An electroencephalogram (EEG) is a test that detects electrical activity in your brain using small, metal discs (electrodes) attached to your scalp. Your brain cells communicate via electrical impulses and are active all the time, even when you're asleep. This activity shows up as wavy lines on an EEG recording.
An EEG is one of the main diagnostic tests for epilepsy. An EEG can also play a role in diagnosing other brain disorders.
An EEG records the electrical activity of your brain via electrodes affixed to your scalp. EEG results show changes in brain activity that may be useful in diagnosing brain conditions, especially epilepsy and other seizure disorders.
An EEG can determine changes in brain activity that might be useful in diagnosing brain disorders, especially epilepsy or another seizure disorder. An EEG might also be helpful for diagnosing or treating the following disorders:
An EEG might also be used to confirm brain death in someone in a persistent coma. A continuous EEG is used to help find the right level of anesthesia for someone in a medically induced coma.
EEGs are safe and painless. Sometimes seizures are intentionally triggered in people with epilepsy during the test, but appropriate medical care is provided if needed.
You'll feel little or no discomfort during an EEG. The electrodes don't transmit any sensations. They just record your brain waves.
Here are some things you can expect to happen during an EEG:
A technician attaches discs (electrodes) to your scalp using a special adhesive. Sometimes, an elastic cap fitted with electrodes is used instead. The electrodes are connected with wires to an instrument that amplifies the brain waves and records them on computer equipment.
Once the electrodes are in place, an EEG typically takes up to 60 minutes. Testing for certain conditions require you to sleep during the test. In that case, the test can be longer.
Ambulatory EEGs (aEEGs), which allow for longer monitoring outside an office or hospital setting, are in limited use. This test can record brain activity over several days, which increases the chances of catching seizure activity. However, compared to inpatient video-EEG monitoring, an ambulatory EEG is not as good at determining the difference between epileptic seizures and nonepileptic seizures.
The technician removes the electrodes or cap. If you had no sedative, you should feel no side effects after the procedure, and you can return to your normal routine.
If you used a sedative, it will take time for the medication to begin to wear off. Arrange to have someone drive you home. Once home, rest and don't drive for the rest of the day.
During an EEG, flat metal discs (electrodes) are attached to your scalp. In a high-density EEG, shown here, the electrodes are closely spaced together. The electrodes are connected to the EEG machine with wires. Some people wear an elastic cap fitted with electrodes, instead of having the adhesive applied to their scalps.
Doctors trained to analyze EEGs interpret the recording and send the results to the doctor who ordered the EEG. Your doctor might schedule an office appointment to discuss the results of the test.
If possible, bring along a family member or friend to the appointment to help you remember the information you're given.
Write down questions to ask your doctor, such as: