Download Visual evoked potential test (VEP) (type:pdf size:128KB)

PATIENT
INFORMATION
Visual evoked potential test (VEP)
Your doctor has recommended that you/your child have a VEP. This document explains the
procedure and aims to answer the main questions you’re likely to have. If you have any additional
questions then please feel free to talk about them with your doctor or nurse before the procedure.
What is a visual evoked potential test?
A visual evoked potential or VEP is a test used to look for problems in the brain that affect vision.
Instrumentation is used which records brain activity related to nerves that make up the visual pathway.
What are the alternatives?
There are no alternative scanning methods available at present which record electrical activity of the
brain. However, many areas of research currently taking place may mean that alternative recording
techniques may become available in the future.
Preparing for your visual evoked potential test
Ensure that the hair is washed prior to the VEP appointment. Do not use any hair products (gel,
hairspray, etc). Any wigs or hair pieces, sewn in hair extensions should be removed prior to the VEP
appointment.
Take any medications as normal unless otherwise instructed by your doctor. Bring to the
appointment a written list of medication you may be taking.
About the procedure
On arrival for the VEP test, it will be necessary to obtain consent before the investigation begins.
The VEP is carried out by a clinical physiologist who will explain each aspect of the test and will be
happy to answer any questions. You will be seated while small silver discs called electrodes are
applied to your head with sticky paste. One of your eyes will be covered with an eye pad. You will be
asked to look at a flashing light/red spot on a checkerboard screen that shifts from side to side. The
brain signals are recorded using a computer.
What to expect afterwards
The physiologist will remove the electrodes. This will not hurt as they are easy to remove. Once the
electrodes are removed you are free to leave. Your daily activities will not be affected.
Getting your results/follow-up
The VEP signals are reviewed by the clinical physiologist and the consultant neurophysiologist who
prepare a report. This takes about a week. The report will go back to the doctor that referred you for
the VEP prior to your follow up appointment.
What are the risks?
During your visual evoked potential study, you will be asked to either look into a flashing strobe light
or at the centre of a screen while a checkerboard pattern moves from side to side. This is called a
flash and pattern reversal stimulation respectivley, and they are required to carry out the test.
We are however required to inform you that looking at the flashing light carries with it a risk of
provoking a seizure in a susceptible person. The checkerboard pattern carries an even smaller risk.
If you do have a seizure at any time, this must be reported to the DVLA and may result in the loss
of your driving licence.
We need to seek your permission to use these stimulation methods. If after reading this form you
are happy to give your permission we will go ahead with the test as usual. If at any time you wish
to stop, you are free to request this at any stage. If you do not want you/your child to undergo
these procedures, we will be unable to perform the test.
Please note that if any visitors are going to stay in the recording room during the VEP, the
comments about the risk of flashing strobe light provoking a seizure will also apply to them. Those
accompanying may chose to look away if this concerns them.
Frequently asked questions
Q. What are the benefits of evoked potentials?
A. These procedures provide valuable information that can help your doctor reach a diagnosis and
assist in the management of your medical problem
Q. Is there any discomfort from the test?
A. Most tests involve no discomfort whatsoever. Of course eyes are very sensitive and we take
special care if we need to take recordings from them.
For further information
www.mstrust.org.uk or 0800 032 3839
www.brainandspine.org.uk or 0808 808 1000
Contact
If you have any questions please contact the Neurophysiology Department on: Tel: +44 (0)20 7460
5773 or Fax: +44 (0)20 835 2430. The Neurophysiology Department is open between 9am - 5pm,
Monday to Friday.
Bupa Cromwell Hospital
162 – 174 Cromwell Road
London SW5 0TU
+44 (0)20 7460 2000 (hospital switchboard)
[email protected]
www.bupacromwellhospital.com
Published: November 2013
Review: November 2014
This information is published by Bupa Cromwell Hospital and is based on reputable sources of medical evidence and experience from
over 30 years of treating patients. It has been peer reviewed by Bupa Cromwell Hospital doctors. The content is intended for general
information only and does not replace the need for personal advice from a qualified health professional. If you have any feedback on the
content of this patient information document please email [email protected] or telephone 020 7460 5901.