EEG (electroencephalogram)

Category: Brain, Nerve & Sleep Tests · All brain, nerve & sleep tests

What it is

An EEG records the brain's electrical activity through small electrodes placed on the scalp. It looks for abnormal patterns that help classify seizures and epilepsy, and assess some other brain conditions.

Why it is done

It investigates blackouts and suspected seizures, monitors known epilepsy, and helps assess encephalitis, some sleep disorders and unexplained confusion. A normal EEG does not exclude epilepsy, and an abnormal one is interpreted with the clinical story.

How to prepare

Wash your hair beforehand and avoid oils and sprays. Take medicines as usual unless told otherwise (the team will advise). You may be asked to be sleep-deprived (staying up late and rising early) before the test to encourage drowsiness and increase the chance of recording abnormalities. Bring a list of medicines.

What happens during the procedure

Electrodes are attached with paste at measured positions — painless. You lie still with eyes closed while recordings run; you will be asked to breathe deeply for a few minutes (hyperventilation) and to watch flashing lights (photic stimulation), both of which can reveal patterns. Sleep may be recorded if you drift off. A routine study takes about 30 to 60 minutes.

Afterwards — recovery & results

The paste washes out of your hair afterwards and you can go home or back to the ward. If you were sleep-deprived, arrange not to drive home. Results are reported by a neurophysiologist to your clinic team, usually within a few weeks unless urgent.

Risks & considerations

There are no risks from the recording itself. The activation procedures (deep breathing, flashing lights) can occasionally provoke a seizure in susceptible people — the team is trained and equipped for this, and you are monitored throughout.

Frequently asked questions

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