The Language of Central Pain

Please email me to suggest additional words to define in the glossary.

  • Allachesthesia is (1) a pain in a location other than that stimulated, or (2) a pain of a different nature than the applied stimulus.”
  • Allodynia refers to pain from non-noxious stimuli, whether or not experienced in the area stimulated. Brief movement or the texture of clothing would be examples of nonpainful stimuli which causes burning pain. Allodynia is a clinical term which can also refer either to pain in one area from stimulus to another. Researchers split “ephapse” (any current from cut neurons which affects neighbor neurons) from “crossed afterdischarge” — a recently observed phenomenon of cut nerves such that although a single stimulus has no effect, but a repetitive stimulus induces “autonomous repetitive firing of passing neighbors.” (See Devor,The Axon, Oxford Univ. Press. p. 540, 1995)

Some authors prefer to use “hyperalgesia” rather than allodynia. Those who prefer “hyperalgesia” may term pain in the area stimulated “primary hyperalgesia” and pain in nearby or other areas “secondary hyperalgesia”. This follows the usage of some early researchers, but at that time, it was not known that neuropathic pain is different from nociceptive pain. The clinical separation of the two types of pain has tended to make that distinction more important than whether the pain occurs in the area stimulated. The problem with using hyperalgesia is that it includes what is now termed nociceptive pain, and it can apply to noxious or non-noxious stimulus.

Allodynia is now used by most physycians to refer to neuropathic, or “bizarre,” pain which occurs as a result of non-noxious stimulus. Other than the fact that clinicians are used to different terminology, there is no reason why an author could not use “primary” and “secondary” as adjectives for allodynia if he or she prefers that usage to touch allodynia and location allodynia.

Pain from motion is kinesthetic allodynia or motion allodynia,but is usually called kinesthetic dysesthesia because the feeling evoked by such movement is dysesthetic burning.

