Evoked Potential Tests
What are evoked potential tests?
Evoked potential tests are neurodiagnostic tests that measure the time it takes for nerves to respond to stimulation as well as the size of the response. The responses are called evoked responses. The types of responses are visual, auditory, or somatosensory.
- Visual evoked response (VER) or potential (VEP) occurs when your eyes are stimulated when looking at a strobe light or a screen with a pattern.
- Auditory brain stem evoked response (ABER) or potential (ABEP) occurs when your hearing is stimulated when hearing a noise sent through earphones.
- Somatosensory evoked response (SSER) or potential (SSEP) occurs when nerves in your arms and legs are stimulated when you receive mild electrical pulses at your wrists and knees.
Why are evoked potential tests performed?
Evoked potential tests are often used to diagnose disorders of the nervous system, such as multiple sclerosis (MS), that impact your response time to stimulation because of damage to the nerves. These tests may be performed to diagnose hearing loss, vision loss, and brain response.
What to expect:
You will be instructed about what to wear to your appointment, what to eat before the test, how the test will be performed, and how the test will feel.
Before an evoked potential test, you may need to stop taking certain medications that impact your nervous system. The night before or the morning of your evoked potential test, shampoo your hair, rinse with clear water, and do not apply conditioner or styling products after shampooing.
Special sensors called electrodes will be placed on your skin in the areas where your nerves will be tested. Where the electrodes will be placed will depend on the type of response being recorded. A stimulus will be provided to measure the time it takes for nerves to respond to the stimulation as well as the size of the response. A computer will measure your brain’s response to the stimulation and will identify the location of any nerve damage.
A nerve conduction test usually takes 30 minutes or more to complete. After the test is over, the electrodes will be removed.