Studies on short latency visual evoked potentials in cases with optic pathway lesions

Abstract

To identify the components of the short latency visual evoked potentials (SVEP), five clinical cases with lesions in different parts of the optic pathway and visual cortex were studied comparatively. Optic nerve potentials were differentiated in the case of optic nerve astrocytoma and they appeared as diffuse weak negative charges on the anterior half of the scalp during a period from 20 to 40 msec. Chiasmal and postchiasmal conduction was clearly demonstrated in the case of left optic tract lesions. Among the brainstem potentials, the P₅₂ focus was considered to have some relation to the pupillary light reaction from the mid brain in the case of tonic pupil. Occipital cortical potentials were suggested by three negative occipital focuses at 40, 65 and 85 msec in the case of optic radiation lymphoma. The N₄₀ focus, shifted to the parietal region, was suspected to be due to the extrageniculate conduction in the case of Riddoch's phenomenon.

Key Words:

• short latency VEP
• optic pathway lesions