Why do they do an EMG for diagnosing MS?

[MissLauraI]

Hi everyone-
I had my EMG today (ouch) and it all came back normal. My feet turned purple so the dr. thinks I have peripheral neuropathy but knows this does not explain my MS symptoms. So my question to all of you who are experienced- why do they do an EMG for MS?

Is a normal EMG indicative of no MS or just ruling out other stuff? I am confused about this.

Also my leg was so weak and I am now so fatigued after the test- is this normal?
Thanks for all your answers!!

[mexicanrose48]

I too have burning feet. Usually the burning will start when I'm starting to rest.,& the burning will last for about 1hr. The bottoms of my feet become quite red, & my toes burn. When the toes start to burn, I know without looking that the bottoms of my feet will be red. I have had a spinal MRI which shows that I have several bulging discs, with many degenerating discs. Also, there are places at the bottom of the spine on both sides that are medium-to severely narrowed. There is no mention of nerve impingement.
Nerve Conduction test & EMG are normal...but I have since learned after doing a lot of research that these tests don't detect small fiber neuropathy.
Blood tests have come back completely normal. I see my Neuro again Feb. 1 so will ask for skin biopsy & whatever else tests may be available to explain this burning. I also get the odd feeling of pins/needles in my calves too.
My Neuro said that according to my history & physical exam, she did not see an indication of MS. Although a Neuro, she also has a sub-specialty in MS.

[MissLauraI]

Ess and Bob-
I think since the doctor mentioned both small nerve peripheral neuropathy and Raynauds, that is why I am confused. But now reading both your posts...I do have lots of burning pain in my feet, so bad that just putting them on the floor hurts.

I also have the bright red/purple coloring and cold/hot temp. issues in both feet and hands. So maybe he was considering both. He said it was not connected to all my other symptoms, however. He also did not give me any solution/treatments. Thanks for giving me more info on that.

Sumana- I think maybe it is important as part of the elimination process from wht I am gathering here. Where are you at in your dx process?

Cheesymum- that is one of the great things about the forum. Sometimes you don't even know you don't know. I have found that out by reading here. So much I never knew about MS. Like who would know to ask if UTIs are an MS symptom? They seem so unrelated. Yet they seem to be common. Things like that. We all get to benefit by each others experiences. Very HELPFUL!

[COBOB]

Small fiber neuropathy is detectable by nerve biopsy.  It is also unique in that small fiber typically causes burning/itching pain, not numbness.  A small punch biopsy and histopathology can be used to rule out SF Neuropathy.

Bob

[essdipity]

Well, hold on just a sec. You may have small fiber neuropathy, which is not detectable by EMG/NCS.

These are nerves close to the skin, and are not myelinated. I think they have a lot to do with temperature sensation, but I suggest you google this for better info. Small fiber neuropathy is a kind of peripheral neuropathy, that much I'm sure of. My neuro has diagnosed it in me, but it is quite incidental to my MS, and nothing to do with it.

I continue to have severe neuropathic pain in my right ankle, stemming from a fracture and surgery. Whether its origin is central or peripheral is unknown, and they're not interested in finding out, because the treatment is the same. One would expect that it's peripheral, but the CNS can do strange things too, especially in an MS patient.

So this isn't quite so cut and dried as it may apppear.

ess

[Sumanadevii]

I've never had an EMG....Hope it isn't important once MS is dx!!!  I do think it is one of those tests used to rule out other issues.....

[cheesymum]

Thank you so much for asking this question!  It's one to which I needed an answer but didn't know I needed it.  ( I know that sounds weird but...)  I, too, had a normal EMG a couple of months back and I wasn't sure what that meant but I had forgotten about it until you asked that question.  Thank you!

[MissLauraI]

Oh that is right he said something about  Raynaud's. Thanks Bob. I think i got mixed up :D

[COBOB]

What make you think you have peripheral neuropathy?  If you have peripheral neuropathy you will have an abnormal SNAP on the EMG/NCS.  

If you mean you have paresthesias, and sensory symptoms, that is not the same as peripheral neuropathy.  Peripheral neuropathy is damage to the peripheral nerves and it is normally diagnosed by EMG/NCS or nerve biopsy.

Your feet turning purple seems to be more an indication of a vascular issue than a neurological issue.  Raynaud's or PAD maybe.

Bob

[MissLauraI]

Thanks Lulu! I love it when tests come out "unclassical". It is like the platypus of the medical world :D

cainer- yes the nerves...the big ones...sre fine according to the EMG. I guess the little nerve fibers have the peripheral neuropathy.

Bob- I see...that makes nore sense to me. I am still a little unclear why he said the test was normal yet I have peripheral neuropathy.

Ess- I see how that would work. So I guess that is why the next test is the EEG?

Thanks for all your help!! Greatly appreciated!

[essdipity]

I'd say this boils down to a rule-out test for MS. Most of us have had it, at one point or other.

If the EMG is normal, then the problem is not in the peripheral system. Figuring out what's going on in the central system is the logical next course of action.

Good luck with this,
ess

[COBOB]

Technically, MS is a disease of the central nervous system (brain and spinal cord.)  EMG/NCS tests peripheral nerves to the root nerves of the spine.  A normal EMG/NCS means the peripheral nerves and root nerves are fine.  MS should not effect the EMG/NCS results.

Now pain and/or motor issues in a limb can be caused by either CNS, peripheral nerve damage or both.  A normal EMG/NCS typically points the clinician to look for a CNS cause for neurological issue in a limb.  An abnormal EMG/NCS says there is peripheral diaease, but doesn't rule out the CNS as a contributor.  

Bob

[Lulu54]

Funny, but that darn EMG can tell them whether the nerve damage is from peripheral neuropathy or if it is part of the wonky central nervous system.  THEN there are people like me who have an EMG that gives both results.  Yep, I have PN and MS damage to my right leg.  It really confounded the doctors when they read my results and had the test done a second time.  It was still the same.

hope your legs stop jumping and twitchiing, soon.  
Lulu

[cainer]

nerve damage  - so your doin good!! but your leg, just going through a emg will drain me-
maybe some will answer with more knowlege!!  hugs