Routine, Ambulatory and Video EEG: Which EEG Test Do You Need?

An electroencephalogram (EEG) is a painless test that records the electrical activity of the brain. It is one of the most important tests for evaluating seizures and epilepsy, and it also helps neurologists investigate fainting-like spells, episodes of confusion, unusual movements during sleep and some causes of memory or thinking problems.

Not every EEG is the same. Our office offers routine EEG, 24–48 hour ambulatory EEG and video EEG. Each records the same type of brain signal, but over a different length of time and in a different setting. Choosing the right one depends on what your neurologist is trying to capture.

How an EEG Works

The brain's nerve cells communicate through tiny electrical signals. When many cells fire together, the combined activity can be detected through the scalp. For an EEG, small metal disc electrodes are attached to the scalp with a conductive paste in a standard pattern. Wires connect the electrodes to a recording unit that displays the brain waves as lines on a screen.

The EEG only listens. No electricity is sent into the brain, there are no needles and the test is safe for children, adults and pregnant patients.

Neurologists look at the rhythm, frequency and symmetry of the brain waves and search for specific abnormal patterns. "Epileptiform" discharges, such as sharp waves or spikes, suggest a tendency to have seizures and can help identify where in the brain seizures start. Slowing of the background rhythm in one area or across the brain can point to other kinds of brain dysfunction.

Routine EEG

A routine EEG is the most common type and is usually the first step. The recording itself typically lasts about 20 to 40 minutes, and with setup the visit often takes around an hour.

During the test you lie back or recline with your eyes closed. The technologist may ask you to:

• Open and close your eyes on command.
• Breathe deeply and quickly for a few minutes (hyperventilation), which can bring out certain types of seizure activity.
• Look at a flashing light (photic stimulation) to check for light sensitivity.
• Relax and, if possible, fall asleep, since some abnormalities appear mainly during drowsiness or sleep.

Sometimes a sleep-deprived EEG is requested. You would be asked to stay up late or sleep only a few hours the night before, which makes it more likely to record both sleep and abnormal activity.

The main limitation of a routine EEG is time. Abnormal discharges in people with epilepsy may come and go, so a short recording can be normal even when epilepsy is present. A normal routine EEG does not rule out a seizure disorder.

24–48 Hour Ambulatory EEG

An ambulatory EEG extends the recording to one or two days (sometimes longer) while you go about your normal life at home. The electrodes are applied in the office and secured, often with a cap or wrap, and the wires connect to a small portable recorder worn on a belt or shoulder strap.

Because it captures many hours of brain activity, including a full night of sleep, an ambulatory EEG is much more likely to record infrequent abnormalities or an actual event. It is particularly useful when:

• A routine EEG was normal but seizures are still suspected.
• Episodes happen often enough that one is likely to occur within a day or two.
• Your neurologist wants to know how often abnormal discharges occur, or whether they happen mostly in sleep.
• Spells need to be classified, for example to tell seizures apart from fainting or other conditions.

Living with the recorder

You will be asked to keep a diary of activities, meals, sleep and any symptoms, and to press an event button if you feel something unusual. Family members can press the button if they notice an episode. You cannot shower or wash your hair during the recording, and you should avoid activities that cause heavy sweating or could pull on the wires. At the end, you return to the office to have the electrodes removed, and the full recording is reviewed by the neurologist.

Video EEG

A video EEG records your brain waves and a synchronized video of you at the same time. When an episode happens, the neurologist can see exactly what your body was doing at the moment the brain activity changed.

This is valuable because many different conditions can cause "spells": epileptic seizures, fainting, heart rhythm problems, sleep disorders, movement disorders and non-epileptic events related to stress. Seeing the behavior and the brain waves together often provides a clearer answer than either one alone. Video EEG also helps classify seizure type and locate where seizures begin, which guides medication choices and, in some patients, evaluation for surgery.

Video EEG may be performed for a few hours in the office, combined with ambulatory recording at home with a camera, or, for longer and more complex monitoring, in a hospital epilepsy monitoring unit.

Comparing the Three Tests

• Routine EEG: short, done in the office, a good first test; may miss abnormalities that come and go.
• Ambulatory EEG (24–48 hours): longer recording in your normal environment including sleep; better chance of capturing infrequent changes or events.
• Video EEG: adds video so events can be matched with brain activity; best for classifying spells and seizure types.

It is common to begin with a routine EEG and move to a longer study if the first test does not answer the question.

How to Prepare for an EEG

• Wash your hair the night before or the morning of the test and do not use conditioner, oils, hair spray or gel. Remove hair extensions or weaves if possible, as they can block electrode contact.
• Keep taking your medications, including seizure medications, unless your neurologist gives different instructions.
• Follow sleep instructions carefully if a sleep-deprived study was ordered, and arrange for someone else to drive you if you are very tired.
• Avoid extra caffeine on the day of the test, since it can make it harder to relax and sleep.
• Eat normally. Low blood sugar can affect the recording.
• For ambulatory testing, wear a button-front shirt so you do not have to pull clothing over your head, and bring your event diary back with you.

After the Test

Once the electrodes are removed, the paste washes out with warm water and regular shampoo. You can return to normal activities right away, unless you were sleep-deprived. Your neurologist reviews the recording, which for a 24–48 hour study means examining many hours of data and every marked event. Your doctor will discuss the findings with you and explain how they fit with your history and examination.

EEG results are always interpreted in context. Some people without epilepsy have minor nonspecific findings, and some people with epilepsy have normal recordings. That is why your description of the episodes, and an eyewitness account when possible, remains one of the most important parts of the evaluation. If you have recorded an episode on a phone, bring the video to your appointment.

EEG Testing at Our Westwood Office

Dr. David D. Van Slooten is board certified in Clinical Neurophysiology, and his specialized interests include video EEG and epilepsy monitoring. Having routine, ambulatory and video EEG available in one practice means your testing can be matched to your needs without being sent to multiple locations.

If you or a family member has had a seizure, unexplained spells or episodes of confusion, learn more about seizure diagnosis and treatment, review our neurology services or find directions on our contact page.

This article is for general education and does not replace advice from your own physician. If you think you are having a medical emergency, call 911.