Sleep Deprived Electroencephalography (SDEEG)

Please read this information carefully before coming in for your Sleep Deprived Electroencephalography (SDEEG)

What is an SDEEG?

SDEEG stands for Sleep Deprived EEG. It is a recording of the electrical signals from the brain, whilst you are awake and asleep. An EEG looks at how the brain is working instead of taking images you would see in a scan. It is a non-invasive, painless procedure and you will not have to shave or cut your hair.

Why have an SDEEG?

You may be referred for an SDEEG if you have been experiencing possible fits, seizures, faints, or funny turns. The SDEEG will assess your ongoing electrical brain activity.

What happens during an SDEEG?

An SDEEG take around 90 minutes in total. 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. Two electrodes will also be applied to your arms or shoulders to measure your heart rate during the EEG.

You will be asked to relax on a bed with your eyes closed, the lights will be turned off and you will be allowed to drift off to sleep.

Sleep deprived EEG

For this test we ask you to stay awake for a full night before coming to the appointment. This will mean you are very tired and more likely to fall asleep during the recording.

A video will also be recorded alongside the EEG which can be useful if you have any symptoms during the recording.

Once the recording has finished all electrodes will be removed and your head wiped with warm water. You may still need to wash your hair when you get home.

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 also ask that you avoid drinking coffee or other caffeinated drinks before the test as this can affect your ability to fall asleep. You should have something to eat before coming for the test, preferably within 1.5 hours as you are more likely to sleep if you are full.
• Continue to take 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 to explain more about the procedure.

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 SDEEG 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 on the back of this leaflet 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 in 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 July 2025. Review due July 2028. NBT003799.