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Nerve
damage healing process |
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Upon
your advice, I went to see a neurologist and had an EMG.
The doctor told me that I had nerve damage due to the
three surgeries I had in October. He said that the nerves
would eventually regenerate and gave me a prescription
for amitriptyline. He wants me to work up to 50mg daily.
Right now I am up to 40 mg. I notice a very slight improvement
in the pain, burning, numbness, etc. Can you tell me how
long the nerves could take to repair themselves? Am I
looking at possibly a year or even more? It is the nerve
that runs from the groin down both sides of the thigh
and across the knee. Thanks for your comments.
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Answer |
Nerves
grow very slowly, about 1mm/day, you can almost compare
it to how fast a hair grows and you will have a ballpark
figure. So it takes usually anywhere from 6 to 18 months.
Amitryptilline and other drugs like it help relieve nerve
pain such as yours so this should help and you should
start noticing some improvements. |
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CMAP
question |
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I
know that in MND\ALS the CMAP are normal initially, later
it is abnormally low. my question is: in VERY early denervation,
there are many new motor units - that were formed to compensate
the loss. So, is it possible that in the very early phase
of denervation, the CMAP (which is the measure of number
of motor units) will be slightly pathologically higher
- I mean for example that the affected leg would have
higher CMAP than the non-affected one? I relate to the
very FIRST WEEKS OR DAYS OF DENERVATION |
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Answer |
In
early denervation, there are no newly formed units, there
are surviving units who take over muscle fibers from the
units which were denervated from the loss of their axons.
If the reinnervation is adequate, most denervated muscle
fibers are reinnervated in this fashion, but the total
number of muscle fibers in the muscle remains the same
so the actual size of the CMAP does not change. The CMAP
size decreases only when enough muscle fibers are denervated
and cannot find surviving units to take them over.
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EMG
electrode needle |
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HI
Does the size and type of a needle used during an EMG
can affect the number of motor units which are recruited.
(Does a fine needle recruits less mups in a MAXIMAL effort)?? |
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Answer |
Two
things the size of the needle does with smaller electrodes:
1) It has a smaller pick-up area, therefore you see
less muscle fibers
2) The amplitude of the action potential drops much
faster when you move the needle electrode, so unless
you're real close to the muscle fibers in your pick-up
area, you don't see them very well. You will have small
rounded potentials.
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Comment |
What
did you mean by less muscle fiber seen? During exertion,
more and more motor units appear, until there is a full
interference pattern - If you use a very fine needle does
it take more time to get the full interference pattern??? |
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Answer |
Think
of an electrode as a microphone and the muscle fibers
as musical instruments. If you have a small, highly selective
microphone, which you put in front of the solo violin,
you will only hear the sound coming from that violin and
very little else. Whereas if you have a large fairly non-selective
microphone which you hang high above the orchestra you
will capture the sounds of many more instruments, although
not as "faithfully" as the small selective microphone
real close to the violin. So large sees more (or hears
more) and small sees less. |
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Comment |
You
mentioned that the bigger the needle is, the more fibers
it collects: what about motor units -1. Are more motor
units recruited with larger needle? so does it take more
time to reach the full interference pattern with the smallest
and finest needle? 2.Does the needle picks up motor units
from neighboring muscles or just from the muscle where
the needle is??? I mean: is it possible that the muscle
where the needle is placed is dead (all the motor units
are dead) and the needle will pick up motor units from
neighboring muscles in exertion? (Which will make hard
to know the condition of this specific muscle)
THANKS FOR READING THIS POST |
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Answer |
Replies
to your post:
1. No motor units are recruited by the nervous system
in response to a demand for increased effort so needle
size has nothing to do with it.
2. No the needle electrode picks up motor units only
for the muscle it is in.
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Comment |
This
is sort of an interesting issue and the discussion has
raised several questions in my mind.
I have read about how the MUP drops off significantly
as it's distance from the needle increases. When you do
an insertion and sample in a given direction, how many
MU are studied (spontaneous or voluntary activity) in
that position? I realize this depends a lot on the size
of the units, density, etc. so lets say a muscle with
a large number of MU such as the bicep.
And in a related question when sampling in multiple directions
how big of a "radius" is studied from that one
skin insertion point. Thanks again for your kind help.
Regards, |
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Answer |
Muscles
fibers compose the MUP. Each MUP reflects about 15 muscle
fibers or less depending how close to electrode. In routine
EMG needle examination (nearly always we speak about it
in this site), the size of the needle whether thin, thick,
short or long, all have similar action and function. Interference
pattern or pick up area is the same whether short or long
needle, because the recording surface is the same (conventional
EMG needle electrodes), which is used in most clinical
examinations, called concentric needle electrodes. The
other point; the muscle is recognized by its anatomy.
