EEG - Electroencephalogram

Routine EEG

An Electroencephalogram (EEG) is a test commonly performed to look at the electrical activity of the brain - that is, the brain waves or how the brain is functioning. Brain cells communicate by producing tiny electrical impulses. Seizures are a result of abnormal electrical activity, so it is logical to perform the EEG first.

If a person is thought to be having seizures, they are referred to a clinic to have an electroencephalogram (EEG). It is a simple, painless test and involves no needles or injections.

A normal EEG recording (Picture Courtesy of Wilkipedia)

During the test, small discs called electrodes are placed on the surface of the scalp by parting the hair and holding them in place with temporary glue, or sometimes a special cap. The EEG machine then records the electrical activity of the brain on disc, computer or to paper.

An EEG usually takes about one hour. It is important to be relaxed because movement can affect results.

Most of the test is performed with the eyes closed, and sometimes you will be asked to open them briefly. It is routine to be asked to breathe deeply (hyperventilate) for a 2-3 minutes and later have a flickering strobe light, flickering at various speeds. These forms of stimulus can provoke EEG changes in some forms of epilepsy.

For the test, it is important to have clean hair and scalp. Do not apply any hair products such as gel or hairspray on the morning of the test. It is also important to inform the person doing the test of any medications you are taking.

Many people who have epilepsy have normal EEGs in-between seizures.

An EEG recorded during sleep can also give added information. This may sometimes be required if your first EEG returns normal.

Also, no electrical current from the machine passes into the person's brain during the procedure.

The technicians cannot read your thought processes or know what you are thinking.

Other types of EEG recordings

EEG video monitoring / telemetry
This is a more sophisticated method of recording the EEG over long periods, which uses both EEG and video recording. This is done in hospital, either on one of the wards or in a specialised video-telemetry unit.

This procedure aims to simultaneously record persons episodes (by video) and the brains electrical activity (EEG). This combined information is valuable in diagnosis and understanding a person's events and their correlation with EEG. The advantage over routine EEG is the doctor is able to study exactly what happened during any attacks on the video and match this up with the simultaneous EEG recording.

This monitoring may be needed for hours or days, depending on the frequency of symptoms and episodes.

Monitoring is usually done in hospital and is a good way for the doctor to determine an accurate diagnosis. It is also used in the lead-up to surgical treatment of epilepsy.

The disc electrodes are glued to the scalp and wrapped in a bandage. There is a head-box which is sometimes wrapped on top of the head, or placed around the neck or directly beside you. There is a lead from this head-box it to monitoring equipment, confining the you to the hospital room. The camera is focussed on you and can be moved to different positions in the room. There is a also ‘seizure alarm’ button to press if an event occurs.

Video-telemetry is, of course, quite restricting. It is important to remain in view of the camera for most of the time, and you are often given a remote control to move the camera when or after you move. This means being in or on the bed or in a chair at the bedside. Of course, the camera cannot record in the bathroom or toilet. However, if you are in hospital for several days, you will not be connected to the system for every second. The cable connecting the head-box to the videotelemetry system can be unplugged quite easily, allowing for showers etc.

Most institutions require a family member or friend to stay with you as a 'buddy'. This person is also needed to quickly alert staff to a seizure.

It is preferrable that some hobbies or activities are taken into hospital to keep you occupied. It can be a long and sometimes frustrating process. Many institutions also encourage you to wear everyday clothes rather than pyjamas (it is easier with clothes that button or zip up the front rather than pull over the head).

Sleep deprived EEG / video telemetry
Some people may be asked to have a sleep-deprived EEG or video telemetry to record sleep and increase the chance of detecting abnormal brain activity. If your routine EEG has been normal or has shown features which are suspicious but not clear enough to make a definite diagnosis, the doctor may ask for a sleep EEG. This is because abnormalities can become more apparent in EEG during drowsiness and light sleep - particularly some abnormal brain activity seen in epilepsy.

The EEG changes significantly during sleep and sometimes these changes can trigger abnormal EEG changes seen with epilepsy.

For this procedure you will be asked to reduce your sleep time the night before. This increases the likelihood of recording abnormal electrical activity. It is not a disaster if you do not sleep as there is still the likelihood of detecting abnormal activity, especially if you are drowsy.

The test can be performed in the same way as for a routine EEG or video telemetry, depending on the unit, but the person is asked to sleep during the test. Occasionally sleep is induced by a mild sedative, which is given about half an hour prior to recording, but most times you will be put in a quiet, relaxing environment with a bed and lights out.

EEG ambulatory monitoring
Sometimes abnormalities, episodes, or seizures are not picked up on the above tests. The hospital setting is far from normal, and often you are not under the everyday stressors that can trigger events. If the doctor would like something more definitive to diagnose your condition, an ambulatory recording may be asked for.

In certain cases it is necessary to obtain a recording over several hours or days making it more likely to detect any abnormalities or episodes. The electrodes are glued to the scalp and connected to the a compact portable EEG recorder. This is worn to record brain activity while you carry out normal daytime activities, and during sleep. This device can be taken home and you will also be asked to keep a diary of symptoms.

There is often a button you can press to mark an episode on the device.

This allows the EEG to be recorded over a much longer period than a routine EEG - for several days if need be - and in a normal setting. This greatly increases the chances of detecting abnormalities.

It is also more likely to actually record the EEG during an attack, particularly if these are occurring quite often. This may allow doctors to distinguish whether the episodes are epilepsy or not. The recording may also give a very clear picture of any patterns or how often they are occurring.

For more information about EEG's....Click here.

1300 EPILEPSY (1300 37 45 37)
Australia wide Priority Call