Electroencephalogram (EEG)

EEG helps doctors rule out or confirm possible causes of disorders in the brain. It also provides valuable information that can help guide treatment decisions. While it measures electrical activity, an EEG does not measure cognitive ability or impairment.

Perhaps the most common use for an EEG is in diagnosing Epilepsy or other kinds of seizures. It is also helpful as a diagnostic tool in cases involving:

• Encephalitis (a form of inflammation of the brain)
  
• Encephalopathy (a form of neural dysfunction)
  
• Head injuries
  
• Sleep disorders
  
• Stroke
  
• Tumors in or near the brain
• Headache
• Confusion

Other uses: An EEG helps doctors determine if a comatose person has suffered brain death. It can show if there are neurological problems related to dementia and is used to monitor surgery patients receiving general anesthesia.

• Most EEGs are standard and noninvasive. They take 30 to 60 minutes and can be performed in a doctor's office without any major preparation.
  
• Sleep EEGs monitor a person's brain waves while they sleep. These may take three hours or longer.
  
• Ambulatory EEGs record your brain activity while you go about your normal day. The electrodes are attached to a small portable device which records activity for up to 24 hours.
  
• EEGs to diagnose seizures may require a hospital stay and often employ video equipment to monitor body movements simultaneously with brain waves.

EEG is a noninvasive procedure, which means no equipment enters your body. The test is therefore painless.

Preparation

• Because EEG requires electrodes placed on your head, it's a good idea to avoid using haircare products (gels, creams or sprays) before you have the test. These can interfere with the readings.
  
• Starting about six to eight hours before the test, avoid foods that contain caffeine. These include coffee, tea, colas, energy drinks and chocolate.
  
• Tell your doctor if you take sleeping pills, tranquilizers or medications to control seizures. Your doctor may ask you to avoid these for a day before your EEG because they could affect the test results.
  
• If your EEG is part of a sleep study, you may need to sleep during the test. In this case, your doctor may ask you to reduce or avoid sleeping before your test and may give you a sedative to help you fall sleep once the test begins. If this is the case, arrange for someone to drive you home.
  
• If you are having seizures, you may need to have your EEG in the hospital, where you can be monitored by a video camera during the procedure.

During the Test

• You'll sit in a chair or lie down on a bed or padded table.
  
• An assistant will measure your head and mark the spots where electrodes will be placed. Most EEGs require between 16 and 20 electrodes.
  
• The electrodes, shaped like small metal disks, will be placed on your head using a conducting gel and an adhesive. Wires attached to the electrodes transmit readings to a computer which records the data for later analysis.
  
• If your EEG is part of a sleep study, you may be asked to wear a special cap that has electrodes attached to it, and you may be given a sedative to help you fall asleep.
  
• A standard EEG will take about 30 to 60 minutes to perform. You'll spend most of this time relaxing with your eyes closed. At some points you may be asked to perform simple tasks like deep breathing, reading or blinking.

If no sedative was used, you can return to your normal routine as soon as the electrodes are removed and the test is complete. If you received a sedative, you'll need some time to recover before being driven home.