What is a visual-evoked potential test?

A visual evoked potential, or VEP test, is a measure of the electrical signals your visual cortex—a part of your brain generates in response to visual stimulation. Another name for this test is a visual evoked response, or VER.

A more technical description of what a VEP test does is that it checks out the healthiness of your visual pathway, which is comprised of your:

• Eyes
• Optic nerves.
• Optic chiasm-that space in your brain where some optic nerve fibers from one eye cross optic nerve fibers from the other eye.
• Optic tract-the pathway between the optic chiasm and your brain.
• Optic radiation-that part of your visual pathway that is wired to convey visual input from your retina, optic nerve, and optic tract.
• Cerebral cortex.

The VEP test will be sensitive enough to identify any condition that affects the visual pathways or the visual cortex in the brain.

What does a visual-evoked potential test diagnose?

Visual-evoked potential tests can diagnose or lead to suspicion for the following conditions:

• Multiple sclerosis is commonly known to start as optic neuritis, which is the most common indication for ordering a visual-evoked potential test.
• A glioma along your optic nerve, commonly because of neurofibromatosis type 1.
• Compression of your optic pathways, for example, hydrocephalus or a pituitary adenoma.
• Head or brain trauma resulting in damage to the visual pathway.
• Certain medicines or other toxins, such as carbon monoxide, cause toxic optic neuropathy
• Other forms of optic neuropathy, including anterior ischemic optic neuropathy
• Visual pathway infections like meningeal tuberculosis.

VEPs can also be of interest to physicians to track the progression of some already diagnosed neurodegenerative disorders. These are:

• Multiple sclerosis (MS).
• Leber optic neuropathy (LON).
• Kjer-type dominant optic neuritis (DON).
• Friedrich's ataxia.

How does a test for visual evoked potential take place?

A test for a visual evoked potential involves attaching electrodes to parts of your head and showing you a visual stimulus, usually a flashing pattern of a checkerboard.

Electrodes placed on top of the head monitor the electrical impulses, or signals, transmitted between cells in the brain. As the visual pattern flashes, your visual pathway interprets and reacts to the stimulus. Electrodes record the resulting electrical activity in your head. VEP tests are conducted behind an electroencephalogram.

The evoked potential machine averages the EEG signals following multiple visual stimuli to assess the function of your visual pathway. It records the electrical response to visual stimulation on several channels or traces. The brain, particularly the visual cortex, has waveforms that appear at specific times in response to a visual stimulus.

A technician will then examine the wave patterns and scan for unusual activity, which can indicate a range of problems with your visual pathway.

How should I prepare for a Visual Evoked Potential test?

Your doctor will tell you in advance what you can do and what to expect during the test. Never express your concerns or ask questions. Please be sure to follow their preparation instructions.

Before a test, you must ensure your hair is clean and free of hair sprays, oils, or gels. Such substances may interfere with the electrodes' functions.

What happens during the visual-evoked potential test?

VEP tests vary, but one may expect some of the following:

• A healthcare provider will place electrodes- small metallic disks—in specific places on the scalp using removable glue. Electrodes then attach to a machine that feeds information to your provider regarding your brain's activity.
• A patch over one eye, looking at a flashing visual stimulus, usually a checkerboard pattern that is projected onto a monitor will be experienced by you. Once the healthcare provider has completed evaluating one eye, you will have the test completed for your other eye.

What is the duration of a visual-evoked potential test?

The test may be up to 60 minutes in length.

What do results from a visually evoked potential test mean?

The results of a visual evoked potential test can indicate differences in the areas of perception where certain visual stimuli are perceived as being flickering, static, or otherwise nonflickering.

Once a specialist interprets your VEP results, they assemble a report and send it to your health care provider. Your provider will then inform you of the results.

VEPs can diagnose several unrelated conditions along your visual pathway. Each of those problems has a different presentation regarding the wave's shape and the amount of time it takes from when you are stimulated to when your brain is active. For example, the VEP test reflects an increased delay in your brain's responses in demyelinating optic nerve conditions, such as in MS.

Again, your provider will interpret the results for you and may also need to order additional studies.

To seek an expert consultation

Call us at +91-9076972161
Email at care@tenderpalm.com