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Sympathetic pain
Unlike what it's name suggests, sympathetic pain has nothing to do with the emotion of sympathy. It refers to the sympathetic division of the autonomic nervous system. This is also known as the "involuntary" nervous system which regulates such things as heart rate, blood pressure, temperature, stomach acid secretions, and skin sweating to name a few. Usually, this part of the nervous system activates excitement and stress within our bodies and can set our "voluntary" nervous system (ie., our muscles) on edge or in readiness mode. The "flight-fight" response is regulated by the sympathetic nervous system.
The International Association for the Study of Pain, in their 1994 taxonomy and book of pain disorder classifications has eliminated the term "reflex sympathetic dystrophy" in favor of type I and II complex regional pain syndrome (CRPS). This is because too often cases do not have sympathetically maintained pain and not all were dystrophic.
Complex Regional Pain Syndrome Type I (reflex sympathetic dystrophy)
".a syndrome that usually develops after an initiating noxious event, is not limited to the distribution of a single peripheral nerve, and is apparently disproportionate to the inciting event (injury). It is associated at some point with evidence of edema, changes in skin blood flow, abnormal sudomotor activity (sweating) in the region of the pain, or allodynia (pain response to non-painful stimuli) and hyperalgesia (excessive pain responding)."
Diagnostic criteria include:
- presence of initiating event/injury.
- persistent pain, alloying, or hyperalgesia disproportionate to injury
- evidence of edema, changes in skin blood flow, abnormal skin sweating in region of pain.
Complex Regional Pain Syndrome Type II (causalgia)
Occurs after partial nerve injury (usually the median, sciatic, tibial or ulnar nerves) and results in constant and burning pain exacerbated by light touch, stress, temperature change or movement and sometimes by auditory or visual stimuli and emotional disturbances. Abnormal skin blood flow/skin temperature/color, edema, hyper-hypohydrosis.
Diagnostic criteria include:
- persistent pain, allodynia or hyperalgesia after nerve injury but not necessarily in distribution of the nerve injured.
- edema, changes in skin blood flow, temperature, sweating in region of pain.
Sympathetically Maintained Pain
Sympathetically maintained pain is believed to be maintained by the sympathetic nervous system or by circulating catecholamine. This is a feature of several chronic painful conditions. When treating a painful condition with sympathetic drugs and a positive response is obtained it is often concluded that the pain was sympathetically maintained. Sympathetically maintained pain may occur in some patients with CRPS but does not occur in all cases.
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