EEG stands for electroencephalogram, a test used to evaluate and measure the electrical activity in the brain. EEGs use small discs called electrodes that are placed on the scalp. These electrodes pick up tiny electrical impulses in the brain and transmit them via wires to a machine that creates a graph depicting the activity.
EEGs are used to diagnose an array of issues related to the brain, including:
epilepsy and other seizure disorders
encephalopathy (brain dysfunction)
encephalitis (brain inflammation)
sleep disorders including apnea
EEGs are noninvasive and painless. Measurements of the skull are taken first to determine the optimal placement of the electrodes, then the skin in these areas may be carefully cleaned of oils to enable the electrodes to adhere better. In some cases, the electrodes may be attached to a close-fitting cap instead of directly to the scalp. Then, the electrodes are connected to the EEG machine using a series of wires. EEGs may be conducted while the patient is awake or during sleep. During the test, patients may be asked to open and close their eyes, read or perform other simple activities to measure the brain’s activity. EEGs performed on patients who are awake typically take about an hour.
While “standard” EEGs take about an hour to perform in the office, ambulatory EEGs are performed over a longer period of time, typically a day or more, to enable doctors to gather information about the brain’s activity throughout daily routines and activities. During the test, the patient wears a small portable recording device that’s attached to the electrodes on the scalp. The electrodes are covered with a cap or hat. Patients will be asked to perform their regular routines and to keep a diary of their activities to help the physician identify patterns or issues.
Video EEGs use video monitoring performed at the same time as the EEG to “match” a person’s physical activity during the test. Video EEGs can be very useful in patients with seizures, including those with epilepsy. Video EEGs usually record sounds as well to determine if the patient makes any noises during a seizure or other event.