  • Adequate stimulus refers to the manner in which a given component is most effectively stimulated.
  • Crossed afterdischarge is the ability of damaged sensory neurons to induce autonomous passive firing in uninjured neighbor neurons.
  • Deafferentation refers to long nerve fibers from the medulla or elsewhere which are cut at the axon somewhere in cord injury, thus depriving the proximal end of input from the peripherae, leading to spontaneous firing without logical input. Another name for Central Pain.
  • Delay with Overshoot refers to hyperpathia, or an overblown response to aspects of noxious sensation. (e.g. sharpness, heat, and texture). Confusion can occur during the pin prick test because the needle is so sharp, which in hyperpathic states, causes extremely severe pain. The point of delay has been bypassed by the sharp pin. Von Frey hairs are required to examine this clinically. When the point of sensation is reached, the apprehended filament feels painful due to the steep touch/pain curve.
  • Discriminative information refers to three dimensional and mass features, sharpness, crampiness, or one of the qualitative aspects by which the pain system defines the qualities of the pain sensation. The poorly localized flare after reflex withdrawal of a hand from a hot stove exemplifies nondiscriminative pain. Texture appreciation is the exception, and is typically hyperpathic.
  • Dorsalis refers to the tracts which run in the back of the spinal cord. These are large, insulated, speedy tracts which carry the rapid part of pain to the brain.
  • Durable, in the context of Central Pain, refers to the persistence of burning after the stimulus is discontinued, also termed “afterburn”. The burning is slow to appear but is slow to leave. Depending on the level reached the burning may last from a few seconds to twenty minutes or more. Subtle cooling, pleasant distractions, or some other phenomenon accelerates the quieting of the skin. Any cooling is best done by ambient temperature and not by any direct cold air. Only when the burning is outrageously severe will direct cold actually benefit the patient. In more moderate stages the attempted remedy, i.e. cold air directed at the skin, may well cause renewed burning.
  • Dysesthesia is a bizarre sensation which cannot be described. It is an unpleasant sensation with was unfamiliar until onset of the Central Pain, a novel mix of some of the primary pain components. It is usually associated with burning, but the patient has never felt this sensation before contracting neuropathic disease. The message perceived by the brain is one of “tissue destruction” with burning the most prominent component. (Pain is a construct).
  • Electrophysiological refers to any test that measures nerve transmission rates, usually somatosensory evoked potentials.
  • Embryonic position of the nerves: Nerves form high in the body and grow outward as body develops. Referred pain, e.g. from gallbladder, may be felt in shoulder where gallbladder nerve originates in the fetus.
  • Ephapse is signal jumping from one nerve fiber to another creating a sensation in the brain of a nonstimulated area of the body
  • Epidural is the space where spinal fluid circulates around the cord. Medicine placed here can selectively block sensation without shutting off motor function entirely.
  • Erythrosin-B is a chemical used to create a rat model of Central Pain by making the cord more sensitive to lasering.
  • Gradients are often oversimplified. Dysesthesia follows loss of fine touch, while hyperpathia follows retention of fine touch. By convention, however, these usually occur distally and proximally respectively, as described below.
  • Distal increase refers to distal/proximal gradations, which may result in sensory discrimination decrease and burning increase distally, or at more distant part of the body such as fingers and toes. Dejerine termed such gradations, “onion peel” skin. It is thought possibly related to the disproportionate over-devotion of somatosensory cortex/neurons to distal areas. Increasing gradients of dysesthesia follow decreasing gradients in retention of “normal” touch sensation. Because touch is usually most impaired distally in Central Pain, this website refers to distal increase.
  • Proximal increase is a gradient in opposite direction from distal increase. The Central Pain hyperpathic response is greatest where dysesthesia and loss of touch sensation are the least. Barring a complete lesion, touch tends to be spared going proximally on the body. Consequently, this website refers to proximal increase as it pertains to hyperpathia, which follows touch retention.
  • Humoral pertains to body fluids or substances contained in them such as chemicals and other molecules which circulate in the blood.
  • Hyperexcitation refers to overstimulation, too much electrical current.
  • Hypersensate means extra-sensitive.
  • Hyperpathia means increased pain from stimuli which are normally painful. The most common example is increased sharpness from a pin prick.
  • Hyposensate means less sensitive than normal.
  • Isometric pain is muscle pain associated with ongoing movement, usually prior activity yielding instant quasi-“lactic acid buildup”.
  • Isotonic pain is not related to movement and has been termed “confinement cramps”.
  • Lanciating is shooting pain, sort of like an electric shock, or the radiating pain of a bee sting.
  • Motor memory is a developed motor skill, such as the ability to perform motor acts in an experienced way and to remember this motor behavior in such a way as to repeat it with little reflection, such as tying shoes, shooting baskets, etc.”
  • MRI is magnetic resonance imaging, a type of radiologic imaging which creates a picture from the weak magnetic activity of spinning ions in tissue.
  • Neuraxis means the brain and spinal cord.
  • Neuropathic means pain which comes from injury to the nerves themselves and not from injured body parts. Central Pain is the type of neuropathic pain which covers the greatest portion of the body. If just one peripheral nerve is injured, the pain may be severe but is limited as to the body surface or part involved.
  • Neurosyphilis is syphilis that has reached the central nervous system. Because such patients have shooting pain which is like Central Pain, and because neurosyphilis is thought to originate from the dorsal columns in the back of the cord, a contribution to shooting pain in Central Pain has been theorized.
  • Neurotrauma means any injury to the nerves.
  • Nociception is the sensation of pain in normal people.
  • Paresthesia is a “buzzy” or funny feeling from nerve injury. It is nonpainful.
  • Proprioceptive is ones sense of body position.
  • Referred Pain is pain felt in one area of the body which actual originates in another.
  • Relieved by deep pressure refers to those aspects of Central Pain which are benefited by deep pressure or massage applied for a few minutes. Pain from prolonged deep pressure is allodynic and exaggerated. Since the skin is so sensitive, only deep structures experience this benefit and the pressure must be applied without friction to the skin.
  • Reticulospinal refers to a tract in the spinal cord going from reticular nucleus near the thalamus to the spine; downward going tract.
  • Slow Summation refers to evoked burning which appears at persistent touch or persistent stimulus application. If newspaper is laid on the skin, a patient may experience light touch for a few moments without pain, but at some point a rather steep curve develops which eventually causes an unbearable sense of dysesthetic burning. It is easily detected clinically.
  • Somatosensory Evoked Potentials: see above under electrophysiological.
  • Spatial Summation refers to a sort of synergistic increase in perception of a pain with increases in the area of skin receiving pain inducing stimulus. An example in Central Pain testing would be an increase in dysesthetic burning when a stimulus of plastic sheeting the size of a pencil eraser is increased to one which is a foot square. It refers to an increase in pain perception which is displayed in various ratios of increase as a function of the skin area which is involved. The increase is not merely linear, but exceeds the straight-line graph. It is not pain over a greater area, rather it is greater magnitude of the pain wherever felt. Clinical questioning must be precise.
  • Spindle Pain is pain which originates in the sensory part of the muscle spindle, about one in two hundred fifty muscle fibers is actually modified to relay back information on state of contraction of the muscle.
  • Spinothalamic refers to a tract going from spine to the thalamus, the pain tract, the tract which causes Central Pain
  • Spontaneous Burning refers to a raw, crude, poorly localized sensation which conveys no or incorrect discriminative information. Evoked burning is a slow onset rise to unbearable levels which is induced by non-noxious stimulus (most commonly the touch of clothing, rubbing, or a change in temperature).
  • Synapse is the connection between two neurons in relay toward brain.
  • Syringomyelia is a type of cord injury. The central cord (also called the spinal medulla) contains a small canal for spinal fluid to circulate. With cord injury or disease, this central canal expands so that a cavity in the cord results. This condition is syringomyelia.
  • Thalamocortical loops neuron circuits between thalamus and cortex which control excitation and inhibition of the pain system.
  • Topoesthesia is the inability to locate a sensation on the body.
  • Translocated means shifted or moved.