Evoked Potentials Test (EP)

An evoked potentials (EP) test evaluates the amount of time it takes for a stimulus to reach the brain. The stimulation may be through touch, sight, or sound.

What is an evoked potentials test?

An EP test can help identify irregularities of the central and peripheral nervous systems. These irregularities are captured by placing electroencephalogram (EEG) electrodes on the scalp and measuring the electrical activity of the brain when a stimulus is applied. This stimulus can occur visually, such as in the form of flashing lights; auditorily, such as in the form of sound clicks; or through the electrical stimulation of peripheral nerves.

Types of evoked potentials tests include the following:

  • Auditory EP assesses the auditory nervous system by playing sounds via earphones.
  • Visual EP assesses the visual nervous system by flashing lights or a checkerboard screen.
  • Somatosensory EP uses electrical stimulation of peripheral nerves to activate neural structures along the somatosensory pathways of the upper and lower extremities (arms and legs).

Why is an evoked potentials test performed?

An EP test may be performed as a part of a presurgical evaluation or during surgery. Recommendations for an EP test are based on the area needing to be evaluated as well as the type of stimulus. A surgeon may request this test before surgery to establish baseline information that will be available to them during a surgical procedure.

What can I expect during an evoked potentials test?

Electrodes will be applied to your child’s scalp using a glue known as collodion, and a special cap will be placed over the electrodes. Then, your child’s head will be wrapped with gauze. The electrodes are connected to a wire or cord attached to a cassette, a nearby wall, or a machine. The electrodes will be checked regularly to ensure that EEG activity is recorded. Benadryl may be given if your child experiences itching from the cap and glue. It is important to keep your child from scratching the electrodes.

Once the electrodes are in place, the test will begin and your child will be asked to watch the flashing lights, listen to clicks, or remain still while parts of their arms or legs are stimulated. The amount of time it takes to complete an EP test varies from person to person. If all three EPs are ordered, the process can take anywhere between 1 and 6 hours depending on your child’s ability to remain quiet and relaxed during stimulation. The technologist will remove the electrodes when your child is able to return home. Do not remove the electrodes yourself or allow your child to remove them.

How can I best prepare for an evoked potentials test?

EP tests are noninvasive procedures that are often well tolerated and require minimal preparation. Before your child is admitted to the epilepsy monitoring unit (EMU) for VEEG testing, be sure to wash their hair. Please do not use any hair products, including conditioner, gel, mousse, oils, and hairspray.

Care Team Approach

UT Health Austin Pediatric Neurosciences at Dell Children’s, a clinical partnership between Dell Children’s Medical Center and UT Health Austin, takes a multidisciplinary approach to your child’s care. This means your child and your family will benefit from the expertise of multiple specialists across a variety of disciplines. Your child’s care team will include epileptologists, pediatric neurologists, pediatric neuropsychologists, pediatric neurosurgeons, pediatric physical medicine and rehabilitation specialists, hospitalists, anesthesiologists, nurses, advanced practice providers, social workers, psychologists, child life specialists, dietitians, physical therapists, occupational therapists, speech therapists, neurodiagnostic technicians, pharmacists, and more, who work together to provide unparalleled care for patients every step of the way. We collaborate with our colleagues at the Dell Medical School and The University of Texas at Austin to utilize the latest research, diagnostic, and treatment techniques, allowing us to identify new therapies to improve treatment outcomes. We are committed to communicating and coordinating your child’s care with other healthcare providers to ensure that we provide comprehensive, whole-person care.

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