Evoked potentials tests

Author:  Maria Yiallouros, PD Dr. med. Gesche Tallen, erstellt am 2007/12/19, Reviewer:  Prof. Dr. med. Ursula Creutzig, English Translation:  Hannah McRae, Last modification:  2015/04/23

Evoked potentials tests assess the electrical activity in the brain after stimulation of perception, hearing or vision. These studies are performed regularly in patients with brain tumours, for example to find out whether these stimuli travel through the central nervous system (CNS) properly.

The reaction to the stimuli is picked up by electrodes attached to the patient's skin, amplified, and displayed as lines with characteristic patterns on a monitor for the doctor to interpret.

Depending on which sensory organ is stimulated, specialists use the terms "auditory evoked potentials (AEP)","somatosensory evoked potentials sensitive (SSEP)", and "visual evoked potentials (abbreviated VEP)" for the different tests.

If certain pathways in the CNS are impaired, for example by a tumour, the patterns of the displayed evoked responses may be altered. Information on the nature and location of the potentially underlying CNS disease can thereby be obtained. AEP, SSEP, and VEP are very sensitive measurements and particularly useful for diagnostics of intraspinal tumours, tumours of the posterior fossa (brainstem and cerebellum), and the visual pathway.

Evoked potentials tests are frequently performed even while surgically removing a brain tumour to warn the surgeon on time, if he/she gets close to eloquent nerve tissue, thereby preventing surgical damage.