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I
need some help to understand EMG Terminology |
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Can
anyone help me interpret this: triceps has a mild increase
in recruitment, amplitudes and 70% polyphagia. The only
definition that I can find for "polyphagia" is food related
eg. hungry. These segments are from my EMG. Thanks for
any ideas or help.
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Answer
1 |
Like
any field in science, EMG has its own terms to describe
the findings that tell us what kind of abnormality is
there. First of all we use term polyphasia and not polyphagia
(s not g). Polyphagia is related to eating, whereas, polyphasia
(poly=many, phase=peak) means more than 4 phases of the
EMG signal or response. Amplitude indicates the height
of the response, either small or high compared to normal
values. It is electrical term too. Recruitment is the
way in which the muscle is responded to voluntary contraction.
This term is derived from military, I think, to indicate
a second line is moving to support the first line in defense.
The muscle behaves likewise. However, the combination
of these suggest either myopathic, neurogenic or of course
a normal muscle. |
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Answer
2 |
Hard
to answer your question without more details. What is
your complaint? ie neck pain, injury... With a nerve injury,
recruitment of motor units is typically decreased, which
means you have fewer squirrels running the wheel. As we
require our muscles to produce more and more strength,
we "recruit" more and more units, faster and
faster. If you don't have the motor units left due to
damage you end up with weakness in that muscle. Since
you mentioned polyphasia and what I assume are large amplitude
units, this indicates some level of reorganization of
the damage is happening, which is a good thing. Again,
this is a difficult question to answer without a little
more info.... |
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Why
stimulation is repeated in nerve conduction velocity testing? |
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After
placement of two skin electrodes on my forearm I received
four "shocks" , each stronger than the previous. The location
of these two electrodes was not changed during this. I
asked the tech doing the test how much stronger I could
expect the current to get & was told that it would get
as strong as I "could take" & that electricity would be
passed thru these same electrodes on the same site in
increasing increments until I refused to take any more.
Would you please tell me if this is standard practice
for administering a nerve conduction velocity test? |
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Answer |
I
do these tests (26 years) and I'm afraid you were given
a pretty feeble explanation of the execution of the testing.
A nerve is made up of many tiny "fibers", each
of which is activated by a different strength of shock.
The very first shocks you are given only activate a small
part of the nerve. In order to have accurate testing,
the ENTIRE nerve must be activated. This can require a
rather large shock. It is common practice, though, to
start at a low level of shock, and gradually build the
strength up until the reading of the machine shows the
technician that the whole nerve is activated (i.e.--the
"bump" on the trace no longer gets bigger).
Generally, shocks are given to one or two (but sometimes
more) sites along any one nerve. Several nerves are done
in this manner for the typical test. Patient's reaction
to these shocks is quite variable. Some cannot tolerate
even the tiniest of the shocks, and I have had a patient
or two SLEEP through the whole thing!! The average patient's
reaction is "I can put up with it for a little while,
but I wouldn't want to do it every day".
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EMG
and Nerve Conduction report interpretation needed |
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Please
help, Can anyone define and explain to me what this report
means? EMG: This study provides electrical evidence to
support mild chronic left L-5- S1 radiculopathy without
acute on going denervation. Nerve Conduction: This study
provides electrical evidence to support a left posterior
tibial motor neuropathy with proximal involvement. The
prolongation of the left H-reflex suggests an L5-S1 pathologic
process. |
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Answer |
Before
I do interpretation. Please let me explain that EMG reading
or interpretation depends generally on presence or absence
of certain discharges (denervation activity), which usually
suggest acute lesion in radiculopathy, and changes in
the motor unit potentials, which helps to see the degree
or duration of lesion. Therefore, if you have only motor
unit changes of chronic nature without denervation activity,
then this could explained that the lesion in chronic.
The prolonged H reflex also supports that the lesion is
in S1 distribution. I hope this is clear. I will be happy
to help further if needed.
