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Glossary
| The Language of Central Pain
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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.
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Adequate stimulus refers to the manner in which a given component is
most effectively stimulated.
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Crossed afterdischarge is the ability of damaged sensory neurons to induce
autonomous passive firing in uninjured neighbor neurons.
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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.
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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.
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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.
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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.
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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.
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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).
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Electrophysiological refers to any test that measures nerve transmission rates,
usually somatosensory evoked potentials.
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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.
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Ephapse is signal jumping from one nerve fiber to another
creating a sensation in the brain of a nonstimulated area of the body
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Epidural is the space where spinal fluid circulates around the
cord. Medicine placed here can selectively block sensation without shutting off motor
function entirely.
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Erythrosin-B is a chemical used to create a rat model of Central Pain
by making
the cord more sensitive to lasering.
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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.
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Humoral pertains to body fluids or substances contained in them such as
chemicals and other molecules which circulate in the blood.
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Hyperexcitation refers to overstimulation, too much electrical current.
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Hypersensate means extra-sensitive.
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Hyperpathia means increased pain from stimuli which are normally
painful. The most common example is increased sharpness from a pin prick.
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Hyposensate means less sensitive than normal.
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Isometric pain is muscle pain associated with
ongoing movement, usually prior activity yielding instant quasi-"lactic acid
buildup".
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Isotonic pain is not related to movement and
has been termed "confinement cramps".
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Lanciating is shooting pain, sort of like an electric shock, or
the radiating pain of a bee sting.
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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."
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MRI is magnetic resonance imaging, a type of
radiologic imaging which creates a picture from the weak magnetic activity of spinning
ions in tissue.
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Neuraxis means the brain and spinal cord.
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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.
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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.
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Neurotrauma means any injury to the nerves.
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Nociception is the sensation of pain in normal people.
- Paresthesia is a "buzzy" or funny feeling
from nerve injury. It is nonpainful.
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Proprioceptive is ones sense of body position.
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Referred Pain is pain felt in one area of the body which actual originates in
another.
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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.
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Reticulospinal refers to a tract in the spinal cord going from reticular
nucleus near the thalamus to the spine; downward going tract.
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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.
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Somatosensory Evoked Potentials: see above under
electrophysiological.
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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.
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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).
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Synapse is the connection between two neurons in relay toward brain.
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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.
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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.
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Translocated means shifted or moved.
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Disclaimer:
All material on PainOnline is strictly the opinion of the
authors of the material on this Web site. PainOnline does not attempt to
offer medical advice. If you have concerns about your health, please see a
qualified health care provider.Copyright © 2001 by David Berg
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