Low Back & Leg Pain - Part II

LL burning and weakness “p. neuropathy vs. myasthenia” Top

Question

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 Myathenis 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.

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.

Numbness after a myeloscopy Top

Question

After a lamenectomy in 1992, I began having severe pain in my left leg. I started getting steroid injections, which lasted only a short time. Was told I had a lot of scar tissue pressing against my nerve and a myeloscopy would remove some of the scar tissue. After having this done, I woke up having decreased feeling in my left leg and mostly my foot. It has s been 15 months and there is no change. I limp and have limited flexion in my ankle. I’ve been through therapy and it hasn’t helped. Doctor is not mentioning an EMG, could I request this or even demand that I want it done? This is compensation and I have been back to work but it is very difficult to function.

Answer

EMG should be helpful in your case to confirm the lesion and how severe particularly because you have numbness and limited flexion of the ankle, suggesting muscle weakness. At this stage (15 months passed from second procedure), if EMG changes seen could be related to lesion 15 months ago or from the older lesion of 1992.

Effect of hand Squeezing on LL NCV Top

Question

When Having my conduction velocities study, It seemed that the neuro could not get what he wanted when giving me the electric stimulation to my legs (peroneal, tibial nerves), he then told me to squeeze tightly my hand and only then did he got what he wanted to get and said all was fine.

Dear doctors! What do you think he could not get (I think I recall he said It was the Amplitude)? Was it "legal" - I mean I am just curious whether getting "the wanted NCV result" that way is all right and not "cheating"? THANK YOU FOR READING THIS AND RESPONDING!

Answer

That's is usually to get the F-wave (http://www.teleEMG.com/Chapters/jbr070.htm) in the lower extremity, and it is a "legal" maneuver.

Answer 2

Squeezing the hand during EMG helps to get better amplitude fro the evoked response: F-wave, H-reflex or a motor evoked response. Squeezing the hand is also asked to at times, by physicians during a clinical examination to obtain better deep tendon reflexes.

Hand contraction with EMG of LL Top

Question

In read in previous post that it is quite common to ask the patient squeeze his hand in an EMG. A month ago I had my EMG and the neuro said he was not getting good CAMP amplitude as He had wished to, so told me to squeeze my hand. He also "hit" me with tremendous currents, and then he got normal CMAP. (Also read posts in this forum about it)

About the nature of CMAP amplitude - A. How far can it change with higher currents, can it get from 2 to 15 MV (in supramaximal stimulation+25%)? in MU - How much can it change in low and high currents? B. In which current does he have to stop? Is there a "limit current" in which more current would not produce higher amp or "the sky is the limit"? C. And about the "squeezing the hand" thing - IN MV- HOW higher can it get? I mean, how much additional MU can squeezing the hand yield? (2,5,10,15)? And MOST importantly for me why some people get the right CMAP amplitude without squeezing the hand while others should do so - Does it depend on the physical condition of one's nerves or not - I mean if he asked me to do so - Is there a problem (even minor) with my nerves?

Hope to get your insights on these "CMAP THINGS"

Answer

As pointed out in previous posts that squeezing increases the motor response, it works by enhancing the response. Of course it will work to certain limits. To answer your point, it may increase from 2 mV to 15 mV. Once the maximum level or value is reached, then any further increase of current will lead to stimulation of the nearby nerves giving a false result. Therefore, only a 25% increase of stimulus is added after obtaining the maximal CMAP response to avoid such stimulation of other nearby nerves. All commercial EMG machines have limit of stimulation, which cannot be exceeded for patient safety. This squeezing method does not reflect any pathology of the nerves but just a physiological variation between individuals.

Comment

What Do you mean by maximal response? How can the examiner know when is the maximal response for a certain nerve? Because as you said, the higher current you give the higher amplitude you get! So how Does the examiner know when he had reached the point where he gets false increase from nearby nerves? How does he know what is the real "maximal CMAP response for a nerve”?? (And that from now on he crosses the limit of stimulating neraby nerves)

* What would be the range of normal CMAP for the peroneal? , Tibial? And ulnar?

