Everything You Need to Know about EEG Test for Brain

If you or a loved one has been referred to take an EEG test, you may be curious about what it is, how it works, and why it’s necessary. In this article, we’ll explore everything you need to know about EEG test for brain, including its use in diagnosing various medical conditions, such as epilepsy and sleep disorders.

What is an EEG test?

Electroencephalography (EEG) is a non-invasive diagnostic test typically used to evaluate brain activity. It records electrical signals that come from the brain via small metal discs called electrodes, which are attached to the scalp using a special adhesive. These electrodes detect the electrical impulses produced by the brain and transmit them to a machine that translates them into wave patterns.

EEG tests are commonly used to diagnose a range of neurological conditions, from epilepsy and seizures to dementia and sleep disorders. They may also be used to evaluate a person’s brain function following a head injury or stroke.

What happens during an EEG test?

An EEG test is a painless and non-invasive procedure that typically takes between 45 minutes to an hour to complete. Before the test, you will be asked to wash your hair thoroughly and avoid using hair-styling products, such as hairspray. You may also be asked to avoid caffeine or other stimulants before the test.

During the test, you will sit in a comfortable chair or lie down on an examination table. A technician will attach electrodes to your scalp using an adhesive gel or paste. The electrodes are then connected to a recording machine, which measures the electrical activity in your brain. You will be asked to relax and remain still during the test, although you may be asked to perform specific tasks, such as closing your eyes or hyperventilating, to see how your brain responds.

After the test is complete, the technician will remove the electrodes, and you can return to your normal activities immediately.

How long does an EEG of the brain take?

EEG tests generally take between 45 minutes to an hour to complete. However, the duration of the test may vary depending on the specific conditions being evaluated. In some cases, your doctor may request a longer EEG test (24 to 72 hours), to monitor your brain waves while you sleep or to track any seizure activity.

Why would a doctor order an EEG?

A doctor may order an EEG if they suspect that a person may be suffering from a range of neurological conditions that affect the brain, including epilepsy, migraines, sleep disorders, and dementia. EEG is a non-invasive diagnostic tool that helps doctors evaluate brain function, identify changes in brain activity, and monitor the effectiveness of treatments for conditions such as epilepsy and seizure disorders.

10 conditions diagnosed with an EEG

An EEG can be used to diagnose a variety of neurological conditions, including:

  1. Epilepsy and seizure disorders
  2. Sleep disorders, such as sleep apnea or narcolepsy
  3. Brain tumors
  4. Migraines and other types of headaches
  5. Dementia and cognitive decline
  6. Attention-deficit/hyperactivity disorder (ADHD)
  7. Stroke
  8. Traumatic brain injury (TBI)
  9. Multiple sclerosis (MS)
  10. Encephalopathy

What is an EEG test used to diagnose?

EEG tests are used to diagnose a variety of neurological conditions, including:

  1. Epilepsy and seizure disorders: EEG is one of the primary diagnostic tools used to identify seizures and determine the type of seizure a person is experiencing.
  2. Sleep disorders: EEG can help diagnose sleep disorders such as obstructive sleep apnea and narcolepsy by monitoring the brain waves during sleep.
  3. Brain tumors: EEG can be used to detect the presence of brain tumors and evaluate their location and size.
  4. Migraines and headaches: EEG can help identify the brain patterns associated with migraines and other types of headaches.
  5. Dementia and cognitive decline: EEG can help diagnose cognitive decline associated with conditions such as Alzheimer’s disease and dementia.
  6. Attention-deficit/hyperactivity disorder (ADHD): EEG can help evaluate brain function in children with ADHD.
  7. Stroke: EEG can help diagnose the location and severity of a stroke.
  8. Traumatic brain injury (TBI): EEG can help assess the extent of brain damage caused by a head injury.
  9. Multiple sclerosis (MS): EEG can help diagnose the severity and progression of MS.
  10. Encephalopathy: EEG can be used to diagnose brain disorders such as encephalopathy, which causes changes in brain function.

How far back can an EEG detect a seizure?

The length of time that an EEG can detect a seizure depends on various factors, including the type of seizure, the frequency of seizures, and the duration of the EEG test. In general, EEG can detect seizure activity that occurs within a few minutes to an hour of the test.

EEG test full form

The full form of EEG is electroencephalography.

How long is an EEG test for seizures?

EEG tests for seizures typically last between 45 minutes to an hour. However, in some cases, the test may last up to 24 to 72 hours to monitor seizure activity during sleep.

EEG waves

EEG waves are patterns of electrical activity that are measured by an EEG test. There are four primary types of EEG waves, each with different frequencies and amplitudes:

  1. Alpha waves (8 to 13 Hz): These waves are associated with relaxation and calmness and are typically present when a person is resting quietly with their eyes closed.
  2. Beta waves (14 to 30 Hz): These waves are associated with alertness and concentration and are typically present when a person is awake and actively engaged in mental activity.
  3. Theta waves (4 to 7 Hz): These waves are associated with drowsiness and daydreaming and are typically present when a person is falling asleep or waking up.
  4. Delta waves (less than 4 Hz): These waves are associated with deep sleep and are typically present when a person is sleeping.

What can an EEG show that an MRI cannot?

EEG and MRI are both diagnostic tools used to evaluate brain function and diagnose neurological conditions. While they are similar, they offer different types of information:

  1. EEG measures electrical activity in the brain, providing real-time information about brain function and changes in activity over time.
  2. MRI uses magnetic fields to produce images of the brain, providing detailed information about the structure and size of different brain regions.

While both tests are valuable diagnostic tools, EEG is particularly useful in monitoring brain activity during seizures and evaluating brain function in real-time. MRI is more useful in identifying structural abnormalities in the brain, such as tumors or lesions.

EEG test for kids

EEG tests are commonly used to diagnose neurological conditions in children, including epilepsy, autism, and developmental delays. To make the test more comfortable for children, pediatric EEG tests are typically conducted in a child-friendly environment and are designed to be non-invasive and painless.

During the test, children may be asked to watch a movie, read a book, or play a game to help them relax and stay still. Parents may also be present during the test to provide comfort and support.


EEG testing is a valuable diagnostic tool that can help identify a range of neurological conditions and evaluate brain function. By understanding what an EEG test is, how it works, and what conditions it can diagnose, you can feel more prepared and confident if you or a loved one is referred for this test.

Remember, an EEG test is a non-invasive and painless procedure that can provide valuable information to help doctors diagnose and treat neurological conditions effectively, so don’t hesitate to ask your doctor any questions you may have about the test.