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What does an EEG test do?An electroencephalogram (EEG) records activity in the brain. Your brain constantly produces tiny electrical signals. During an EEG test, small sensors, called electrodes, are placed on your scalp. The electrodes are connected by wires to an EEG machine. Electrodes are attached using a special paste glue or paste. After the electrodes are removed, you may still have a lot of glue in your hair. Hair conditioner can help to remove the glue afterwards. The electrodes pick up the electrical signals from your brain and record them on a computer. They only pick up the electrical signals. They don’t interfere with your brain and they don’t cause you any pain. The electrical signals look like wavy lines that show your brainwave patterns. The EEG test can only show your brainwave patterns at the time the test is carried out. At different times, your brainwave patterns may be different. A highly trained specialist, called a clinical neurophysiologist, can recognise if your EEG test shows a brainwave pattern that is different to most other people. Some of these patterns point to a strong possibility of epilepsy. When are EEG tests done?Your doctor might ask you to have an EEG (electroencephalogram) test for one of the following reasons:
Sometimes an EEG is done to check whether someone is in non-convulsive status epilepticus. Non-convulsive status epilepticus can change a person’s level of awareness or cause confusion, but might not be recognised as a seizure without an EEG. The results of an EEG can help doctors to make the correct diagnosis and decide on the best treatment. They should always be interpreted by a doctor who specialises in reading EEG results. This is because reading an EEG incorrectly is one of the most common reasons for people to be given the wrong diagnosis. Where are EEG tests done?An EEG is usually done in hospital in an outpatient clinic. People with epilepsy have told us that they found it helpful to go with someone to the appointment. Some people find the process quite tiring and there is a very small risk you might have a seizure during the test. You may find it useful to plan how you will get home after the appointment. You might be asked to take a simple piece of portable recording equipment home with you. You will be shown how to operate this. What information does an EEG test give?An EEG test gives information about the electrical activity that is happening in your brain at the time the test is carried out. Many people with epilepsy only have unusual electrical activity in their brain when they are having a seizure. The rest of the time the brain activity may be entirely normal. So, if your EEG test doesn’t show any unusual activity, it only means that there is no epileptic activity in your brain at the time the test is being done. This doesn’t prove that you don’t have abnormal activity in your brain at other times. And it doesn’t exclude you having epilepsy. People with some types of epilepsy have unusual electrical activity in their brain even when they are 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. A small number of people have unusual EEG test results, even though they never have seizures and they don’t have epilepsy. These could be caused by other medical conditions, problems with their vision, or brain damage. So, an EEG that shows unusual brainwave patterns doesn’t always 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, the doctor will look at where it is happening in the brain. With focal (partial) seizures the activity is only happening in some areas of your brain. With generalised seizures the activity is more widespread. But unless you have a seizure during the recording the doctor cannot be absolutely sure what type of seizures you have. Can an EEG test show if there is any damage in my brain?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. An MRI can do this. Will I have to have more than one EEG test?There are several ways an EEG test can be done. And there are several reasons why you might be asked to have further EEGs.
Are there risks to having an EEG test?Will an EEG test cause me to have a seizure?There’s a very small risk that you could have a seizure during an EEG test. This could be caused by looking at a flashing light or breathing deeply. These activities are usually part of the test. You will be closely monitored and medical professionals will be there to help if you do have a seizure. Your doctor might ask you to have less sleep than usual before you have some types of EEG tests. This is done to increase the chances of catching abnormal activity during the test. This might also increase the risk that you would have a seizure around the time of having the test. Will having a seizure during an EEG test affect my right to drive?If you hold a driving licence, having a seizure could mean that you have to stop driving until you have been seizure free for 12 months. If you are concerned about the risk of having a seizure, talk to the doctor who has asked you to have the test. Will I have to give my consent (permission) for an EEG test to be done?You will usually have to give your consent to having an EEG test done. This is because it is important that you are aware of why the test is done and of its risks, however small they might be. A video recording is usually recorded as part of the EEG test. Your consent will also be needed for this. If you give your consent, but then change your mind, you can withdraw your consent at any time. The NICE guidelines say you should be given information on the reasons for tests, their results and meaning, the reasons for of specific investigations, and how they will be carried out. What types of EEG tests are there?
How long will it take to get my EEG results?You will not normally get your EEG test results on the same day. This is because the recordings will need to be studied by the specialist first and then sent to the doctor who requested the tests. It will usually be a few days or weeks before they can discuss your results with you. If you have any other questions about an EEG test, you could ask your family doctor, epilepsy specialist, epilepsy specialist nurse or the person who will carry out the test. Further readingDownload our booklet on Epilepsy DiagnosisDiagnosis, healthcare and treatmentHere to support youCall the Epilepsy Action helplineIf you would like to talk to someone about epilepsy, our trained advisers are here to help. 0808 800 5050 Send us your questionSend a question to our trained epilepsy advisers. (We aim to reply within two working days). Contact us today Sign up for the latest updates from Epilepsy Action"*" indicates required fields What happens if EEG is abnormal?Abnormal results on an EEG test may be due to: Abnormal bleeding (hemorrhage) An abnormal structure in the brain (such as a brain tumor) Tissue death due to a blockage in blood flow (cerebral infarction)
What are 10 conditions diagnosed with an EEG?10 Conditions Diagnosed With an EEG. Seizure Disorders. The primary use of EEG is diagnosing epilepsy and other seizure disorders. ... . Sleep Disorders. Sleep disorders range from insomnia to narcolepsy. ... . Brain Tumors. There are many types of brain tumors. ... . Brain Injury. ... . Dementia. ... . Brain Infections. ... . Stroke. ... . Attention Disorders.. What problems can an EEG detect?An electroencephalogram (EEG) is a noninvasive test that records electrical patterns in your brain. The test is used to help diagnose conditions such as seizures, epilepsy, head injuries, dizziness, headaches, brain tumors and sleeping problems. It can also be used to confirm brain death.
What happens after an EEG test?What happens after an EEG? After your EEG, the technician will remove the electrodes and clean your scalp. Your hair and skin may feel sticky, so you'll want to wash your hair at home. You can drive and return to your usual activities unless your healthcare provider says you shouldn't.
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