Effects of hyperventilation on pattern-reversal visual evoked potentials in patients with demyelination.

The effects of hyperventilation on the pattern-reversal visual evoked potential (VEP) were studied in seven normal subjects and 13 multiple sclerosis patients with visual pathway involvement. Significantly greater reductions in P100 latency occurred in the multiple sclerosis patients than in controls and normalisation of the half-field response topography occurred in one patient after hyperventilation. The VEP changes are attributed to improved impulse transmission in demyelinated fibres in the visual pathway as a result of the alkalosis and changes in ionised calcium levels induced by hyperventilation.