Description

• Complex regional pain syndrome (CRPS) is a pain syndrome that can be chronic and debilitating. It is divided into two subtypes and can have significant physical and psychosocial short- and long-term disability. Most cases are a result of a physical insult to an extremity such as trauma or surgery.
  • Type I: no nerve injury (reflex sympathetic dystrophy [RSD])
  • Type II: associated with a demonstrable nerve injury (causalgia)
• Synonym(s): traumatic erythromelalgia; Weir Mitchell causalgia; causalgia; RSD; posttraumatic neuralgia; sympathetically maintained pain

Epidemiology

• Incidence of 5.46 to 26.2/100,000 for type I and 0.82/100,000 for type II in United States (1,2)
• Peak age 50 to 70 years
• Predominant gender: female > male (3:1, 60–81%), favoring postmenopausal
• Recent studies found 3.8% occurrence after wrist fracture and 7% occurrence after intra-articular ankle fracture—both independent strong risk for CRPS (3)[B].
• More prevalent in patients that report higher than usual expected pain in early phases of trauma. Latency depends on normal injury recovery time—prolonged pain after injury hints at diagnosis (3).

Etiology and Pathophysiology

• Poorly understood activation of abnormal sympathetic reflex that lowers pain threshold
  • Increased excitability of nociceptive neurons in the spinal cord; “central sensitization”
  • Exaggerated responses to normally nonpainful stimuli (hyperalgesia, allodynia)
• Type II is associated with physical injury to nerve.
• Emerging information reveals CNS changes (functional, anatomic, biochemical) in addition to spinal level changes. Increased levels of immunomodulators suggest autoimmune component (2).

Genetics
No known genetic pattern

Risk Factors

• Minor or severe trauma (upper extremity fracture noted in 44%)
• Surgery (particularly carpal tunnel release)
• Lacerations
• Burns
• Frostbite
• Casting/immobilization after extremity injury
• Penetrating injury
• Polymyalgia rheumatica
• Myocardial infarction (MI)
• Cerebral vascular accident

General Prevention

• Early mobilization after fracture, stroke, and MI has proven benefit in reducing incidence of CRPS.
• One study of wrist fractures found that addition of 500 mg/day of vitamin C lowered rates of CRPS.
• There is evidence that limiting use of tourniquets, liberal regional anesthetic use, and ensuring adequate perioperative analgesia can reduce the incidence of CRPS-I.

Commonly Associated Conditions

• Serious injury to bone and soft tissue
• Herpes zoster
• Postherpetic neuralgia results from partial or complete damage to afferent nerve pathways.
• Pain occurs in dermatomes as a sequela of herpes zoster.
• Signal exists for patients having comorbid painful conditions or psychiatric diagnosis at increased risk of developing CPRS.