Electroencephalography is a non-invasive diagnostic tool that records electrical activity of the brain using small metal discs called electrodes attached to the scalp. Hans Berger recorded the first human EEG in 1924, revolutionizing how clinicians study brain function. Voltage fluctuations resulting from ionic current within the neurons of the brain are detected and amplified, then displayed as a continuous waveform on a monitor or paper. Nurses must understand that an EEG measures electrical potential differences over time, reflecting the functional state of the central nervous system rather than structural anatomy.
Brain waves are categorized by their frequency measured in Hertz (cycles per second) and amplitude measured in microvolts. Healthy adults display distinct patterns depending on their state of alertness.
Clinicians order electroencephalograms to evaluate various paroxysmal or continuous cerebral dysfunctions.
Preparing a client for an EEG requires careful instruction and physical readiness. The nurse must advise the client to wash their hair thoroughly the night before and avoid using oils, sprays, or gels, as these substances impede electrode contact and signal transmission. Unless specifically ordered otherwise, stimulants like coffee, tea, and soda should be restricted for 12 hours prior because they alter baseline brain wave rhythms. For sleep-deprived EEGs, the nurse instructs the client to remain awake for all or part of the preceding night to provoke latent seizure activity.
During the recording, the client lies quietly on a bed or recliner. The technician applies paste or gel and attaches about 16 to 25 electrodes using the international 10-20 system. The nurse monitors the client for comfort and watches for seizure activity, especially if provocative techniques are used. These techniques include hyperventilation, which induces mild cerebral vasoconstriction and hypocapnia to trigger spike-and-wave discharges, and photic stimulation, where a flashing light tests for photosensitive epilepsy.
Once recording finishes, the technician removes the electrodes and cleans residual conductive paste from the client's hair and scalp using warm water or acetone. The nurse assists the client with personal hygiene and offers assistance if they experienced sleep deprivation or a provoked seizure. If sedatives were administered, standard post-sedation safety precautions apply, including bed rest and supervision during ambulation until full alertness returns. The nurse documents the client's tolerance of the procedure and ensures follow-up appointments are scheduled for results discussion.
Interpreting an EEG requires correlating electrical traces with the client's clinical presentation. Normal records show organized background rhythms reacting appropriately to eye opening and closing. Abnormal findings include focal slowing, which points to a localized structural lesion like a tumor or stroke, and generalized epileptiform discharges, indicating a systemic or genetic seizure tendency. Artifacts caused by eye blinking, muscle movement, or electrical interference can mimic abnormalities, so nurses should recognize that high-quality technical setups prevent misinterpretation.