What is an EEG?

EEG is an abbreviation for electrocephalogram. An EEG is a test to detect any abnormalities in the electroactivity of the brain. “Electro” means electrical activity, “cephalo” means brain, and “gram” means the study of.

How is the EEG performed?

The brain cells communicate by producing tiny electrical impulses. In an EEG, electrodes are placed on the scalp over multiple areas of the brain to detect and record patterns of electrical activity and check for abnormalities. The test is performed by an EEG technician in a specially designed room and you will be asked to lie on your back on a table or reclining chair. The technician will apply between 16-25 flat metal discs (electrodes) in different positions on your scalp. The discs are held in place with a sticky paste. The electrodes are connected by a wire and to an amplifier and then a recording machine. The recording machine converts electrical signals in a series of waving lines that are seen on a computer monitor and recorded onto the computer hard disc. You may be asked to lay still with your eyes closed because any movement can alter the results. You may be asked to do some things during the recording such as breathe deeply for several minutes or look at bright flickering light.

How to prepare for the EEG

You need to wash you hair the night before the test. Do not use oils, sprays, or conditioner on your hair before the test. Your healthcare provider may want you to discontinue some medication before the test. Do not change or stop medication without first consulting your healthcare provider. You should avoid all foods containing caffeine 8 hours before the test. Sometimes it is necessary to sleep during the test so you may be asked to reduce your sleep the night before. Infants and children, sometimes they will fall asleep during the test if they are sleep deprived or come in during their usual naptime. Otherwise, sometimes they are given sedation.

Why is the EEG performed?

An EEG is used to diagnose the presence of types of seizure disorders, to look for causes of confusion, and to evaluate head injuries, tumors, infections, degenerative diseases, and metabolic disturbances that affect the brain. It may also be used to evaluate sleep disorders and investigate periods of unconsciousness. The EEG may be done to confirm brain death in a comatose patient. The EEG cannot be used to read the mind, measure intelligence, or diagnose mental illness.

What are the risks?

The procedure is considered very safe. If you have a seizure disorder, a seizure may be triggered by flashing lights or hyperventilation (heavy breathing). The healthcare provider performing the EEG is trained to take care of you if this happens.

What happens after the EEG?

After the test is completed, the electrodes will be carefully removed. You may have some paste in your hair which will come out easily once you shampoo or clean your hair later that day. The test is read by a Neurologist trained in EEG. The results will be sent to your referring physician. The abnormalities in the test may indicate the following: seizure disorder such as epilepsy, structural abnormalities such as brain tumors or abscess, head injury or inflammation of the brain such as encephalitis, Sleep Disorders, abnormal EEG findings in those with medical disorders such as kidney or liver failure, or abnormalities from medications.