Introduction to Reflex Sympathetic Dystrophy

What is Reflex Sympathetic Dystrophy?

Reflex sympathetic dystrophy (RSD), also known as complex regional pain syndrome (CRPS) Type I, is a complex, chronic, pain syndrome that can affect any part of the body, however, it occurs most frequently in the extremities - hands, feet, arms, legs, shoulders or knees. It has been recognized by many clinicians as a distinct clinical condition for over 100 years and has been known by various names including algodystrophy, Sudeck's atrophy, causalgia, and sympathetically maintained pain.

Reflex sympathetic dystrophy is characterized by:

  • Severe, chronic, pain - often described as stinging or burning
  • Sensory abnormalities - allodynia (extreme sensitivity to touch)
  • Motor changes such as tremor or stiffness
  • Edema (tissue swelling) and hyperhydrosis (excessive sweating)
  • Progressive changes to skin, hair, nails, muscle, and bone
  • Increasing dysfunction of the affected limb

Reflex sympathetic dystrophy causes great suffering and distress in most patients. In addition to severe pain, which in some people remains chronic and unremitting, patients may also experience serious physical disabilities and reduction in their quality of life. Most patients with reflex sympathetic dystrophy who experience severe and chronic pain where their quality of life has been significantly impacted also experience symptoms of psychological distress, including:

  • Depression
  • Fear
  • Anxiety
  • Anger

The syndrome of RSD is not well understood but it occurs most often after trauma such as a bone fracture or surgery to an extremity. The trauma can also be very minor such as a splinter, sprained ankle, or following intravenous needle insertion. RSD can also occur following a serious medical condition such as a heart attack or stroke. In up to 25% of RSD patients, however, no apparent cause can be established with certainty. Although the symptoms and clinical features of RSD can vary from patient to patient, the one common cardinal feature that is shared by all patients is severe pain that is disproportionate to the original injury. Reflex sympathetic dystrophy does not exist in the absence of pain.

The perception of pain is a complex event and relates to physiological as well as psychological components. Usually pain is perceived immediately following a precipitating event such as trauma and, after the pain stimulus has been eliminated, the body returns to the previous state of being pain-free. When pain continues beyond an acceptable time period and/or appears to intensify, the pain is said to become pathologic. This is the essence of RSD. As the body responds for a prolonged time period to pathologic pain, it can cause permanent structural or functional changes within the affected extremity and, ultimately, in the central nervous system. Even within the variability of individual perception, tolerance, and response to pain, the pain of RSD is totally out of proportion to the precipitating event.

Although the term reflex sympathetic dystrophy has been used to describe the condition since the 1940s, it has recently come under scrutiny since it is misleading for several reasons, including:

  • There is little evidence of involvement of a reflex mechanism
  • Symptoms of RSD reflect a complicated interplay of several neurological systems, such as the peripheral and central nervous systems, not only the sympathetic nervous system
  • Only a subset of patients respond to a treatment to reduce pain called a sympathetic block which interrupts the activity of the sympathetic nervous system indicating that not all RSD pain is sympathetically mediated
  • Dystrophy (degeneration of muscle or tissue) is present only in a subset of RSD patients (approximately 10%)

In response to these inconsistencies, the International Association for the Study of Pain (IASP) adopted the term complex regional pain syndrome (CRPS) in 1994 to describe a debilitating pain syndrome that develops after a relatively minor injury to an extremity (arm or leg) but lasts longer than the actual injury and is more severe than would otherwise be expected from such an injury. There are two types of CRPS:

  • CRPS Type I- also known as reflex sympathetic dystrophy where the pain is not associated with an identifiable nerve injury
  • CRPS Type II - also known as causalgia where the pain can be traced to a nerve injury

Despite extensive research over the past several decades, researchers still do not understand clearly the underlying pathological mechanisms involved in the initiation and progression of RSD including:

  • Why RSD develops in some people and not others.
  • Why RSD goes into remission for some people and not others.
  • Why some people experience recurrence of RSD.
  • What are the most effective treatments for RSD?
  • How to prevent RSD from occurring.