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The Joy Of Evoked Potentials

The Joy Of Evoked Potentials

The process of diagnosing someone with Multiple Sclerosis is not easy. There is no one test that guarantees you have MS. Instead, doctors rely on a series of tests and then look at the combined results to help make the diagnosis. In the past, I’ve shared my experience with a few of these tests, namely the MRI and Spinal Tap. Today, I want to talked about my experience with the other common test used in a Multiple Sclerosis diagnosis, Evoked Potentials.

Evoked what?

When I was going through the process of getting diagnosed and was told I’d be having some Evoked Potentials done, I had zero idea of what they were talking about. MRI, sure, I knew what that was. Spinal tap, OK, I had a pretty good idea of what that was too, at least in the most general terms. This other test was extremely foreign to me. Was I going into another dark tube? Or getting some fluid extracted from some other part of my body? How painful and scary was this going to be?

Turns out, not really as tough for me as the other exams. Evoked potentials are a series of tests that help measure and record the electrical activity of the brain in response to stimulation. Essentially, they help identify the delay of signals from the brain to other parts of the body. In MS, the signals our brain is sending throughout the body often don’t make it to their destination as fast as they should or at all. That’s because the myelin layer around the nerves (where these signals travel) is damaged or eaten away by our own immune system. So measuring the speed that it takes for signals to travel is a pretty good way to identify this type of myelin damage.

Wait, are they going to electrocute me?

While it may sound a little scary and painful, it really isn’t. You get a number of electrodes attached to various parts of your body, with a conductive gel, you are then subjected to different types of stimuli. Some examples: Looking at a screen with an alternating checkerboard pattern, just sitting there and looking at it, no big deal (this is a Visual Evoked Potential test). Putting on some headphones that play a series of clicking noises, again, nothing to strange about that (this is a Brainstem Auditory Evoked Potential test). Then the interesting one, where short electrical pulses were sent through my arms and legs (the Sensory Evoked Potential test). It was maybe a little startling but not at all painful.

How’d it go?

These tests were most definitely the easiest of the big three MS exams to me. It may feel a little weird to have a bunch of electrodes attached to you, but for someone with a touch of claustrophobia, I’ll take that over an MRI any day! While the doctors were already pretty sure I had MS by the time I took these, the Sensory Evoked Potential really confirmed it. The signals in my right arm and leg were not traveling at the speed they should have been. Even though I had only been having problems with my legs at the time, this showed that there was damage in areas that I couldn’t notice. To me, my right arm seemed to be working with no issue, but through Evoked Potentials, they were able to identify another demyelinated area. Sure enough, over time, visibly noticeable issues developed with my right arm. The early damage picked up in the Evoked Potential worsened over time as the myelin was slowly damaged. Being able to identify an area that seemingly has no symptoms is one of the main benefits of these types of exams (a great reminder that just because someone may seem symptom free, doesn’t mean that damage isn’t still happening).

Thanks for reading!

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.


  • whisper13
    1 year ago

    Nice article! Thanks for sharing it!

  • itasara
    2 years ago

    After I was dx’d in 2005, just by MRI and short history, I had one of those tests to determine optic nerve transmission. Not painful, very boring, and for a long time I had to look at a red dot against a checkered background of black and white squares.
    Years later my opthomologist started a test where I stare at a star in an electronic machine with each eye; it doesn’t take long at all. My opthomologist said she was doing it as an extra test for glaucoma in addition to the pressure readings done.. After several times, she said I don’t have glaucoma and it is probably indicative of my MS and it was still 15% under normal. So this test is a lot easier than the original one I had years ago. She was doing this every 6 months but now she repeated it at my yearly check up.
    After reading some of the comments here, I don’t think I would have wanted the evoked potentials test although it may be better and not invasive like a spinal tap. . Is this done because an MRI was not specific to diagnose MS? My MRI was pretty specific for diagnosis plus history that my daughter had been diagnosed three years before me. She had two specific relapses (I had one of them) and a couple MRI’s and that was all the was needed for her diagnosis.

  • itasara
    2 years ago

    PS the opthomologist test I believe is called OCT.

  • SuzyF.
    2 years ago

    My experience w/ the visual evoked potential diagnostic test was made MUCH worse by my insurance company. They would not allow me to stay longer in the hospital so I had to have it a while after a lumbar puncture after which you are cautioned to strictly remain in a horizontal (rather than upright) position in order not to get “the headache”. I, of course DID get “the headache” which was only lessened by trying to stay “horizontal” even at work. This brutal headache was only resolved by returning after three days in awful pain only to undergo another lumbar puncture for a “patch” procedure where they drew blood and inserted it into the hole where the original puncture was performed. Hopefully the insurance companies are more knowledgeable and kinder now…

  • Senator
    2 years ago

    Reading these comments on Evoked Potentials leaves me speechless. The last test I had on the road to my MS diagnosis was the Evoked Potential muscle nightmare. This test was done at Mayo Clinic so I figured they are fairly adept at administering it. First off when the Neurologist told me I was needing the test I inquired as to the pain level I could expect. In her leaving the room she said ` It will be uncomfortable ` as she scurried away not leaving me any chance to have her to expand her analysis. Before this test I had to endure an EMG test in my legs twice. Once years ago for a different medical problem, then again when the Mayo PCP I needed to see for an eval before referred to Nero, insisted it is different here. Later found out she had a test EMG on her arm, and that`s what she based it off. Very painful and I had listed as a 9, on a scale of 10, with ten being moat painful. Well move over EMG, muscle Evoked Potential knocked you out of 9 so you are an 8. Evoked Potential in my legs was the most painful thing I have ever experienced. People here talking of hooked up to their head leaves me wondering why I had to endure test in my legs ?

