EEG tests and epilepsy
These pages are about EEG tests that are done in the UK. If you are looking for information about EEG tests in other countries, please contact your local epilepsy organisation.
Acknowledgement
Epilepsy Action would like to thank Sue Hargreaves, Professional Services Manager of Paediatric Neurophysiology at Royal Manchester Children’s Hospital and the Epilepsy Nurses at The Walton Centre, Liverpool for checking this information.
Introduction
Your doctor might ask you to have an EEG (electroencephalogram) test if you have epilepsy, or if they think you might have epilepsy. This is a painless test, which records the electrical activity in your brain. The results of an EEG may help doctors when they are making a diagnosis, or when they are making decisions about your treatment.
There are several different types of EEG test and the aim of this information is to tell you how they work.
In this section:
- What does an EEG test do?
- Routine EEG tests
- Ambulatory EEG tests
- Sleep EEG tests
- Sleep-deprived EEG tests
- Video-telemetry tests
- What information does an EEG test give?
- Can an EEG test show what type of seizures I have?
- Can an EEG test show if there’s any damage in my brain?
- Will an EEG test cause me to have a seizure?
- Will I have to have more than one EEG test?
What does an EEG test do?
Your brain is constantly producing tiny electrical signals. During an EEG test, electrodes (flat metal discs) are placed on your head. The electrodes pick up the electrical signals from your brain and send them to an EEG machine.
The electrodes only pick up electrical activity from your brain, they don’t give out electrical signals. This means that electrodes don’t affect your brain and they don’t cause you any pain.
The EEG machine records the electrical signals from your brain on a computer. They look like wavy lines. These wavy lines represent your brainwave patterns. The EEG test can only show your brainwave patterns at the time the test is carried out. At different times, brainwave patterns may be different.
Most people have brainwave patterns that look similar to everyone else’s. Sometimes, the EEG test shows that a person has unusual brainwave patterns, which are caused by unusual electrical activity in their brain. These can sometimes indicate that the person has epilepsy.
Routine EEG tests
Usually, you have a routine EEG test at an outpatient’s appointment at the hospital. The appointment normally lasts about one hour. You can go home as soon as the test has been done.
During the test, you sit or lie down. The person who does the test may be a nurse or a technician. They attach the electrodes to your head with a sticky gel. They may ask you to open and close your eyes, breathe deeply for some minutes and look at a flashing light. All of these activities can change the electrical activity in your brain. This can help the doctor to make a diagnosis.
It’s helpful to keep as still as possible during the test, because any movement can also change the electrical activity in your brain. This can affect the results.
Ambulatory EEG tests
Ambulatory means designed for walking. Your doctor may ask you to have an ambulatory EEG test if they want to record the activity in your brain over a few hours, days or weeks. This allows more time for the test to pick up any unusual electrical activity in your brain, than during the routine EEG test.
An ambulatory EEG uses electrodes similar to those used on a routine EEG test. However, the electrodes plug in to a small monitor that records the results. You can wear the machine on a belt, so you are able to carry on with your life as normal. You don’t usually stay in hospital while the test is being done.
Your doctor may ask you to keep a brief diary while you’re wearing the ambulatory EEG. This can show if there is anything you do or any particular situations that cause your brainwave patterns to change.
Sleep EEG tests
Your doctor may ask you to have an EEG test while you’re asleep. This could be because your seizures happen when you’re asleep or when you are tired. Or, you may have had a routine EEG test when you were awake, but it didn’t show any unusual electrical activity. When you’re asleep, your brainwave patterns change and may show more unusual electrical activity.
A sleep EEG test is usually done in hospital, using a routine EEG machine. Before the test, you may be given some medicine to make you go to sleep. The test lasts for one to two hours and you usually go home once you’ve woken up.
Sleep-deprived EEG tests
A sleep-deprived EEG test is done when you’ve had less sleep than usual. When you’re tired, there’s more chance that there will be unusual electrical activity in your brain. Your doctor may ask you to have this test if you’ve had a routine EEG test, but it didn’t show any unusual electrical activity.
