| |
30-40%
false negatives results in EMG |
|
| |
|
|
|
| |
In
your answer to a previous post you stated that some studies
have indicated that needle EMG can give false negatives
30-40% of the time in detecting a root lesion. Why is
this? Also does this apply strictly to testing for radiculopathies
or other disease processes as well?
|
|
| |
|
|
|
| |
Answer |
Yes,
thanks for the clarification; the 30-40% false negatives
in the studies I quoted applies only to radiculopathies.
This is due to many factors, including the fact that
while radiculopathies may be painful, they may actually
not cause any nerve damage (which is what is picked
up by the needle exam of the muscle), sampling or interpretation
errors, detection error due to poor relaxation, timing
of the exam etc..
|
|
| |
|
|
|
| |
Comment |
Are
there any general statistics in regard to false negatives
or diagnostic accuracy in general for EMG? Or are there
statistics for individual disease processes such as neuropathies,
myopathies etc? |
|
| |
|
|
|
| |
Answer
1 |
Well,
generally speaking, in compression or entrapment neuropathies
(such as Carpal Tunnel, Ulnar, Radial or Peroneal Neuropathies,
or Bell's Palsy), the yield is pretty high (I do not have
numbers) even though there are still false negatives.
In root lesions, as I mentioned before, the yield drops,
as it does in neuropathies and myopathies, probably again
in the 30-40% area. EMG is considered to have the highest
yield in entrapment/compression neuropathies. |
|
| |
|
|
|
| |
Answer
2 |
I
would like to tackle this point by talking about how the
electrodiagnosis contribution to diagnosis of myopathies
in form of false positive or false negative. First of
all, it is important to keep in mind, unfortunately, that
none of the abnormalities in EMG is pathognomonic or specific
for any single myopathic disease. Second, EMG is important
but general guide to diagnosis, but we should keep in
mind again that exceptions do occur. Now, the question,
could EMG be false positive in myopathies? The answer
is yes, due to technical reasons (MUP measurement, over-reading),
also it can be false negative, due to again technical
reasons (MUP measurement, simply missing mild changes)
or mistaken the changes to be due other cause. Regarding
neuropathy, again, false positive can occur due to technical
reasons, temperature and age. While the false negative
can also be due to some technical reasons in the recording.
|
|
| |
|
|
|
| |
|
|
|
| |
Best
time to perform EMG |
|
| |
|
|
|
| |
My
physician has referred me for an EMG. He has advised that
I wait until I am symptomatic. I want to be sure I schedule
it at the best time. My symptoms relapse and remit lasting
for about a month with a two-month downtime between. I
have: numbness and tingling in extremities, my knees buckle,
vision disturbance, short bouts of tremor in arms, tightness
in knuckles of fingers and toes, slight difficulties with
fine motor skills in fingers--hesitancy, impaired balance.
Last time, I even had a brief bout with facial paralysis
(around my mouth) and difficulty swallowing. The visual
and numbness/ tingling symptoms are the most constant,
the others can last anywhere from a couple hours to 5
days. Which symptoms will assure the most thorough results
from EMG testing? |
|
| |
|
|
|
| |
Answer |
The
only time it makes a difference to be symptomatic or not
for an EMG is when a doctor is suspecting diseases of
neuromuscular transmission such as myasthenia gravis,
because the findings do tend to vary. For other diagnosis
such as peripheral neuropathy (causing the numbness or
tingling) or entrapment or compression neuropathies, the
general rule of thumb is that if you have a lesion there,
it would be positive on EMG regardless of the timing of
symptoms. So it is important to know what your doctor
is suspecting before you decide to wait until symptomatic
or not to have the study.
|
|
| |
|
|
|
| |
Comment |
I
think my doctor suspects a neuromuscular origin for my
problems. Which symptoms (described earlier) would be
most sensitive for testing? I.e. would a day with say
vision disturbance, intermittent knee buckling and jerky
pinky movements is a better day than just one with lots
of tingling, balance and vision problems?
