Can you help me a bit? I promise I will ask my doctors these question.
Lets see if I understand this correctly. IF I have a mild latency within normal parameters in my right eye and a mild signal loss in my left eye. Wouldn't that reflect something might not be balanced right and is causing my vision issues?
What you are saying is that there may be axonal loss in my optic tract but not likely ON. Okay. I'm fine with that. :) Doesn't it still kinda sound like I may need to request an OCT to you?
N75-P100 is a voltage differential and has to do with signal. Latency is demyelination. Loss of signal is related to retinal or axonal loss in the optic nerve.
Bob
Oops - typo:
VEP
Trace N75(ms) P100(ms) N145 (ms) N75-P100 (uv)
Norm 3.5
Ch1:Oz-Fz: R GAvg 76.2 100.4 133.6 4.05
Ch1:Oz-Fz: L GAvg 81.6 95.7 132.4 2.58
L-R Norm <4.5 <2.9
L-R 5.4 4.7 1.47
Okay, I received a copy of my VEP. This is the conclusion: The above Visual Evoked Potential study reveals normal latencies bilaterally. The latency of the right was longer and the amplitude on the left was slightly decreased compared to the right...
This is what the rest says:
VEP
Trace N75(ms) P100(ms) N145 (ms) N75-P100 (uv)
Norm 3.5
Ch1:Oz-Fz: R GAvg 76.2 100.4 133.6 4.05
Ch1:Oz-Fz: L GAvg 81.6 95.7 132.4 2.58
L-R Norm <4.5 <2.9
L-R 5.4 4.7 1.47
I don't expect both sides be the same. I understand that the P100 is significant if it shows greater than P120. Do you know what the N75 - P100 is (which must be the reference to the amplitude being slightly decreased)?
What does the gradient imaging do? I can't tell the thickness of the slices. Maybe it's on my MRI images? I do have the scans on disc.
I guess I'm surprised that they did the gradient imaging on the c-spine. Maybe the slice thickness or something else is driving up the SAR. Anyhow, the sequences seem close to what I would expect. The important variable is the slice thickness for the brain and the cord.
As far as the VEP, the important result is the P100 time. It is possible to have Optic Neuritis that was "silent." There can be demyelination of the optic nerve, but without the typical symptoms. The VEP is pretty sensitive for detecting demyelination of the optic nerve. At less than 60 years old, a P100 (named for the typical max positive peak 100 milliseconds after stimulus) greater than 120 milliseconds is considered "abnormal latency."
Bob
I am getting a copy for my next appt. but I haven't seen them myself. I just received "it's negative." I'm totally confused by the results just based on the conversation I had with the technician... she told me it was abnormal.
I am also not on any medication at the moment. Not even vitamin supplements. I was taken off all supplements when my labs were good. I am negative on all test results (except for my initial physicals when I was really sick) all the CT scans, MRI's, EEG, EMG, VEP and labs for other diseases were negative ... but have so many residual symptoms something doesn't add up right so I'm going for a "third" opinion. I had an appt. with an MS specialist as my second opinion but it appears he had nothing to go physically off of with all the negative results.
It was not done on a 3 Tesla Machine. It was a 1.5T I believe... I know it wasn't a 3 Tesla machine.
Were your images done on a 3 Tesla MRI? Essentially, the study looks a lot like an MS protocol. Gradient Echo studies are done on 3T MRIs in place of Spin Echo studies on 1.5T MRIs. Many time you will see spin echo studies listed as T2W and gradient echo are T2*.
The typical brain sequences for an MS brain MRI are Sagittal FLAIR, Axial FLAIR, Axial T2,
and Axial T1 pre/post gadolinium. You may also see Axial proton density (PD) and 3D IR T1 gradient echo sequences.
The main cord sequences include Sagittal T2, Sagittal PD or STIR, Sagittal T1. Sometimes you may see also see 3D IR T1 gradient echo sequences.
Some imaging centers may use MT-MRI (magnetic transfer) or DW-MRI (diffusion weighted) sequences. These are non-standard, but may provide superior imaging, especially in the spinal cord.
The MS protocol can be found at: http://www.mscare.org/cmsc/images/pdf/mriprotocol2009.pdf
Bob
I don't know how to read an MRI I am just curious if you asked for a copy of your VEP test? It will state the results on the report so it may give you some more insight.
Are you on any anti inflammatory drugs to help with the inflammation especially during your monthly cycle. Not sure if they would help but its worth a try.
Hopefully someone will chime in with an answer to your question about the MRI and give you some answers.
Good luck,
Paula