Lesions vs. Symptoms (Health Page) Question for Quixotic1
Hi. I just read the 'Lesions vs. Symptoms' health page. I have a question that I'm hoping you or someone can answer. It said that lesions in the spine are more in line with our disease. I know that the MRI is one way to find them, but does an SSEvokedPotential test that is 'abnormal' reveal lesions through the test results? Is that, in effect, showing a blip on the screen where lesions are causing a problem?
I think wonko may be right, but I'm not sure. I hope Quix reads your question, b/c I'm sure she knows the answer. I have not had Evoked Potentials done. STILL waiting on my LP results. Best of luck in finding your answer!
I had this test, too. I don't think it shows lesions like blips. The way it was explained to me, it measures the signal from where they shock you to where the peripheral nervous system meets the central nervous system and then from there to when the signal is received by the brain. I found an old post where Quix says "the speed of the signal, and the preservation of the wave form is what is looked for."
My results were abnormal because "the normal peripheral responses coupled with the increased central conduction time for the median responses and absent scalp (P40) responses with tibial stimulation suggest a lesion or lesions in the median and tibial somatosensory pathways from the level of the spinal cord to the cortex." I will bump up another old post where Quix explains this in plain English in case it helps.
My understanding is the SSEP is pretty non-specific. That is, it tells you something is wrong, but not what. The conclusion on my report just says *suggests* lesions. I had previously been dx'd with idiopathic peripheral neuropathy and when I said something to the neuro about being glad to get away from that because the idiopathic thing drove me crazy, he just looked at me and said, "Well, you have idiopathic *something*."
I think, because the SSEP measures the signal in the peripheral nervous system as well, it could also show abnormalities there, although it isn't commonly used for that. Maybe that's why they want you to do the QSART? Did your report say where the abnormality is?
The report said, "The right lower extremity somatosensory evoked potential is normal. The left one is mildly abnormal because of the delay in both P37 and N45 waveforms of 5 msec. Clinical correlation will be necessar to determine the significance of this finding." The neuro has all my symptoms that I have journaled throughout the last 3 months. Although, the neuro that I see was not there to look at my results, so another read through my chart quickly and decided to do the QSART test.
I'm just getting to the point where I need to know what this is. It's been a while ... And, I do know that the dx may never come. My neuro told me it may take a long time to figure this out, and we may never find out. That was hard to take. But, as I told my husband ... it's time to move on to someone who maybe has new ideas. This QSART may not be a bad idea, I guess.
Today's not a good 'thinking' day. Got a call yesterday evening from my son. "Mom, Mom, I think I've been in an accident!" He described a little to me then said he'd call me back. I was SO upset ... Then he called 3 minutes later, "Mom, I think I've been in an accident!" I knew he was in trouble then. Long story short, they took him to Allegheny General Hospital and did X-rays, CT Scans, etc. He was a very lucky man. Concussion, injured knee (has to see Ortho), elbow injury, 3" gash on his head, bumps and bruises. A woman hit him head on after hitting black ice and then overcorrecting the vehicle. I was up till 5 AM after getting him and his wife home, and then dealing with the stress and pain myself. So, my mind's not what it should be today. It's funny how the body works though ... must be adrenaline that allows us to do what we have to do without feeling much of anything, but when it all calms down, WOW and OUCH! I'm just so thankful to God that my son's going to be okay. I'd take all his pain if I could.
Thank you all for your replies. You've been extremely helpful. Have a low-pain kind of day.
Well, I know that Quix mentions that lesions in the brainstem and spine are "stronger" evidence for the presence of MS. She mentions stronger because there are more disorders to look into where brain lesions are concerned than there are spinal lesions. So if you have spinal lesions too, it's just additional evidence or support pointing in that direction. Obviously, there are so many other factors to consider depending on the clinical picture.
MS is in the end a clinical dx. Ok, now for your real question, you ask about abnormal SSEP results. This I know less about. But Shoshin explains it well.
This workup does take awhile unfortunately. We certainly know this feeling - it's so difficult. What has the Dr. lined up so far? I'm sorry if you've already posted this, and I'm just so behind w/everyone. If so, just point me in the direction, and I'll find it.
