EEG (or Electroencephalogram) during Sleep Study

EEG testing allows sleep doctors to measure and study electrical activity happening in the brain at certain times of the day (or night) or when the person is put under special circumstances. The test is sometimes referred to as a brain wave test. EEG involves placing electrodes on the patient’s head. During a sleep study, or polysomnography, EEG is one of the monitoring tests applied to study possible sleep disorders in a patient. At the sleep center, approximately 15 to 25 electrodes will be placed at various locations on the scalp using a sticky putty material. All the electrodes, each with a metallic sensor attached to the end, are connected to a special machine that amplifies and records electrical impulses. EEG can be particularly useful for sleep experts who want to study brain activity while a certain patient is experiencing a deep REM, or rapid eye movement, cycle.

When the EEG test is complete, a computer will show a visual representation consisting of special patterns, or lines, that should correlate to the electrical impulses shot off inside the brain during the test. The results will look like a bunch of wavy lines drawn on graph paper. Since the sleep study patient is unconscious or dreaming during a sleep study, the EEG results are not very controllable. However, during other EEG tests, such as those performed while a patient is conscious and awake, may require the patient to the respond to certain stimuli (lights, breathing, etc.) in order to provoke brain activity. In general, EEG is painless, although patients who have to do the test during a sleep study may have trouble sleeping with all the electrodes attached.

Preparing for an EEG Test

It’s important to have your hair cleaned and out of the way before the electrodes are placed. Avoid using hair products or conditioners that can make the hair too slippery—or the electrodes will fall off your head. Certain medicines might also cause complications, but as these vary, you should talk to your doctor about what medications you are currently taking for better advice. Caffeine should also be banned from your diet for at least 8 hours before the test starts, as it can botch results. The electrodes also emit a very small amount of electricity into the head, so the test is not dangerous.  If you're looking for more information about an EEF test, ask a free question to a sleep expert.