What you can expect

During the test

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 measures your head and marks your scalp with a special pencil to indicate where to attach the electrodes. Those spots on your scalp might be scrubbed with a gritty cream to improve the quality of the recording.

• 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.

• You relax in a comfortable position with your eyes closed during the test. At various times, the technician might ask you to open and close your eyes, perform a few simple calculations, read a paragraph, look at a picture, breathe deeply for a few minutes, or look at a flashing light.
• Video is routinely recorded during the EEG. Your body motions are captured by a video camera while the EEG records your brain waves. This combined recording can help your doctor diagnose and treat your condition.

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.

After the test

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.