What you can expect

By Mayo Clinic Staff

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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 may be scrubbed with a gritty cream to improve the quality of the recording.
  • A technician attaches flat metal 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 — makes bigger — the brain waves and records them on computer equipment.

    Once the electrodes are in place, an EEG typically takes up to 60 minutes. If you need to sleep for the test, it may take up to three hours.

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

After the test

After the test, the technician removes the electrodes or cap. If no sedative was given, 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 a little while for the medication to begin to wear off. Arrange to have someone drive you home. Once home, rest and don't drive for the remainder of the day.

May. 20, 2014