SYPATHETIC PAIN
Unlike what its 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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