Before a sleep-deprived EEG test, your doctor may ask you not to go to sleep at all the night before, or just to wake up much earlier than you usually do.
The beginning of the sleep-deprived EEG test is the same as the routine EEG test. You then try to fall asleep or doze while the EEG is still recording the activity in your brain. The test lasts for a few hours and you usually go home once you’ve woken up.
Video-telemetry tests
You would usually only have a video-telemetry test if you have already been diagnosed with epilepsy. Here are some examples of why your doctor might ask you to have a video-telemetry test.
- It’s not clear what type of seizures you have.
- Your anti-epileptic drugs are not working well.
- There’s a possibility that your seizures are not caused by epilepsy, but something else.
- You are considering having epilepsy surgery.
During a video-telemetry test, you wear an ambulatory EEG. At the same time, all your movements are recorded by a video camera. After the test, doctors can watch any seizures that you had and see if there were any changes to your brainwave patterns at the time of the seizure(s).
If you have a video-telemetry test you need to stay in hospital. The test is usually carried out over a few days. Sometimes your anti-epileptic drugs may be reduced or withdrawn. This is to increase the chances of recording your seizures.
What information does an EEG test give?
EEG tests give information about the electrical activity that is happening in your brain at the time the test is carried out.
With many types of epilepsy, you only have unusual electrical activity in your brain when you’re having a seizure. The rest of the time your brain activity is normal. So, if your EEG test doesn’t show any unusual activity, it doesn’t mean you don’t have epilepsy.
People with some types of epilepsy have unusual electrical activity in their brain all the time, even when they’re not having a seizure. When they have an EEG test, the results can show certain brainwave patterns that doctors recognise. This information is very helpful for doctors when they are making a diagnosis. An example of this is children who have typical absence seizures.
A small number of people have EEG tests that show unusual results, even though they never have seizures and they don’t have epilepsy. This could be caused by other medical conditions such as encephalitis (swelling of the brain) or vertigo (dizziness). Some people inherit unusual brainwave patterns from their parents. Therefore, an EEG that shows unusual brainwave patterns doesn’t necessarily mean that you have epilepsy.
Can an EEG test show what type of seizures I have?
When an EEG test picks up unusual electrical activity, it shows the areas of your brain where it’s coming from. Each electrode picks up the activity in the part of the brain directly underneath it. If you have generalised seizures, unusual electrical activity would be recorded from the electrodes on both sides of your brain. If you have partial seizures, unusual electrical activity would be recorded from electrodes on certain areas of your brain.
Can an EEG test show if there’s any damage in my brain?
No. An EEG test only gives information about the electrical activity in your brain. It doesn’t show if there’s any damage or physical abnormalities in your brain.
Will an EEG test cause me to have a seizure?
There’s a very small risk that an EEG test would cause you to have a seizure. This could happen when you’re looking at a flashing light or breathing deeply. The risk of having a seizure would also increase if your doctor asks you to reduce your anti-epileptic drugs or have less sleep than usual before you have an EEG test.
If you hold a driving licence, having a seizure could mean that you have to stop driving until you’ve been seizure free for 12 months.
If you’re concerned about the risk of having a seizure, it’s advisable to talk to the doctor who has asked you to have the test.
Will I have to have more than one EEG test?
If you have an EEG test that doesn’t show any unusual electrical activity in your brain, your doctor may ask you to have another. It can be helpful, if possible, to have an EEG test at times when you’re more likely to have a seizure, for example early in the morning or, for some women, around the time of your period.
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Comments
I have recently had an EEG and my GP tells me it is abnormal. I then attended a physician who says while it is abnormal he does not feel it is anything to worry about. As a followup I was sent for an MRI, the results of this have not come back yet. The physician says that he is 99% certain that this test will be normal. I am still worried as to why the EEG read abnormal in the first place.
Can anyone give me advice on this?
