Doctor Forums

Evidence of Re-Innervation in EMG findings

In terms of reinnervation findings of EMG, including increased recruitment, instability of MUP, increased Amplitude of MUP (?), etc, which of these features are reliable to predict the true re-innervation in morphology? The reasoning process of EMG physiology is not specific to predict morphological changes.

Answer 1

One of the first things to appear after denervation is fibrillations and positive waves of course. Following that (in about 2 months) the first signs of reinnervation are an increase in the number of phases of a motor unit, polyphasic potentials (check out: https://www.teleemg.com/new/jbr120.htm Neurogenic Motor Unit), and increased instability of the MUAP (high jiggle) with decreased recruitment followed by an increase in the amplitude.

Answer 2

Further comment on evidence of reinnervation in addition to concentric EMG findings. The Fiber Density (FD) increases after reinnervation due to collateral sprouting. The increase of FD indicates that muscle fibers increased for the same motor unit. The FD therefore, is a most sensitive method to quantify reinnervation, and therefore, the local organization of motor unit (morphology!). Also, FD corresponds to type grouping in pathology.

EMG Technique (fasciculations)

Is there a way to distinguish between benign and malignant fasciculations ELECTROMYOGRAPHICALLY and most of all CLINICALLY? Is it true that rhythmic fasciculations tend to be benign while a singular big thumps tends to be malignant? is it true that brief fasciculations tend to be benign. Is it true that coarse fasciculation are usually benign while the malignant ones are very fine ones? What of all that is true and how it reflects in EMG.

Answer 1

This is a very common concern and generally no single answer is satisfactory because almost every single rule you make to define a benign versus malignant fasciculation has an exception. Generally speaking though I can tell you that Neurologists rely on far more than the presence (or absence) of fasciculation potentials to make the diagnosis of ALS. If fasciculations become worrisome to a patient, I generally recommend they seek a qualified neurologist’s opinion to ease their fears, because the worst thing they can do is to self diagnose them with the disease.

Answer 2

The best measure of benign versus malignant fasciculation potentials comes from the EMG needle exam by the company they keep…in other words… if fibrillation potentials and positive sharp waves are present with large motor unit potentials and polyphasic waveforms with poor recruitment…along with fasciculations…this would tend to suggest a more ominous potential…A good history and physical exam is a priority…remember an EMG exam is only an extension of our physical examination.

Single Fiber Amplifier Settings

I am having a minor debate on Amplifier settings for SFEMG. (I believe the Filters were changed on my system.) What are the recommended settings and have there been any recent changes in them? Specifically, I am concerned about the Low Frequency Filter Setting. What would be the upper limit? What is the typical setting?

Answer

The recommended or typical filter settings are LFF 500 Hz and HFF 10 KHz. I may use LFF 1KHz (narrower settings). This LFF setting would reduce the disturbing distant muscle fibers. This setting, however, affects the shape of the single fiber potential. But it should not affect the jitter value or fiber density reading. I am not aware of recent changes. However, if detailed measurement is needed for the shape of action potential, then use more open filter settings LFF 2 Hz and HFF 20 KHz.

Theoretical guidelines vs. practical for thoroughness of EMG studies

Having read the guidelines in the online EMG manual for the thoroughness of the study of a muscle (i.e. testing 20-25 units for both spontaneous and voluntary activity, calculating average amplitude phase etc.) I am curious why it seems these guidelines aren’t followed more often. Having had a number of EMGs in the past year in both local and university settings and in all cases only 3-4 units (1 insertion 3-4 directions) was sampled. One of these EMGs was overseen by a very renowned name in Electromyography (no names, but odds are you have one of his books on your shelf,) and even then 1 needle insertion per muscle. In a dialog with a doctor who does follow these guidelines, I was told many of the patients he performs EMG on tell him that his study is far more thorough than that done by their own neurologist. I fully understand the reasoning behind the 20-25 MUP guideline if for no other reason than to increase diagnostic accuracy. My questions then are twofold. Do most Electromyographers routinely follow these guidelines or are they followed only when the situation/case dictates. Secondly, how much diagnostic accuracy is there when only 3-4 units per muscle are tested, for example during a MND workup, and no abnormalities are found?

Answer

I agree not all EMGers follow these guidelines, although I do catch myself sampling less frequently in follow-up studies when I am only looking for changes.

Comment

My EMGs have been done locally. I certainly understand your comment about less stringent testing when verifying a change. My main concern is with initial testing where the results are negative, no sign of any disease process. With what degree of certainty can the electromyographer state that the muscle tested is normal when only testing 3-4 units in that muscle? Are they any statistics or figures on how the number of units sampled in a muscle corresponds to diagnostic accuracy rates? I can calculate numbers based on basic probability theory but was curious if any formal studies or accepted statistics existed. Thanks again and kind regards.

