Introduction to Complex Regional Pain Syndrome (CRPS)

Complex regional pain syndrome (CRPS) is a neuropathic pain condition that can often be challenging to diagnose and even more challenging to treat. It is a condition in which the patient feels a response to an injury-producing painful experience over and over again, at the same level of acuity as if the painful event had just happened. It is considered by most to be a multisymptom, multisystem syndrome, usually affecting one or more areas, but mainly the extremities. An understanding of the history of how the syndrome’s diagnostic criteria evolved will help to clarify the vital importance of making the right diagnosis at the right time.

For some patients, living with CRPS may seem like continuous torture. Very often, the instinctive response is to avoid moving the affected body part(s). If the symptoms do not improve, further complications can develop. The ongoing severe pain and eventual disability that usually accompanies CRPS can also understandably lead to a higher risk of psychological comorbidity, such as depression, anxiety, and even post-traumatic stress disorder (PTSD). Ironically, since the signs and symptoms of CRPS can be so unusual and variable over time, and since, on presentation, they may no longer be linked to a specific pain-provoking event, there may be a lack of understanding that this is a true medical problem.

Diagnostic Criteria and Assessment

CRPS was formerly known as reflex sympathetic dystrophy, or RSD. The name reflected the understanding that the cause of the pain was due to disruption or dysfunction of the peripheral sympathetic nervous system. In 1994, the International Association for the Study of Pain (IASP) changed the name to its current designation, acknowledging that there are both peripheral and central mechanisms at play. Some pain experts believe the syndrome is best understood if both names are used, and they refer to it as reflex sympathetic dystrophy/complex regional pain syndrome, or RSD/CRPS.

Scientifically validated diagnostic criteria were developed that are inclusive, sensitive, and broad. They identify two forms of CRPS, Type I and Type II:

  • – Type I: without evidence of major nerve damage (higher incidence)
  • – Type II: with evidence of major nerve damage (lower incidence)

The 1994 diagnostic criteria also included:

  1. 1. The presence of an initiating noxious event or cause of immobilization.
  2. 2. Continuing pain, allodynia (pain from a stimulus that is not normally painful), or hyperalgesia (pain disproportionate to any inciting event).
  3. 3. Evidence, at some time, of edema, changes in skin bloodflow, or abnormal sudomotor activity (nerve fibers controlling the sweat glands) in the region of pain.
  4. 4. This diagnosis is excluded by the existence of conditions that would otherwise account for the degree of pain and dysfunction.

These diagnostic criteria have been refined and revised as follows: persistent pain, disproportionate to any noxious event, with:

  1. 1. At least one reported symptom in three of these four categories:
    • – Sensory: hyperesthesia (increased sensitivity) and/or allodynia
    • – Vasomotor: body-temperature asymmetry and/or changes in skin color and/or skin-color asymmetry
    • – Sudomotor/edema: edema and/or changes in sweating and/or sweating asymmetry
    • – Motor/trophic decreased range of motion and/or motor dysfunction and/or trophic changes

    And evidence of at least one sign (observed) in two or more of the four categories:

    • – Sensory: hyperalgesia to pinprick and/or allodynia to light touch and/or deep somatic pressure and/or joint movement
    • – Vasomotor: body-temperature asymmetry and/or changes in skin color and/or skin-color asymmetry
    • – Sudomotor/edema: edema and/or changes in sweating and/or sweating asymmetry
    • – Motor/trophic: decreased range of motion and/or motor dysfunction and/or trophic changes
  2. 2. There is no other diagnosis that better explains the signs and symptoms1.

A series of visits are required to make the diagnosis since signs and symptoms can vary over time, and to rule out any other cause. Some pain experts believe the syndrome is best described if both names are used, and they refer to it as Reflex Sympathetic Dystrophy/Complex Regional Pain Syndrome or RSD/CRPS.

Disease Progression and Treatment

Once the diagnosis is made, early intervention is crucial to interrupt what is essentially an endless cycle of pain that often leads to progressive disability. An important component of treatment is encouraging a realistic degree of normal use, if tolerated. Patients also need to understand that active physical therapy may cause pain but that it is part of the treatment plan.

Unfortunately, there is often no “cure” for CRPS, but with persistent multimodal intervention, which may include medication, nerve blocks, psychological support, and aggressive rehabilitation efforts, patients can have the best chance of successful treatment and, it is hoped, regain a good quality of life. This usually requires a team of clinicians, a supportive family, and a motivated patient who will stay with the treatment plan.

My Experience with Two Patients

For 25 years I had an anesthesiology practice at a community hospital in Long Island, NY. I had memorable experiences involving two patients with CRPS that illustrate the extreme circumstances that can result from this syndrome. I hope that sharing these stories will help other clinicians gain some insight into CRPS.

The first patient was an electrician who suffered electrical burns to one of his arms while working on a job. The burn appeared to have healed well, but after it healed it continued to be painful, red, and swollen, with the patient complaining of excruciating pain mirroring the initial burn. While his arm was functionally intact, over time he stopped using it, suffered from muscle and tendon contracture, and lost ability to continue to work or function, with a dramatically decreased overall quality of life. He would writhe in pain. The clinicians who were treating him desperately tried to help, but nothing worked, and he described that living his life with that amount of pain was unbearable to him. Eventually, after all options were presented to him, he chose to undergo an amputation to get rid of the pain. I was in the operating room the day of the amputation. It was one of the most extreme therapeutic interventions I have ever witnessed. While amputation is the most extreme measure I can imagine for a chronic pain syndrome, CRPS is a pain condition that may sometimes call for such drastic measures.

The second patient that comes to mind was a nurse I knew from my hospital. She had severely injured one of her fingers and required hand surgery. After she healed from the surgery the pain in her finger continued at the same level of acuity that she had experienced in the immediate postoperative period, and actually became worse, despite the fact that from an orthopedic perspective, she was doing quite well. The various measures her surgeon suggested did not work. I recognized that her pain and inability to use her hand was increasing. I had a high suspicion that she had developed CRPS and needed to get into an aggressive treatment program with a pain specialist as soon as possible, to avoid permanent loss of function. Unfortunately the pain management group that served our community was unable to see her in a timely fashion. Knowing that quick intervention was essential I called another pain specialist I knew. This happened to be Dr. Charles Argoff, a well-known pain expert. He was located farther away, but said he would see the nurse that same day. He then began her in an intense rehabilitation program that led to her full recovery, with full function and no pain.

These two cases confirmed to me the importance of making the right diagnosis at the right time so that the proper treatment program can begin quickly.


  1. 1. Harden RN, Bruehl S. Introduction and diagnostic considerations. In: Harden, R, ed. Complex Regional Pain Syndrome: Treatment Guidelines. Milford, CT: Reflex Sympathetic Dystrophy Association (RSDA) Press; 2006; 1-9.