My neuro just called about results...

[cardiactec]

My neuro just called about my evoked potential test results .... He said the visual part was normal and that my arms were normal (with the sensory part) but that my legs were not ...... he said he's not sure specifically what is going on but said that my EMG abnormality could be caused by a central nervous system problem, but that it also could still be peripheral ....

at this point he said he wants an MRI - which for me will require surgery due to the fact that i have a stomach pacemaker implant....

He said he doesn't think I have MS, but wants the MRI anyway .....

What would cause evoked potential test to be abnormal just in the legs?? Could it still be MS??

[cardiactec]

Very interesting information. My neuro pretty much said the same thing you said, Bob. At this point it is hard to tell if this is central or peripheral issue but soon to shed some light into all this will be with the MRI. I am in the process of scheuling surgery to remove my stomach pacemaker so I can actually GET the MRI.

Phew.... tough ride lately.

Thank you ALL for listening to me and contributing your thoughful and helpful insight regarding my situation!

[COBOB]

EMG is kind of a two way test. Stimulus (shock) goes up.  This is the SNAP (Sensory Nerve Action Potential.)  It travels up to the CNS and comes back as CMAP.  SSEP is a one way test.  It measures from the stimulus to the brain.  Someone mentioned "small fiber neuropathy."   My understanding is that the diagnosis of small fiber disease can really only be made with a peripheral nerve biopsy.  This is a sensory disease of the axon conduction  unrelated to myelin since small fibers don't have myelin insulation.  The large nerves running from the spinal cord roots down the limbs are myelin covered and are not considered "small fiber."   The problem here is that even if small fibers are damaged, the stimulus may be enough to exceed the action potential threshold of large myelinated nerves.  

A lot of neurodiagnostics is dependent upon technique.  You also have to look at all of the data (stimulus voltage and time, SNAP, "P" times, etc.)  There is actually a subspecialty in Neurology for Neurodiagnostician.   There is also some emerging research that say MS may have effects on axons, so it may be more that just myelin being attached.  If that os the case, we may find that MS has has a different set of effects in the peripheral nervous system.

Bob

[Nancy T]

I don't know the answer to your question about whether BAER can show problems with swallowing and TN (I do not think so, but I'm definitely no expert). BAER tests (only??) the auditory pathways, I think.

But I do know that even an abnormal BAER can be blown off.  I had "highly abnormal" results on both sides--literally off the charts--and yet the neurologist who ordered the test, a specialist in dizziness and hearing, didn't seem too concerned. He chalked it up to "cranial neuropathy" and that was that. No further testing because my MRI only showed small scattered lesions (which he didn't even tell me).

So, you might get the BAER but not get any answers anyway. Stumping the best neuros in town is not as unusual as you might think. In fact, I think it's quite common, to judge from my own experience and many other people's stories that I've read.

As you might have guessed, I was never diagnosed with anything.

But I hope you find out what's going on with you. Good luck!

[cardiactec]

Hey Bob,

Just wondering if you had any insight to the above? I'm going to try and summarize the above to my neurologist when I see him in a few weeks, but just wondering if you might have any thoughts on it in the meantime ....

THANKS A BUNCH!!

[cardiactec]

Thanks Bob for your detailed and understandable explanation. Makes sense.

What I don't get is how my EMG (not the NCV) was abnormal in both my left arm and left leg and that the SSEP was NORMAL in my arms (both), including my left arm, which has been giving me the most symptoms trouble wise. My right leg (and left) on SSEP was also abnormal on SSEP and I have had little to no symptoms in my right leg, except for two episodes (brief) of burning
thigh. But also, just to add (and don't ask me why this wasn't done), my right side on the EMG/NCV was not even tested so there's no way to know if the same abnormalities (mild polyphasia/reinnervation) was going on with that side of the body too, and, if that might be why the SSEP was abnormal on my right leg also.

Can things like mild polyphasia/reinnervation throw off test results of the SSEP? If so, if I  have polyphasia and reinnervation going on with both my left ARM and left leg, why weren't abnormalities detected in my left ARM during SSEP?