Answer

Tough question to answer. I don’t know of any studies of predictive statistics (for the number of muscles tested vs. diagnostic accuracy rate) That would be an interesting study. As for number of units tested, naturally if you find the abnormality in the muscle early on (with 3-4 units), you don’t need to go any further. But if you don’t, the general rule of thumb is to be more thorough to increase your chances.

Answer 2

I agree it would be an interesting study. From a strictly mathematical perspective it should be fairly easy to compute the “odds” of finding abnormalities. This is a lot like the classic probability problem of given that a person throwing darts can hit the bulls eye x% of the time, how many times must they throw the dart to have a given percent chance of getting a bulls eye. In the case of EMG the “x” can be the percentage of units in the muscle involved in the disease process. The number of throws would be the number of units tested and percent chance of getting a bulls eye would correspond to the odds of hitting an involved unit. The equation for this would be: ln(a) = ( ln(i)) / (n)) In this equation the variables are: a – the percent chance of hitting an involved unit expressed as a decimal (i.e. 56% = .56) i – the percentage of units in the muscle involved in the disease process as a decimal n – the number of units sampled in the muscle I have made several assumptions in this equation. 1. The involved units are randomly distributed throughout the muscle. 2. When the needle hits an involved fiber, the pathological signs such as fibs, positive waves, polyphasic units etc. will be visible to the EMGer. 3. The insertion points will be randomly distributed across the muscle. This is not entirely accurate since there would probably only be 4-5 actual insertions through the skin and then testing in multiple directions to get the 20 units. However assuming the insertions were not all done in the same spot, the equation holds. The results of this calculation clearly show why sampling more units can yield more accurate results. Examples: Sampling 20 units in a muscle with 10% involvement gives you a 90% chance of finding an involved unit Sampling 4 units in a muscle with 10% involvement gives you a 56% chance of finding an involved unit. Sampling 20 units in a muscle with 25% involvement gives you a 93% chance of finding an involved unit. Sampling 4 units in a muscle with 25% involvement gives you a 70% chance of finding an involved unit. Sampling 20 units in a muscle with 50% involvement gives you a 97% chance of finding an involved unit. Sampling 4 units in a muscle with 50% involvement gives you an 84% chance of finding an involved unit. So sampling more units in a muscle greatly increases the chances of finding an involved unit, especially early in the disease process. Kind regards

Answer 3

I read the interesting discussion on this point. I believe that few additional factors may influence the number of motor unit tested. Firstly, the experience of the neurologist or electromyographer. Secondly, the clinical examination of the patient. And finally, the degree of patient’s cooperation during sampling. It is also, basically, the same argument could be applied to the number of F-waves should be obtained for shortest latency. My kind regards,

Answer 4

Very interesting subject. About 4 years ago I was in Italy / Milano/. At the very famous S.R. Hospital I saw the following practice. The electromyographer there does not catch even one potential at single muscle. They say to the patient to do a slight effort, then observe moving potentials (do not record), after e period of few minutes they made conclusions e.g. MUP with growth of amplitude and area. I asked them how long of a period is needed to become proficient in this method: – 3 months

Single proximal conduction block, significance?

How significant should a single or isolated motor nerve proximal conduction block be as diagnostic sign, for instance in multifocal motor neuropathy, inflammatory demyelinating polyneuropathy or the “new entity” the multifocal inflammatory demyelinating neuropathy. Occasionally, I come across such an isolated finding, rechecked to exclude technical.

Answer

No single “isolated” abnormality should be diagnostic for a specific lesion. What is the waveform morphology? Abnormal temporal dispersion is usually absent in MMN. “Inching” along the course of the nerve often can demonstrate if the CMAP diminishes abruptly as in MMN, or progressively as in chronic axonal loss or demyelination. What clinical signs are present upon examination? Asymmetric distal weakness generally is present in MMN versus symmetric, proximal weakness in CIDP. The presence of a single proximal conduction block across common sites of entrapment is not helpful in establishing a diagnosis of MMN.

NCV “latency”

The Latency that is measured: 1.Does it depend on the distance taken by the examiner? 2.Does it depend on the amount of electric stimulation (such as the CMAP amplitude)? 3.Is it better when high or low?

Answer

Yes, the latency depends on the distance, the greater the distance, the longer the impulse has to travel and the greater the latency. It also depends on the amount of electricity you use; if you are submaximal, you are not stimulating all the fibers and your measurement will be inaccurate. That’s why in nerve conduction it is advised that you use supramaximal stimulation which is maximal stimulation + 25% over that to ensure stimulation of all the nerve fibers.

