DocCornerThe Mnemonic of Central Pain 

“If it isn’t strange, it isn’t dysesthetic.”

Dysesthesia is pain not experienced by a normal nervous system. In Central Pain it has concomitants of sensory impairment and phantoms (see below). It is here that Central Pain patients most confuse their physicians. Dysesthetic burning has been called “Dante-esque” pain. The terminology used to describe it is usually interchangeable with descriptions of Hell in classic literature.

Hell’s Hottest Knives Have No Points

Central Pain patients frequently state that dysesthetic burning corresponds with what they imagine a hell might be like. Some of the descriptions given by patients include:

 – “Like Hell’s hottest knives tearing at my flesh”
– “Like my flesh is being consumed in a fire” (Boivie 1989)
– “Like my flesh is being torn from my body”
– “Like my flesh has been burned off”
– “A pain worse than pain” (Riddoch 1938)
– “Indescribable burning”
– “Like an alien pain monster has taken over my body and has ignited my flesh”

Central Pain also contains a feature of “nerve proximity” which refers to the directness or unstoppable access which the pain has to the consciousness. The closest thing in normal nociception to this feeling is the very direct sensation one gets when chewing on tinfoil against a dental filling. Because of the similarity, Central Pain patients often speak of a “metallic” quality to the pain.

Dr. Patrick Wall, a pain researcher, wrote of an early patient with Central Pain who said it feels “like tinfoil under my skin”. This type of descriptive comment nearly always disappears after several years as the patient enters into the phase of Central Pain where it actually becomes their reality and the only one they can remember. Talking to these patients is like talking to someone who has been in solitary confinement for many years. They have a world of their own, a pain world. Researchers interviewing longstanding Central Pain are often misled by the fact that the patient no longer remembers in what way Central Pain is different from normal. Questioning bordering on interrogation is sometimes necessary to get patients to reflect on what they have learned to ignore and suppress. Such questioning sessions are frequently followed by periods of depression, as the patient mourns the lost self.

Dysesthetic burning is the “bluntest” pain of which the human body is capable, and is characterized by the absence of accurate discriminative information. (i.e. it doesn’t communicate sharp, cramp, or anything but burn). Why then would a Central Pain patient describe a blunt, poorly localized pain as “hells hottest knives”? It is because Central Pain is much more than just dysesthetic burning. This particular patient was almost certainly trying to describe poorly discriminative, burning pain accompanied by lancinating pain which is “sharp”.

The national media printed a postmortem description from a Central Pain suicide victim who said her pain was “like having millions of ice picks jabbed into me while I was on ice while I was thrown into a furnace”. Although at first gloss the patient’s words are not recognizable, they are a very good restatement of Bowsher’s criteria for Central Pain, with an added description of lancinating pain. The clinician must listen clearly and give the patient time to reflect on their own sensations, which may be complex, distorted, and poorly localized.

Central Pain Resembles the Most Primitive Pain,
Protopathic Pain

When a nerve is injured in the body, the last pain to be lost and the first to recover with healing is a dull, poorly localized burning, historically referred to asprotopathic pain. This is very similar to the burning in Central Pain. Central Pain dysesthesia is best thought of as an “afterburn”, like the pain of having just touched a hot stove. There is a kind of “flare” which has poorly defined boundaries. It lacks the instantaneous “you have just touched something hot” information which the brain processes rapidly, and is really something other than the initial pain. If such a pain were to appear without the initial event of having touched something hot, the patient might be tempted to think of a sunburn, even though severe Central Pain is orders of magnitude greater than a sunburn. And so descriptive words vary from patient to patient.

In Central Pain, Dysesthetic Burning Has Two Components, Spontaneous and Evoked

The clinician must be prepared to determine which type of dysesthetic burning the patient is describing. There is a steady state level of dysesthetic burning in Central Pain., which Tasker has named, spontaneous pain. Temperature change and heat both sensitize the process and raise the level of the steady pain. This pain upgrades with tonic light touch, phasic rubbing, or rough textures to become evoked pain, as Tasker named it.

Evoked Dysesthetic Burning:
The Worst Pain Known To Man?

Severe evoked pain is terrible and extreme by any measure. The patient cannot endure the touch of clothing. The patient’s entire life becomes an exercise in avoiding evoked pain. It causes difficulty in obtaining rest because bed-clothing contacts the skin. It drives the patient to a hysterical search for relief of the pain, which ends in some degree of resignation and frequent depression. Patients indicate that it has robbed them of their identity, since their values and mental priorities are so consumed by its avoidance

What is the Meaning of Life? The Central Pain Perspective As one patient said while describing how they felt with the words, ” Like anyone else who is being burned at the stake”, Central Pain has a way of distilling all of life’s questions down into just one, “How can I minimize this burning?

Evoked Pain:
Like the Proverbial Frog Slowly Boiled in a Pot of Water
 Evoked pain does not come on simultaneously with the onset of light touch or thermal stimulus, although it can appear suddenly from “scratchy” rubbing. Even suede leather may be very “scratchy” to an hyperpathic Central Pain patient, so the word really means anything with an appreciable texture in the Central Pain context. (Researchers have identified different neurons for scratchy and smooth stimuli).In light touch or thermal evocation, there is a time delay, termed “slow summation” of minutes wherein there is apparently some sort of supersensitization occurring. This temporal delay allows patients some degree of function during the day when they can move limbs away from textured surfaces after a time.

Burning is Greatest Where the Loss of Sensation is Greatest Significantly, evoked pain is always worst where sensory deficit is greatest. This is just another way of saying the manifestation of nerve injury is greatest where nerve injury is the greatest. Evoked pain is also very durable, lasting as long as a half hour after the light touch stops. It decreases around twenty-five percent as soon as the stimulus is removed, and then gradually diminishes back to the ground level spontaneous pain. In thermal evocation, the rate of disappearance can be accelerated by bringing the skin temperature to the temperature window of greatest comfort.

The Phantom Because Central Pain originates centrally, the pain is felt over a large part of the body surface, frequently the entire body. In this, the patients differ from amputee phantom pain and conventional RSD, who experience pain in smaller areas of the body. Nevertheless, Central Pain patients display a phantom in areas where dysesthesia and “subclinical sensory loss” are present.The phenomenon of a “phantom” is familiar to anyone who has imagined they have a fat lip as dental anesthesia is wearing off. The lip is not really fat, the plastic brain is simply compensating for decreased information from the lip by utilizing resources which localize poorly and create an impression of greater size. Significantly, Central Pain patients have the most phantom in the areas of greatest sensory loss and burning. The limbs loose their sense of size and feel as if they were ballooned large from the phantom, at the same time as the sensory loss makes the limb seem to “shorten” or “disappear” from the “screen” in the brain which normally monitors that limb. No wonder patients have trouble describing what is going on. They don’t know whether they are describing something or the absence of something.

Sensory Ataxia: “My Feet Don’t Seem to Touch Bottom” This sensory loss of the feet gives rise to what is called “sensory ataxia“, meaning there is simply insufficient sensory feedback to walk securely. The patient cannot tell precisely when her feet have reached the maximal impact of weight bearing and so clumsiness occurs. Trips and falls are much more common in such patients. If greater proprioceptive and positional sense are preserved in the hands, then a cane may substitute for information lost from the feet.