Visual evoked responses in multiple sclerosis: comparison of two methods for pattern reversal.

Visual evoked responses have been elicited by reversal of a black and white checkerboard pattern and also by a display of light-emitting diodes (LED) generating a reversal of a pattern of illuminated red circular areas. In a control group the LED display produced responses of lower amplitude and shorter latency compared to responses to checkerboard stimulation. In patients with a definite or probable diagnosis of multiple sclerosis the stimulators were equally effective in evoking pathological responses; in patients with a possible but less certain diagnosis abnormal responses were found in a higher percentage when the LED stimulus was used. Differences in stimulus field size and in stimulus colour are discussed as possible reasons for this result.