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Curious
about nerve conductive velocity test & EMG for ankle
neuropathy |
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I
am experiencing numbness, tingling in my right ankle and
top of foot and big toe. My doctor has me set up for a
Nerve Conductive Velocity Test and EMG on April 10. Can
you tell me what to expect? Will the EMG just be done
on the ankle area? My internist said my problems could
be bone spurs in ankle or even some problem in spine.
I am just wondering if test will cover spine too? |
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Answer |
For
more info on what to expect from EMG Nerve conductions,go
to:
http://www.teleemg.com/emgfaq.htm
The EMG will also explore problems originating from
the spine as well, not just the ankle.
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Comment |
I
just had my first NCV and EMG this week. I had reported
a problem predominantly in the lower left leg. The NCV
was performed on the left leg, front and back, but not
the back itself. The EMG was performed on the leg AND
the lower back. I suspect the EMG involved the spinal
area since it's the root of so many nerve problems. I'm
also going for an MRI follow-up per the good doc's recommendation.
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What
are normal motor units parameters (amplitude and Duration)? |
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What
are the normal ranges for the amplitude and duration of
normal healthy motor units? |
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Answer |
The
duration of the MUP is typically between 5-15 msec and
is generally affected by several factors, number of muscle
fibers in the motor unit and how do they fire (depolarize),
muscle by itself, age of the subject and temperature.
While the amplitude of MUP is again variable but greater
than 100 uV but usually less than 2 mV, but be careful,
It varies depending on how close the needle is to the
motor unit, number of muscle fibers in the motor unit,
their diameter and way of firing. |
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Drugs
before the EMG test to calm / pain reduction? |
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What
about Valium / Xanax / or others before the test to calm
the patient who has a driver???? I am rather needle phobic
(though getting less each test) If a drug will help me
feel better about the test and will not interfere with
the test results than I would like some feedback. I am
currently taking Vicadin and Oxyctin 10(at night time
only). Anything with the word "NEEDLE" freaks me out.
Sticking me multiple times, and leaving it in seems worse.
Though many have told me that the EMG is not pleasant
but bearable I still would like to know about possible
med's for scary cats like me. |
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Answer |
Although
EMGers utilizes needle electrodes, in majority it is well
tolerated. However, an analgesic may be used in some cases.
It is up to the treating doctor to order it, according
to the patient's condition. It does not interfere with
the EMG test.
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EMG
and EKG are they similar? |
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I
would love to hear an opinion on a situation my mother
recently encountered after having an EMG Test/NCT. She
has had difficulty breathing since the day she had her
test. This has continued for about one week now. She says
she is experiencing "breathlessness". It started the evening
after the test. I would appreciate any feedback on this
situation. |
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Answer |
Can
a EKG be used similar to a EMG? My doctor had me sit for
EKG test, and then he dropped the leg portion so that
my legs were dangling. He then did a EKG. When I questioned
him as to why, he mumbled something about the feet. I
am totally baffled as to what a EKG has to do with my
heart and feet and the severe spinal stenosis that I have.
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Can
muscular tension affects discovery of signs of denervation? |
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I
know that tension in the muscles can cause spontaneous
activity (fasciculations), but what about fibrillations?
Can muscular tension cause them also? (Because they represent
muscles fibers which lost their primary innervation) |
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Answer |
The
spontaneous activity needs a relaxed muscle to be recognized.
Therefore, muscle activity or "tension" either voluntary
or involuntarily would interfere with proper identification
of spontaneous activity being fasciculation or fibrillation.
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Stability
of MUP and significance of spike duration and rise time |
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What
are the parameters for motor unit stability? What is the
significance of the spike duration and rise time? Does
it have something to do with measuring stability? |
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Answer |
The
MUP stability is determined by the shape of MUP waveform.
Normally, the MUP waveform does not change with firing
or discharge. When components of the waveform is changeable;
fire earlier or later or even disappear, they result in
an unstable MUP. It occurs in processes of neurogenic
or myopathic lesions. The duration and rise time are parameters
used in quantitative measurement of MUP not for stability.