Answer

The following should help to get the best response. First of all the examiner should be familiar with the anatomy of the peripheral nerves. A surface electrode is used for stimulation; it is easier and less uncomfortable for the patient. The cathode of the stimulating electrode should be placed over the nerve closet to the recording electrode. The anode is placed parallel to the nerve, away from recording electrode, you may rotate it to minimize stimulus artifact. The nerve should be stimulated with stepwise increasing strengths. Enough current must be applied to activate all of the axons of the nerve. This amount, called supramaximal response can be obtained with an electrical stimulation of 10-75 mA and pulse duration of 0.1-0.5 ms. Over stimulation would produce latency artifactually short or a conduction velocity too fast for that nerve. Also, stimulation of adjacent nerves could produce CMAP larger than expected and has initial positive deflection (except tibial nerve). That how I would make sure it is a response from that particular nerve and no contribution from other nerves. This problem is encountered commonly between unlar and median nerves at thr wrist. Normal values from Liverson and Ma 1992: ulnar CMAP between 4-22 mV. Tibial CMAP 5.8-32 mV. Peroneal CMAP 2.6-20 mV.

Nerve damage and treatment for severe pain in LL Top

Question

Had ACL reconstructive surgery 7 months ago and about 5 months ago I started having severe burning pain in my thigh. Like someone holding a branding iron to it. The pain is from my hip to my knee in varied spots. My neurologist has done many tests and his conclusion is that I probably injured it in PT. The nerve either got compressed or stretched. Is this something that goes away on it's own. He has suggested that I take steroids. Should I stay off of my legs? Because walking really irritates it. What are some other things I could do to help this heal?

Thank you I'm so desperate

Answer

In your case seems to be compression of the lateral femoral cutaneous nerve (meralgia paresthetica). But please tell me what is ACL stand for?. If it is meralgia paresthetica, then usually the symptoms would ease with the time which is variable between one patient and another. About the steroids, it is actually up to your treating doctor to decide the best treatment for you. Nerve conduction studies may help to diagnose although technically may be difficult and EMG needle examination may be done to rule out other causes. However, it is primarily a clinical diagnosis.

Comment

Thanks so much for your reply. ACL is one of the ligaments in the knee. I tore it in an injury and bruised my shinbone. So I had surgery to replace the ligament on 10/18/99 and the pain in my thigh started around mid Dec. For nerve damage is it usually recommended to stay off your feet? Cause it seems to hurt so much more after walking etc. If not, should I use it as normal and exercise as well? Is icing recommended for nerve damage? Thanks again for your comments.

Answer

Thank you Laura, gradual building up of excerice is good idea, but of course this depends much on your knee. I would also recommend the cooling therapy. All the best.

Can exercise delay or will it help to nerve healing after damage? Top

Question

I am so confused about what to do to help with the healing process of a compressed or stretched nerve in my thigh. It hurts so much after walking. The pain has neither gotten worse nor better in 7 months. But it does subside if I don't use my leg at all. As soon as I go back to regular activity the pain starts. My question is this: Can exercise prolong the healing or will it help to heal it. So should I grin and bear the pain and eventually it will go away or should I stay off my leg. Am I damaging it more by exercising? My thigh muscle is just about gone at this point form atrophy. Help!!

Answer

I think physiotherapy would help but it should be under care of physiotherapist. Taking advice from Pain clinic is another option.

Is it neuropathy or not? Top

Question

In letters to my G.P. my neurologist has noted that I have "decreased pin sensation, temperature distally in the lower extremities. Position sense and vibration sense are normal. Deep tendon reflexes are absent in the lower extremities and +1 in the upper extremities..Babinski's sign is absent." He recommended EMG/NCS. After testing, he reported ". Normal sensory nerve conduction in the left superficial peroneal nerve with distal latency of 3.68mS..motor nerve conduction in the right peroneal nerve is within normal limits with a velocity of 40 meters per second and distal latency of 6.40 mS and left peroneal nerve with a velocity of 44 meters per second and distal latency of 5.20 mS. The H-reflex in the right and left tibial nerves is abnormal in that there are no responses. He concluded ". Not enough findings to really indicate definite neuropathy since the sensory and motor nerve conduction are normal." Entering the left superficial peroneal nerve distal latency of 3.68mS and the appropriate age, sex, and height (41, M, 190cm) into the appropriate boxes on your lower extremity sensory/H-Ref teleEMG calculator (thank you very much) produced an MRV of -4.2. I wasn't sure how to use the lower extremity motor calculator, but it may have produced negative MRVs of -1.1 or closer to zero. Three questions: 1) Neuropathy or not? , and 2) Can you recommend an unrelated source for normal values of EMG/NCS (I'm looking for corroboration) including books, and 3) recommend additional means of investigation and/or wait for progression. Based solely on reported findings (no foot problems, though arches somewhat high, thanks for asking), and slow progression over perhaps eight years or longer (just detected this, though deep tendon reflexes gone for at least six years), I am inclined to suspect some sort of very mild hereditary sensory neuropathy? Please reply. Thank You.

