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.

• 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.
• 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.
• 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.

• 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.
• 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.
• 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.

• Article written By:
• William W. Deardorff, PhD, ABPP

March 11, 2003

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