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Comment |
So
what is the significance of spike duration and rise time
in neurogenic process? Would they be increased? |
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Answer |
The
duration is increased in neurogenic process, but the rise
time is used in neurogenic lesions, but only to determine
whether the MUP should included for measurement or not.
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Comment |
What
is the difference between the spike duration and the "duration"
of MUP? ARE THEY BOTH PROLONGED IN NEUROGENIC PROCESS? |
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Answer |
Strictly
speaking the term spike is used commonly in electroencephalography
rather than EMG. The term Spike is a wave of short duration.
But in EMG we usually and practically refer to the duration
of MUP, which is increased in neurogenic process. Spike
duration is the duration of the major spike component
of the MUP.
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Motor
unit changes with advancing age |
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I
read in several textbooks that motor units size vary quite
significantly with age. Yet I never could understand how
does it vary? Are the motor units getting larger or smaller
with age (by amplitude and duration)?? , Would we found
smaller or larger motor units in old people, comparing
with young people My understanding is that as people get
older, they lose muscle bulk and that loss is more significant
than any loss of anterior horn cells, so as we get older,
there are less muscle fibers with relatively the same
amount of anterior horn cells, so each motor unit contains
less muscle fibers and therefore gets smaller on average,
as we get older. This is my assumption, never read it
... |
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Answer |
Where
you're getting confused is with the relationship between
muscle bulk and motor unit size. A muscle can be atrophic
and have large motor units. The reason for that is that
with the loss of anterior horn cells with age, the anterior
horn cells, which remain, take over the territory (ies)
of those which have died resulting in larger motor units.
Because they may not be able to take over all the denervated
muscle fibers, the muscle, in total, still has a positive
loss in the number of innervated muscle fibers and may
atrophy while those motor units inside of it that have
survived are actually larger than normal.
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Comment |
You
mentioned the loss of anterior horn cells with age.. I
thought that muscle fibers actually degenerate also (without
respect to the anterior horn cells, the same as all body
tissues degenerate -skin, cartilage....)
and I thought that the loss of muscle fibers is more
prominent than the loss of anterior horn cells...
The question is: IN the old... does the EMG get "neurogenic"
(large amplitude and duration...., with fewer motor
units, due to loss of anterior horn cells)
or "myopathic" (small motor units, due to
loss of muscle fibers)?
Which is more prominent: THE LOSS OF MUSCLE FIBERS
OR THE LOSS OF ANTERIOR HORN CELLS AS WE GET OLDER according
to your experience with older and younger patients
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Answer |
The
EMG tends to get more neurogenic with age
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Question
about normal values for peroneal and tibial nerves latency.
Also what about safety? |
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What
would be normal values for peroneal and tibial nerves
(latency in ankle, motor amplitude...) |
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Answer |
Peroneal
nerve values: Terminal Latency: 2.6-6.2 ms Amplitude:
2.6-20.0 mV Motor velocity: 42.9-55.0 m/sec. Tibial nerve
values: Terminal Latency: 3.0-6.1 ms Amplitude: 5.8-32.0
mV Motor velocity: 40.0 -62.1 m/sec All the best. |
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Comment |
I
wanted to ask about THE EMG safety also... what is the
amount of electric stimulations (the maximal) you give
in EMG? (in Ampere) I read somewhere it is 10-75 MA WHICH
AMAZED ME AS I KNOW A CURRENT OF 30 MA is enough to kill
a person!!! So how come it is safe?? (May be it is micro
Ampere rather than Milli Ampere???)
Also, Does the electricity you give really travels
through our body or it just the sensory stimulation
(natural) that travels?
Are there any web site with information on EMG SAFETY
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Answer |
Thank
you for this point. It is important issue. Your numbers
are correct, in mA (maximum 100 mA), not MicroA. The point
is that this amount of stimulation is given for very brief
period range from 0.05-1.0 milliseconds only. There are
always safety regulations and no EMG machine is approved
unless it fulfills all safety rules by law. The patient
safety is always on the top.
