The EEG

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Electroencephalography is a test used to detect and record the electrical activity generated by the brain. The resulting tracings are known as an electroencephalogram (EEG), which are electrical signals from a large number of brain cells (neurons). Our brain cells communicate through electrical impulses an EEG measures and records these electrical impulses to detect any abnormality.

How is an EEG done?

After asking you to lie or sit on abed, the technologist will attach 22 electrodes on your scalp, applying a small amount of conductive gel on each electrode to facilitate brain activity recording. Don't worry: EEG is painless. The technologist will ask you to open and close your eyes, relax and, if necessary, sleep. You will also be asked to hyperventilate (breathe rapidly and deeply) for 3 minutes, then look at lights flashing in different frequencies (photic stimulation). Routine EEG recording takes about 45 minutes to an hour; sleep-deprived EEG lasts 1 hours; while EEG recording for newborn requires two hours.

Why did my doctor order an EEG?

EEG can help diagnose diseases affecting the function of the brain, such as epilepsy, brain tumors, migraine headaches, or head injuries.

How should I prepare for an EEG?

  • Make sure your hair is clean and free of any hair sprays, creams, gels, or any other hair product.
  • You can take your usual medication and meals unless your doctor says you need to take sedatives prior to the test.
  • Your doctor may have ordered medication as well as sleep deprivation on the night prior to the test. If this is the case, you should only have two to four hours of sleep the previous night and stay awake until you come to the laboratory.
  • Do not take coffee, tea, or any stimulant on the day prior to the procedure.
  • Be prepared to give a brief history of your health and symptoms. Bring a list of your medication and allergies.

If your baby will undergo the procedure, you can feed her with infant milk formula prior to the recording to help her fall asleep. If a sedated recording is requested, your child should not take anything by mouth eight hours prior to the procedure.

Children who will undergo the test must be sleep-deprived. Have your child sleep two hours later than his usual bedtime and wake him up two hours earlier than his usual wake-up time. Keep him awake until you reach the laboratory where the EEG will be done.

Excerpt from Recording Brain Activity to Maintain Health, St. Luke's Medical Center advertorial.