An analysis of VEP components in optic neuritis.

Various VEP parameters were analysed in 126 patients with multiple sclerosis, isolated optic neuritis or isolated myelopathy. The single most common deviation in eyes with clinical evidence of optic neuritis was a prolongation of the latency to P100. After the findings concerning P100 and N70 were combined two patterns of abnormalities emerged: 1) delayed P100 and delayed N70, 2) delayed P100 and absence of N70. In a few cases only one of the potentials was affected. Also in eyes without clinical evidence of optic neuritis the same patterns occurred but discrepancies between N70 and P100 were more common, especially the combination of normal P100 and delayed or absent N70. In about half of these cases the latency to P100 was close to the upper normal limit. It is concluded that in such cases the additional findings of an absent or delayed N70 is strongly suggestive of visual system dysfunction and that the inclusion of N70 in the analysis of VEP may increase the diagnostic yield of the examination.