Regarding the electricity, it travels only through
the nerve under study. For the web sites, I am sure
there are web sites for EMG Safety but I do not recall
or have any at present.
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Comment |
About
the safety...
Do you know of any researches about the long term effects
of an EMG test (the "electric part") such
as possible nerve problems, cardiac problems (that show
up after long time) etc... For example with people who
had several EMGs over the years?
Do you know of any short-term hazards? (Such as people
who feel bad or faint right after the EMG?
* I read somewhere that increased exposure to electric
shocks has been linked to a variety of fatal disorders
such ALS and renal cancer... (That is why pilots get
more ALS and RENAL CANCER according to this research...)
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Answer |
I
am not aware myself and I did not read about any long
term effects of our "diagnostic" nerve stimulation
electrical tests, even if several tests are performed
per year for a normal person or patient in child or adult,
female or male, animals or human. For short term, talking
usually about minutes, pain (variable between persons),
usually tolerable. I have not seen a person fainted from
nerve stimulation tests. The final point, I am not sure
what sort of electrical shocks and for how long the exposure
to be linked to fatal disorders. It would be interesting
if I can read this article. |
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Comment |
here
is the article....
Electric shocks linked to Gehrig's disease
August 18, 1998
NEW YORK, Aug 18 (Reuters) -- A study of utility company
employees in Denmark suggests a link between amyotrophic
lateral sclerosis (ALS) and exposure to electromagnetic
fields or electric shocks, according to a study published
in the August issue of the American Journal of Epidemiology.
ALS -- also known as Lou Gehrig's disease -- is a rare,
fatal disease characterized by weakness and atrophy
of muscles and a degeneration of the nerves that transmit
messages to muscles in the brain and spinal cord.
In the study, Drs. Christoffer Johansen and Jorgen
H. Olsen with the Danish Cancer Society in Copenhagen
examined National Death Certificate files for the cause
of death in 21,236 men employed in 99 utility companies
in Denmark between 1900 and 1993. Medical records were
obtained to determine cases of ALS.
Overall, 3,540 deaths were noted in these workers,
slightly fewer than the 3,709 expected based on national
mortality rates. Analysis of the records revealed a
twofold increase in deaths from ALS in these men and
a tenfold increase in deaths from electrical accidents
on the basis of 14 and 10 deaths, respectively. Death
from ALS was also found to increase with time since
first employment in a utility company.
"The excess mortality from amyotrophic lateral
sclerosis seems to be associated with above-average
levels of exposure to electromagnetic fields and may
be due to repeated episodes with electric shocks,"
the authors write.
However, the study did not find that increased rates
of other neurological conditions such as senile dementia
and Alzheimer's disease in these men, nor an increased
risk of suicide. Previous studies have linked these
conditions and suicide to above-average exposures to
electromagnetic fields.
"The pattern of mortality from ALS, however, suggests
an association within jobs entailing medium to high
exposure to 50-Hz EMFs (electromagnetic fields), possibly
due to an increased number of episodes with electric
shocks," the authors conclude.
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So what is your opinion on that Doctor? Is there a great
difference between the electric shocks they mention
there and the electric shocks in EMG?
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Answer |
I
am sorry for being late in reply. I will not discuss whether
the relation is proven or not, but I want to say this
kind of electrical exposure (EMF) is different from that
used in field of nerve conduction studies. The exposure,
however, in nerve stimulation is low and very brief indeed.
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Motor
unit changes with aging |
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I was just wondering after attending a neurobiology lecture what happens to motor units in muscle as people get older? Do they just decrease without use or stay the same? |
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Answer |
Aging
brings about a decrease in the number of motor neurons
in the spinal cord. Given that a motor neuron with its
axon and all the muscle fibers it innervates is traditionally
referred to as the "motor unit", there is a
drop-off in the number of motor units with aging. Motor
units which survive begin taking over the muscle fibers
of those which lost their motor neurons and therefore
the surviving motor units increase in size. So with aging
you have a combination of a drop-off of motor units and
an increase in size of the surviving ones.
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