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EMG/NCS. What do they show?

I've been referred for EMG/NCS due to weakness in my right leg & drop foot but I'm not sure I want to go ahead with the tests as I don't know exactly what they show and how helpful they will be. I've had discectomy L5S1 but been told this doesn't explain weakness in whole leg and loss of sensation in calf.

I've read up on the tests, but I'm not sure I fully understand what they can/can't show. Do they distinguish between damage to the nerves and spinal cord? If so, can they tell how much damage there is and the extent to which this should affect strength in your leg/sensation/pain?

I'm guessing that even if they do say if there is damage, they can't give an indication of how this was sustained especially if an MRI shows no compression of the nerve roots. I'm wondering what will happen if they come back normal or if they show minimal damage which doesn't correlate to the problems I'm having.


  • dilaurodilauro ConnecticutPosts: 10,760
    on Spine-Health EMG
    and some more EMG/NCS

    Ron DiLauro Veritas-Health Forums Manager
    I am not a medical professional. I comment on personal experiences
    You can email me at: rdilauro@veritashealth.com
  • Thanks Ron. Can anyone share their experiences of tests. I'd really like to know if anyone has weakness in leg and foot drop which doesn't show up as damage to nerve on these tests and what else this could be?
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  • dilaurodilauro ConnecticutPosts: 10,760
    My foot drop definitely showed up in some of my EMG tests. They noticed the number of dead nerves I had in my lower right leg.
    But that was just part of my foot drop.

    Because of the number of spinal surgeries I had and then add the two total hip replacements, my legs are not that strong. I am in a Catch-22 situation. I can exercise my legs to get them stronger, but there is a limit as to what I can do. Too much, and I start to have problems with my Iliac crest and prioforis muscle. Don't do enough and I have more problems with balance and foot drop.

    So, beyond nerve damage, you always have to take into consideration the condition of your muscles.
    Ron DiLauro Veritas-Health Forums Manager
    I am not a medical professional. I comment on personal experiences
    You can email me at: rdilauro@veritashealth.com
  • itsautonomicitsautonomic LouisianaPosts: 2,294
    I did and something I think gets missed is that these nerve tests only show damage to large fiber nerves , it doesn't show damage to small fiber nerves that can give a sensation of weakness, pain, loss of sensation, temperature issues etc. May have absolutely nothing to due to in your case but I think important to know
    Do your due dilegence, trust you know your body and question everything if it does not fit. Advocate for yourself and you will be suprised what will be revealed trusting your body and instinct.
  • For all your comments. I'm sorry to hear of your situation Ron, it must be very frustrating and difficult to know when you've done too much exercise. I will let you know what my tests show when they come around. Hoping to get some answers and have information which explains my foot drop.

    Yes, I have sensation problems and can't feel temperature properly in my leg. The doc explained this was different to the motor strength, but I wasn't sure exactly how this was the case so thanks for explaining. Is there a way of looking at the small fibers? I'd really like to read up on all of this so I'm better informed. I've read all the information on this site. Are there any books which explain more broadly about spine and nerves?

    Thanks for all your comments. It's always really nice to hear from other people. It can sometimes feel like a lonely place to be when you experience spinal problems!
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  • itsautonomicitsautonomic LouisianaPosts: 2,294
    Mine was diagnosed through QSART/sweat test and verified with punch biopsy. Punch biopsy is the easiest , cheapest way to go though. 10 min , a few little holes and you are done , the samples are sent in and analyzed.
    Do your due dilegence, trust you know your body and question everything if it does not fit. Advocate for yourself and you will be suprised what will be revealed trusting your body and instinct.
  • Thanks for this info, really helpful, I'll speak to my doctors about this!
  • itsautonomicitsautonomic LouisianaPosts: 2,294
    Lily I would suggest reading up about the small and large fiber neurapthy prior to that conversation. If you live in a small town and this isn't a neurologist I can almost promise you this may be something that dr isn't versed in or fully understands when dealing with small fiber damage., which may not even be what you are dealing with. Just a word of caution, to verify this fact I would bet not a single person here was ever told that their EMG/ conduction would not reveal small fiber nerve damage. It's all just process of elimination to find oroblem
    Do your due dilegence, trust you know your body and question everything if it does not fit. Advocate for yourself and you will be suprised what will be revealed trusting your body and instinct.
  • edited 01/03/2016 - 8:43 PM
    this is my 3rd attempt at posting so I am going to post the info I found I will add from my situation that will make more sense I will say I had 2 tests one in march and one in november in 9 months I went to chronic on a nerve root and it can not be regenerated. It is also the nerve thats supposed to feed the paraspinal muscle which is now showing atrophy. The more i try to exercise engage in activity it gets worse legs are going numb low back pain...and i'll mention my pain started in my leg never had back pain until surgery. I am glad I had the test. I did leave the 2nd test in tears but my damage was much worse then the one in march...if our test sounds like popcorn ask why....

