Neurology• Updated 21 October 2026
EEG (Electroencephalogram)
A test that records the brain's electrical activity using small sensors on the scalp.
Results: A few days
Quick Summary
Primary Purpose
To help diagnose epilepsy and other conditions affecting brain activity.
What It Measures
Brain wave patterns.
Preparation
Wash hair the night before without oil or conditioner; sometimes sleep deprivation is advised.
Overview
An EEG is painless.
A normal EEG doesn't rule out epilepsy.
What It Measures
Brain waves
Abnormal patterns linked to seizures.
How It's Performed
- 01
Setup
Electrodes stuck to the scalp.
- 02
Recording
Rest quietly; may involve deep breathing and flashing lights.
- 03
Done
About 30–60 minutes.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.