Complex Regional Pain Syndrome, Type I

(Reflex Sympathetic Dystrophy)

Definition
CRPS Type I is a syndrome that usually develops after an initiating
noxious event, is not limited to the distribution of a single peripheral
nerve, and is apparently disproportionate to the inciting event. It is
associated at some point with evidence of edema, changes in skin blood
flow, abnormal sudomotor activity in the region of the pain, or
allodynia or hyperalgesia.

Site
Usually the distal aspect of an affected extremity or with a distal to
proximal gradient.

Main Features
Pain often follows trauma, which is usually mild and is not associated
with significant nerve injury. It may follow a fracture, a soft tissue
lesion, or immobilization related to visceral disease, e.g., angina or
stroke. The onset of symptoms usually occurs within one month of the
inciting event. The pain is frequently described as burning and
continuous and exacerbated by movement, continuous stimulation, or
stress. The intensity of pain fluctuates over time, and allodynia or
hyperalgesia may be found which are not limited to the territory of a
single peripheral nerve. Abnormalities of blood flow occur including
changes in skin temperature and color. Edema is usually present and may
be soft or firm. Increased or decreased sweating may appear. The
symptoms and signs may spread proximally or involve other extremities.
Impairment of motor function is frequently seen.

Associated Symptoms and Signs
Atrophy of the skin, nails, and other soft tissues, alterations in hair
growth, and loss of joint mobility may develop. Impairment of motor
function can include weakness, tremor, and, in rare instances, dystonia.
Symptoms and signs fluctuate at times. Sympathetically maintained pain
may be present and may be demonstrated with pharmacological blocking or
provocation techniques. Affective symptoms or disorders occur secondary
to the pain and disability. Guarding of the affected part is usually
observed.

Laboratory Findings
Noncontact skin temperature measurement indicates a side-to-side
asymmetry of greater than 1°C. Due to the unstable nature of the
temperature changes in this disorder, measurements at different times
are recommended. Measurements of skin blood flow may show an increase or
a reduction. Testing of sudomotor function, both at rest and evoked,
indicates side-to-side asymmetry. The bone uptake phase of a three-phase
bone scan may reveal a characteristic pattern of subcutaneous blood pool
changes. Radiographic examination may demonstrate patchy bone
demineralization.

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