    Have the test done by a neurologist I did mine with no meds now this is my choice....but I wanted nothing to interfere with the reading
    I had nerve root damage thats chronic along with other issues to date I also had a discogram after my micro on l4 l5 but i still had an annular tear so i needed a fusion

    heres the research I found helpful I AM NOT A DR....I AM NOT DIAGNOSING.....I AM PASSING ALONG INFO I DID NOT HAVE DROP FOOT
    There are generally three types of mechanical injury that can occur to a nerve; compression such as from a disc herniation, blunt impact (this can also occur from a disc herniation) and finally, a stretch injury. Stretch injuries occur from an arm or leg stretching beyond normal limits such as an arm forcefully stretched due to fall onto an object. If a nerve is stretched, it may simply recoil to its original length when the stretching force is released or the nerve may completely snap, similar to the stretch and snap of a rubber band. In general, a nerve can stretch about 6% of its length without injury. A stretch of more than 15% of the nerve’s length will cause irreversible damage.

    When the nerve cell is injured, generally the nerve membrane is damaged or the insulation (myelin sheath) is damaged. When the nerve cell membrane is damaged, the signal can be blocked which prevents the message from continuing down the nerve. The opposite effect can also occur. Injury to the membrane can cause “leaks” or ions to flow into the nerve at the wrong time, triggering an unintended impulse.

    The block of a nerve membrane prevents the signal from travelling up or down the nerve. This would result in numbness of the area served by the nerve or weakness of the muscle supplied by the injured nerve. A good example is foot numbness resultant from a herniated disc causing an L5 nerve injury. Foot drop is the inability to raise up the foot due to the muscle weakness caused by blocked signal from the L5 nerve (occasionally the L4 nerve).

    An unintended impulse that spontaneous occurs from the “leaky” or injured membrane (called an ectopic stimulation) will produce symptoms from that nerve just as if the far end of the nerve had been stimulated. A good example of this is foot pain due to an L4-5 herniated disc. Nobody has put a nail through the foot but nonetheless, the foot is still painful due to the injury of this nerve in the spinal canal. The brain cannot distinguish between stimulation of this nerve at the level of the foot vs. stimulation of this same nerve at the level of the lumbar disc.

    A nerve injury may have the possibility of significant recovery after the initial trauma or may never recover. Recovery depends upon the type of nerve injury. Unless there has been an obvious direct injury to the nerve (a knife or a gunshot wound), it is impossible to know what type of injury has occurred to the nerve. That is; was only the nerve cell damaged, only the insulation damaged or the entire nerve and insulation both been damaged? This makes a difference in healing potential. Unfortunately, MRIs are not powerful enough to look at microscopic anatomy to determine the type of injury to the nerve.

    The only way to know if the nerve will heal is to provide it the best environment to heal and then wait. Many times this means surgical decompression if a disc herniation or a large bone spur compresses the nerve. After decompression, only time will tell what injury the nerve had suffered and what recovery is possible.

    Muscle Weakness

    Muscle weakness is caused by the lack of some muscle cells in one muscle group receiving the signal to contract. This is due to injury to portions of the nerve bundle connecting to each individual muscle cell. (A nerve is really a collection of thousands of nerve cells in one bundle- something like a telephone cable with thousands of individual wires within the cable).

    Obviously, if the entire nerve was severed, the muscle would have no ability to contract and the joint would be “limp”. Weakness means that the nerve is still partially intact but not all individual nerves are functioning. Due to the loss of some neurons, only a small portion of the muscle cells will fire in that muscle group. Since many of the muscle cells are not getting the signal from the brain to contract, the ones that are still connected are too few to yield a full contraction. These working but overloaded muscle cells fatigue easily as they are overtaxed with work and cannot “keep up” with the load. This is why with continued exercise, the involved leg or arm feels even weaker.

    Forum rules state ..........
    0.05 Any outside content or material directly quoted must include a reference to the location the source from which it came.

    Liz, Spine-health Moderator
    This can't be happening
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