Normal pain conveys a wealth of discriminative information to the brain, such as the precise location, and a simple way to classify the pain (i.e. hot, cold, sharp, electrical tingling, etc.). In Central Pain much of this discriminative information is not present. In the modern era doctors finally began to understand the complex nature of pain. In fact, as they dug deeper they realized that it is one of the most complicated and densely filled sensations a human can experience. Patients experiencing nerve damage pain find themselves at a loss to find the language to communicate the sensations they are experiencing. On top of this, and irrational as it may seem, it is not uncommon for the patient to feel embarrassed about their pain.

If you are a physician treating a patient with Central Pain, it is important to remember that language is relative. A patient only has words to describe sensations that are familiar, and Central Pain brings an overwhelming range of seemingly bizarre, unfamiliar sensations that are unrelenting and extraordinarily painful. The Central Pain patient is typically a very poor historian since they lack the discriminative information and the necessary words. They are living with a debilitating condition that physically, mentally, and emotionally overwhelms them. And since they look perfectly normal, they often have been told repeatedly that it all must be in their heads.

Preconceived notions about pain must be discarded. Nothing else is Central Pain, and Central Pain is nothing else, yet the patient is forced to rely on the vocabulary of “something else” when they attempt to communicate their condition. For example, if a patient says “Touch burns me,” what they may really mean is “touch which persists for sufficient time,” since one of the common trademarks of Central Pain is delay of onset for touch and pain sensations. “Burns” may be the closest word available to describe the sensation, which resembles a type of burning, but also may include a complex mix of elements such as cold, clamminess, and a kind of “galvanic current” or “metallic” quality. One of Dr. Patrick Wall’s patients described this metallic sensation as “like tinfoil under my skin.”

Remember that pain is a physical sensation that reaches beyond the physical self, and affects emotion, thought, speech, and even one’s sense of self-identity. It is incumbent upon the physician to listen carefully for what the patient is not saying. There is no vocabulary to describe Central Pain. The physician must open their mind and allow, or even encourage, the patient to borrow terms from other conditions and situations. If you feel that this is frustrating, just imagine what it is like for the patient, who is trapped within their body with these never-ending sensations that seem totally alien, leaving them feeling totally alone and helpless.

Yet another challenge is that one of the defense mechanisms of the mind when it faces tremendous pain is to try not to think about it. The mind attempts to focus on anything besides the terrible pain, and this can happen to such an extent that the patient may have a difficult time remembering the torturous sensations. The patient has forgotten what “normal” feels like, and the constant pain is their new world, leaving them without a “normal” existence to offer a comparison. Though Central Pain consists of a diversity of pain symptoms, for the victim of Central Pain this terrible array becomes a single enemy and it is all the more difficult for them to describe their symptoms as a collection of different sensations.

Modern technology provides physicians with many tools to assess a patient’s condition. Blood tests, imaging studies, and many other tests are available to offer an objective view of what is happening in a patient’s body. Unfortunately, pain is a subjective and relative symptom and we must still rely upon the patient to describe their personal experience.

In recent years researchers discovered that it is possible to detect evidence of severe pain through imaging studies, such as PET scans, by measuring differences in blood perfusion in various parts of the brain. For example, in the face of an overwhelming onslaught of pain messages the thalamus, which ordinarily acts as a gateway and regulator for pain messages entering the brain, shuts down as an act of self-defense to avoid cell death. Pain messages then flood into the brain unhindered.

An apparent contradiction in the imaging studies is that the measurements are not always consistent, even in the same patient. One thing that must be kept in mind when viewing these test results is what they are measuring; the brain's reaction to and reflection relating to pain from the various stimulus that it is receiving at that particular time. This is an indirect measurement of the pain the patient is experiencing, not a direct measurement of the pain itself. Another thing to keep in mind is that the pain signals recruit a variety of responses, such as emotion, surprise, etc. We don't understand the brain well enough to distinguish between an emotional response and a straight pain response. Even the thumping of the magnet in the MRI machine may cause a reaction in the patient's brain. The most advanced imaging equipment available cannot tell if the patient is subject to the same level of stimulus as the last time they had the test. Consider the following questions and the many other possibilities that may play a role in this sort of study. 

• Is any attention being paid to the level of stimulus applied during the study?
• Is the patient thinking about the burning in their bladder because they need to go to the bathroom?
• Are they thinking about stubbing their toe on the front step of the hospital?
• Did the patient’s pain interfere with sleeping the night before the test?
• Is the patient wearing clothing that feels similar to that particular patient as other patients who have been studied? (The light touch of clothing can cause severe pain in Central Pain Syndrome.)

The pain messages sent to the brain in Central Pain are the product of a damaged central nervous system. The pain signals are therefore damaged. 

Pain does not run a straight line to pain centers in the brain. It hopscotches around to pick up emotional components and gives off discriminative information to alert various other systems in the body, such as the systems to arouse us to take action to prevent further injury. In the normal patient, the pain signal aggregates with other information to form a highly integrated message with information about severity, rate of rise, duration, location, boundary, danger, and priority.

Knowledge is the best tool to aid in the fight against Central Pain. There are many sources, but the leading published text to study is “The Textbook of Pain,” by the great pain scientists Dr. Patrick Wall and Dr. Ron Melzack. The leading medical journal is “Pain.” Also, physicians and anyone suffering nerve injury pain should read the excellent articles on pain research in “Science” magazine, October 10, 1997, which can be found at most large university and public libraries.