Follow-up studies on the usefulness of the flash visual evoked potential.

Thirty patients with possible demyelinating disease or visual system disorder were referred for Visual Evoked Potentials (VEP) and had abnormal flash (FL) but normal pattern reversal (PR) responses. Patients with confirmed organic brain disorders had significantly longer latencies to P100 from FL than in the unconfirmed group, but the subgroup, later proven to have demyelinating disease had the most significantly abnormal latencies to FL. Even the PR responses, although within normal limits, showed significantly longer latencies in the organic brain disorder group, compared to the unconfirmed group. For patients who could be followed-up, 45% of them proved to have demyelinating disease. A visual disorder was confirmed in 53% and an organic brain disorder in an additional 13%, so that 2/3 of all patients had one of the latter two conditions. These data argue for the use of flash, in addition to the pattern reversal stimulus, in the protocol for visual evoked potentials.