Evoked potential tests can help diagnose neurological conditions. These tests are noninvasive and involve the use of electrodes and a stimulus to record your brain’s electrical activity and responses.
Evoked potential tests measure the electrical activity in areas of your brain and spinal cord in response to certain stimuli. The tests involve electrodes placed on specific parts of your scalp and/or other parts of your body and delivery of a stimulus (such as images, sounds or electrical pulses). The electrodes “catch” your brain’s and nerves’ electrical signal responses to the stimulus.
Evoked potential tests record how quickly and completely nerve signals reach your brain. They can find damage along nerve and brain pathways that are too subtle to show up during a neurological examination. The damage also may not yet be noticeable to the person. Healthcare providers use evoked potentials in combination with other tests to help diagnose neurological conditions.
The three main types of evoked potential tests include:
Healthcare providers use evoked potential tests to show abnormalities in the function of nerve and brain pathways that can result from neurological conditions. They also use SEPs during certain surgeries to monitor your neurologic function during the course of surgery.
Providers most commonly use these tests in an outpatient setting to help diagnose multiple sclerosis (MS). But they use them to help diagnose other conditions, as well.
For example, a visual evoked potential test can help diagnose optic nerve tumors or optic neuropathy. A brainstem auditory evoked response (BAER) test can assess hearing ability (especially in infants) and can point to possible brainstem tumors.
No, an evoked potential test and an electroencephalogram (EEG) are different tests. However, healthcare providers who perform evoked potential testing are often those who also perform EEGs.
The difference is that an EEG measures and records your brain’s electrical signals as they naturally happen. Evoked potential tests measure how quickly your nerves respond to certain stimulation.
An evoked potential test involves electrodes placed on specific parts of your scalp (and potentially other parts of your body) and delivery of a stimulus. This is so your healthcare team can record your brain’s electrical response to the stimulus.
To understand how this test works, it helps to know how your nervous system functions. Your nervous system consists of a vast network of nerves that send electrical signals to and from other cells, glands and muscles all over your body. These nerves receive information from the world around you. Your brain then interprets the information and controls your response. It’s like an enormous information highway running throughout your body.
In an evoked potential test, electrodes on your scalp measure electrical signals (impulses) as they travel between brain cells. As you experience the stimulus — either a visual pattern, series of sounds or very mild electric pulses or “shocks” — your nervous system responds to and interprets the stimulus. The electrodes on your scalp record the electrical activity in your brain that results. Healthcare providers run evoked potential tests by analyzing electroencephalogram (EEG) response (brainwaves) as it reacts to the stimulation.
The evoked potential machine averages the EEG signals following multiple stimuli so that it can assess the functioning of a specific neurological system. The evoked potential machine records the electrical response to the stimulation on several channels or traces. Your brain has specific waveforms that occur at very specific times in response to a various stimuli.
A specialist then interprets the wave patterns and looks for abnormal activity, which can point to various issues with your brain, spinal cord or nerves.
Your healthcare provider will go over what to expect during the test and what to do before it. Don’t hesitate to ask questions, and be sure to follow their preparation instructions.
Before the test, you’ll need to make sure your hair is clean and doesn’t have any hair sprays, oils or gels in it. These products can interfere with the function of the electrodes.
There are several different types of evoked potential tests, so the process may vary.
You can generally expect the following for each type:
The time it takes to complete an evoked potential test varies based on the type. In general, the tests last 60 to 90 minutes. Your healthcare provider will give you more specific details on what to expect.
Specially trained neurologists or neurophysiologists will interpret the results of your test and put together a report. They’ll send it to your healthcare provider. Your provider will then share the results with you. They’ll let you know if you need any other additional tests.
Your healthcare team may consider the results of the test in addition to findings from other tests, such as a neurological exam or MRI, before making a diagnosis.
A note from Cleveland Clinic
An evoked potential test is a noninvasive way to help diagnose certain conditions that affect parts of your nervous system. Your healthcare provider will walk you through the process before and after the test. Don’t be afraid to ask questions — they’re available to help you.
Last reviewed by a Cleveland Clinic medical professional on 02/03/2023.
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