Abnormal VEP

[Quixotic1]

I am a Co-CL on the MS Forum.  One of our members was told by her neuro-ophthalmologis that the VEP was useful on in detecting malingers.  Her results were


            Latency       Amplitude
OD       183msec      4.6uV
OS       173msec      6.0uV

Normal <106msec   2-20uV


She was told two other things.  1)  These results indicate she should be blind so are not reliable (she is not blind but was suspected of having optic neuritis).  2) She was told that since her fundoscopic exam was normal she could not possibly have optic neuritis.

My questions are this  1) How abnormal can the VEP be in optic neuritis, without suspect that the exam was botched.

2)  It has been my understanding from reading the medical literature (I am a physician) that, if the demyelinating lesion in MS is far enough back, that the fundoscopic exam may not reveal optic nerve pallor or other signs of optic neuritis.  I have also read repeatedly that in, documented optic neuritis, the fundoscopic exam may be normal in more than 50% of MS patients.  I have reported this on the forum.  Am I correct?

Thank you

Quixotic1

[Sandra M Brown, MD]

VEPs are notoriously affected by technique.  At one point someone (for a joke) hooked electrodes up to a grapefruit and manufactured a measurable VEP.  I usually pay attention to VEPs when they are grossly abnormal, but not otherwise, AND there is clinical corroboration.  In any event, your poster has normal amplitudes and mildly prolonged latencies which is not at all a "blind" VEP.

Mild attacks of optic neuritis that are fairly far posterior might not lead to obvious focal or diffuse disc pallor.  Also, since there is a range of normal disc color, if your poster has had attacks in both eyes or in the optic chiasm, s/he might actually have mild, symmetric bilateral pallor (relative to the original baseline) that is not out of the absolute range of normal for a human, and is therefore mistaken as bilaterally normal.

During acute retrobulbar optic neuritis, the optic disc appearance is almost always totally normal.

[Quixotic1]

Thank you, Dr. Brown, I appreciate your time and expertise.

Quix, MD