The experience of the examiner is important in this aspect.
If the muscle is atrophic or fibrosed (dead motor units),
you may record MUP from nearby muscles. These are identified,
as they are distant and low in amplitude. So these are
not taken into account. I hope this answered your queries. |
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Fibrillations
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Hi
upon the insertion of the needle in my EMG a few weeks
ago there were popping sounds that lasted until I activated
this muscle (exertion) the popping sounds last for quite
long time in a rather rhythmic way It was pop pop pop
pop pop pop pop pop... in a very regular way until exertion
and then they stopped they were not slow but they were
neither very fast. I asked the doctor if these were fibrillations
and he said "no, relax your muscle" how could he be so
sure?? Does it sound like fibrillation? Do fibrillations
fire with long intervals? Are they rhythmic? DO they last
for long time? And most important: does it sound like
a POP POP POP or more like a brief BIP - bip or pop??.. |
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Answer |
It
is usually easy for electromyographer to recognize whether
fibrillation or not is seen by needle EMG. When he asked
you to relax, it means that it was likely to be voluntary
motor unit firing and not fibrillation. To come back to
your point about fibrillation; each single fibrillation
fire regularly (rhythmic) and has initial (down going)
positive deflection. However if many fibrillations fire
at the same time it would sound like irregular firing
because their firing rates are different. I believe the
best description for fibrillation sounds like "raindrops
on tin roof". Its frequency is usually close to 10
Hz. It has short duration less tha 3 ms. |
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Comment |
You
mentioned: raindrops on tin roof: 1.does it fire in equal
intervals? Like tu-tu-tu-tu 2.how long does it last from
the moment the needle is in: does it start and stop and
start. 3.and again about the sound: does it have a relatively
thick sound (tu-tu-tu-tu..) or like a bip? |
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Answer |
Hi,
yes it fires usually regularly at fixed intervals. It
lasts for variable interval. They vary in abundance, from
few to profuse everywhere for variable period. Regarding
the sound, only I tried to make it easier to appreciate
the sound, but you may have never heard raindrops on tin
roof or crinkling cellophane. Therefore, we should consider
other features of fibrillation in addition to sound. I
hope this will help. |
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Comment |
Does
it sound like 1. a tap that has been left opened and its
drops hit the washbasin rhythmically-drop by drop: tip
tip tip tip 2. Or more like a sound of rain drops - many
of them that you cannot distinguish by sound each one
of them (of the many rhythms) - because there are many
rhythms as you mentioned - so you get irregular sound
my questions refer only to the sound produced by the EMG
- regular and rhythmic or not? THANKS IN ADVANCE! |
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Answer |
OK.
It is similar to pattern 2. Many fibrillations (commonly)
fire at same time, sound like irregular firing. |
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Comment |
How
would you define the SOUND of fibrillation seen in an
EMG? What sound is made according to your experience? |
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Answer |
Have
been following the discussion thread. All I can tell you
is that learning to distinguish fibrillation potentials
from other activities by EMG is fairly simple and straightforward
and one of the first things EMGer learns, so I would trust
your doctor's judgment on that. |
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EMG/NCV
test |
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I
have to go for an EMG/NCV test. What are these tests and
how are they done? Are they painful? Are they long test?
I have swelling of the wrist and a lot of pain in moving
it, also numbness in hand. |
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Answer
1 |
The
test is uncomfortable. The word is not really painful,
but somewhat unpleasant. It is very necessary and can
prevent a miss-diagnose. I didn't realize that a nerve
up in your neck could make pain in your hands then wrist,
and arm. My neck doesn't hurt or isn't stiff. But I was
given a cortisone shot for Carpal Tunnel when I didn't
have CT. so GO FOR THE TEST. |
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Answer
2 |
The
test usually takes anywhere from half an hour to 45 minutes.
