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LL
burning and weakness “p. neuropathy vs. myasthenia” |
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If
a patient presented with leg burning, bilateral, and leg
weakness, would not an EMG/nerve conduction study be one
of the first tests a doctor might do? These were my symptons,
and after two years, five neurologists, not one doctor
did an EMG, until ten days ago. Diagnosis. Peripheral
Neuropathy and possible Myathenia Gravis. From what I
have read, it appears if the legs are burning, pain caused
just by the touch of a hand, a sheet, or clothing, that
an EMG should have been one of the first tests completed.
What is your expert opinion? Thank you.
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Answer |
Your
symptoms are a definite indication for EMGs. The burning
feet are due to what we call a small fiber neuropathy,
usually seen in patients with Diabetes or nutritional
disorders. Symptoms of Myasthenia include fatiguability,
double vision, droopy eyelids etc. It is important to
find out how sure is the Doctor who did the study on you
of the Myasthenia diagnosis, or if he/she needs to refer
you to a specialist in this disease, because if you have
it, you need to be treated.
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EMG
assessment for Myasthenia Gravis |
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I
was diagnosed with myasthenia gravis in l995 with the
positive aChR. antibody test and positive tensilon test.
My neuro. is sending me to another neuro. at a MG Clinic
at their medical school where they notified me that they
will do a EMG/NCV w/Rep Stim testing after my office visit
with the new neurologist. My question is: If my EMG should
be negative, will I be diagnosed as NOT having MG? I am
presently on social security disability and would not
want to risk losing that. I have been notified to stop
the mestinon the day before the test. I also take prednisone,
Paxil and Klonopin but they did not ask about any other
medication I was taking. I would appreciate any information.
Thanks |
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Answer
1 |
A
positive antibody test is a very specific indication that
it is Myasthenia. Repetitive stimulation needs to be performed
in an involved muscle in order for it to be positive (it
is important that you do not take the Mestinon prior to
the test). A more sensitive test for Myasthenia is called
Single Fiber EMG which has a higher diagnostic yield than
repetitive stimulation. Good Luck.
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Answer
2 |
You
are already diagnosed as MG. Therefore, it seems that
the reason behind repetitive nerve stimulation test to
check the degree of weakness or probably trying to reduce
your medication. He advised you to stop mestinon before
the test because it affects the result. A normal repetitive
nerve stimulation test (decrement test) does not mean
that you do not have MG. We know the test can be normal
in MG. Just go ahead and all the best.
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Question
about MCD and MSD? |
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Thanks
so much still wondering if you can tell me about these
results. Single Fiber EMG: Extn.Dig.Com Rt Number of Recordings
analyzed: 25 and Number of Recordings with blocking: 16%
Mean Test Values are: MCD 55 / MSD: 56 / Percentage of
recordings with blocking 64% I searched Medline but the
information about Electromyography studies does not give
normals either for the MCD or MSD I was hoping you could
answer what these results mean. I was told that 16 out
of my 25 nerves tested had 80% blockages how does this
differ from the Percentage of recordings with blocking
stated as 64%? A few people on the list will mention that
they were told their EMG's showed 50% but they haven't
understood that either in regards to SF EMG testing. Is
that the MCD and MSD? Are my results as MCD 55 and MSD
56 percentages based on something? If so what? Thank you
so much for your help and for answering all of my other
questions? Kind Regards, |
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Answer |
The
neuromuscular junction is concerned with impulse transmission
from the nerve to muscle. Normally, it takes time, this
time is calculated very precisely for each muscle in normal
persons. Normally there is little variation in this transmission.
It is termed jitter i.e. there is normally a jitter up
to a limit, once exceeded it is considered as abnormal
for that muscle. This is calculated in mathematical way
using the Mean value of Consecutive Differences MCD and
Mean Sorted-data Difference MSD (Standard Deviation SD
was not used because it would give erroneous results).
All these done nowadays by computer analysis in the EMG
machine. Practically the MCD value is used (only in certain
situation MCD/MSD index and MSD are used). The normal
value for MCD (jitter) for EDC muscle is 40 us (for the
method used in your case, axonal stimulation). So value
of MCD is compared to normal value obtained from normal
persons for same age. I hope this will answer all your
queries. Please write again for further question or unclear
point.
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Comment |
Am
I to understand then that the MCD and MSD are for jitter
results and the other result is for the blocking percentage
on all 25 nerves tested even though only 16 of my nerves
showed blockages?
I know these are the two things they are concerned
with, from what I read, in testing for Myasthenia Gravis.
When a neurophysiatrist states then that an EMG showed
a percentage of something then they are talking about
the overall percentage of blockage in the total of nerves
tested? Is this correct? I was told that 16 of my nerves
had 80% blockages even though the final percentage stated
is 64%.
Another way of asking since I don't understand the
terminology for electromyography tests is: Is this percentage
then based only the total of nerves tested against those
that were found to have blockages? In other words this
overall percentage is more important than knowing the
total of blockage percentage of each individual blocked
nerve.
You mentioned that the MCD and MSD are not usually
tested. Is this because Myasthenia Gravis is one of
the diseases that effects jitter and needs to be obtained
for a MG diagnosis?
