Complex Regional Pain Syndrome

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Basics

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.
  • 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 (greater than 2 months) after injury hints at diagnosis.

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.

Genetics
No known genetic pattern

Risk Factors

  • Minor or severe trauma (upper extremity fracture-particularly distal radius noted in 44% of those with CPRS)
  • 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.

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Basics

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.
  • 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 (greater than 2 months) after injury hints at diagnosis.

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.

Genetics
No known genetic pattern

Risk Factors

  • Minor or severe trauma (upper extremity fracture-particularly distal radius noted in 44% of those with CPRS)
  • 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.

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