Visual evoked potentials in experimental allergic encephalomyelitis

We have compared the clinical signs, brain pathology and visually evoked responses (VEP) of guinea pigs with experimental allergic encephalomyelitis (EAE). Animals immunized with myelin basic protein had a milder disease, both from the clinical and histological points of views, compared to those immunized with crude white matter extract. However, VEP findings were quite similar in both groups. The VEP of the majority of animals from both groups showed changes before or at the same time that neurological signs appeared. Electrophysiological responses were usually characterized by abnormal wave shapes and prolonged latencies. Recovery of the VEP usually preceded the recovery from clinical signs. In contrast, the severity and incidence of brain tissue pathology was not correlated to either clinical signs or VEP changes. Possible explanations of the electrophysiological, clinical and histopathological changes and their time-course are discussed.