As for why my neuro would order SSEP after what he referred to as "essentially normal" EMG, speaking of the polyphasia and reinnervation, which he said could be indicative of either peripheral or central nervous system disease OR a variant of normal, I think he was honestly investigating the possibility of making the picture clear (or clearER) by doing SSEP to see if he could distinguish btwn peripheral or central issue (from what I picked up on)......because the visual part of evoked potential was normal and my arms as well, he's not so sure it's MS anymore but still wants an MRI because of the abnormal SSEP in the legs ( I guess most people with MS have abnormalities on visual evoked potential (???) and because mine were normal, that is why he doesn't think MS (???).....

On a side note to the above, none of the testing done with evoked potential or EMG/NCV explains the symptoms I'm having with swallow problems, chewing problems, and face/jaw pain/spasms..... Not sure If they can evaluate central or peripheral issues with emg/NCV and/or evoked potential for the swallowing, chewing, and/or face pain problems.... If so, no testing was specifically done on those areas on my body (throat/face)....testing with EMG was done on my neck (the back) region and also in two places on my back (including lumbar region) and testing in those areas was normal.

Confused? YES! But even worse than MY confusion is the fact that all of this has seemed to stump BOSTONS FINEST for neuros!!

[essdipity]

Actually, peripheral neuropathy is quite possible with a normal EMG/NCS. That is, if it's small fiber neuropathy, which I'm told I have (I wonder, though.).

I also have normal SSEP and MS, as well as essential tremor.

ess

[COBOB]

Normal EMG/NCS pretty much rules out peripheral nerve problems (neuropathy.) SSEP is easier to evaluate if you also have an EMG/NCS to look at.  Normal EMG/NCS with abnormal SSEP indicates CNS issue.  Abnormal EMG/NCS from a limb makes me wonder why you would do SSEP from that limb.  Te value in an SSEP is when the peripheral wiring tests good (or at least "pretty good.")

Well, the legs come into the spinal cord via the "horse tail fibers" in the lumbar.  The arms come into the spinal cord at the cervical level. Keep in mind, that the front of the spinal cord has most of the motor nerve connections and the back of the cord has most of the sensory nerve connections ( the ventral spinothalamic paths) . If it is both legs, I'd think -- lesions in the spine. If you have local segmental reflexes issues I'd think spine.  If it was just one leg and a normal EMG/NCS and you had brain lesions on the opposite side, I'd really think a cerebral lesion.  

We write off the small lesions in the white matter, but the primary somatosensory cortex right behind the primary motor cortex in the that runs right through the parietal lobes of the brain. So pain and motor issues in one limb on one side of the body could be related to issues up the the cerebrum of the brian.  This is what the Neuros get paid to figure out.  This is not all that simple to evaluate.

Bob  

[cardiactec]

Thanks Bob for the Neuro Anatomy and Physiology 101 lesson with your link. LOL. VERY informative! Let me know if you ever need a lesson in cardiac arrhythmia's - I'm your girl for cardiology! ;o)

[cardiactec]

Thanks "Red". So you have both neuropathy and MS? I had the nerve conduction test which was normal. It was the needle stick EMG that showed some mild neurogenic changes in my left leg and left arm....I'm actually surprised that the arm portion of my sensory evoked potential was normal because my left arm has really been acting up .... it was only my legs that were abnormal on the evoked potential....

If you have MS and have had a brain/spine MRI, did you have lesions on your spine? From what I've read, spinal lesions would cause leg symptoms along with bladder incontinence, which I have both (along with a host of other symptoms) .....

[RedFlame]

I had the same outcome, if I am reading your message correctly.  My evoked potentials were OK with the exception the SSEP which was grossly abnormal.  I had nerve conduction tests that showed absence of electric activity in both legs.  My current 'general neurologist' interpreted that as neuropathy.  

It is possible to have MS with neuropathy.  

I hope you have answers soon.