Timing of benign vs. pathological fasciculations

One small question, in your electronic EMG manual you state that benign fasciculations generally occur at 8-second intervals whereas pathological ones occur at a slower rate of 3.5 seconds. In another online resource that has video files of EMG findings: http://www.med.ohio-state.edu/physmed/videos/EMGvideos.html They say the opposite, “Non-pathologic fasciculations usually recur at a very slow rate (less than 3 per 10 seconds), while pathologic fasciculations most commonly occur more frequently than 3/10sec.” While I know that without other EMG findings (or lack of) it is tough to say one way or the other if fasciculations are good or bad but I am curious about these different viewpoints. Thanks again for providing such a valuable resource!

Answer

I am aware of the discrepancy in the literature on benign vs. malignant fasciculations. Over the years, I find myself no longer regarding this as black and white but rather find myself relying more heavily on many factors such as the shape of the fasciculation potential their distribution and what else I am finding. For instance, the more complex and “polyphasic” the morphology, the more likely I am to consider them pathological (I don’t like the term “malignant”). Other factors that enter my mind is their widespread distribution and the presence of other signs of ALS such as fibs and positive waves and neurogenic units. So I now rely on the “environment” in which I find the fasciculations rather than on one or two factors alone. Thanks for your kind words.

Comment

Thanks for the reply. I understand your point about what else you find being the true diagnostic criteria. I am curious though which theory is “supposed” to be correct or is there no real consensus? Also if it isn’t too complex what is the reasoning behind one being “slow” and one being “faster?” Again thanks for taking the time to help not only me but all the people who come here with questions. With kind regards,

Computer assisted EMG!

I know that some of the neurologists use computer program for the analysis of EMG needle insertion results. However, I am not sure how advanced these computer programs are! In my EMG exam I got the results within minutes after it ended (normal) and the neurologist told me that his computer program makes much of the analysis for him rapidly – for example MOTOR UNIT ANALYSIS! He said this advanced program analyzes the motor units! MY QUESTIONS ARE: 1.Does it sound possible (motor unit analysis done by a computer program? 2. some of the results of a muscle were (motor unit) (tibialis anterior) AMP (normal), Duration (normal), poly (normal) STABILITY (normal) INTERFERENCE PATTERN (normal) Is there any computer program that can analyze these features of MUP “alone” – I mean check these MUPS features for the neurologist without he analyzing it by himself? MY question refers mainly to motor unit stability (but also AMP, duration, IP and poly) – can the computer check if the MUAPs are STABLE without the neuro “doing this job”, can the computer tell by “itself” the motor units are stable and not polyphasic?

Answer 1

It is amazing what computers can do. I think we have not seen anything yet, still more to happen in the future. I can recall an American association of EMG and Electrodiagnosis session in 1984 about role of computers in EMG by Joe Jabre and David Hampton. The Computer program was able from that time to perform MUP parameter analysis. The software is getting better. The point that the computer is willing to help but I think working experienced human brain is always needed to rectify the technical problems, for instance, quite frequently you need to correct the position of markers during MUP analysis otherwise you may end up having false prolonged polyphasic unstable MUP.

Answer 2

Thanks for this interesting question! The truth is computers have come a long way since the early 80’s and can “assist” EMGers a great deal but not make diagnosis. There are still a lot of things that an experienced EMGer can pick up that can be missed by the computer. More importantly if the recording electrode is not placed in the appropriate area of the muscle, you feed poor quality data to the computer and as the saying goes “garbage in, garbage out”. So yes computers can be very helpful but no they are not smart enough to replace humans.yet.

Comment

I know computerized EMG is of great value! Your insight on this fascinating use of computers will be highly appreciated! My question is: (using the most sophisticated computer programs) – does the computer calculates and prints out specific answers or just “normal”/”abnormal” – for example MUAP A. Stability – does its output is: “normal stability”/ “reduced stability”,/”slightly reduced” or just “abnormal stability”. And for B. amplitude and duration – can the computer calculate them and “decide” by its own – whether these are within normal ranges? C. And what about the IP – can it “distinguish” several levels of reduced IP or it can just decide “normal/abnormal”? * I would appreciate your insight on these 3 features of the computer analysis (stability,amp-dur and IP) * when It does this MUPS analysis by “ITS OWN” how many motor units does it check (10,20,30,40) How much time does it take for it to check this number of MUAPs (seconds???) THANK YOU FOR READING THIS AND I WOULD APPRECIATE YOUR INSIGHT!

Answer 1

Yes the computer does all those functions, but of course with manual help i.e. operator should accept/reject the potentials. The system can take any number of MUPs, the operator should again decide that number.

