There are limitations of routine EEG recordings in detecting the often intermittent abnormalities seen in epilepsy. One way to improve the information gained is to perform what is known as an ambulatory (‘walking’) EEG recording. This involves recording the brainwaves of someone who is walking around, freely mobile and not confined to the testing room in an EEG department.
Standard EEG electrodes are placed on the scalp, but a smaller number than with a routine recording. The wires from these electrodes are plugged into a small portable relay box and the EEG signals are recorded on a hard drive or a memory card in a battery-operated recorder worn around the chest or waist.
Once the ambulatory EEG recorder has been fitted and tested, the person goes home and carries on with normal daily activities, returning about 24 hours later to have the device removed. If a longer recording is needed, the batteries and scalp electrodes are checked before the person returns home for a further period of recording. It may seem a little odd to be walking around with EEG electrodes on the head, but most people quickly adapt to this and are able to carry on with their normal daily lives.
This technique is used with both adults and children. There are two advantages to ambulatory EEG recording. First of all, it allows the EEG to be recorded over a much longer period than a routine EEG – for several days if need be. This greatly increases the chances of detecting abnormalities. The second advantage is that it may be possible to actually record the EEG during an attack, particularly if these are occurring quite often. This may allow doctors to distinguish whether the attacks are epileptic or not. The recording may also give a very clear picture of how often attacks are occurring in someone who is known to have epilepsy. People having this type of EEG will be asked to keep a record of any attacks that occur during the recording, noting the time and a short description of what occurred.