An evoked potentials test measures the speed of nerve messages along sensory nerves to the brain and is sometimes used in the diagnosis of MS.
The most commonly used test is called visual evoked potentials (VEP), which measures messages sent from the eyes in response to being shown a flashing chessboard pattern on a computer screen.
Tests of sensations from the skin (somatosensory evoked potentials), which involve tiny electric shocks, and of hearing (auditory evoked potentials), using clicks, can sometimes also be carried out, though much less commonly.
Visual evoked potentials work on the basis that it is possible to measure how long it takes for input from the eye to get to the visual cortex at the back of the brain where this information is processed. As damage to the optic nerve in MS can slow messages down, evoked potentials tests can indicate the presence of an area of scarring that is not causing any obvious symptoms (described as clinically silent). Delays of as little as 10 milliseconds can indicate that there is damage to the nerve pathway.
- Journal of Neurology, Neurosurgery and Psychiatry 2005;76 Suppl 2:ii16-22. Full article (PDF, 257KB) The clinical role of evoked potentials.
Last updated: 12 August 2014
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