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EEG (Electroencephalogram) Test: Purpose, Procedure, Results & What to Expect

By Dr. Atul Prasad in Centre For Neurosciences

Jun 10 , 2025 | 6 min read

You might’ve heard the term before, but most people aren’t sure what an EEG (Electroencephalogram) Test does. To keep it simple, it checks the electrical activity in your brain. Just like how an ECG checks your heartbeats, an EEG checks brain waves. Doctors use this test to figure out what’s going on when someone has blackouts, seizures, or sleep problems. It’s one of the safest ways to check the functioning of your brain.

It’s often recommended if you have unexplained fainting, fits, confusion, or you’re being checked for conditions like epilepsy or stroke recovery. No needles, no pain, just sticky patches on your head that record your brain’s signals.

What Is an EEG Test?

An Electroencephalogram, or EEG, checks how your brain sends signals to the rest of your body. Your brain uses tiny electrical impulses all the time, even when you’re asleep. It records them and shows them as wave-like lines on a screen, which helps doctors see which parts of your brain are working normally and which parts might be too active or not active enough.

By looking at these patterns, doctors can find out if you might have problems like epilepsy, sleep issues, brain injury, or other brain-related conditions.

Read more about - Types of Epilepsy and Women with Epilepsy.

Why Is an EEG Test Done?

Your doctor may ask for an EEG for different reasons depending on what symptoms you're having. Here’s how it helps:

1. To Diagnose Seizure Disorders

If you’ve had seizures, fainting spells, or sudden blackouts, an EEG helps check for things like epilepsy or febrile seizures in children. It also helps when the cause of blackouts isn’t clear.

2. To Monitor Brain Disorders

People who have had a stroke, brain tumour, or serious head injury may need an EEG to see how well their brain is functioning. It also supports diagnoses in memory loss or dementia cases.

Learn more about - Brain Tumours Causes and Prevent Brain Stroke.

3. To Assess Sleep Disorders

If you feel tired even after sleeping, if you snore heavily, stop breathing during sleep, or act out your dreams, an EEG helps detect things like sleep apnea, REM behaviour disorder, or narcolepsy.

4. To Evaluate Brain Function in Coma

If someone is in a coma or unconscious, an EEG can help doctors see if the brain is still active and how much.

Types of EEG Tests

1. Routine EEG

This is the basic version, and it's done in the hospital, which takes around 20 to 40 minutes.

2. Ambulatory EEG

This is a portable EEG. You take the machine home and it records your brain waves for 1 to 3 days while you go about your day.

3. Sleep EEG

This test is done when you’re asleep or after keeping you awake for a long time to make you sleep during the test. A sleep EEG can capture brain activity during these times and help doctors find out if there’s a condition like sleep apnoea, narcolepsy, or nighttime seizures that needs treatment.

4. Video EEG Monitoring

This version includes a camera recording your body movements while the EEG records your brain. It's helpful in seizure cases. You may be in the hospital for a few days for this one so that doctors can observe your brain activity and your behaviour at the same time. The video EEG records both what your body is doing and what your brain waves look like during a seizure or unusual episode. This helps them figure out exactly what kind of seizure it is and how best to treat it.

How to Prepare for an EEG Test?

Getting ready for an EEG Test doesn’t need much effort, but a few small steps can make sure the test goes smoothly and the results are accurate. Your doctor may give you specific instructions based on the type of EEG you’re having. Here's what you can generally expect before the test.

Wash your hair the night before or the morning of the test. You can't apply any oil, gel, or spray.
Avoid caffeine, like coffee, tea, cola, or chocolate, at least 6-8 hours before the test.
Tell your doctor about all your medications. Don’t stop having any unless they ask you to.
For a sleep EEG, the doctor might ask you to stay up late the night before so you’re more likely to sleep during the test.

What Happens During the EEG Procedure?

During the EEG procedure, you’ll be asked to sit in a chair or lie on a bed. The technician will place small stickers (electrodes) on your scalp using a sticky paste. These are connected to wires that go into the machine. You’ll be asked to relax, close your eyes, maybe breathe deeply, and sometimes look at a blinking light. You might even be allowed to sleep if the doctor needs that data. The whole thing takes about 30-60 minutes, depending on the type of EEG.

EEG Test Results: What Do They Show?

The wave patterns recorded in your test are reviewed by a neurologist. If something looks off, they’ll study it more closely.

A normal EEG means no unusual brain activity was found.
An abnormal EEG might show things like;

Seizure patterns (even if you didn’t have one during the test)
Changes caused by a brain stroke or brain tumour
Brain slowing linked to dementia
Sleep disorder or issues

You usually get your results in a couple of days, unless it's an emergency.

Explore the expert guide - Sleeping Disorders Causes Symptoms and Brain Stroke Symptoms.

Risks and Safety of EEG Test

This test is completely safe due to no use of injections, no pain, and no shocks. It doesn’t change anything in your brain; it just listens to the signals your brain is already making.

In epilepsy-related tests, flashing lights or deep breathing might trigger a seizure, but only if that’s already part of your condition. If that happens, the team is trained to handle it.

What to Expect After the EEG Test?

Once the EEG test is done

The electrodes are removed
Your scalp is cleaned
You can go home

Unless told otherwise, you can eat, drive, go to work, or rest as usual. If you were sleep-deprived for the test, get some sleep after. Your doctor will call you for a follow-up to explain what the EEG showed and discuss what comes next.

Conclusion

The EEG Test is a helpful way to check how your brain is working. Whether it’s seizures, memory loss, or poor sleep, this test gives real insight. It doesn’t fix the issue, but it helps doctors understand what to do next.

If you’ve been feeling off, blacking out, or just want to check brain function, it’s worth considering this test. It’s easy, safe, and doesn’t take long.

At BLK-Max Super Speciality Hospital, we do EEG tests with the right mix of expert care and modern equipment. If you or someone in your family needs one, we’re here to help, from booking the test to explaining the results.