Answer 2

This is a very general question as you can gather and different machines have different programs for different tests so it is impossible to answer this in a “wholesale” fashion. However, as far as motor unit analysis is concerned, most programs used usually give printouts of measures (numbers) for amplitude, duration and number of phases and some do firing rate analysis. Some do Turns and Amplitudes analysis. Some of these numbers are generated as numbers and some are plotted against a “cloud” of normal reference values and those, which fall outside the cloud, are called abnormal. Generally speaking, and realistically, only 5-6 different motor units can be properly analyzed from one needle location, because, as more motor units are recruited, the tracing becomes too complex for the program to analyze and the data generated less reliable. Most programs today on commercially available equipment can reasonably follow a contraction up to 30% of maximum and after that they become unreliable. To do a reasonable computerized motor unit analysis, it usually takes anywhere between 30-45″ or up to a minute per insertion.

Comment

It was pleasure for me to have your insight on the computer assisted EMG issue. You said you do not know what program did he use: well, He said this “is the most sophisticated EMG program and that it is able to do mups analysis almost alone! Yet; another question. What about positive waves and fibrillations- Is the program capable of detecting (distinguish them from other activity) and count them and at last print How many of them there were? (I think HE said it can) The output of the computer was: (all the insertions) fibs -0/10 PSW- 0/10 What DO these numbers mean? Is there any computer, which can pick up fibs/PSW by its own, distinguish them, count them and print their number without the examiner doing that?

Answer

Sorry, I cannot comment on all the specifics as these vary greatly from system to system and EMGer to EMGer

Comment

My question is again about the use of computers in a regular EMG test. Is there any computer program nowadays that can pick up fibrillations, count them and distinguish each one of them by its own. And then output for example: “3 fibrillations”? I know that each fibrillation has its own rhythm so that is why I am asking if there is ANY computer program that is able of distinguishing each one of them and of course, recognizing a fibrillation and distinguishing it from any other activity and all by its own?????? (MY main question is about the ability of any computer program to identify and recognize a fibrillation and distinguish it from any activity)

Answer 1

In the ones I am familiar with it is the doctor that picks the number of fibrillations he or she sees in the muscle and enters them into a report generation software in the computer which then prints it

Answer 2

Although there is none at present time but it sounds like a potentially possible idea to make a computer program to do such fibrillation and PSW detection and counting, similar to spike detection in EEG. Perhaps, it is a matter of time

EMG “Interference & recruitment”

What about the interference pattern and motor units recruitment?? Is There any computer programs that can “decide”” if the IP was full? What is the output normal/abnormal or it can also distinguish different levels of poor recruitment?? and motor unit stability? What is the output in this case? (stable/unstable or various degrees)? * In my EMG the neurologist told me the computer does mups analysis all by its self within less than a minute per insertion The results were: “stability: normal, IP: normal” and he told me his new computer program can decide and check these two parameters by its own. Is it possible (regarding these two parameters)? And what would be the output (the question above)

Answer

Again not knowing the specifics I can only answer this question in general terms: The IP is (usually) studied with a program called the Turns and Amplitudes analysis. This is pretty rapid and can give an idea of the interference pattern. It usually plots the data inside a normal population cloud. If your data is inside the cloud the IP is OK, if it’s outside it is not. So the output here is graphic. Stability is decided upon by what is called a “jitter” between the various components of the motor units, and again, since motor units are only adequately analyzed at a 30% level of maximum, only those which could be appropriately analyzed can be called stable or unstable. So the output here essentially is text

60 Hz Electric interference

When putting the needle (in my EMG) in left triceps, there was a very steady wavy line instead of the normal straight normal line my neurologist just could not reach the desirable wavy line. (I think there was not any sound) – during voluntary activity everything was normal. IT was a steady (“sine like” or “snake like” wave) – I think It was not fibs- because there was no sound and fibs look more like spikes – mine were very very wide “tall”, “fat” regular steady waves. They were upward negative (thus, not PSW). And it was so steady. I think I recall He said It was nothing pathological, but an electric disturbance from the background. Does my description sound like such known electric disturbance from the background? What else could it be? And if it is an electric disturbance from the background – Does it have ANYTHING to do with the condition of one’s muscle (poorly relaxed for example) because it was normal straight line in the right triceps.

Answer

What you describe sounds like pure 60 Hz interference from nearby devices or a poorly attached ground. None of that is pathological, just electrical artifact.

Can EMG test flexibility?

Could anyone advice me if EMG can test flexibility and if so are there any references you could give me.

Answer 1

Certainly the muscle flexibility is important in sports and athletics. It generally would reduce injuries. In “routine” or the conventional EMG, we do not measure or test for muscle flexibility.

Answer 2

Routine EMGs cannot assess the flexibility of the muscles rather it is only a diagnostic tool. Flexibility is best measured clinically.

Answer 1

Certainly the muscle flexibility is important in sports and athletics. It generally would reduce injuries. In “routine” or the conventional EMG, we do not measure or test for muscle flexibility.

Answer 2

Routine EMGs cannot assess the flexibility of the muscles rather it is only a diagnostic tool. Flexibility is best measured clinically.

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.

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.