Answer

Looking at your history and NCS data; you have some symptoms and signs to suggest neuropathy, and some data in NCS to support that (absent H reflex, right peroneal latency of 6.4 ms and CV of 40 m/s). Absent H reflex is definite abnormality (neuropathy is one cause but not the only one), and peroneal nerve, to me, it is slightly slow but it varies according to laboratory normal limits, but anyhow, not enough by itself to say peripheral neuropathy even if abnormal. However, additional information would be useful and important for instance, sural nerve, amplitudes of motor and sensory responses, F wave and needle EMG examination and perhaps additional test for small fibers (sympathetic skin response). Looking at the duration of symptoms seems to be very slowly progressive if any. I think a follow up study is worthwhile after several months. About the last point being hereditary or not, I would say, this study cannot tell you that, you need more information in the history and further genetic study that could be discussed with your neurologist. I hope this is helpful.

Comment

Isn't a conduction velocity of 40 completely normal for the preoneal nerve?

If not what are the limits for this nerve in your laboratory?

Answer

MCV for peroneal nerve is 41 m/s or faster.

Relationship between Sciatic Nerve Problems and Femoral Nerve Problems Top

Question

I recovered from Sciatica about 6 weeks ago, thanks to a series of acupunture treatments (Which I highly recommend to anyone with this problem). I was told this could be due to problems with one of the discs slipping slightly in my lower back and resting on the Sciatic Nerve.

I now have pain in the front of the same leg due to I think Femoral Nerve Problems. Are both these afflictions related? Could it be the same disc slipping in another direction?

I am currently taking anti-inflammatories and will be attending the acupuncturist again, but I would like to know what preventative therapy I can do in order to not have either problem recur?

Answer

Sciatica is common problem, derived from sciatic nerve as the name implied, but actually it is not compression on sciatic nerve but due to slipped disc at lumbosacral level. Other synonyms are radiculopathy, prolapsed intervertebral disc. According to your description, your symptoms are closely related but due to adjacent slipped discs. However, I assumed that your pain in the front of "leg" is related to the slipped disc and not due to femoral nerve because the later one would have the pain in the front of the "thigh" and not the leg. Clinical examination and EMG will be very helpful in your case. General measures to avoid or prevent disc problems are rest, give up smoking (to reduce coughing), avoid constipation, avoid lifting heavy objects, to pick up something kneel rather than bending your back, etc. Other instructions and exercises could be obtained usually from physiotherapist.

Goosebumps on thigh  Top

Question

For the last three months or so, my husband and a friend of mine have been experiencing goosebumps on their right thighs. No pain involved, but it happens whether they are sitting or standing. Both are pretty muscular.

Answer

As there is no pain (or other symptoms), these Goosebumps seems to be?” Fasciculation=twitching" confined and repeated at single same place, this is benign, and physiological or could be related to exercise. If they are widespread, then you may seek neurologist advice.

EMG Test after injury to Cauda Equina  Top

Question

I had a laminectomy 8 months ago to relieve compression of my L5/S1 nerve root and L4/5 large herniation. I have bladder, bowel, sexual dysfunction and numbness in both my saddle area and left foot. What can EMG tell me about my prognosis?

Answer

EMG can be used to assess the extent and severity of the lesion, these are important in determination of prognosis. Also, it could detect the signs of nerve regeneration. Thus, it can predict functional recovery.

Fever and Jaundice followed by abnormal gait  Top

Question

My son is a 13-year-old Pakistani boy- 4 years ago he had 2 episodes of prolonged fever and 1 attack of Jaundice and 1 attack of Measles in 3-4 consecutive months.... Since then he has developed a gait - he puts all his weight on the toes and his feet are flat- he walks abnormal dragging his feet and legs stiffened...