Though uncomfortable it will be useful for you to find
out what the problem is. |
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Can
EMG determine if the nerve injury is old or new? |
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If
a person has symptoms of nerve damage or entrapment but
EMG (3 separate tests) shows no nerve damage, then 6 years
later after an accident develop the same symptoms but
much worse and EMG is positive. Can tests prove that the
damage came from the most recent injury? And what would
have made the person have those symptoms without tests
being positive with the first accident? |
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Answer |
I
don't know why the EMGs were negative 6 years ago but
the answer to your question is that yes, EMGs can usually
determine if a lesion is over 6 months old or not. |
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EMG
“insertional activity” |
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First,
I would like you to know that I as well as many other
patients appreciate the fact you are sharing so much productive
information with us! My question is that: according to
medical textbooks a normal resting muscle is electrically
silent. However, from what I have read in this forum and
told by my neuro, It is quite common to have "a noisy
insertion" - what so called benign conditions "create"
benign insertional activity in rest that also have a "WAVE
FORM" (by wave I mean the morphologic wave such as fasics,
fibs, and positive waves but a benign wave? what are the
benign activities which have a wave form that MORPHLOGICALLY
may look like fibrillations? |
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Answer |
Hi
Bobby. What you're describing refers to end-plate noise,
which is the activity generated by the muscle when the
needle is inserted near the point where the nerve enters
that muscle. You can read up on it at: http://www.teleEMG.com/jbr110.htm
where you can get a good description.
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Comment |
Thank
you for your thorough reply! What about cramps/poorly
relaxed muscle - Don't they also "create" benign
waves? Is it possible for voluntary units to fire during
rest? (And then again we have "benign waves") |
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Answer |
Cramps
or poorly relaxed muscle don't sound anything like the
end-plate noise I described above. hey look like regular
motor units, which is what they are. Normally voluntary
motor units do not fire in a fully relaxed (uncramped)
muscle. Voluntary units firing at rest are called fasciculation
potentials. |
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EMG
Results in sensory polyneuropathy |
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I
apologize for the length, but I wanted to be sure I present
the pertinent info. I have been having problems with numbness
and tingling in my hands and feet/legs. My back feels
fine-no pain, great range of motion, with mild sciatic
pain on occasion with certain movements. 12 years ago
I had a lumbar laminectomy, which was quite successful.
Recent MRIs and X-Rays of my cervical region were completely
negative, as was brain MRI. MRI of lumbar showed marked
narrowing of the L5-S1 space with a few mildly bulging
discs. No evidence of nerve impingement. Neurosurgeon
thought my lumbar spine was not causing the problem. Had
EMG/NCS on a left arm. EMG was normal, however NCS was
not. Left ulnar sensory was unobtainable. Left Median
sensory was not normal although not absent. When the neuro
did the leg, following the arm he did not do the EMG.
Only NCS. Sural was unobtainable. (I could tell something
was wrong during the test, because in certain areas when
he jolted me, I could not feel a thing, or felt a lessened
response. I have had previous tests years ago and could
definitely feel it). The interpretation was as follows:
This is an abnormal nerve conduction study due to low
amplitude in the left median sensory and marked slowing
of nerve conduction velocity, absent ulnar sensory and
absent sural. This is consistent with a sensory neuropathy,
apparently both axonal and demyelinating. The results
were reviewed by several other neuros who agreed with
the diagnosis of sensory polyneuropathies. I have been
thoroughly tested for the cause, and have been labeled
"idiopathic." One neuro told that because my arm EMG was
normal, it showed there was no cervical nerve root involvement.
I have a few questions regarding the EMG/NCS. First, why
would the neuro not perform the ordered EMG on my leg?
I have a sneaking suspicion that my lower leg paresthesia
could be due to lumbar nerve root involvement, which I
assume the EMG would have shown. He simply did the NCS.
Also, can an impinged spinal nerves cause demyelination?
I can't seem to get an answer from the docs. Would they
be able to differentiate between idiopathic PN and lumbar
problems on the NCS? I just want to know for sure if my
lower back is causing the lower extremity problems, and
the EMG/NCS is Greek to me! |
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Answer |
In
cases like yours, these findings would indeed indicate
to me the presence of a peripheral neuropathy. Peripheral
neuropathies can be due to a host of things, first and
foremost diabetes (or a family history of diabetes), alcohol
consumption, toxic or occupational exposure to heavy metals
or solvents, thyroid disease, gout, multiple myelomas,
dysproteinemias, immune deficiencies etc. only to name
a few. Leg paresthesia could indeed be due to a lumbar
nerve involvement which could only be detected by the
needle exam, but given the whole picture, of course it
could also simply part of the neuropathy. An impinged
spinal nerve can cause demyelination, which is difficult
to detect from the routine nerve conduction studies. And
finally, it is very difficult, by NCS alone, to distinguish
between a lumbar problems and peripheral neuropathy. I
hope this helps.