If I am experiencing newer symptoms would they show
up less than symptoms that have repeated?
|
|
| |
|
|
|
| |
Answer |
Yes
usually neuromuscular transmission problems manifest themselves
primarily in visual disturbance (double vision or droopy
eyelids) and fatigability. So the days that these symptoms
are worse will probably be better days to be tested.
|
|
| |
|
|
|
| |
Comment |
I
am experiencing my 3rd month-long attack. Will older symptoms
show up better than new ones? |
|
| |
|
|
|
| |
Answer |
Probably
so. |
|
| |
|
|
|
| |
Comment |
It
appears after doing some checking, that having an EMG
+ NCS while symptomatic will be logistically impossible
because they cannot be scheduled on short enough notice.
I have described my relapsing and remitting symptoms
in previous posts. While I think my doctors would like
to rule out problems of neuro-muscular origin, they
lean much more toward CNS disorders at this time.
I have difficulty believing that if I have this testing
done while I am symptom-free and my nerves are functioning
normally, that the EMG will be able to pick up the problem.
How successful are the tests at recognizing difficulties
like I've described?
|
|
| |
|
|
|
| |
|
|
|
| |
How
deep should the needle be insterted in EMG? |
|
| |
|
|
|
| |
Is
it important to insert the entire needle to the muscle??
The doctor who did my EMG told me that the active part
is in the tip of the needle... |
|
| |
|
|
|
| |
Answer |
Enough
part of the tip and the cannula need to be in the muscle
to appropriately record the signal.
|
|
| |
|
|
|
| |
|
|
|
| |
Sedation
for infants during EMG NCV testing |
|
| |
|
|
|
| |
My
16-month-old daughter was born with a left clubfoot, and
bilateral PIP contractures of digits three and four. We
were told she has distal arthrogryposis. The clubfoot
did not correct completely with casting and bracing. She
will be having surgery. The neurologist wants to rule
out muscle and nerve disorders first. Can she be sedated
for this test? Will the results be accurate? |
|
| |
|
|
|
| |
Answer |
Sedation,
most often, is not needed for EMG because the test is
tolerable and the muscle voluntary contraction is required
which cannot be done under sedation. However, the doctor
should be able to assess this need. The EMG in your child
should give useful information about the status of the
muscles and nerves.
|
|
| |
|
|
|
| |
Comment |
Thank
you for your reply. My daughter has a tremendous fear
of doctors. In fact, we were unable to get x-rays of her
foot, because she was so afraid of the technician and
cried and climbed off the table etc...Therefore, knowing
her, she won't cooperate at all. I feel the only way is
to sedate her. How much of the test will be reliable if
I do? Will she wake up from the sedation when the electricity
goes through, or when she feels the needles? Thanks! |
|
| |
|
|
|
| |
Answer |
Thank
you for your email. Usually the doctors and technicians
in EMG have their own kind way of dealing with patients
from all ages, even infants. Therefore, I would not expect
real difficulty during the test. However, the sedation
does not affect the results of nerve stimulation. If she
awakens during the test, it does not affect the result,
even if there is a little pain or discomfort. |
|
| |
|
|
|
| |
|
|
|
| |
What
is difference between acute and chronic? And does temperature
effects NCV? |
|
| |
|
|
|
| |
Results
of my EMG/NCS - Right lower extremity Temp = 33.3C Conductions.
Sensory conduction velocities at the lower end of normal,
but within normal in the leg with normal amplitude. Motor
conductions at the lower end of normal, but within normal
with normal F-waves in the lower 60's. - Needle exam Evidence
of chronic low-grade denervation with increased numbers
of polyphasic appearing units, but no significant giant
units. Complex repetitive charges are noted in abductor
hallucis and abductor digiti minimi pedis in both feet,
and rare myokymia in abductor hallucis in right. No significant
evidence of acute or chronic denervation is seen in more
proximal musculature. Significant fasciculatory activity
in seen in intrinsic foot muscles and in calf and anterior
compartment muscles, slightly more prominent in the calf
muscles than in the anterior compartment musculature.
-Right upper extremity Temp= 33.6C Minimal slowing of
sensory nerve conductions distally in the hand with conduction
velocities in the low 40's. Motor conductions in the upper
extremity are normal with normal F-wave latencies. I've
had fascics for, probably, 15 years. No weakness at all.
