EEG remains the cornerstone for diagnosis of epileptic seizures. The Comprehensive Epilepsy Center performs more than 4,000 EEG studies per year. Our facilities rank among the largest in the nation, with eight dedicated patient rooms for video EEG monitoring in Barnes-Jewish Hospital. In addition, we offer routine EEG studies throughout Barnes-Jewish Hospital and at our outpatient facility in the Center for Advanced Medicine (CAM).
What Is an EEG?
An EEG, or electroencephalogram, is a test that detects brain waves, or electrical activity in the brain. Sensitive electrodes are placed on the scalp to pick up electrical charges spreading through the brain. These charges are then mapped on a recording or a computer screen. The mapped electrical activity is interpreted by a neurologist who specializes in reading EEG studies and treating epilepsy. This information helps the neurologist identify the type and location of the seizure.
Is an EEG Safe?
EEG has been used safely for many years and does not cause any pain or side effects. During the test, tiny electrodes are pasted to the scalp. These electrodes detect brain wave activity and transmit it to a computer. The electrodes don’t cause any tingling or other sensation, as they are just recording the electrical activity of the brain and not creating any electrical activity themselves.
Patients typically are asked to lie very still, relax and sleep. Pasting the electrodes and preparing for the EEG usually takes one hour for typical or "routine" EEG studies. During the test, patients may be asked to perform activities that could prompt a seizure, such as rapid or deep breathing, or looking at a bright or flashing light. More advanced EEG studies, such as video EEG recordings, are much more comprehensive and may last for up to a week.
What Does the EEG Show?
EEG findings vary depending on the activities during the study. For example, during sleep the brain exhibits a different brain wave pattern as compared to wakefulness. The brain also generates different wave patterns depending on the type of epileptic seizure. The most informative pattern of change on routine EEGs, which occurs in between seizures, is called an epileptiform discharge. This is an abnormal buildup of electrical activity that typically occurs in the area of the brain causing the seizures.
Importantly, brain waves vary unpredictably in between seizures, and only 35-50 percent of people with epileptic seizures will show a definitive epileptiform discharge on routine EEG studies. Understanding these epileptiform patterns, along with a complete neurological exam and medical history, lets our neurologists determine the type of epilepsy and make recommendations for the best course of treatment.
When routine EEG studies do not result in clear findings, there are several options for further testing. A repeat routine EEG study, sometimes performed in the morning after a sleepless night (also called a "sleep deprived EEG") will bring out informative abnormalities on the EEG. In some cases, additional tests may be needed to supplement the routine EEG results.
The best test to assess the cause of seizures is to perform a video recording of seizures while recording the EEG at the same time. This test is called video EEG recording or video EEG telemetry monitoring, and is offered at the Comprehensive Epilepsy Center at Barnes-Jewish Hospital.
Interpretation of advanced EEG studies, such as video EEG studies, requires specialized training in epilepsy. After general neurology training, our physicians go on to fellowships in clinical neurophysiology and epilepsy. Because of the large number of EEG studies and available specialized personnel, the facilities of our comprehensive epilepsy center remain among the most modern and largest in the country.
To make an appointment with a Washington University epileptologist, neurologist or neurosurgeon at Barnes-Jewish Hospital, call 855.925.0631.