Evoked potential test

An evoked potential test can help your provider diagnose multiple sclerosis (MS), peripheral neuropathy, acoustic neuroma, optic neuritis, and more.
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An evoked potential test measures how long it takes your brain to receive (and respond to) signals from your nerves.

You may need an evoked potential test if you have signs of nerve damage. These signs include:

  • Dizziness or balance problems
  • Hearing loss on one side
  • Numbness or tingling in your hands or feet
  • Loss of sensation, or a reduced sense of touch
  • Unexplained vision loss
  • Weakness in your arms or legs

When you have an evoked potential test with University of Iowa Health Care, you’ll find yourself in skilled hands.

Our tests are performed by certified technicians in a lab that’s fully accredited by the American Board of Registration of Electroencephalographic and Evoked Potential Technologists.

Accreditation is only given to medical centers that have up-to-date equipment, specially trained staff, and strict quality standards. This means you can feel confident about the accuracy of your test results.

How an evoked potential test works

Evoked potential tests are noninvasive procedures that show whether certain nerves work properly. These include: 

  • Nerves in your spinal cord 
  • Nerves in your arms and legs (peripheral nerves) 
  • The main nerve in your inner ear (auditory nerve) 
  • The major nerve in each eye (optic nerve) 

This test include two key parts: 

  • EEG: We’ll place small metal discs (electrodes) on your scalp and, in some cases, your spine. These electrodes connect by wires to a special machine. Together, they record your brain’s electrical activity, or brain waves. 
  • Nerve stimulation: We’ll use noise, visual cues, or a mild electric current to activate (stimulate) your nerves. Then, with the help of the EEG, we’ll see how your brain responds. 

By stimulating your nerves, we can measure how quickly and completely they send sight, sound, or touch signals to your brain. 

Types of evoked potential tests

Our providers use three types of evoked potential tests, in both clinic (outpatient) and hospital (inpatient) settings. The type of test you’ll need depends on your symptoms or the type of surgery you’re having.

Somatosensory evoked potential

Somatosensory evoked potential (SSEP) tests evaluate the nerves that help you feel texture or temperature when you touch something. We activate these nerves with “stimulating electrodes” that generate mild electrical pulses when they touch your skin.   

We offer outpatient SSEP testing to help diagnose medical conditions such as multiple sclerosis. And we use it during certain types of surgery—especially spine surgery—to help prevent nerve damage. 

Visual evoked potential

A visual evoked potential (VEP) test assesses the health of your optic nerve (which helps you see). We stimulate this nerve by having you watch a flashing checkerboard pattern on a screen.

This is usually an outpatient test. It can help us confirm whether your vision changes are caused by a condition such as multiple sclerosis or optic neuritis.

Auditory brainstem response

Also known as a brainstem auditory evoked potential, this test evaluates the auditory nerve.  

Your auditory nerve helps you hear; it carries sound from your inner ear to your brainstem. We can activate this nerve by playing a series of clicks or tones through headphones placed over your ears. 

We mostly use this test during certain types of brain surgery or head and neck surgery. For example, if we’re removing a brain tumor, we may monitor your auditory brainstem response to make sure we preserve your sense of hearing.  

What to expect during an evoked potential test

If you’re having an outpatient evoked potential test, it may take up to two hours from start to finish.

Before your procedure

An evoked potential test doesn’t require a lot of special preparation.

Before your procedure, you can eat a meal and take your normal medications.

It’s also ok to shampoo your hair and wash your body the night before (or the day of) your test. However, do not use any conditioner, hair styling products, face or body lotions, or cosmetics. These items can make it harder for electrodes to stick to your scalp or body.

During your procedure

No matter which nerves we’re testing, each type of evoked potential test follows similar steps. The key difference between tests is where we place the electrodes and how we stimulate your nerves. 

  • First, we’ll mark the areas where we need to place the electrodes. These areas may include your scalp, ears, and spine. We may gently scrub these areas with a gritty cleanser.
  • Next, we’ll attach the electrodes using a sticky paste. This paste easily washes off.
  • During the test, you’ll be able to sit or lie down.
  • If you’re having an SSEP test, your technician will place a stimulating electrode on various points of your body. This may include your arms, legs, ankles, or wrists. You may feel some mild discomfort or muscle twitches, but it shouldn’t hurt.
  • If you’re having a VEP test, you’ll simply need to look at flashing images on a screen.
  • Once your test is complete, we’ll remove the electrodes. You can then go home or return to your normal activities.

After your procedure

Your results will be reviewed the same day as your procedure, by a neurologist with special training in evoked potential tests. They will write a report summarizing your results and send it to the provider who ordered your test.

Your provider will help you understand what the test showed and discuss next steps including further testing or potential treatments.

Who can benefit from an evoked potential test?

When used with other tests, such as MRI scans, evoked potential tests can help confirm whether you have nerve damage—and whether this damage is caused by certain medical conditions.  

These medical conditions include:

Our Care Team

Rup K. Sainju, MBBS portrait

Rup K.
Sainju
MBBS

  • Neurology
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Locations and Offices

Neurology Clinic

2007 Roy J. Carver Pavilion (RCP)
Level 2, Elevator E
1-319-356-2571
Clinic
Neurology Clinic at UI Hospitals & Clinics
In University of Iowa Hospitals & Clinics
200 Hawkins Drive, Iowa City, IA 52242

Related Health Topics

Somatosensory Evoked Potential test (SEP)
July 2, 2016
This guide describes what the SEP test is used for, procedures, and other frequently asked questions.

Awards and Recognition

Accredited by ABRET
Our evoked potential lab is accredited by the American Board of Registered Electroencephalographic and Evoked Potential Technologists (ABRET). This designation confirms we offer the highest level of testing quality, accuracy, and safety.