  • ASAPcindy
    1 year ago

    I had that test done on my legs and have to have it again. It was one of the most painful things I have ever experienced. I had two unmedicated natural childbirths when I delivered my kids, and I think that test was way more painful than delivery. Who knows? Maybe I am making a big deal out of nothing, but if I take a Valium before the test will it bias the results?

  • allinjay
    2 years ago

    Wow. Article brings back a funny visit to my Neurologist. Electrodes attached to MY FACE. OMG, when juice turned on my cheeks,mandible,nose were scrunched together sorta like squeezing out a round sponge full of water. She and I laughed together so much that even when I see her we on any occasion we both giggle!!

    2 years ago

    You did a fantastic job of explaining EP’s. I am/was a neurodiagnostic tech and did EEG’s, EP’s and sleep studies. And then I was struck down with M.S. Just wanted to applaud you for this writing.

  • Julie
    2 years ago

    This was the first thing I had done after the eye doctor saw optic nerve damage.

    My parents took me to the appointment and afterward took me to out to lunch. I looked at myself in the mirror and said no, no way I was going out into public with my hair standing on end all greased up. My sweet daddy told me I was beautiful, who was I to argue?

    Walking around the buffet at the Chinese restaurant I ran smack into my old pastor. That was uncomfortable but nothing was hurt but my pride. Easiest test I had during my diagnosis.

  • potter
    2 years ago

    That would be a interesting test to take, the only test I had was a MRI and some kind of eye/ brain wave test with the electrodes on your head. My neuro said with the 5 lesions on my brain and family history I didn’t need any other tests. Potter

  • bethybright
    2 years ago

    I’ve never even heard of this before. Loved learning about this one. Now I have yet another thing to ask my specialist about at my next appointment. Good piece, Devin. Thanks for writing.

  • corgi9
    2 years ago

    Had the Evoked Potential back in the Spring of 1979 and was diagnosed right away. i DO remember those electrodes being attached to my legs and when I looked back saw my legs flapping around. My eyes searched the room looking for Dr. Frankenstein but I didn’t see him or Igor !…..Still ambulatory at age 71 but slowing down; foot drop and left leg weakness. I have had the Pins & Needles since 1979…non-stop….24/7. After 39 years with MS I just tolerate the P&N…..but I would really enjoy a day without it.

  • Kathy Reagan Young
    2 years ago

    I appreciate this article about Evoked Potentials. It was a scary process when I was going through it – especially because I had asked several questions, then my doctor told me to quit asking questions!! Needless to say, I never saw that doctor again!! BTW – there actually is a new blood test that will tell you quickly and accurately whether or not you have MS – alleviating the need for things like the EP and the Lumbar Puncture! It’s called IsolateMS and it’s through the IQuity biotech company in Nashville. Your doc has to order it (it’s no new most docs don’t even know about it yet) and as of now, insurance isn’t covering it – but it’s a definitive answer (90%+ accuracy) quickly (within 1 week).

  • mrsaristotle
    2 years ago

    I had an EVP in 2008 my electrodes were on my head ugh they made a mess getting them off. Flashing chequer board and just sitting still. No biggy. I had mine done as in 2000 i went blind on holiday and when i came back off holiday had another episode which was IGNORED by my local GP he put it down to the heat.

    I went on to have eye issues until 2006 when i collapsed and went off sick. My eye issues blurry and pain etc on and off were put down to DRY eyes.

    Anyway i had my first brain MRI in 2007 which was inconclusive because of my age.

    Then i had further stuff going on so the neurologist wanted to check my optic nerve.

    The results showed i had bilateral issues worse on the left eye but still a slowing in the right. Still no diagnosis of MS.

    Over time fast forward until 2015 November i had another VEP test after having a colour screen test in my neurologists office which i failed apparently.

    In December I had another attack of vision issues. Nothing from Nuero with results.

    January 2016 finally got a letter off my neurologist to see me saw him in February.

    My VEP test was positive for another episode of demyelination of the optic nerve, called optic neuritis and with the 3 different lesions they had found over the few years in different places in my spine, i was finally diagnosed with progressive MS.

    Oh I had the LP. It showed O bands but the blood test alongside that showed inflammation which makes the result negative for MS.

    Anyway the VEP test is the easiest test i think. I saw my MS nurse recently who did that colour chart thing again, and it showed my left eye is now not seeing colour correctly.

    The VEP test for me is my friend as finally after 16 long years i got my label to sew on my jumper and I jokingly call mine the VEP SANDWICH LOL.

  • Devin Garlit moderator author
    2 years ago

    Thanks so much for sharing mrsaristotle! The gel used with the electrodes certainly does make a bit of a mess!

  • mrsaristotle
    2 years ago

    LOL tell me about it, in the end when i got home we had to cut some of it out i think it is my very strong italian hair didnt like it.

    Its good though to share these things as the unknown can be scary but its nothing to be scared off. I loved your article it made me chuckle.

    Have you had the muscle electrodes? Now that is another story lol.

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