Some people can have an abnormal EEG. This does not necessarily mean someone has epilepsy, because abnormal patterns can occur for other reasons. However, it might be epilepsy. You could discuss this with your doctor, but they may not be able to give you any information until your investigations are complete.
Mark @ Epilepsy Action
We are taking our 24 yr old daughter down to Kings to discuss the possiblilty of telemetry leads being inserted in to her brain. She has had eegs performed numerous tiems. Has anyone any information about this to guide our questioning or any experiences, good or bad for when we go down for the outpatient appointment?
My child is 8 and had a unprovoked seizure lasting a couple of minutes a few days ago. It was treated by paramedics and then emergency room Doctor. They all took it pretty lightly and said it was most likely onset by video game playing since he had been playing games on the computer just before he seized. We scheduled MRI and a EEG a couple days later as the ER was very busy that day and said it would be better to do those on our own. They took some blood as well. It looked as though they were right about it being video game related because all tests were comming back normal until the last one which is the EEG. It came back abnormal and I have no Idea how serious that is. My Dr. didn't tell me, the nurse did, and they said they would get back to me when the nuerologist appt. would be and I didn't hear back today. Now I have to hope they can get him in right away tomarrow? some one on some site said they had to wait four months. Thats crazy what if it is a brain infection, shouldn't it be caught right away. Is there anything that can give a false abnormal. If it truely is abnormal will they know why by the current test or will they have to do more tests?
I have done EEG yesterday and told me that is not yet the time to stop the medication I am using tegretol 200 in the morning and 400 evening ! It has been five years since my last attack yeton medication just am taking now diazepam to 6mg a day can someone tells me why EEG is not right ?! if i havent got attack for 5 years ?!
I recently had an eeg due to four instances of aura-like symptoms (deja vu), feeling faint, then altered state of consciousness for about 15 minutes, and the eeg was negative so the neurologist thinks it may be caused by low blood pressure and referred me back to a cardiologist.
I looked up causes of deja vu, and can find NOwhere a link between heart and that symptom. So, the eeg may not pick up if I am having seizures??? How effective has it been in diagnosing you or a family member?
The doctor is concerned that you may have neurocardiogenic syncope. That is why he is referring you to a cardiologist. This condition is low blood pressure and causes you to have seizure like episodes that mimic epilepsy.
I had an EEG earlier this year and it was abnormal. Specifically, slow activity in the right posterior quadrant with sharp waves. I have no idea what this means and only know that I have been having seizures since last November. The neurologist has said that this makes it seem more likely that the attacks are epileptic in nature, but I had a normal MRI. Does this mean that I do have epilepsy? The neurologists mentiones commencing an anti-epileptic medication but I feel like I'm in limbo at the moment...I can't place myself under any standardised definitions that I've seen here and I'm desparately frustrated that I have no answers that will allow me to start getting on with my life again. Any advice would be appreciated.
I have had an EEG and MRI test. My EEG has come back with 'some features of epilepsy' and I have not yet had the results of my MRI scan. My new neurologist now wants me to have a sleep deprived EEG scan. I am so glad that after 17 years of having seizures and days at a time not having the strength to even clench my fist so that I can hold a pen, my symptons are now being taken seriously. Having said this I am really worried that I won't be allowed to sleep in the position I can only sleep in. I sleep with all my weight on my left hand side (my fits occur on the left hand side of my body) so that if anything happens in my sleep my weight hopefully stops it. Can anyone tell me will I be allowed to sleep on my side? During my EEG and my MRI My left arm, hand and leg were jerking and the feeling was scarey, and I like to be in control of that jerking all the time hence my sleep position.
