Please read this information carefully before coming in for your Electroencephalography (EEG)
What is an EEG?
EEG stands for electroencephalogram. It is a recording of the electrical signals from the brain, looking at how it is functioning rather than taking images as you would see in a scan. An EEG is a non-invasive, painless procedure and you won’t need to shave or cut your hair.
Why have an EEG?
You may be referred for an EEG, if you have been experiencing possible fits, seizures, faints, or “funny turns”. The EEG will assess your ongoing electrical brain activity.
What happens during an EEG?
A routine EEG takes around 60 minutes. 20-30 minutes of this time involves measuring your head, and attaching small electrodes with a sticky paste. The rest of the time is to take the recording.
Your head will be measured, then rubbed gently before 28 small metal electrodes attached to wires are applied using a soluble sticky paste. 2 electrodes will be applied to your arms or shoulders to measure your heart rate during the EEG. You will relax on a bed with your eyes closed for most of the recording. Every so often the physiologist will ask you to open your eyes. After several minutes of recording, you may be asked to do some activation techniques including hyperventilation and photic stimulation.
Hyperventilation
You will be asked to take deep breaths for 3 minutes with your eyes closed. You may feel lightheaded or have tingling in your fingers or lips during this, but these feelings will usually pass quickly once the task has finished.
Photic Stimulation
You will be asked to look at a series of bright flashing lights with your eyes open and closed for 10 seconds at a time. During this part of the test there is a very small chance, if you are sensitive to flashing lights, that it may provoke a seizure. The physiologist will be watching the EEG at all times and if you appear sensitive they will stop the light immediately.
Preparing for the test
- You must arrive with clean, dry hair free from grease, gel, wax or other hair products. You may wish to bring a comb or brush to tidy your hair after the test.
- We advise you have something to eat before coming for the test, preferably within 1.5 hours, as you are more likely to be comfortable during the test.
- Continue taking all regular medication as normal prior to the test.
- You will be asked if you understand this information and whether you consent to the test before we start. At your appointment, you are welcome to ask the neurophysiologist doing the test to give you any further information or explain more about the procedures.
When will I get my results?
You will not get your results straight after the test or see a doctor on the day as the EEG needs to be fully analysed.
A full report will be sent to the GP or consultant who referred you within 2 weeks, they will then contact you to discuss the results. Please note, results are not sent directly to you.
Contact details
This information is intended as a guideline only. If you have any further questions about your test (excluding about results) please contact the department on the numbers below and a member of staff will be happy to help.
Your responsibility as a patient
Outpatient services at North Bristol NHS Trust are in great demand. Even so, every week an average of 600 patients fail to attend, which wastes appointments. Please tell us with as much notice as possible if you no longer need your appointment and we can allocate this to another patient.
What if I am unwell or need to change my appointment?
If you have an infectious condition, such as COVID-19, measles, mumps, chickenpox, flu, stomach upset, have head lice, or are unable to attend your appointment for any other reason, please let us know with as much notice as possible so that your appointment can be rescheduled and offered to someone else.
If you want to change the appointment for a second time, we cannot offer you another date unless there are exceptional circumstances.
What if I don’t attend?
We will assume that you no longer require your appointment, and we will not offer you another one. We will write to the consultant/doctor who referred you and inform them that you did not attend.
© North Bristol NHS Trust. This edition published December 2024. Review due December 2027. NBT003739
