Abnormal VEP/Optic Neuritis Questions

[bubblebabe]

Can someone please explain to me what an Abnormal VEP actually means? Let’s see if I can articulate myself properly, lol.

Basically I want to know does it mean you DID have an episode of ON?
Does it mean the Optic Nerve has no Myelin left on it or does it mean that there are lesions on it?
Does it mean you are actively in an episode of ON or is it evidence of a past episode?

My questions stem from the fact that (I am already diagnosed with MS so I’m just curious) I had an abnormal VEP (left eye) which my Neuro nurse said was a separate attack from any lesions in the brain or spinal cord. BUT I do not recall ever having any issues or trouble with my vision and my vision is 20/15 in both eyes. So did I have an episode of ON with no symptoms or am I going to have an episode of ON?

Thanks for your help!!

[MSer102]

My ophthalmologist told me that there is a lot of misunderstanding about ON and VEP's. Too many people think the VEP is a test just for ON and it isn't.

A VEP tests from your eye all the way across your brain so an abnormal VEP can come from problems anywhere across the brain not just the optic nerve. That's why you can have an abnormal VEP without ever having ON. So no it doesn't mean you had ON just because your VEP is abnormal. It just means that you've lost some myelin somewhere between your eye and the back of your brain.

Mild cases of ON sometimes don't cause enough damage to make a VEP abnormal and sometimes eyes that did have ON heal to the point where the VEP is normal again and there's no way to tell that it ever happened.

Your MS nurse isn't quite right in saying that you must have had a separate "attack" for the VEP for the left eye to be different on the left side. Sometimes that's just how the demyelination shows up. Demyelination is very often in the optic nerve but it doesn't have to be.

So that doesn't mean that you have no myelin. It just means that there has been enough lost somewhere to slow down the speed of the electrical signal. There's no way you could see 20/15 if you had no myelin.

If somebody has or had ON, the VEP can be the same if the episode is active or if its evidence of an old episode. There isn't any way for the VEP to tell what's new and what's old. And there's no way to predict the future and tell if you're ever going to have an episode of ON based on your VEP today.

A lot of people with MS have abnormal VEP's who have never had ON. That's why its a good test to use in testing for MS because it shows general demyelination all the way across the brain.

An abnormal VEP doesn't mean somebody has had ON and a normal VEP doesn't mean that somebody hasn't had ON.

My ophthalmologist gets a little frustrated because so many neurologists don't understand what a VEP really shows and they give their patient the wrong impression of what the test is used for and what the results mean. He gets tired of having to explain it over and over so I made sure I understood it the first time.

[Alicious]

I can't answer your questions specifically, but both my ophthalmologist and my neuro-ophthalmologist have told me it's clear I've had ON in both eyes at some point, even though I've only ever noticed it in one. Damage can occur to your optic nerves that you never even notice.

[bubblebabe]

Thank you!!

Thank you MSer102 and Alicious for the great replies!

MSer102, I really appreciate you taking the time to give me such a thoughtful and detailed explanation. I really got no explanation from my Neuro or my Neuro Nurse and they both usually give me conflicting information. My Neuro said the abnormal VEP didnt mean anything unless I had loss of vision and my Neuro Nurse said it was evidence of another "attack" so I was really confused!!

Thanks again for helping me understand!

[MSer102]

My Neuro said the abnormal VEP didnt mean anything unless I had loss of vision

This just cracks me up! If your neuro thinks that an abnormal VEP doesn't mean anything then why did he order the test? Too funny! No wonder my ophthalmologist gets so peeved at some neurologists.

[bs957]

MSer102 stated:

"If somebody has or had ON, the VEP can be the same if the episode is active or if its evidence of an old episode. There isn't any way for the VEP to tell what's new and what's old. And there's no way to predict the future and tell if you're ever going to have an episode of ON based on your VEP today."

My first experience with ON was 7 yrs ago. I lost vision in a quadrant of my left eye. It took 18 months for the eye to resolve itself before I could see "normally" out of that eye again.

Fast forward to this time last year, (a year ago today in fact), ON showed up in my right eye with a vengeance. My vision went from 20/25 in that eye to 20/400 overnight. This time, it resolved itself eight months later. My vision in that eye is now at 20/35.

I did not have a VEP done until after this second episode. It showed that there was signal latency in both eyes at about the same levels. Keep in mind that these episodes were 6 years apart.

I'm currently in Limbo-Land right now. Lots of blood work done, 9 mris sice sept 2012 to prove that I have a brain, a stiff neck (cervical), and a backbone (thorasic and lumbar). (LOL) . The visit I had with the optho-neurologist before he blew me off called me an "enigma", and my regular neurologist is not sure what to think as almost all my tests come back non-remarkable. The brain mris come back with a couple of lesions but not ms-presenting. He has referred me to a colleague of his whose specialty is ms-related stuff. That will be middle of next month. I sure wish I knew what was going on in my body, but for now it is just one day at a time even though some days are harder than others.

Blane