The gate control theory of chronic pain in action
How the theory of chronic pain works
The brain commonly blocks out sensations that it knows
are not dangerous, such as when the feel of tight-fitting
shoes that are put on in the morning has all but vanished
by the second cup of coffee. A similar process is at
work in processing some moderately painful experiences.
The following outlines two brief case examples of how
the gate control theory of pain may be experienced.
1. This case example shows how the experience of
pain may change as information is processed in the
brain.
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Applying a clothespin to one’s arm initially
produces pain that may be quite intense as the
skin and surface muscles are compressed. Peripheral
nerve fibers detect this pressure and transmit
a pain signal to the spinal cord and on to the
brain. At first it is the fast pain signals that
get through, and the intensity of the pain experience
is fairly proportional to the amount of pressure
applied. Everyone would agree that this is acute
pain.
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The slower pain signals are not far behind,
however, and a dull ache may soon be noticed.
After a short while, the pain coming from the
pinched tissue will begin to be decreased by the
closing of the spinal nerve gates. This is because
the brain begins to view the pain signals as non-harmful.
The pressure may be painful initially but it is
not injuring the person in any way. As time goes
on, the pain message is given less priority by
the brain and the person’s awareness of
it decreases greatly.
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The brain knows that the clothespin is not causing
any injury. Therefore, the brain gradually “turns
the volume down” on the pain message to
the point of it being barely noticeable after
about thirty minutes. The compression on skin
and muscle is still occurring, but it is now perceived
as a mild discomfort if it is noticed at all.
2. This case example shows how other factors can
sometimes play a major role in the experience of pain.
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The patient reports that she thinks her back
pain is due to a spinal tumor. A thorough physical
examination and medical history reveals that her
spine is normal, except for the onset of the back
pain after a recent period of extreme stress.
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The stress involved the patient’s elderly
father, who had just been diagnosed with a spinal
tumor. The patient reported that her father’s
symptoms had also initially included back pain.
-
Upon questioning, it became quite clear that
the patient had an extreme fear that she also
was suffering from a spinal tumor. This belief
was creating intense suffering, which in turn,
made the back pain worse.
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The patient’s MRI showed no problems with
her spine, and the diagnosis of stress related
back pain was made. After experiencing tremendous
relief that the back pain was not the result of
a tumor, the patient’s symptoms began to
dissipate rather rapidly and she returned to normal
activities
As the above examples illustrate, pain is much more
complex than was previously understood (e.g. the
specificity theory) and the spine medicine community
is now beginning to understand and recognize other
factors that contribute to the experience of pain.
With this new understanding, it is accepted that
treatment of an underlying anatomic lesion may not
always relieve the pain (and pain may be present
with no anatomic problems)—rather, pain is a complex
process that is experienced differently in various
situations and is influenced by myriad factors.
By:
William W. Deardorff, PhD, ABPP
March 11, 2003
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