What is the role of visual evoked potential (VEP) tests in electrodiagnosis?

Updated: Mar 01, 2019
  • Author: Adam B Agranoff, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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Answer

Answer

In VEP tests, [27] the practitioner uses a photoelectric, checkerboard-pattern flash to stimulate the optic nerve. This pattern is then recorded on the cortex, arriving at the occiput, near the visual centers. The pattern usually takes 100 milliseconds to arrive and is referred to as the P100. Injuries along the optic nerve, including demyelination, result in a delay of the latency and loss of the amplitude of the signal, similar to the results in NCVs.

A P100 at greater than 102 milliseconds is considered beyond the reference range in most laboratories. In cases of multiple sclerosis, for example, abnormalities in the VEP are often the first indicator of the disease process. Optic chiasm tumors also produce recordings suggesting abnormalities. Visual acuity may be determined in infants with suspected visual disturbances.


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