Thanks for any replies
Kate
My son had his first seizure at 14. He had a few during the night and then one during an EEG. (Although he said he had twitching in his arms throughout the day for several months. His neurologist diagnosed it as a complex partial seizure and started him on trileptal. He was seizure free for 2 years and taken off meds. 6 months later he had another seizure and then another 4 nights later. He's back on trileptal. His seizures start in his right arm and then generalize to a tonic (freeze and lose breath and consciousness but no shaking) seizure. He had a normal EEG while sleeping this last time. I'm reading about seizure types and it appears to me he has juvenile myoclonic seizures but he wasn't diagnosed with that and it didn't show up on his EEG. Can he have Juvenile Myoclonic seizures and have a normal EEG? Also, if he has seizures at night will they most likely always occur at night?
I am now 47 and have lived my life with epilepsy
i started with epilepsy when i was about 11 and was given medication from that time on. The start of the epilepsy corresponded with the fact my periods started and i set a chip pan on fire and the hospital blamed the epilepsy on the accident saying it was delayed shock. Over the years i coped with the medication carbamazapinem, epilem phenytoin epineuten getting various side effects such as headaches and sleeping on my school desk. I met my man got married the thought of having a baby gave me mixed thoughts would i cope? can i have a baby.? The seisures continued but we asked the doctors. They decided to take me off my medication and i fell pregnant. Throughout my pregnancy i had no attacks again changes in the body hormones. Nine months later i had a ceseran as the hospital decided the birth would be too risky. As soon as i had my son my fits started again. i was again giving medication and went on bringing my son up, me having fits.. About 5 years ago my fits became less and eventually stopped my consultant took me off my medication. I have had a couple of occasions where i have felt "out of sorts" Not knowing i had done something or a bit forgetful my monthly cycle is less timed and i am waking up in bed at night sweating again a change in my hormones. Is it time to say women with epilepsy can be linked with their hormones etc. I have been driving and feel on top of the world to be independant passing my test and advanced test waiting 45 years to do it. I feel fine except for this feeling of loss can medication help i dont want to go back to been labelled an epileptic every one panics i think they need the medication to cope not me
Dear everyone,
I am desperately seeking assistance. My Nuerologist specialist has done a recent sleep-deprived E.E.G. study on me. During the flashing lights I was uncomfortable but she continued throughout the whole process. I didnt have any trouble breathing deeply. The results were abnormal. My doctor told me all that the results meant is my brainwaves are slow during drowsy periods. I was wondering if any one had any information on this. I am trying to get a normal eeg reading for the military. I do not have seizures.
I have a 6 year and 3 months old boy.He was a premature baby(20 days) and weighed app 1.8 kgs at birth.He had a seizure 2 years back due to high temperature.An EEG taken at that time revealed NORMAL.Again few days back from now,he had another seizure again due to high temperature.Doctors say that Seizure during high temperature is common for children below the age of 5 and since the boy is 6 years old,another EEG was advised.I hope that the second EEG will reveal normal.Kindly guide whether I should do further diagonise on him and if so what Should I Do.
Hiya everyone!.
I just wondered if anyone could give me any advice on my experience...Here's my story..
Im 22 years old and got a pretty stressfull job at times of working with children with autism. One morning a couple of months ago when i was sleeping my partner woke up to the sound of me taking a deep breath and saw that i was half in and out of bed with my body jerking this lasted arouind 40 secs..after the seizure he tried talking to me and i was mumbling back i eventually came around fully a few minutes later with no recollection of what had happend...i'd bit my tongue on both sides cut my foot and bruised my legs..i also had red spots just under my eyes and on my neck. I was then taken to casualty as that was the advice they gave from NHS direct, i had bloods taken and was given oxygen, they said they wouldnt put me on meds as it was my first ever seizure and arranged for an ECG, MRI and EEG tests to be done...My ECG and MRI came back clear but my EEG (the breathing test) came back abnormal when i spoke to the consultant he said this could be why i had a seizure and increases my chance of further ones..problems iv got now..is not being able to drive for a year which really upset me but iv got over that now and Iv not being allowed back to work since as because i work with children, my work wanted to know that i was safe to and got in touch with my doctor with a list of questions which included if i was able to work alone with children (in this job it means a lot of the time) and the doctor said he could see no reason why i couldnt work but that i shouldnt be on my own and should be with other staff...this at the moment is not possible..so im worried as i carnt go back until i can work soley with the children..
