The bifid visual evoked potential-normal variant or a sign of demyelination?

OBJECTIVE: To prospectively evaluate the diagnostic significance of bifid VEP at initial presentation. MATERIALS AND METHODS: A hundred and sixteen patients (46 males and 70 females, age 15‐54, mean 28.8), with a clinical suspicion of multiple sclerosis (MS), underwent pattern‐shift VEP investigation between 1992 and 1998. They were further followed by clinical, CSF, MRI means for at least 5 years (mean 7.2). Twenty‐six patients remained healthy, while 90 developed demyelinating disease (in 71 MS and in 19 optic neuritis was the final diagnosis). Fifty healthy persons (20 males aged 18‐51, mean 28.8 and 30 females aged 18‐48, mean 26.2) represented the control group. The number of persons with bifid VEP in each group are analyzed. RESULTS: In the controls one out of 50 exhibited bifid VEP configuration. Of 26 patients with unconfirmed suspicion for MS again one had such responses. Bifid VEP were significantly more frequent in patients with demyelinative pathology (nine out of 90, 10.0%, P (chi‐squared) < 0.01). CONCLUSIONS: Bifid VEP is rarely observed in healthy persons. Its presence should suggest the possibility of demyelinating disease and prompt further investigation and follow‐up.