Visual evoked potentials in multiple sclerosis patients treated with interferon beta-1a.

AIM To study pattern-reversal visual evoked potentials (VEP) in patients with relapsing-remitting multiple sclerosis on interferon beta-1a treatment. METHODS In a randomized, prospective, non-blinded, placebo-uncontrolled study, VEP were studied in 9 patients (18 eyes) with relapsing-remitting multiple sclerosis treated with interferon. Three of them have had an episode of unilateral optic neuritis. VEP were first recorded before interferon treatment and then followed up for 12 months, at 3-month intervals, in the time when patients were receiving interferon, 11 microg twice weekly. All patients did not appear regularly at 3-months intervals follow-up, except for 6-month follow-up. P100 latency and P100 amplitude in responses to full field, right and left half-field stimulation were evaluated. RESULTS For the group of 18 eyes, there was no statistically significant difference in P100 latency and P100 amplitude before and after 6 months of treatment. In individual cases P100 latency was delayed in 3 eyes of 3 patients with a history of optic neuritis before treatment. At follow-up, P100 latency remained delayed in 3 eyes with a history of optic neuritis. Further, in 3 eyes of two patients who have had normal P100 latency before treatment, P100 latency became delayed. Overall, P100 latency was at follow-up delayed in 6 eyes of 5 patients. CONCLUSION Interferon beta-1a therapy (22 microg per week) administered for 12 months during 1998/99 in Croatia showed no statistically significant VEP changes in the group of relapsing-remitting multiple sclerosis patients. However, VEP may reveal evidence for asymptomatic deterioration.