Pain Perception

At OSR we are faced with patients suffering from injuries as well as chronic pain. According to Wikipedia, pain is “an unpleasant feeling often caused by intense or damaging stimuli”, something as simple as a cut or something that is more serious like a broken bone or torn muscle.  Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

One common result of pain is overcompensating for the pain in an area with the rest of your body. It is a natural reaction to withdraw from the damaging situation in order to protect the painful area while it is healing. Smaller scale pain will usually end promptly after the painful stimulus is removed, such as with a burn. Although with more damaging pain it can persist regardless of the removal of the stimulus like back pain. Pain is the most common symptom of all of our patients here at Oahu Spine and Rehab in Kailua and we know that pain can significantly interfere with a person’s quality of life and general functioning.

The University of Calgary describes the theories of pain as follows:

 

Theories of Pain Perception

There are three different theories to how pain works based on the way that your body and brain work together. These all involve your pain receptors and the nerves that are running throughout your body. The three different theories are specificity theory, the pattern theory and the gate control theory.

Specificity Theory

Specificity theory is one of the first modern theories for pain. It holds that specific pain receptors transmit signals to a “pain center” in the brain that produces the perception of pain. This theory is correct in that separate fibers for pain signals do carry pain signals to the brain eventually. However, the theory does not account for the wide range of psychological factors that affect our perception of pain. For example, soldiers may report little or no pain in relation to a serious wound in war time that would otherwise be excruciating.

Pattern Theory

Pattern theory holds that pain signals are sent to the brain only when stimuli sum together to produce a specific combination or pattern. The theory does not post specialized receptors for pain nor does it see the brain as having control over the perception of pain. Rather, the brain is merely viewed as a message recipient. Despite its limitations, the Pattern Theory did set the stage for the Gate Control theory that has proved the most influential and best accepted pain theory so far.

Gate Control Theory

Ronald Melzack and Patrick Wall proposed the Gate Control Theory in 1965. The theory can account for both “top-down” brain influences on pain perception as well as the effects of other tactile stimuli (e.g. rubbing a banged knee) in appearing to reduce pain. It proposed that there is a “gate” or control system in the dorsal horn of the spinal cord through which all information regarding pain must pass before reaching the brain. The Substantia Gelatinosa (SG) in the dorsal horn controls whether the gate is open or closed. An “open gate” means that the transmission cells (i.e., t-cells) can carry signals to the brain where pain is perceived; a “closed gate” stops the t-cells from firing and no pain signal is sent to brain.

Researchers distinguish between two general types of pain based on its time course: acute pain and chronic pain. Acute pain is typically defined as a pain response due to tissue damage that lasts less than 6 months. Chronic pain lasts more than 6 months and can be recurrent, progressive, or constant. According to the University of Calgary:

“We also know that there are two aspects to pain: sensory and emotional. The sensory aspect of pain refers to the sensations caused by stimulation of the pain receptors; the emotional aspect refers to the pleasantness/unpleasantness of the pain. Thus, to some degree, pain is a subjective feeling that differs across individuals and situations. Factors such as previous experience with pain, knowledge of the stimulus, and current physical state can all affect the interpretation of a pain signal. Although there is no consensus yet regarding all the factors that are involved, pain perception is a very complex process.

Pain is produced by the brain in response to threat or the perception of threat.  We have danger receptors called “nociceptors” in our body that can transmit things like chemical, mechanical, and thermal nociceptive information to our brain. Tissue damage and chemical inflammation can heavily influence the CNS leading to more sensitization and pain output. But, ultimately the decision is up to your brain based on it’s evaluation of the situation and perception of the “state of the tissues”. Think about phantom limb pain in amputees (no tissue damage with lots of pain) or in the opposite idea soldiers to have significant injury with no pain (lots of tissue damage with no pain).   If the brain evaluates the situation and believes you’re in more danger than safety, it will produce pain or may change motor control to protect you.

Pain changes motor control in all sorts of ways. The concept that the nervous system may redistribute and reallocate the function of certain muscles in response to threat/tissue injury. They also suggest how changes happen on multiple levels in the nervous system. This is partially the explanation for why there is no “one response” of muscle function with pain or injury. Although common patterns may exist each person will ultimately have a unique pain experience, pain neurotag, and movement adaptations in response to injury. This supports why needing an individualized treatment program for their issue is so important.”

Here at Oahu Spine and Rehab we are dedicated to making your life pain-free. With our physical therapy services here in Kailua along with the rest of our integrated healthcare team, we are able to put together the best program possible for your body in its’ healing process.

RECOMMENDED READING

*Do You Need a New Mattress?

*How to Prevent Foot Pain

Resources:

http://ucalgary.ca/pip369/mod7/tempain/theories

http://ucalgary.ca/pip369/mod7/tempain/impo

http://en.wikipedia.org/wiki/Pain

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