I was very stressed and upset the week leading up to having the seizure and im just wondering whether is all connected in some way with my breathing..?
I would just like to know if anyone else has been in my position of if anyone can offer advice thankyou
Rachel
i have a scheduled eeg the 23rd of this month .i been having problems with periods of lower levels of conciousness ,a feeling of getting dizzy but nothing actually spinning but i lose control of my whole body i meen i dont start to shake or nothin but i lose all motor function..i cant walk i sound drunk i cant talk right my whole family is concerned...they just put me on topamax because they thought it was a type of migraine but the nero says it can be aura or possible seizures ...does anyone here possibly have the same problem and could it be epilepsy????thanks hope to get lots of replies
Hi Eric
I have been backward and forward the Hospital for over a year and half now, my gp thought that i had, had a stroke and was refered to the stroke clinic, it wasnt long before they realised that I had not had a stroke and that there must be some other problem. My symtom started with numbness down one side I would speak as if I had been drinking all day, total lack of coordination. When I have funny turns as I call them I collapse my hole body feels as if someone has put a lead wait on me and I cannot move this can go on for sometime and has happend offten when I have been on my own, I can now feel the funny turns coming on and I try to fight them but I always loose, after these events I cannot speak I can hear everything people are saying I just cant respond, my husband has called the ambulance a few times but they just treat me like im mental. I dont know if you become very dixlexic after a funny turn as I call them? I know I do. I also find that my reactions are very slow also. I am due to have a electronenecphalogram this week. wish me luck. I hope everything works out for you and it is good that you have the support of your family.
PS: Sorry for any spelling mistakes this is yet another symtom, its not that im stupid
hi, i'm going into kings soon for an intracranial mat and was wondering if anyone could share their experience with me as i'm not going to see the surgeon until november, it's driving me mad not knowing what to expect.
I was looking for some information.
My sister (32 yrs old) was on holidays in Cyprus recently and whilst out having dinner felt a bit unwell and light headed. Her friends took her outside and she collapsed backwards hitting her head off the ground. She came round and then passed out again. She started feeling sick so they called an ambulane. After having a scan at the hospital she was told that she had fractured her skull in three places and had a brain haomerage (can't spell it!). After a further scan she was told that she didn't faint she had an epileptic episode which brought on the seizure. She has been in hospital for 10 days and is now allowed to fly home. She has been told to have an MRI and EEG test done when she gets home. Does this mean she has epilepsy? We have heard of another person who has been diagnosed with epilepsy after having one seizure whilst on holidays (this happened on two separate holidays although he has never had a seizure at home)- is this more common than we think. I'd be glad to hear your views.
I had an MRI scan, an EEG which was normal, followed by a sleep deprived EEG which was also normal. After having the tests done I got a letter back from the doctor saying both were normal. I then went for a five day long EEG and an ECG. This time they are sending a letter back saying no major abnormailities, not that the test result is nomral, and that they will review me at their out patient clinic in due course.
I do not know if this means that the test is normal, or simply that there is a small abnormaility.
Can anyone let me know?
Genetically linked seizure: You're not getting any seizures because of the medication. If you were to stop the medications you may get the seizures back. The thing with seizures is that they cause more seizures to occur in the future, so stopping all seizures from occurring is the best way to treat them. Furthermore, just because you haven't gotten one in 5 years doesn't mean you're cured.
Trauma linked seizure: There's no data for anyone to be on anti-epileptics for more than 7 days. I would taper the dose down and then stop the drugs.
2 mths ago i collapsed blacked out its never happened before i was taken to a&e were i was addmited to hospital the same evening in hospital i had taken 3 seizures, i was given a vitamin drip and kept in for observation for 3 days .
I still havnt heard anything from the seizure clinic and im at the end of my terrior .
hi i have a eeg scan aboot my fits..can u tell me if i will be forced to take a fit wen i am havein the scan please...
