The Electroencephalogram (EEG) is a non-invasive medical test that measures the brain’s electrical activity, providing physicians with a map of the brain’s function. The EEG is frequently used to help diagnose conditions such as epilepsy, sleep disorders, and other neurological issues. The procedure is painless and generally straightforward, but many patients worry about hair preparation, specifically whether their head must be shaved. This common concern is easily addressed, allowing patients to focus on the test itself.
The Necessity of Head Shaving
For a standard diagnostic EEG, head shaving is not required and is almost never performed. The small metal discs, or electrodes, that record the brain waves are designed to be placed directly on the scalp. Technicians use specialized techniques to ensure proper contact even with a full head of hair. Modern electroneurodiagnostic technologists have the tools and skill to part the hair and apply the electrodes precisely.
However, highly specialized procedures may require trimming or shaving a small area of hair. This is primarily reserved for long-term monitoring or invasive procedures, such as intracranial EEG (iEEG) or stereo-EEG (sEEG). These procedures involve placing electrodes beneath the skull or directly into the brain tissue. For the vast majority of patients undergoing a routine, ambulatory, or sleep-deprived EEG, the hair remains intact.
Essential Preparation Steps
Since shaving is unnecessary, the primary focus of preparation is ensuring the scalp is clean to achieve a clear electrical signal. Oils, dirt, and hair styling products act as insulators, increasing the electrical resistance between the electrode and the scalp. High resistance can distort the brain wave recordings, making the data difficult for the physician to interpret accurately.
Patients are instructed to wash their hair thoroughly the night before or the morning of the test. It is important to avoid using any hair products afterward, including conditioners, gels, sprays, oils, or mousses. The hair must be clean and dry upon arrival for the appointment. Removing hair extensions, weaves, or thick braids may also be necessary to allow the technician clear access to the scalp.
The EEG Procedure Explained
Once the patient is comfortably seated or lying down, the technologist measures the head and marks specific points on the scalp according to the internationally recognized 10–20 system. These markings ensure the electrodes are placed over the correct areas of the brain to capture activity from different lobes. The technician then gently prepares the marked skin areas, often using a gritty cream or mild abrasive to remove remaining dead skin cells or oils and improve signal quality.
Small metal electrodes, usually numbering between 16 and 25, are attached to the scalp using a highly conductive, water-soluble paste or gel. In some cases, a cap fitted with electrodes is used instead. The electrodes do not transmit electricity; they only record the tiny electrical impulses generated by the brain’s nerve cells. A routine EEG recording typically takes between 20 and 40 minutes, but the entire appointment, including preparation, may last up to an hour.
During the recording, the patient is asked to remain still and relaxed, often with eyes closed. The technologist may introduce activation procedures to provoke certain types of brain activity that might not appear during rest. These standard procedures commonly include hyperventilation, where the patient breathes deeply and quickly for a few minutes, and photic stimulation, which involves looking at a bright, flashing light. After the test is complete, the electrodes are removed, and the paste is cleaned off. The patient may need to wash their hair again at home to remove all residue.