What is a visual-evoked potential test?
The visual evoked potential (VEP) test measures the electrical signal generated by the visual cortex (a brain region) in response to visual stimulation. This examination is also known as a visual evoked response (VER).
A VEP test evaluates the function of your visual pathway, which encompasses your:
- Optic nerves
- Optic chiasm (the region of the brain where optic nerve fibres from one eye cross those from the other)
- Optic tract (the connection between the optic chiasm and the brain)
- Optic radiation (the portion of the visual pathway responsible for transmitting visual information from the retina, optic nerve, and optic tract)
- Cerebral cortex.
On the VEP test, any abnormality that affects the visual pathways or visual cortex in the brain can manifest as an abnormality.
What is diagnosed by a visual-evoked potential test?
Visual evoked potential tests can assist in the diagnosis or identification of the following conditions:
- Multiple sclerosis (MS), which causes optic neuritis frequently, is the most prevalent reason medical professionals order a visual evoked potential test.
- A glioma on the optic nerve (typically caused by neurofibromatosis type 1)
- Compression of your optic pathways as a result of hydrocephalus or a pituitary adenoma,
- Damage to the visual pathways caused by head or brain trauma.
- Toxic optic neuropathy caused by certain medications or other contaminants, such as carbon monoxide
- Other varieties of optic neuropathy, including anterior ischemic optic neuropathy.
- Infections affecting the visual pathway, such as meningeal tuberculosis.
VEPs can also assist physicians in determining the progression of certain neurodegenerative conditions that have already been diagnosed.
How do I prepare for a visual evoked potential test?
Your healthcare provider will discuss what to expect during the examination and what to do beforehand. Be bold and ask queries or express concerns. Follow their preparation instructions precisely.
Before the test, you must ensure your hair is clean and free of hairsprays, oils, or gels. These items may impede the functionality of the electrodes.
What should I expect during a visual-evoked potential test?
As there are numerous varieties of VEP tests, the procedure may vary.
Generally, you can anticipate the following:
- Electrodes will be attached to your scalp using releasable adhesive by a medical professional. The electrodes are connected to a machine that provides your physician with information about your brain's activity.
- You will wear a patch over one eye and view a monitor displaying a flickering visual stimulus (typically a checkerboard pattern). Once the provider has examined one of the eyes, you will repeat the procedure on the other.
How long does a visual evoked potential test take?
The test could be completed in up to 60 minutes.
What do visual-evoked potential test results indicate?
After interpreting the results of your VEP, a specialist will compile a report and submit it to your healthcare provider. Your provider will then provide you with the results.
VEPs can detect multiple issues within the visual pathway. Each case presents differently regarding the wave's shape and the duration between the stimulus and the brain's activity. For instance, the VEP test reveals a delay in cerebral responses in optic nerve demyelinating conditions (such as MS). Again, your healthcare provider will explain the results and determine if additional testing is necessary.