EMG Techniques - Part III

Sedation for infants during EMG NCV testing  Top

Question

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.

Definition of Polyphasia in voluntary motor units  Top

Question

here is a quote from an EMG site: "- EMG Findings in Specific Conditions: - Normal Study: - normal insertional activity; - silent rest activity; - biphasic and triphasic potentials; - complete interference;"

http://www.medmedia.com/o2/204.htm
my question refers to the statement: "biphasic and triphasic potentials;" Does it mean that units with 4 phases are not as normal as the ones with 1/2/3 phases?

*** Looking in my EMG report (quantitative analysis), there were many units with 4 phases (as well as 3 and 2, but many with 4) THANKS

Answer

What is difference between acute and chronic? And does temperature effects NCV? Top

Question

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) What is difference between 'acute' and ‘chronic’?

--> 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) Were the temps in foot and hand low for this type of test?

--> The temps are within acceptable range

3) I gather low temps can impact conduction velocities. Is it correct to assume that needle exam is relatively unaffected by temp.

Generally speaking the needle exam is unaffected by temp except for fascics which may be decreased or altogether suppressed by low temps.

4) Any of this look at familiar? They seem to think I was pretty unique.

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  Top

Question

What is the current perception threshold test? Does it replace EMG

Answer

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 Top

Question

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 Top

Question

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? Top

Question

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? Top

Question

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 Top

Question

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 Top

Question

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.

I need some help to understand EMG Terminology Top

Question

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.

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.

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....

Why stimulation is repeated in nerve conduction velocity testing? Top

Question

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?

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".

EMG and Nerve Conduction report interpretation needed Top

Question

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.

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.

Curious about nerve conductive velocity test & EMG for ankle neuropathy Top

Question

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?

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.

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.