What does an Electroencephalogram (EEG) Test?

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An electroencephalogram (EEG) evaluates electrical activity produced by the brain, which can signify or rule out certain conditions, most commonly seizure disorders. The test takes about an hour to complete, and the results are automatically sketched on paper, while a video monitor records the movement of the patient, which can disrupt the test.

It is easier to read an EEG of an adult than one of a child, since there is less variance in brain activity. There is often so much variance in brain activity that a reading taken on a child may be consistent with epilepsy where none exists. Generally, seizure disorder in children, without the presence of identifiable seizures, requires additional testing to have confirmed results.

As a test progresses, if it is used to examine seizure disorder, a person may be directed to look at flashing lights, which might trigger a seizure. The lights are stopped if the readings show that a person is in pre-seizure mode. This means that the person generally doesn’t have a seizure during the test, but that it shows electrical activity consistent with what would become a seizure.


An EEG may also be used to evaluate other conditions. For example, people who come to a hospital in an altered state of consciousness, perhaps after a head injury, would probably have this test performed. Migraines have been shown to produce similar patterns, and people who suffer from them may have this test run to confirm a diagnosis. Some psychiatric disorders that are organic in nature can also show a distinct pattern of electrical activity.

People with tumors or with brain abscesses may also show lack of electrical activity in some aspects of the test. An EEG can also measure a total lack of brain activity, confirming the death of a patient.

Generally, this test is most helpful in measuring a patient who can be compliant. A screaming child, for example, or a patient with extreme mental disturbance who cannot remain calm will have corrupted results. For children, it is usually scheduled during a child’s naptime.

Not all brain functions can be measured by an EEG. X-rays or more complex scans would probably follow a test that suggests a tumor or cranial swelling in order to confirm the diagnosis. The electrical patterns of the brain are measured against “normal scans,” so the test can be an excellent tool for suggesting variance. Medical professionals may have to look further to confirm the actual meanings of these variations, however.


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Discuss this Article

Post 23

At times when I was walking I just fell as if somebody has kicked my legs from behind and I will wake up quickly as if nothing has happening. if I don't sit i will collapse. Please, i need help.

Post 21

My child is nine years old after four years he got Fibber fides and doctor suggest for an EEG test. We have already had a CT scan test and chest test. All tests are in order. could you suggest to me please which things I should follow for my child. We are from Northern areas of pakistan which is too far flung area from cities of Pakistan.

Post 20

My son is five and needs an eeg done as the school says he is having suspected absences. what will the test show them and what will it involve?

Post 18

About two months ago, I was very sick and throwing up for about 12 hours. when I got to the hospital and was lying on the table, I could see these red and green lights. they started slowly and then got faster and my body was flapping with the speed of the lights. What do these lights mean??

Post 17

i had a head injury 18 mounts ago and still I am experiencing head pain. The MRI doesn't show anything. The STI scan does not show any major problems. i have to take an EEG test. I really want to find out why i have head pain. is this EEG test going to show what is going on?

Post 16

my child has been having convulsions for the past two and a half years and i want her to undergo an eeg test. After that, what next?

Post 15

i am not getting sleep. For the last ten years my master health check up has been normal and a normal brain scan also normal. my eeg is also normal.

i am not getting even 10 minutes of sound sleep. Please, i am suffering a very big problem. Please suggest to me what is my problem.

Post 14

i am 20 years old and i had an eeg test last year. My result was abnormal but still i am not having seizures, but my result is abnormal so i want to know the exact reasons. But i am having headaches. i can't sleep at night.

Post 13

I'm 20 years old and I had eeg test for an aviation exam. The result was Abnormal(slowing). I don't have any problems of seizure but still the result was abnormal.

So please help me and tell what's the exact reason behind it? Is there any way so that my eeg can be normal lifelong?

Post 12

ana57133- please research info on Infantile spasms. It needs to be controlled ASAP.

Post 11

anon36132: I know everything you are going through with your 9 year old son must be difficult. i recommend having him tested by a neurologist to rule out any possible abnormal brain activity. Last result is a spinal test for meningitis.

Post 10

Ask the doctor or neurologist these questions. I don't mean to be rude but these are grade school questions. I just went through five days of video EEG testing and I am not in the dark, generally speaking.

Do some research and ask questions in person. Enough of this internet information era!

Post 9

My child is eight months old. He was premature and subsequently caught an infection and so remained hospitalized for a month.

Now his EEG test was performed because we observed him jerking. His reports show evidence of multi focal spikes, burst suppression and conclusion says "modified hypsarrythmia".

The doctor prescribed Delta Cortal tablets 3 times a day. Please comment on this if the medication suggested is incorrect.

Post 8

My six-year-old daughter had a seizure (convulsion/fits with fever) of a very short period of a minute. doctor suggested eeg test. is it necessary to carry out this test?

Post 7

my son's eeg test found some variations. The doctor suggested some drugs but there are some side effects. Does anyone know any other way for it.

Post 6

my son's eeg test results shows "Background activity is normal. There are few bursts of bi synchronous bilaterally symmetrical sharp waves. EEG is abnormal shows potential seizure activity". Please give your comments for recovery from this.

Post 5

My six-year-old son had a seizure (fits with fever) of a very short period of a minute. Had an eeg test and found no abnormalities. Any other tests to be carried out?

Post 4

my son is 9 years old with a mild speech difficulty. He had two episodes of dizziness, staggering movement, falls which he could not control, sweating, pale lips and mild weakness. Afterwards, his echo and MRI were normal. what further test should he have? Please advise.

Post 3

Can an EEG detect a brain aneurysm?

Post 2

My child (4) has speech difficulty and an EEG has been recommended as a means to rule out epilepsy. As there is often so much variance in brain activity of children the result may be consistent with epilepsy where none exists. What else can we learn from this test i.e. could it help identify possible concentration issues or disruption to the auditory process and brain interpretation thereof?

Post 1

My son had an 48 hour eeg test and I think I saw red and green lines during some of the test. What do the red and green lines mean on an eeg test?

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