Hi Rachel,
Just came over your comment.
I am a Primary School Teacher and have also been signed off work due to recurrent seizures.
Unfortunately,my episodes have been ongoing for 7 years, but it is only these last few months that I have needed time off work as it is starting to impact on my job. As I am sure is the case with yourself, I absolutely love my job and not being able to work is having a huge effect on me.
I have mostly dealt with the cardiologists who up until now felt my collapses were due to 1. Low heart rate ( pacemaker was inserted for this) 2. Vaso vagally sensitve ( put on Beta Blockers) 3. Hypotensive ( felt I was collapsing due to drops in my blood pressure - even though there was no evidence to support this) 4. Hyperventilation - panic attacks ( was sent for a test to the respiratory clinic where it was confirmed that I was not prone to hyperventilation). I never felt any of these suggestions were correct, but I am not a doctor and I am being guded by them.
It was only after a 'seizure' at my doctors surgery, have I now been taken down the Neurology route. I had an EEG which came back normal, but only last week my husband filmed one of the seizures and we managed to take this into the neurologist. Whilst he feels there are some elements which suggest epilepsy there are other features which he'd expect to see that are not there. The good news, is they are now saying it is a seizure and not just a 'faint' which has been suggested in the past.
I am waiting for a referral for Video-Telemetry and a prolonged EEG which will hopefully shed more light on the situation. I also hope to be referred to an epilepsy Specialist.
I totally understand your situation and really hope you can get things sorted out. Why don't you go back to your GP and suggest going to a Respiratory Function Service where they could carry out a hyperventilation assessment? By having all the tests done, you can find out one way or another.
My advice to anyone is not to give up. Whilst I do not claim to be medical expert , I do know my own body and can tell when something is not right. We are all entitled to get the treatment we deserve.
All the best
Lisa
Hi,
I'm wondering if anybody can help? In June 2009 after a night out and feeling abit worse for wear the next morning I had my first fit. Needless to say I gave my partner and the rest of my family a fright! Im 28 and this is the first time anything like this has happened.
For about a year before this I had problems with my hearing. My hearing would change and suddenly everything around me went really loud! It was magnifyed and I felt like people were shouting. This happened daily or some times only once a week. Of course I went to the doctors and got my ear cleared as they thought it was just wax ha ha. After looking at various website I hadnt heard of anybody having the same as me! Somebody said it might have been an aura. Has anyone had this problem? or anything simular? Neurologist said he had never heard of this in his life!
Anyway when my first fit happened I was taken to hospital, bloods taken etc and everything was fine & I was told it was prob due to blood sugar levels being low but my blood came back fine! Following this I had 3 more fits (4 in 7weeks).
Got an MRI scan, clear. Then an eeg and this was fine too, everything was normal. I have since been put on lamacital 225mg in the morning and 250mg at night but OMG the side effect were terrible, insomnia, headaches, spots, sore bones etc the list could go on. Finally the effects have gone and I dont notice being on tablest anymore.
After all my fits, tests and being on medication the neurologist said he wouldnt commit in saying it was epilepsy! Is anybody else in the same position or had hearing problems like me??
At the end of the road, hate being left alone, work no that confident with me incase I have another and the big think is no license for a year.
thank
barry
hi eric, ive just come across this web page & your the first person ive come across with the same symptoms as me.my symptoms started in october last year, my head was hurting really bad just on one side a lot wosre than a head ace. ld lose my speach, i couldnt walk,lose all concentration,forget things & everything as you said.& just feeling ill. i thought i was going mad so off to the doctor i go.he does a lot of test & tells me im suffering from a rare form of migraine an aura there is possabilitys that i could start to have seizures. im seeing my doctor every 4 weeks this is because every 2 weeks we are increasing the dosage of my tablets to stop all this happening. i still have my off days now & again but im getting there. i hope this has been helpful to you. go back to your doctor if your not happy as he needs to make sure your on the right dosage.