Clinical: Complex Regional Pain Syndrome
Complex regional pain syndrome syndrome (CRPS) is a condition of spontaneous pain or allodynia/hyperalgesia that arises after an initiating event with (CRPS2) or without (CRPS1) overt nerve damage. There may be past or present evidence of edema, skin blood flow abnormality, or abnormal sudomotor activity.
CRPS type 2 is easier to diagnose, looking for nerve damage during electrophysiology testing or surgery. The cornerstone of diagnosis for CRPS type 2 is a detailed history and physical examination. Every effort should be made to exclude other causes of pain, such as inflammation, tumor, or vascular events, as well as self-inflicted disorders.
Diagnostic criteria sanctioned by the International Association for the Study of Pain but not formally adopted propose that four categories of pain--sensory, vasomotor, sudomotor/edema, and motor/trophic. The criteria suggest that for a diagnosis of CRPS a patient must show one symptom in 3 of the categories and at least one sign in 2 or more. These criteria do not account for patients who may have large areas of hypoesthesia.
Stricter criteria proposed by Harden and Bruehl  may be preferable.
Imaging and other objective tests are largely of confirmatory value and cannot replace a careful history and physical examination.
About three-fourths of CRPS type 1 cases resolve spontaneously without any intervention. The goal should be restoration of function.
The affected limb should be mobilized as quickly as possible, including range-of-motion and stress-loading techniques, to avoid permanent changes in the nervous system. Pain control is important to facilitate mobilization. As with other forms of chronic noncancer pain, intractable CRPS may require interdisciplinary interventions.
Topical lidocaine may be effective in early stages. In established CRPS, medications shown to be effective in various studies include include a short course of oral corticosteroids, gabapentin, pregabalin or tricyclic antidepressants, bisphosphonates, and opioid analgesics (especially during physical therapy), although the latter must be used with care to avoid dependence. (See reference 1. below for recommended courses of medication.)
The prognosis of CRPS 1 and 2 varies widely depending on the magnitude of symptoms, the degree of limb guarding or immobility, the presence of CNS changes, the nature of the interventions, and the psychological state of the patient. Even those who continue to have symptoms can regain a satisfactory quality of life.
- ↑ Mailis-Gagnon A and Chaparro LE, Diagnosis and Management of Complex Regional Pain Syndrome, Journal of Musculoskeletal Medicine 25:10 (2008)
- ↑ Harden RN, Bruehl S. Diagnostic criteria: the statistical derivation of the Four Criterion Factors. In: Wilson PR, Stanton-Hicks M, Harden RN, eds. CRPS: Current Diagnosis and Therapy. Progress in Pain Research and Management. Vol. 32. Seattle: IASP Press; 2005:45-58.