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Time
lag before fasciculation |
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Is
there any time lag between when nerve damage occurs and
fasciculations make their appearance i.e. can they appear
almost immediately after the damage, unlike the fibs and
sharp waves which don't appear for two months? Thanks
a lot again. |
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Answer
1 |
Fasciculations
are very different animals than fibs and positive waves
and are usually seen in diseases such as ALS (Lou Gehrig's
disease) and not following simple nerve damage |
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Answer
2 |
I
am not sure what do you refer to by "nerve damage".
However, fasciculation is not a feature of traumatic nerve
lesions. It occurs in anterior horn disease, radiculopathy,
and demyelinating neuropathy. I must say that I do not
encounter any time lag between the onset of illness and
development of fasciculation. Unlike the fib and positive
sharp waves. Also, the finding of fasciculation alone
is not pathological. Another point that complete relaxation
is needed to recognize reliably the fasciculation. Furthermore,
there should be ample time or pause between the needle
movements |
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"Benign
fibrillations" |
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Can
a fibrillation be also benign (without serious pathological
meaning)? I have read somewhere that a person was having
an EMG in MAYO clinic and the doctor found one fibrillation
in his thigh and told him that the test does not suggest
ALS or other form of denervation. I have also read that
people who exercise a lot have sometimes fibrillations
in EMG. So, can a fibrillation be totally benign? |
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Answer |
Yes,
fibrillation may have no or unexplained clinical significance.
In a way it could be considered as benign, why? Perhaps
because they are present in certain muscles in good number
of asymptomatic subjects. Let me give you some numbers;
in foot muscles, fibs and PSW reported in 6-29% of "normal"
subjects. In lumbar paraspinal muscles, fibs and PSW seen
in 15% of "normal" subjects and in about 30%
of an older group above 40 years of age. Because those
subjects are asymptomatic, isolated fibs and PSW in those
muscles are not necessarily indicative of neurogenic process.
The presence of fibs in other muscles, therefore, is significant.
However, isolated fibs in the thigh (as in your case)
do not mean ALS because it did not fulfill the other criteria
of EMG findings in ALS, it could be radiculopathy. The
fibs and PSW to be clinically significant, they should
meet 2 criteria. They should be recorded away from end
plate. Secondly, they should be recorded in at least 2
muscle sites. The important point is to keep in mind that
their presence should always be interpreted in the clinical
context, as EMG is only an extension of clinical medical/neurological
examination. Thanks.
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Comment |
WELL,
THANKS for the thorough answer. So if there is a disorder
of benign fasciculations where a bunch of muscle fibers
fire spontaneously, maybe there is a condition where singular
fibers fire spontaneously!
My question is: Have you ever seen patients with benign
fasciculations AND such harmless fibrillation? |
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Answer |
In
brief, no, I did not recall a "normal" subject
with combination of fasciculation and fibrillation in
the same muscle. They do indicate pathology, but maybe
insignificant if no other muscles are involved and the
patient is asymptomatic, for instance, isolated changes
seen in foot muscle (ext. dig. brevis), however, a follow
up is recommended. I think practically, it is appropriate
or safe to say that finding a fibrillation is abnormal
unless proved otherwise (not the same rule for fasciculation).
Of course, fibrillations are harmless but an important
clue to diagnosis within clinical context. |
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Accuracy
of an EMG test in muscle weakness and tenderness |
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I
have Chronic muscle tenderness along with weakness for
four and a half years, a recent EMG was normal and suggested
no myopathy was responsible. I am concerned that such
persistent muscle pain is not due to some disease activity
- could the EMG test have missed something, because only
my left upper arm and my leg muscles were tested. Thank
you |
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Answer |
What
you describe sounds like fibromyalgia which causes muscle
aches, generalized fatigue and sleep difficulties. An
EMG is generally negative in Fibromyalgia. Physicians
who specialize in Physical Medicine and Rehabilitation
(also called Physiatrists) usually are more familiar with
this condition and its treatment. Best of luck. |
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Normal
EMG recording from the muscle at rest |
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Does
increased insertional activity look exactly like fibrillation
and positive waves or it may have totally another form?
From what I read both have the same form but increased
insertional activity never becomes spontaneous/ when you
say a normal resting muscle is electrically silent, does
it have to be "completely straight line" like a "dead
heart" Because on my EMG there was not straight line (in
some of the muscles) but like regular "wavy line" - I
know these were not positive waves because they were upward
(negative) and not downward and I think It was not a fibrillation
either because these waves were wide (according to the
books the fibrillation wave is vary narrow - very short
duration) . Could this be increased insertional activity?
