory and nutritional blood flow testing help to quantitate and quantify distal extremity autonomic function as reflected in thermoregulatory and nutritional blood. A form of stress—thermal or emotional— improves reliability and reproducibility (Fig. 9.1).

Isolated cold stress test has been described to assess dynamic sympathetic response of an extremity to changes in environmental temperature.
It permits the measurement of skin surface temperature of the digit, which is a reflection of total blood flow. It is highly sensitive to vasomotor disturbances that occur in 80% to 90% of patients with RSD. It is not specific for CRPS.