Effect of body temperature on visual evoked potential delay and visual perception in multiple sclerosis

Seven multiple sclerosis patients were cooled and four heated, but evoked potential delay changed in only five out of 11 experiments. Control limits were set by cooling eight and heating four control subjects. One patient gave anomalous results in that although heating degraded perceptual delay and visual acuity, and depressed the sine wave grating MTF, double-flash resolution was improved. An explanation is proposed in terms of the pattern of axonal demyelination. The medium frequency flicker evoked potential test seems to be a less reliable means of monitoring the progress of demyelination in multiple sclerosis patients than is double-flash campimetry or perceptual delay campimetry, although in some situations the objectivity of the evoked potential test would be advantageous.