EEG (Electroencephalograph)

    The EEG is a graphic record of the electrical activity of the brain as recorded by a machine called an electroencephalograph. This test is also called an encephalogram.
    Brain electrical activity is most abnormal during seizures, so the EEG is commonly used in evaluation of people with epilepsy.
    EEG, electroencephalography, is the recording of voltages from the brain. In special circumstances, the recording can be done directly from the brain surface, but normally electrodes on the scalp are used.
    The voltage amplitudes are small, typically in the range of tens of microvolts. They are thought to be caused by synchronized activity in very large numbers of synapses in the cerebral cortex. The "centre of synchronization" is somewhere deep in the thalamus or brain stem, but EEG gives only indirect information about those regions.

Why is an EEG performed?

An electroencephalography (EEG) (elek-tro-in-SEF-all-oh-gram) is a neurological test that measures the electrical signals your brain sends to the rest of your body, and records them on a graph. The types of problems for which an EEG might be requested are seizure disorders, head injuries, learning disorders, headaches, brain tumors, dizziness, amnesia, staring episodes, and sleep disturbances. It can also be used to determine the presence and location of brain injuries, abscesses, tumors, intracranial hemorrhages, and to confirm brain death. An EEG does not measure intelligence, thoughts, or feelings. The EEG machine does not send electricity into the brain; it only measures the electricity that your brain produces.

Instruction for preparation of EEG test

Inform the doctor of any medications you are taking. You may be advised to stop taking some medications because they may impact the test results.

Please bring a complete list of medications taken on a regular basis with you when you come for your EEG.

You will be asked about your medical history.

Adult- Normal test is regular routine -Make sure you are well rested and not sleep deprived the night before the exam

Adult-Sleep Deprived is no sleep for 24 hours.

Child- Normal test is keep child awake late or get them up early so they are sleepy for test procedure.

Child-Sleep Deprived is no sleep for 24 hours. If necessary let child take a 1 to 2 hour nap, 12 hours before test time

Meals- No caffeine for 24 hours. No Alcoholic beverages for 24 hours. Otherwise normal. (Infants feed just prior to test time)

Take your normal medications unless instructed otherwise by your doctor.

Wash and dry hair prior to test time. Do not use hair spray, hair tonic, or crème rinse in your hair before test.

No jewelry on neck or ears. If you have dentures you may be asked to remove them for the test.

Lack of sleep, medications, low blood sugar, and movement of the eyes, tongue, head or body, may affect the results.

What happens during the test?

During the procedure, you relax in a reclining chair or lie on a bed either in a hospital or doctor's office. Electrodes are attached to specific regions of the scalp with a special paste or glue. You will then be asked to relax and lie first with your eyes open, and then closed. You may also be asked to breathe deeply and rapidly, or to stare at flashing lights.

The electrode picks up the electrical signals produced by the brain and transmits them to an electroencephalograph, which produces graphs on paper or on a computer screen. The procedure takes approximately 2 hours and is painless. After the exam, the electrodes are removed. Unless your physician restricts you, you may drive home. If you are being evaluated for a sleep disorder, an EEG may be performed continuously during the night while you are asleep.

How long does the test take?

You need to plan to spend about an hour for a routine outpatient EEG, the actual testing takes about 20 minutes, but you have to have all the electrodes glued down, then removed after you are done. If your physician orders a "prolonged" exam, you may be recorded for up to an hour or more.

What are normal results?

A neurologist or other physician will evaluate the type of brainwaves, location and brainwave patterns, and responses to stimulation (such as lights or noise). The basic waveforms are the alpha, beta, theta, and delta rhythms. "Normal" brainwave patterns vary. However, a normal adult in a fully conscious but relaxed state, typically registers regularly recurring oscillating alpha waves that occur at a frequency of 8 to 12 cycles per second. Young children and sleeping adults typically register delta waves of under 4 cycles per second.

What are abnormal results?

"Bursts" or "spikes" of electrical activity can be seen in EEG readings of patients with epilepsy or other seizure disorders. The electroencepyhalograph pattern and location of these waves may also identify the specific type of seizure. The brainwave patterns of other disorders vary widely. Generally, brain wave patterns in patients with brain disease, mental retardation, and brain injury show overall slowing.