1. Hyperalgesia—an exaggerated response to a painful stimulus.
2. Allodynia—pain resulting from a stimulus that does not normally cause pain.
3. Hyperpathia—persistent delayed pain, especially following repetitive stimuli.
These pathologic sensory responses may contribute to the lancinating paroxysms of pain that may follow the slightest movement of or touch to the affected area. Joint movement may be particularly capable of inducing these paroxysms. Spontaneous paroxysms also occur.
In general, both pain and sensitivity are decreased by elevation of the extremity and increased by physical loads, movement, emotional excitement, and temperature changes.
2. Edema. This is initially pitting but later becomes brawny. It may be more marked in periarticular regions, interfere with blood flow, and lead to pain from nerve compression and decreased mobility. These problems may then exacerbate the RSD.
3. Vasomotor and sudomotor changes. These reflect sympathetic activation and may vary dramatically between patients and with time and in location in the same patient. This is because RSD is associated with sympathetic instability and hyperreactivity rather than simply a statically increased sympathetic tone. Mediators released by nociceptors (e.g., substance P) also affect blood flow.
a. Alterations in skin temperature. Skin temperature may be increased or decreased in comparison with the contralateral area, reflecting impaired thermoregulation. Initially, skin temperature is most commonly increased, but it often fluctuates over the affected area both spontaneously and in response to the triggering factors described above. As time passes, hypoperfusion with decreased skin temperature becomes more prominent. It should be noted that "increased" perfusion does not indicate an increase in nutrient blood flow, which is often decreased because of shunting and microcirculatory abnormalities.
b. Alterations in skin color. Skin color, which also reflects blood flow, is similarly variable, ranging from red (hyperemia) to pale or cyanotic (diminished perfusion). These hyperemic and cyanotic alterations are usually associated with warmth and coldness of the affected areas, respectively. Marked local flow variations that lead to a livedoid, reticulated appearance are often seen.
c. Hyperhidrosis, anhidrosis, and piloerection. Increased or decreased sweating and piloerection may occur, reflecting changes in autonomic tone.
d. Trophic changes. Nails may be brittle, ridged, and abnormally colored and may show increased curvature. Hair may be coarse and increased. Skin may be thin and atrophied or hyperkeratotic. Atrophy or edema can lead to loss of skin folds, and finger pulp may be lost. Bony resorption is prominent from the onset and increases with disease duration.
e. Functional impairment initially results from pain and swelling. This leads to disuse, which produces a synergistic effect with the pathophysiologic concomitant features of RSD, so that anatomic alterations and permanent functional impairment ensue. Such changes include severe atrophy of skin and other soft tissues, osteoporosis, nerve damage from compression, and joint capsular and ligamentous fibrosis.
B. Stages of reflex sympathetic dystrophy. The natural history of RSD is often divided into three stages (Steinbrocker classification). However, it should be noted that patients frequently may not demonstrate the full picture at each stage or an orderly progression from one stage to another.
1. Stage 1 (acute, months 1 to 3) is usually dominated by pain and tenderness, edema, and temperature changes, particularly increases. Patchy areas and periods of temperature decrease may, however, be seen. Sudomotor alterations, typically hyperhidrosis, tend to appear later in this phase. Signs and symptoms are initially limited to the region of injury or the surrounding areas but may spread to adjacent or even contralateral areas, reflecting changes at the spinal or even more central areas of the central nervous system.
2. Stage 2 (dystrophic). The pain usually extends beyond the area initially affected. Although still prominent, it may be either increased or decreased in comparison with pain in stage 1. Edema may take on a more brawny quality. Loss of hair and dystrophic nail changes become apparent, and muscle wasting and osteoporosis become more prominent. At this stage, a decreased range of motion (ROM) reflects capsular changes and contractures, in addition to pain and edema. The affected area is usually cool, pale, or cyanotic, reflecting a decrease in blood flow, although as usual marked fluctuations may occur. 3. Stage 3 (atrophic or chronic). Skin and soft-tissue atrophy, bony demineralization, and capsular thickening progress, as does functional impairment. The latter results from and leads to contractures, decreased passive movement, and apparent stiffness of joints. In extreme cases, a "claw hammer" hand or "frozen" shoulder may result.
The importance of staging in treatment is controversial, at least in regard to stages 1 and 2. However, patients who have reached stage 3 are clearly distinct in that they have suffered irreversible damage and will respond poorly to any modality.
C. Movement disorders. Movement disorders become more prominent in the advanced stages (e.g., stages 2 and 3) and may even initially present after pain has subsided. Rarely, they may precede other changes. Abnormalities include tremor with resting, postural, and action components; spasms; myoclonus; focal dystonias; and an inability to initiate movements and complete complex movements that may develop into apraxia.
Hyperreflexia and decreased strength may cause or result from the guarding postures commonly assumed by the patient. However, the dysphasia and difficulty in swallowing that may be found in RSD affecting the upper extremities indicate cortical changes. The "neglect" reported to account for some cases of movement disorder in RSD is also consistent with cortical involvement. This is characterized by delayed, slowed, low-amplitude movements and a decrease in spontaneous movements. The patient feels disconnected from the involved region and may even refer to the affected extremity as "it."
Movement disorders may interfere with physical therapy or become independent causes of morbidity. Dystonias, for example, may lead to total loss of hand function and the development of pressure sores in the "clenched-fist" syndrome, or problems of ambulation resulting from inversion and an equine position of the foot.
Movement disorders result from sympathetic hyperactivity and from plastic changes at spinal and peripheral neurons and muscle spindles induced by sympathetic activity and products of nociceptors. Cortical changes are also involved.
D. Psychiatric disorders. Affective disorders (e.g., depression or anxiety) and behavioral disturbances (e.g., social withdrawal, physical inactivity, chronic invalidism) are extremely common both in patients with RSD and in those with causalgia. It has been suggested that psychological features may be involved in the initiation of the disorder, but this is controversial. However, it is widely agreed that psychological disturbances commonly occur secondary to the pain and disability associated with the disorder. Both "adjustment disorders" (subsyndromal presentation of depressive or anxiety symptoms felt to occur as a reaction to stress) and major depressive disorders (full syndrome felt to be precipitated by the stress of the illness) may occur. Suicidal thoughts may occur in either instance.
Demoralization and frustration with the medical system (because of the not uncommon delays in the diagnosis of RSD and minimization of the significance of this poorly understood illness) on top of chronic pain may make the patient argumentative and otherwise difficult to deal with. This leads to patterns of escalating negative interactions with health care professionals and family members. The family members may be similarly difficult.
Thus, the relationship between RSD and psychological symptoms is complex and variable. However, regardless of the etiology, the psychological concomitant features of RSD must be addressed early in the treatment because psychological factors, such as tolerance of pain, methods of coping with stress and pain, and beliefs and expectations, have a major effect on the patient's willingness and ability to (a) tolerate often painful treatments, (b) avoid the extremes of too much mobilization and too much immobilization, and (c) cope with transient or permanent functional impairments.
The clinical observation that emotional stress may cause disease exacerbations and data linking flares with elevation of catecholamines further underscore the importance of dealing with psychological issues.
Addiction is often overdiagnosed but sometimes does occur.
E. Complications. In a small but significant number of patients, infections, ulcers, and chronic edema may develop. Unrecognized or resistant infections may be diagnosed as refractory RSD or even malingering. Severe dystonias have been discussed above. It has been suggested that complications and motor disorders may be more common in younger female patients with multiple involved sites in the lower extremities and in patients who present initially with decreased blood flow ("cold presentation").
On the other hand, rarely, ulcerative lesions and infections have been the result of self-mutilation.
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