Value of hyperventilation in pattern-reversal visual evoked potentials.

The effects of a standard 3 minutes' hyperventilation on the full-field pattern-reversal visual evoked potential (VEP) were studied in 33 normal subjects, 30 definite multiple sclerosis patients and in twenty-five patients with abnormal VEPs due to either tumourous compression of the anterior visual pathways or optic atrophy of other origin. Significantly greater reductions in P100 latency occurred in multiple sclerosis patients in comparison with controls (p less than 0.05). This change appeared to be specific for demyelinative type of lesion, for it was not found in cases with other types of pathology. Hyperventilation also increased the sensitivity of visual pathway impairment detection in multiple sclerosis.