Please if you could do anything to help my son - I’d be grateful - if You would like to have a chat with me on the internet about his reports - u could write me back the time and date - or if u want to view some of his reports of his tests in India - I could mail them too- whatever it is - I need your help, support and guidance - Please!!

Answer

I read your note and I am not sure I would be able to help but I can give you some ideas. The symptoms you describe in your son's gait seem to originate from the spinal cord. In some of the infections you describe, involvement of the nervous system, particularly of the spinal cord may occur. Some of these diseases may be treatable by antibiotic and some may not. My advice to you is to seek the help of a physician who specializes in infectious diseases that are common in your area, and they will be able to put the whole group of symptoms together, not just the neurological findings, which I do not believe are isolated.

Needle EMG and Radiculopathy  Top

Question

Is a needle EMG always required to suspect that a patient has radiculopathy or can a Dermatomal Evoked Potential Test and/or a Somatosensory Evoked Potential test raise suspicion that a patient has radiculopathy?

Can a chiropractor or a podiatrist perform a needle EMG?

Answer 1

Evoked potentials test the sensory roots (they go from the periphery to the spinal cord) but don't test the motor roots, those which, through the muscle, control movement. Therefore Evoked potentials can only tell you if you have a sensory radiculopathy. Only Needle muscle examination can tell you if the motor root is involved. You should also know that some studies indicate that EMGs may be (falsely) negative in up to 30% or 40% of root lesions.

Answer 2

For your second question, the chiropractor or a podiatrist is not allowed to perform EMG needle examination. It is only allowed and practiced by a qualified medical doctor all over the world.

30-40% false negatives  Top

Question

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

Thanks for the clarification. 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 contribute 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.

Role of EMG in Lower back pain  Top

Question

Is there discomfort with EMG for lower back problems? What can I expect and what is procedure? What can EMG diagnose for lower back? Have small herniated disc L5 S1. Orthopedist can't find reason for continuing back problems. Symptoms recently changed following physical therapist realigning hip joints. Now on L side with pain on buttocks and thigh almost like a mild leg cramp when standing or sitting for more than a half hour, which intensifies with time. Relief after a few hours only by lying flat on back with pillows under thighs. If I get up to stand or sit discomfort comes back.

Answer

EMG is important tool in diagnosis of radiculopathy. It will help you to confirm the root involvement, its level and severity, sometimes when even the imaging studies are normal. The EMG examination utilizes an electrode or needle probe, which is inserted in a muscle. It is not that bad but does cause little discomfort. This discomfort is variable between persons. But it is well tolerated in majority of cases.

Comment from another Patient

I just read your post as I was looking up info on having an EMG test done. We seem to have identical back problems, and I was wondering how everything has turned out for you. If you should get this post, I would love to hear from you.

Comment from third patient

I experienced similar pain, after pt. It should improve in a few weeks or may be a two months at most. Don't be alarmed. If the pain persists see another physical therapist, the one you saw may have over did it.

Role of EMG in chronic upper back pain   Top

Question

I've had chronic upper back pain for over 8 years now. All imaging has come back negative. Recently a doctor sent me to a pain therapist that did a surface EMG. The readings showed that there was a lot of activity even at rest and large spikes at a constant rate (about 1 per second). The chronic pain I feel is much deeper than the surface muscles. Are these readings consistent with chronic pain or could it point to the problem? Would a different type of EMG deeper be of more value? Any advice would be appreciated!

Answer

Chronic back pain can be due to a multitude of causes, one of them being disc disease causing a pinched nerve. So negative imaging simply, in most cases, indicates that there are no disc or disc fragment protrusions, or other spinal abnormalities. Surface EMG explores only the superficial muscles of the back and continuous activity at rest and large spikes are simply an indication of a lack of relaxation of these muscles, such as could be seen in muscle spasms, which you already know you have. I wonder if you've ever had a full EMG done (Nerve Conductions and Needle Exam) or seen by a Neurologist. In most cases the EMG will detect whether or not you now have, or had in the past, any pinched nerve causing your symptoms. If not it would be a good idea to have a full EMG, at least once. Doctors who are specialists in chronic back pain and are familiar with treatment are Neurologists and Rehabilitation Medicine specialists.