Does the higher rate of MCD 55 and MSD 56 which shows
jitter above the normal for the EDC nerve of 40 mean
that it is faster or slower. Is jitter faster in Myasthenia
Gravis or slower? I understand about the nerve synapse
and how the receptor ends are blocked by antibodies
which does not allow the normal impulse from Acetycholine
transmission. So the blocking that is being tested for
makes sense to me. It would seem to me that jitter would
be slower also.
Thank you again for this great forum and the information
you share. This helps so much to understand these tests
and how they help to diagnosis our diseases so that
we can get the help and treatments we need to get back
some kind of quality to our lives.
I am working with AAEM right now as a patient advocate
in Sacramento to fight a bill SB 1600 that was presented
by physical therapist to allow them to do Needle EMG's
and diagnosis patients. We are opposing this bill as
for all the reasons you state in your site that it takes
a qualified physician in neurology to understand and
diagnosis these tests properly. If I had been sent to
someone who did not know about Myasthenia Gravis or
how to even test for it (or what to look for) I would
still be undiagnosed and untreated. This test was my
only confirmation to my MG diagnosis.
I suffered for over 6 years without treatment, so weak,
breathing and choking problems. Loss of my fitness level
and had to close my health club from all my medical
problems. It is very scary to think that PT's who are
unqualified to perform some of these very specialized
tests are trying to also enter this field with only
8 weeks of training. It would be devastating and tragic
to see so many people with neuromuscular diseases go
undiagnosed, misdiagnosed and possible die from not
having some one who is skilled perform their Needle
EMG tests.
Thanks again for this great site and for sharing your
special training and talent in EMG testing.
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Answer |
All
your points are correct and your interpretation and analysis
are correct. However, only one point about MCD, it is
not only usually used to calculate jitter but the standard
in Jitter measurement. Thank you again and you are welcome.
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Attacks
of fasciculations and nystagmus in MG patient on mestinon |
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I
have muscle fasics every day. They are mild and completely
painless. Most of them occur in specific areas of my body
(left bicep, right thigh just above the knee, and right
lower leg). What is happening when this sort of activity
becomes amplified and fasics are occurring all over the
body, from scalp to feet. Nystagmus is so bad that everything
jumps/jiggles when I move my eyes, and with each step
I take? This happened to me about a month ago and I wasn't
too concerned (thought rest would help) until I couldn't
empty my bladder at all. I wound up in the E.R. of a local
hospital, and no one really had any clues, other than
suspected Mestinon overdose (which proved not to be the
case). I do have MG, but I don't believe this "episode"
was related in anyway to the MG. My husband could literally
see my entire face "moving" spastically. This went on
for roughly 2.5 to 3 hours. As mentioned above, I have
fasics each day, but this seemed like a violent attack.
Once the fasics eased off, I could finally void my bladder.
I have been dx'd with spinal stenosis (entire spine) and
have disc herniations (old injury). Any ideas on this
would be appreciated. |
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Answer |
Mestinon
overdosage is known to cause fasiculation and urinary
retention. But it seems you had an additional severe nystamgus,
which is unusual feature. I would recommend seeing a neurologist
with MRI of the brain. Also, he would check if the dose
of Mestinon is appropriate or not.
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Tensilon
Swallowing Test in MG |
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I
am going for a tensilon swallowing test. What kind of
a test is that? I had a positive tensilon test and my
abnormal lung test caused by mg and upper airway obstruction.
I am sero-negative; I also have mild to moderate swallowing
difficulties. I had a throat test where I had to swallow
wires and showed low Les tone. Can you explain that? Thanks |
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Answer |
As you said
that Tensilon test in general is used in diagnosis of
MG. To be specific, if patient complains of swallowing
difficulty caused by MG, then a test injection of Tensilon
should improve your swallowing. This is done by asking
the patient to drink water before and after. This is the
meaning of Tensilon swallowing test. Otherwise I am not
aware of any other objective or quantitative explanation.
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Myasthenia
(Arm tested weak but EMG tested neg) |
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I
am being watched to see if my myasthenia has returned,
my eye is evident for ptosis, my right arm on testing
the right one after a few seconds began drooping, my neurologist
had extra time so we went in and did an EMG. The EMG was
negative. Now my myasthenia is a mild case. And my neurologist
and I are pleasant to each other, so he is not just a
wall type doc to me, but this time he just said, well
must be emotional, and no way to test the eye and left.
So question. Is it correct, is it black and white, negative
EMG, negative myasthenia (at least for the arm) |
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Answer |
The answer
to your question is yes/no: It is difficult to have black
and white in medicine, although we wish to. Now, we have
two kind of "EMG" tests used for Myasthenia
Gravis (MG). The repetitive nerve stimulation (RNS) and
Single fiber electromyography (SFEMG). If you had the
RNS, then it is positive in about 55-77%, but I must say
it correlates very well with the severity of MG. The other
test the SFEMG is more sensitive 77-100%. If the test
is done by experienced electromyographer and the arm is
weak, then a negative SFEMG test in that weak arm means
no MG.
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