Hope we can help you through this and that your Son is doing ok after that accident...
Oh, Lori, I'm so glad your son is going to be okay! and sorry that I didn't get to your question.
The SSEP measures the velocity of a sensory nerve signal from the point of stimulation to its arrival in the brain. The signal is typically measured at 3 or 4 spots along the way, way from the foot to the hip to the spine to the brain.
If there has been a demyelinating lesion (like in MS) the lesion will be in the spinal cord or the brain. So the first or second measurements will be normal because they are measuring the sensation signal out in the peripheral nerves. If the signal shows that the spot of delayed conduction is in the cord or the brain, then the result is suggest of MS.
In MS the signal is measured both in speed and in it;s particular wave form. If the wave form looks good, but the signal is delayed somewhere in the central nervous system, this suggests MS. If the signal is delayed, but the signal waveform is broken up then it suggests some other kind of damage - not MS.
So the SSEP is fairly specific for MS.
Evaluating the results is somewhat subjective. If the signal is just barely delayed ( a few msec) then they may not consider it as a postive test. The computer will (it seems) often call an abnormal result that the neurologist discounts - saying it was not abnormal enough.
Sho is also right. I tried to say the same thing in different words.
Does this make sense.
Idiopathic= without known cause or "the idiots don't know the pathology."
Thanks for your comments. The Dr. now has me going for a QSART test, and he stated it was due to my chronic pain. They scheduled me for Dec. 4th, but unfortunately that's hunting season ... husband will be away ... so I have to reschedule. I have no idea where this will all lead. With all that's gone on with my son (he's doing better btw, thank you for asking), I haven't thought much more about all this. I guess I'll just go with the flow of the tests.
I now have an appointment with a neurologist who is supposed to be exceptional AND she's close to home. I think that has taken a lot of stress from me, knowing that I was able to get in to see her. She had stopped taking new patients for quite some time.
Thanks for your interpretations on the tests. Your posting helped ease my mind.
Thanks for your posting as well. I understand more now what Sho was saying, as you have put it in different words so I can put it all together. The only thing that I'm still not sure of is where you mention "if the spot of delayed conduction is in the cord or the brain ..." Is the P37 and N45 considered in that area then? You'll have to excuse me Quix ... I have been up every night until sunrise from all the stress with my son. I hope I'm asking a question that makes sense from your previous posting.
I truly am going to have to put this all to rest and stop stressing over it. What will be will be. I think I've finally realized that I have no control over what's going on with my body at this point. I could've easily lost my son on Tuesday. When something like that hits a family ... my issues just don't seem as important to me. I've always been a caregiver. It was so hard to become the one being cared for.
If you can answer the last piece of my SSEP puzzle, I will put it to rest. The next step QSART, you can be assured, will be discussed with the woman doing the test so I don't drive everyone here crazy trying to understand it. I've got to get a bit more assertive! lol.
Thank you and everyone who has commented on my posting. You are all such wonderful people. I feel like I've jumped into a big family.
I was so sorry to hear about your son and I hope that he has a swift and full recovery. Those phone calls must've been truly scary.
I'm glad that Quix gave you a clearer, more authoritative answer than I could.
I, too, would like to know what all these P-this number and N-that number things are.
They seem to be sort of hard to look up, but I did manage to find out (from http://www.emedicine.com/neuro/topic69.htm) that P37 is the primary sensory (or somatosensory) cortex so that is definitely part of the brain.
The American Clinical Neurophysiology Society'sGuidelines on Short-Latency Somatosensory Evoked Potentials (https://www.acns.org/pdfs/Guideline%209D.pdf) says P37 "reflects activation of the primary cortical somatosensory receiving area"
So far I haven't been able to find out what N45 is, but apparently it's also under the scalp (AAEM Guidelines for SEPs, http://www.aanem.org/documents/SEPGuidelines.pdf)...
All right, with a little persistence, I found this (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=physmedrehab.section.7259) which says that N45 is "cortical." (click on the figure 5.53 link for a picture of sorts)
Is there anybody out there that knows more about this (to say that I am woefully ignorant of anatomy would be an understatement)? Maybe there's a site somewhere with nice definitions and even pictures?
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