Red

[cardiactec]

Thanks Bob - still haven't had a chance to check out the link you posted but will definitely check it out today.

[COBOB]

It can pickup cranial nerve to brainstem issues.  I'm not sure what it shows "diagnostically"  in context with the other tests.  I know more about the equipment and the theory.  They never let Biomedical Engineers play with the patients. And my military medic experience is way outside dealing with most of this stuff.

I thought that Swallowing page might help you out a little.  

[cardiactec]

Since they didn't do the BAER on me, could they have missed an abnormality there that would have otherwise been picked up to explain the swallowing/chewing/face and jaw pain/spasms issues?

Could BAER not only pick up potential lesions/ issues with hearing but also a potential lesion to cause the swallowing/face pain issues? Just wondering cuz they didn't do the BAER on me and I'm having a lot of swallowing issues/chewing issues/cheek and jaw pain/spasms.....

[COBOB]

The auditory nerve is a cranial nerve.  The typical auditory test is the BAER  - Brainstem Audio Evoked Response and is used to test the Auditory cranial nerve to the brainstem.

[cardiactec]

Would auditory part of the evoked potential be "closer" area to test or check for lesions that might be effecting the cranial nerves?

thanks for the website. i'm gonna check it out.

[COBOB]

VEP tests the Optic nerves that travel from the Retina to the Optical Cortex in the back pf the Cerebrum.  SSEP (Legs) tests from the lower leg up the spinal cord to the brain passing through the brainstem.  It really has a lot to do with SSEP protocol they followed.  TN Pain is related to Cranial Nerve 5 (CN5) with inserts at the brainstem and controls the motor muscles for chewing and provides a lot of the facial sensory information to the brain. It is also one of the 6 pairs Cranial Nerves needed to "Swallow."  All 6 pairs of those Cranial Nerves attach at the brainstem. It is possible to "forget how to swallow" since it is not a reflex, but a pattern-elicited response.  Gag is a reflex.  This is important:  If you gag correctly and can not swallow the defect may be in a "higher motor function." (Think Cerebrum and Motor Cortex.)  If you have issues where your gag fails to function correctly, that is indicative of a reflex failure a point towards the brainstem.

The easiest way to explain a swallow is to point you to a web page on the Neuroanatomy of Swallowing:  http://www.csuchico.edu/~pmccaffrey/syllabi/SPPA342/342unit3.html

Hope that helps,

Bob

[cardiactec]

Bob -

With the evoked potential, where do they have to test (what part of the test, visual, auditory, sensory) would help to potentially see a lesion specific to causing swallowing difficulty, speech problems, and TN pain?

They didn't do the auditory part on me - just the visual (which was normal) and the sensory (which the legs were abnormal, but arms WERE normal) ....

[cardiactec]

Hey Bob -

Just want to thank you, first of all, for being so kind to share your knowledge and insight about my medical questions.

My EMG (the second one they did) in October showed "reinnervation, mild polyphasia only in the left deltoid and the left tensor fascia latae. No myopathic motor units were observed in any of the tested muscles. The NCV of the emg was normal.

My neuro said to me yesterday that central nervous system disease (and of course he didn't specify WHICH disease) could cause these neurogenic changes but peripheral disease could still be to blame. As for the evoked potential abnormality, he didn't give me the technical version of the test, but just said there was a problem in the legs and a hard time pinpointing where the abnormality was originating from.

[COBOB]

Depends on what the P-time is.  The shock is detected as a positive waveform by the scalp electrodes.  There are two things that the look for:  Waveform being well maintained and the time it took the signal to get there.  Increased times means a decrease in conduction velocity.
Changes in the waveform can be peripheral or central.  If you have had normal EMG/NCS of the legs and the SSEP waveform changes on the SSEP, that's a reason to investigate the cord and brain.

That's the simple explanation.  The reading of evoked potentials requires understanding what other tests have been done and looking at all the data.

Bob

[jensequitur]

It could...  It sounds like there's a problem with the spinal cord, which could be MS, or some other problem causing nerve conduction failure in the spine.