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EEG (Brainwave Test)
An EEG records the electrical activity of the brain using small sensors on the scalp. It is mainly used to help diagnose and investigate epilepsy and other conditions.
Quick answer
EEG (Brainwave Test): what it is and what the results mean
An electroencephalogram (EEG) measures the brain’s electrical activity through small sensors (electrodes) placed on the scalp. It is painless and does not send any electricity into the body.
- Why it is done: It is used mainly to help diagnose and classify epilepsy and investigate seizures, and sometimes to assess blackouts, unusual movements or certain brain conditions.
- Understanding results: The recording is examined for abnormal patterns that can support a diagnosis such as epilepsy.
What it is
An electroencephalogram (EEG) measures the brain’s electrical activity through small sensors (electrodes) placed on the scalp. It is painless and does not send any electricity into the body.
Why it is done
It is used mainly to help diagnose and classify epilepsy and investigate seizures, and sometimes to assess blackouts, unusual movements or certain brain conditions.
What to expect
Electrodes are attached to your scalp and the recording is made while you rest, sometimes with flashing lights or deep breathing to help show activity. A standard EEG takes about 30–60 minutes; sometimes longer or sleep recordings are done.
Understanding the results
The recording is examined for abnormal patterns that can support a diagnosis such as epilepsy. A normal EEG does not rule out epilepsy, so results are always interpreted alongside your history and events.
Good to know
Risks and limitations
An EEG is safe and painless. Its main limitation is that it captures only a window of time, so it may be normal even when a condition is present, and it is one part of the assessment rather than a stand-alone answer.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
EEG (Brainwave Test): frequently asked questions
Does an EEG hurt?
No. Electrodes are simply placed on the scalp to record activity; nothing is passed into the brain. It is painless, though the paste used to attach sensors may need washing out of your hair afterwards.
Can an EEG diagnose epilepsy on its own?
Not entirely. An EEG can support the diagnosis, but a normal result does not rule epilepsy out and an abnormal one is interpreted with your history. Diagnosis relies on the whole clinical picture.
Related tests
Other other investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- UK National Screening Committee / relevant professional body
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