Complex Regional Pain Syndrome (CRPS)

CRPS is a syndrome typically occurring in a single extremity following trauma and is characterized by allodynia, hyperalgesia, and vasomotor signs.
A characteristic three-phase bone scan has moderate sensitivity (50% to 80%) but high specificity for the diagnosis of CRPS and predicts a better response to corticosteroid therapy.
Diagnosis is still done clinically
A spinal cord stimulator reduces pain approximately 50% in 50% of patients with severe CRPS.

CRPS type I RSD (reflex sympathetic dystrophy)

A syndrome that develops after an initiating noxious event (injury, surgery, or infarction) or a cause of immobilization.

Spontaneous and continuing pain, allodynia, or hyperalgesia occurs, is not limited to the territory of a single peripheral nerve, and is disproportionate to the inciting event.

There is or has been evidence of edema, skin blood flow abnormality, or abnormal sudomotor activity (i.e., sweating) in the region of the pain since the inciting event.

This diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction.

CRPS type II (causalgia)

Type II is a syndrome that develops after a nerve injury.

All of the above findings for CRPS type I.

Classic signs and symptoms of CRPS:

Pain and swelling in an extremity

Trophic skin changes in the same extremity

Skin atrophy or pigmentary changes

Hypertrichosis
Hyperhidrosis
Nail changes

Signs and symptoms of vasomotor instability

Pain and/or limited motion of the ipsilateral limb including proximal joints (e.g., shoulder–hand syndrome)

Neglect-like symptoms concerning the extremity

Stages of CRPS:

Stage 1 (acute stage): typically lasts 6–12 months, characterized by:
- Pain in the extremity or shoulder
- Swelling in the extremity
- Color change of the extremity (red or blue)
- Movement painful and tendency for immobilization
- Early osteoporosis on X-rays

Stage 2 (dystrophic phase): persists an additional 1–2 years, characterized by:
- Pain usually continues
- Swelling changes to brawny hard edema
- Beginning of atrophy of subcutaneous tissue and intrinsic muscles
- Cooler extremity, can be mottled or cyanotic
- Progression of osteoporosis

Stage 3 (atrophic stage): persists up to several years, characterized by:
- Pain remains constant or diminishes
- Extremity becomes stiff
- Swelling changes to periarticular thickening
- Skin becomes smooth, glossy, and drawn
- Brittle nails
- May see muscle spasm, dystonia, tremor
- Progression of osteoporosis with pathologic fractures

Radiographic findings in CRPS:

The characteristic radiologic appearance is soft tissue swelling and regional patchy or mottled osteopenia. This appearance is especially evident when comparing the involved side with the contralateral side. This X-ray pattern was first described by Sudeck in 1900 and is often referred to as Sudeck’s atrophy. This patchy osteopenia is helpful in making the diagnosis but is actually seen in less than half the patients in most series

Therapy approach for CRPS:

All patients should be treated with a multidisciplinary approach.
All patients should receive information explaining their disease.
All patients should receive physical therapy, occupational therapy, and psychological support throughout their disease course.
Patients with early CRPS, pain and swelling, and a positive three-phase bone scan (TPBS) should be treated with prednisone (60 to 80 mg/day for 2 weeks with taper over next 4 weeks). Corticosteroids can modulate the effect of the inflammatory neuropeptides.
Analgesics: opioids, NSAIDs, tricyclic antidepressants, gabapentin (or pregabalin), and/or carbamazepine. Choice depends on severity (opioids versus NSAIDs) and quality (somatic, neuropathic) of pain. Many patients develop a small fiber neuropathy with a decrease in epidermal nerve fiber density in the affected limb. These patients can benefit from neuroleptics.
If pain is severe (i.e., pain at rest and with movement) then more aggressive therapy should be instituted early. It is clinically impossible to know if the patient’s pain is or is not sympathetically mediated but CRPS is more likely to be as a result of abnormal sympathetic nerve activity early in the disease course. In these patients, sympathetic blocks can be effective. Up to 50% of patients with symptoms less than 1 year can improve with these blocks. However, recurrent sympathetic blocks do not prolong the analgesic effect. Patients who fail to respond to sympathetic blocks are more likely to have their pain mediated by CNS sensitization.
Miacalcic
Bisphosphonate

The following therapies have been most effective for treatment-resistant and/or cases with prolonged symptoms:

An epidural spinal cord stimulator can be used and will reduce pain approximately 50% in 50% of patients.
IV ketamine: because of the importance of the NMDA receptor some patients with CRPS type I benefit from these infusions (5-day inpatient versus 10-day outpatient infusion with slow tapering to maintenance therapy; one infusion every 3 months).
Patients who fail to respond to one of the above therapies may benefit from IVIG which reportedly can improve pain 50% in at least 25% of patients with chronic CRPS possibly by modulating autoantibody effects.

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