Docs don't have a clue except a diagnosis of a 'neuropathic
process with fasciculations and minimal nerve conduction
abnormality, but needle exam findings suggest a very slow
and indolent motor axonal process'. I think they are referring
me a Boston NM expert. A couple questions.....
1) What is difference between 'acute' and 'chronic'?
2) Were the temps in foot and hand low for this type of
test?
3) I gather low temps can impact conduction velocities.
Is it correct to assume that needle exam is relatively
unaffected by temp.
4) Any of this look at familiar? They seem to think I
was pretty unique. |
|
| |
|
|
|
| |
Answer |
In
answer to your questions:
1) In needle exam terminology, acute means the presence
of fibrillations and positive waves, usually indicating
that the nerve injury is recent, more than 2 months and
less than 2 years (these are approximations). Chronic
means at least 6 months old (acute and chronic may coexist
for a while) and indicates that the nerve has begun to
regenerate and reinnervate the muscle.
2) The temps are within acceptable range
3) Generally speaking the needle exam is unaffected
by temp except for fascics which may be decreased or
altogether suppressed by low temps.
4) It is difficult to give an impression on the net.
Findings such as yours can be seen in peripheral neuropathies.
However such a diagnosis does not account for the fascics
or the myokymias. I think a neuromuscular specialist
who can put this together with the clinical symptoms
would be of help.
|
|
| |
|
|
|
| |
|
|
|
| |
Current
Perception Threshold test |
|
| |
|
|
|
| |
What
is the current perception threshold test? Does it replace
EMG |
|
| |
|
|
|
| |
Answer
1 |
I
am not quite sure what the Current Perception Threshold
test is. It certainly does not replace an EMG. If you
have more info on it, I would be happy to tell you more.
|
|
| |
|
|
|
| |
Answer
2 |
Perhaps
this test is similar to the "Sensory Test" given
at my medical institution. Ours involves testing for light
touch, vibration and hot/cold sensitivity. I don't believe
that our testing includes any minimal electrical current
perception, but I suppose this variation may exist. |
|
| |
|
|
|
| |
Answer
3 |
I
think as the name implies, this technique should be able
to perform "non-invasive" and provides a kind
of measure of sensory function using special surface probe.
By all means as pointed out, it does not replace the nerve
conduction or EMG studies. |
|
| |
|
|
|
| |
|
|
|
| |
Breathlessness
encountered after EMG test |
|
| |
|
|
|
| |
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. |
|
| |
|
|
|
| |
Answer |
I
am assuming that EMG/NCS was performed for extremity nerves.
In this case the test by itself does not cause "breathlessness".
Therefore, my advice to see internist for her symptoms.
|
|
| |
|
|
|
| |
Comment |
Thanks
very much for responding. It was performed for persistent
neck, back and leg pain.
|
|
| |
|
|
|
| |
|
|
|
| |
Epileptic
fits started after EMG test |
|
| |
|
|
|
| |
I
had a needle EMG to see if I had carpal tunnel syndrome
and ulnar nerve entrapment, The test was very painful.
I felt terrible shocks through out the test. I told the
dr. how painful it was and he said we were almost done,
well the last needle was inserted in the back of my head,
very near the top of my spine, well the shock felt like
I was being electrocuted. Immediately after that I was
unable to speak without stuttering for at least one month.
When it finally stopped my body was like having terrible
convulsions. Finally that stopped and I started having
seizures. Grand mal type. Now three years late I am diagnosed
with epilepsy and I must take tegretol xr 6 times a day.
What I need to know is if anyone heard of this happening
before. I see a neurologist every 4 to 6 months and he
said he doesn't know. I never had seizures before this
and they are not in my family also I didn't sustain any
other injury, except for getting my hand crushed months
earlier. Please help me find out. |
|
| |
|
|
|
| |
Answer |
Seizures
are caused by injuries (trauma, congenital, vascular etc..)
to the central nervous system or can be due to metabolic
disorders. EMGs come nowhere near any of the above and
seizures are not known complications of an EMG exam. The
timing of your episodes and the EMG exam is understandably
curious, but the connection between the two can't be made
because of what I described above.
