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The New Alphabet Soup of Pain Management
by Onassis A. Caneris, M.D., Division of Pain Medicine
A primary evolutionary function of the sympathetic nervous system is to prepare an individual to react to formidable or life-threatening stimuli. Clinical observation and response to treatment have implicated a link between the sympathetic nervous system and certain chronic pain syndromes. These pain syndromes have been termed "reflex sympathetic dystrophy" (RSD). Contemporary terminology suggests that sympathetically maintained pain is a presumed path physiologic entity implicated in a variety of chronic pain disorders, most notably "reflex sympathetic dystrophy."
Prompt Diagnosis of Pain
After injury or trauma, patients frequently seek medical car , for both evaluation and treatment of their pain. A medical practitioner's experience gives him the knowledge to inform the patient of an expected time frame for recovery and resolution of pain. In some instances, however, a patient's pain and some symptoms do not resolve. In fact, the pain may even intensify-- even after seemingly innocuous injuries like ankle sprains, venipunctures, or fractures. Patients often present with complex pain after having undergone extensive diagnostic evaluation and being told "all tests have been normal" or that no specific abnormalities can be found. Successful treatment often requires accurate and early diagnosis, and so it is imperative that clinicians become familiar with presenting features and current terminology.
Current Pain Terminology
The most contemporary pain terminology terms -- Chronic Regional Pain Syndrome type 1 (CRPS-I) and Chronic Regional Pain Syndrome type 2 (CRPS-II) --were advanced by The International Association for the Study of Pain (IASP) in 1994. CRPS is a term describing a variety of painful conditions with abnormal duration following injury. These CRPS disorders may have sympathetically maintained pain (SMP), sympathetically independent pain (SIP), or both.
With CRPS-1, spontaneous or evoked pain occurs disproportionately to the inciting event and is not limited to the territory of the single peripheral nerve. Additionally, there is evidence of edema, skin blood flow abnormality, or abnormal sudomotor activity. This syndrome was previously described as RSD. CRPS II is an analogous syndrome that develops after a peripheral nerve injury. This was formerly labeled Causalgia.
Sympathetically Maintained Pain (SMP) is pain that is maintained or facilitated by some form of sympathetic nervous system activity. Sympathetically Independent Pain (SIP) is pain that is independent of sympathetic activity. Motor dysfunction is seen frequently in these conditions, and may include limited active range of motion, weakness, or dystonia. The mere existence of comorbid psychological or psychiatric disease does preclude the diagnosis of CRPS. The incidence of RSD is estimated at 1:5000 individuals and may be present in up to 15% of all traumatic injuries17.
Treatment of Pain Syndromes
The treatment of CRPS and other painful conditions involving SMP remains variable. As reported in the literature, more than 30 different treatments regimens have been found to significantly improve reflex sympathetic dystrophy. With an extremely heterogeneous patient population, an individual approach to each patient remains essential. The need for early, aggressive treatment seems to be an emerging factor in obtaining favorable outcomes. Treatment begins with conservative therapies, including mild oral analgesics, physical therapy, and analgesic adjuvants.
The next line of therapy for the diagnosis and, potentially, for the treatment of SMP, is temporary interruption of sympathetic nervous system. Temporary nerve blockade can be accomplished for upper limb pain by a stellate ganglion blockade and for lower extremity symptoms by a lumbar sympathetic blockade procedure. These nerve block procedures may be done as single-dose or continuous-dosing procedures, each with varying degrees and duration of analgesic relief. Continuous sympatholysis combined with aggressive physical therapy emphasizing active range of motion provides analgesia and increases functional outcome. Growing evidence indicates that dorsal column stimulators may offer long term relief to some patients with RSD or CRPS. Additionally, basic multidisciplinary chronic pain treatment is often employed to treat the various facets of an individual's life that have become affected by long-standing chronic pain.
Conclusion
Sympathetically maintained pain conditions are probably more common than previously thought, with some cases resolving spontaneously and some perhaps going undiagnosed. Those cases that do not resolve often become serious if not debilitating chronic disease states. No single treatment paradigm has proven superior for all patients, and thoughtfully constructed treatment regimens must be individualized to meet the needs of each patient.
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