An electroencephalogram, or EEG, is a non-invasive procedure that measures the electrical activity of the brain. This test uses small metal discs, called electrodes, attached to the scalp to detect and record the brain’s electrical impulses, which appear as wavy lines on a recording. Proper patient preparation is necessary to ensure the recorded data accurately reflects the brain’s constant electrical communication and leads to a successful test experience.
Preparing the Body and Scalp
Successful EEG recording relies on a clean connection between the electrodes and the scalp. Patients must wash their hair thoroughly the night before or the morning of the appointment, using only regular shampoo. This cleaning removes oils and dirt that interfere with the electrical signal transmission.
It is important to avoid all hair care products after washing, including conditioners, oils, gels, and hairspray. These substances create a barrier that prevents the conductive paste from properly adhering the electrodes to the scalp. Such interference can result in a poor-quality recording or delay the procedure. Patients should also wear comfortable, loose-fitting clothing, such as a shirt that buttons or zips up, since the electrodes and wires make removing pullover shirts difficult.
Managing Medications and Stimulants
The internal chemical state of the body can alter the brain’s electrical patterns, making substance management important before an EEG. Patients must continue taking all prescribed medications, including anti-seizure drugs, unless explicitly instructed otherwise by the ordering doctor. Stopping prescribed treatment without medical guidance is unsafe and can skew the test results.
Certain substances, particularly stimulants, must be avoided for several hours before the test because they directly influence brain wave activity. This includes caffeine found in coffee, tea, soda, and energy drinks, which should generally be avoided for 8 to 12 hours prior to the appointment. Nicotine should also be avoided on the day of the test. Alcohol and recreational drugs should not be consumed, as they introduce changes to the brain’s electrical background that can obscure diagnostic findings.
Understanding Sleep Requirements
The necessary sleep preparation varies depending on the type of EEG ordered by the physician. For a routine EEG, patients can maintain their normal sleep schedule. However, a sleep-deprived EEG is often requested to increase the likelihood of capturing abnormal brain activity, particularly in the investigation of seizure disorders.
Sleep deprivation enhances the sensitivity of the test, as abnormal electrical patterns are more likely to occur during drowsiness or light sleep. This instruction typically involves limiting sleep to four or five hours the night before, or sometimes staying awake for a full 24 hours. The goal is to arrive drowsy, making it easier to fall asleep during the procedure when requested. Patients must arrange for transportation, as the lack of sleep can impair their ability to drive safely after the appointment.
What to Expect During the Procedure
Understanding the steps of the EEG procedure can help reduce anxiety and promote cooperation. The technician will first measure the head to determine the precise locations for the electrodes, sometimes marking the spots with a washable crayon. The scalp locations may be gently scrubbed with a mild abrasive cream to optimize conductivity before the electrodes are attached using a water-soluble paste or gel.
The test duration typically ranges from 45 to 90 minutes, with the actual recording time often between 20 and 40 minutes. During the recording, the patient relaxes in a comfortable position, often with eyes closed. The technician will perform several “activation procedures” designed to provoke specific brain responses. These include hyperventilation (breathing deeply and rapidly) and photic stimulation (looking at a bright, flashing light), which are standard components designed to elicit brain wave patterns that might not appear otherwise.