|
|
| |
|
|
|
| |
|
|
|
| |
Is
it necessary to move the needle inside the muscle during
EMG exam? |
|
| |
|
|
|
| |
I
had needle EMG today. The Dr performing it, after every
needle stick, moved the needle around roughly causing
a lot of discomfort, is this something done with every
stick; he also had me flex my foot when he was sticking
my leg. I do understand that the nerve pain is at the
insertion of the needle but to continually move the needle
around after insertion, is that necessary. At times he
scraped the needle back and forth after he inserted it,
is this normal for this procedure. I thought when you
are testing the activity of the muscle you have to have
the needle still after insertion. I have had EMG before
and it was nothing like this one. I ask the Dr. if I could
see the results on the screen and he said he did not save
any of it and showed me another pt's results that was
positive for nerve damage. He told me not to pursue nerve
damage any further. Thank You |
|
| |
|
|
|
| |
Answer |
It
is part of needle EMG to move the electrode inside the
muscle, also to ask the patient to activate the muscle
against resistance. This is quite normal procedure. However,
the test is varies between the examiners and type of request
for the test. However, the pain is short lasting and leaves
no squeal.
|
|
| |
|
|
|
| |
Comment
from another
Patient |
The
action of moving the needle through different areas of
the muscle is a necessary part of the examination, as
is the activation of the muscle. The amount of discomfort
can vary because of the kind of needle used, the skill
of the Electromyographer and the muscle being examined
(smaller muscles are often more painful). I speak from
experience from having EMG's performed on me for real
and as a "practice dummy" (I've had the best
to the worst). |
|
| |
|
|
|
| |
|
|
|
| |
EMG
Procedure? |
|
| |
|
|
|
| |
I
am new to the world of EMG's but have been ordered by
my doctor to have one after an epidural went bad. How
long do they normally take? Is there a physical before?
Would I need to bring any information? How many needle
insertions are normally in each leg, (which I am having
done, lower leg nerve damage) and what other procedures
are done along with it? I was freaked after the epidural
went wrong, so this would all help to calm my fears. |
|
| |
|
|
|
| |
Answer |
The
time of the EMG is variable depends on the patient but
usually 30 minutes. You do not need to do physical activity
before. The number of insertions again variable, the electromyographer
decides that. The study consists of two parts, the nerve
conduction studies, you would feel some electrical impulses
stimulating the nerves causing movement of the muscle,
it causes little but variable discomfort. Then the second
part is the insertion of the needle electrode into the
muscles (feeling of little prick). Both tests are put
together to see whether your nerves are affected and how
much. It is very useful and sensitive tests. |
|
| |
|
|
|
| |
|
|
|
| |
Thigh
pain after EMG |
|
| |
|
|
|
| |
I
just had an EMG done, and ever since then, I have had
some moderate to severe pain in my left thigh. I had no
pain there before the test, which was quite painful. The
doctor who performed the test doesn't know why I would
have this pain. Is this a common side effect of the EMG?
If so, how long can I expect it to last? Any help you
can give is greatly appreciated, and I look forward to
hearing from you. |
|
| |
|
|
|
| |
Answer |
The
pain or discomfort at the site of EMG insertion may last
minutes and up to few hours and very rarely up to 24 hours.
If it is longer or moderate to severe, another cause should
be looked for. However, you did not mention how long you
have this pain following EMG and why, to start with, EMG
was performed?
|
|
| |
|
|
|
| |
|
|
|
| |
EMG
and Plaquenil |
|
| |
|
|
|
| |
I
am scheduled to have an EMG. I am currently on Plaquenil
from a former doctor. The Rheumatologist told me to stop
taking the Plaquenil because it could interfere with the
EMG results. Is this true? I asked this question on the
neurology forum and the doctor said they never heard of
such a thing. |
|
| |
|
|
|
| |
Answer |
It
is true that Plaquenil (Chloroquine) has neuromuscular
side effects; muscular weakness or neuropathy, usually
with long-term treatment, among other complications. The
point, I do not know why EMG was requested?, perhaps,
to check that this drug is not affecting your nervous
system. If affecting, then you should discuss it with
your doctor to discontinue or give alternative medication.
Please update me if you wish.
|
|
| |
|
|
|
| |
|
|
|
home
about
us 
patient
forums
doctors
forums
online
store 
contact
us 
