Physicians love this aspect of pain, for with pain they can receive solid feedback from the patient. It alone can provide a verbal photograph. Doctors can rely on it. Pain tells them many things. It allows experienced clinicians to make complicated and difficult diagnoses, even before the hi-tech stuff confirms that they were right. It's so gratifying to know what is wrong after interviewing the patient, with the pathologist and radiologist then relegated to redundant status. This feels very good to physicians, who are, after all, human.

All of this is true about normal pain, but it is completely untrue about Central Pain, and this is what throws physicians about Central Pain. It doesn't sound like pain, the patient doesn't want to use the word pain (because the patient is also accustomed to specific discriminative information being associated with any pain message), and Central Pain doesn't behave like pain...it breaks up into component parts that are somehow blanketed by a kind of burning. The reason for this is that Central Pain comes from what is only part of normal pain, the suffering part, with very little of the discriminative part. This is a very important clue to Central Pain's cause and its underlying physiology. (see below)

The body's need for pain information explains the redundant pathways for pain which make humans capable of very distinct awareness of it. On the other hand, it is not so valuable to remember pain, since the threat is gone, so humans have a very poor memory of pain. It is easy to remember the having suffered but notoriously hard to remember the pain itself.

Thus, the brain devotes many and large structures to sorting out signals which might indicate a threat of tissue damage, but the brain has little interest in calling back up old pain. We can remember that we hated the experience, but we cannot recreate a holographic image of the pain, the way we can recall up the face of our loved ones.

In a similar way, when we have a blanketing pain like the burning of Central Pain, the brain pays attention to this big pain, and we fail to fill out details on the other pains, even if they are more intense. Central Pain patients can always tell the doctor more about their poorly localized burning pain than they can the very intense shooting pains, which also plague them.

Scientific observations indicate that the brain has an image, or map, embedded in it of what sensation from the healthy body should feel like. The brain knows when our shoes are too tight or our scalp itches, even if we aren't conscious of it because we are distracted by other thoughts. The brain also knows, because the tight shoe message is understood and known to be harmless, that it is okay for us to be thinking about something else. The brain memorizes all these sensory inputs and puts them in categories that allow instantaneous sorting. This normal filtering process allows us to carry out our day-to-day tasks without a non-stop string of distractions.

Rapid pain is carried in large diameter, insulated nerves and slower pain information is carried in small, uninsulated nerves. All pain nerves carry signal all the time, but most of the signal doesn't mean much. These signals travel toward the brain, branch off, go through filtering and damping (inhibition), and eventually reach the thalamus, which is located in the center of the brain, at a line back from the eyes.

The thalamus is huge, as brain structures go, and is the central processor of sensory information. The thalamus is also one of the structures which is sometimes shut down in Central Pain to avoid cell death from intense electrical impulses. The conscious brain relies on the thalamus to sort and filter sensory messages into meaningful packages.

When signals sent along connections of the thalamus to the conscious brain don't match the normal pattern the brain is accustomed to, but the brain knows pain is involved, there is alarm over what is regarded as a very important signal, pain. The brain tries to respond, but fails due to the "garbage in-garbage out" concept. The patient perceives a very confusing signal which is slowly burying them in suffering. This condition is known as Central Pain.

Researchers believe that Central Pain is initiated by injury to nerves which supply input to the pain centers, resulting in violent patterns of firing (called bursting). The great paradox of nerves which must be understood before Central Pain can be considered, is that while injured motor nerves simply carry less current, injured pain nerves not only increase their firing dramatically, they also have the power to induce automatic firing in uninjured neighbor nerve fibers. Pain researcher Marshall Devor calls this afterdischarge.

Injury sufficient to bring this vicious cycle to a head, short of killing the nerve entirely, begins to create groups of impulses too strong to be interpreted properly. Do not confuse this summation theorized by Melzack, Wall, and others to initiate Central Pain, with the summation which results from Central Pain, namely the delay in evoked burning which occurs with prolonged light touch. 

If a pain message perceived as dangerous, or a pain message which is indistinct or unclear (a message the brain has no "file" on based previous experience) arrives at the brain, the brain sends out  an alert and begins an immediate investigation. The brain begins to study and examine the pain message until its meaning and degree of threat is analyzed. If analysis fails to supply an answer, the brain devotes more and more resources to the pain, until eventually the electrical signals are so intense that the brain cells risk death from the amount of current reaching them. (This is similar to the damage to retinal nerves that results from looking at the sun). When the hyperexcitation reaches the point where cells risk death, protective parts of the brain begin to shut down the flow of blood to various brain parts to preserve them. These parts are then unavailable for pain analysis, and so the brain vigorously continues the search for the pain's meaning, with the limited resources available.  

If the patient is aware that these events (or similar processes, if science so demonstrates) are occurring, they will realize that Central Pain is not supposed to make sense. It is supposed to be confusing. It is, of course, important for the patient's physician to realize this as well. Bizarre symptoms should be recognized as a diagnostic indicator of Central Pain, rather than leading physicians to discount what is being said.

The bizarre nature of Central Pain may lead to immense amounts of heartbreak as the patient is rejected by a succession of doctors who, despite impressive credentials on their walls,  are ignorant of the clinical manifestations of Central Pain. It is important to find well-trained knowledgeable people when one is suffering with Central Pain. The patient is too involved in just staying alive to have to waste time convincing those who will not learn.

Thus, Central Pain patients appear not to fit in with "proper" pain disease.  If the professional is educated properly, Central Pain patients can rid themselves of this particular bad boy/bad girl stigma of having Central Pain.

Copyright © 2001 by David Berg