*The doctor said It was nothing serious just "something
from the background" and that the muscle is not totally
relaxed and that is why he could not reach the "straight
dead line" - what did he mean, could this be increased
insertional activity? There was "full interference pattern"
in these muscles and normal motor units. THANKS IN ADVANCE |
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Answer |
It
is like that, at rest nothing is seen, no "spontaneous"
activity in normal muscle. It should be as you said completely
straight line (as you said dead heart, it is interesting
term, although this term is not used in our field and
may not be preferable or we did not think about it). However,
this line may not be straight because the patient is not
relaxed or something from background (not pathology).
In your case seems like an electric interference (60 Hz)
which has no significance. It is not prolonged insertional
activity from your description
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Comment |
THANK
you! Can you relate more specifically to the descriptions?
1. Is that true that fibs look like brief spikes and not
like wide waves? 2 Is that true the increased insertional
activity has the shape of fibs and positive waves? And
if not what other shape it might have? 3 and finally,
Does the electric interference you mentioned as a possibility
has something to do with the muscle being tense and poorly
relaxed or it has nothing to do with one's muscle condition
during insertion I would appreciate deeply your answer!
THANK YOU! |
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Answer |
Back
again, sorry for being rather late. Answer 1: Yes, fibs
are spikes but with characteristic features. Answer 2:
No, insertional activity does not look like fibs or PSW.
For 1 and 2, the site contains good description for both.
You may use the search engine. Answer 3: This interference
(artifact) has nothing to do with your muscle or yourself. |
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Effect
of Tegratol on EMG |
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I
am going to have an EMG later this week. I am taking the
following meds: Tegratol XR 100 mg twice daily. Alegra
- twice daily, not sure of the dosage. Will either of
these make a difference in my EMG? Thanks for any information! |
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Answer |
No,
none should affect your EMG results.
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Electric
stimulation and its relation to CMAP amplitude |
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I
think this question is a tough because I cannot find the
answer in any book does the CMAP (compound muscle action
potential) Depend on how powerful the stimulation is?
I am asking that because I had 2 EMG's and although conduction
velocities remain quite similar the CMAP are very different
- in one of test I was given very powerful stimulation
(there the CMAP was much higher) - in the other a very
weak stimulation-lower CMAP. for example, for left peroneus
it changed from 3.4(first EMG) to 13.28 (second EMG) (the
higher were where the stimulation was higher) if it is
not the power of stimulation - what else could make such
a difference ? Thanks for taking the time for reading
this! |
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Answer
1 |
You
are right, the CMAP depends on the intensity of stimulation,
i.e. the stronger the stimulation the higher the CMAP
(up to limits). Also, another factor is the way of stimulation
for instance how close the stimulator electrode or probe
to the nerve
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Answer
2 |
Stimulation
needs to be about 25% above maximum, not more than that,
otherwise you will be stimulating other nearby nerves
and getting volume conduction from them which would account
for the higher amplitude.
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Comment |
thank
you for responding me! You said the higher the amount
of electric current - the higher the CMAP is! As I said
in my case there was great difference (3mv versus 11mv)
- so How the normal CMAP for the ulnar nerves, for example
is defined? When the books say the normal CMAP is XXX,
Do they relate to the one they get in MAXIMAL or MINIMAL
stimulation? (there is great difference!) |
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Answer |
As
discussed in the last few emails. The CMAP is measured
by adding about 25 % of stimulus intensity after obtaining
the maximum response. We do not take the response after
minimal stimulation. |
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Description
of EMG Exam |
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I
am scheduled to have an EMG Test on my calves because
of pain while walking. I looked through here and could
not find a description of the actual test. Could someone
please give me an idea of what to expect, how long it
takes and then what the test will reveal when it's over.
Thank you. |
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Answer |
This
EMG test consists of probe inserted in the muscle and
this test is associated with little discomfort or pain
(quite variable between subjects). The examiner may also
apply electrical stimulation to study your nerves, this
kind of electrical stimulation is mild and tolerable even
in children. Some children having fun with it. However,
EMG would be helpful in your case to find out what is
causing your pain and can exclude nerve compression from
lower back in your case.
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Patient
response to nerve conduction test |
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Today I had a NCV performed and when the doctor tested my Ulnar Nerve (Right Armpit) my right leg jumped! This happened each time he tested it? Any ideas? When testing my left arm my whole body jumped (flexed)? Are these normal or indicative of a particular problem? |
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Answer |
Do
not worry. This does not indicate problem. This seems
like a reflex reaction as somebody is taken by surprise
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