[Contribution of visual evoked potentials (VEP) to neurology]

It is widely admitted that visual evoked potentials (VEPs) are clinically useful for diagnostic purposes in multiple sclerosis (MS). Delayed P100 component to pattern shift stimulation indicates a dissemination of the demyelinating process when routine ophthalmological investigations are normal. The delay of P100 may be observed early in the course of the disease following an attack of optic neuritis (ON); in the absence of previous ON the P100 latency may appear later after the onset. The P100 latency exceptionally returns to normal values. Compared with somatosensory or brain-stem auditory evoked potentials VEPs are the most efficient for the detection of silent lesions in MS. Longitudinal studies demonstrate that the percentage of MS patients with abnormal VEPs increases with time during the course of the disease. Delayed P100 component may also be recorded in patients with heredodegenerative or toxic optic neuropathies, but the clinical context is very different. The detection of bitemporal visual field defects with VEPs is more uncertain. In patients with cortical blindness VEPs may persist. When compared with usual campimetric investigations, VEPs do not represent a simple and reliable means of investigating lateral homonymous hemianopsia.