EEG – Ambulatory
This is an EEG over 24 to 48 hours using a small portable EEG recording device suitable for adults or children and can be worn while going about normal activities. Ambulatory EEG may be advised where a routine EEG has not completely answered the clinical question, symptoms occur in sleep, or if attacks are frequent enough to record one. It may help to confirm whether certain symptoms are due to seizures.
Electrodes are fixed with collodion glue and can often be partially hidden under the hair. They connect to a small recorder worn on a belt (similar to wearing an MP3 player or a personal stereo). The patient keeps a diary noting meal times, sleep times, and symptoms or attacks. They are also asked to press an event marker button on the EEG recorder, if they can, when symptoms occur. It often helps to have someone with the patient, so that if attacks occur that they cannot remember, some help is available to fill out the diary and press the event marker button.
At least two appointments are given for ambulatory EEG, firstly to set up the recording and secondly after 24 or 48 hours to return equipment and remove electrodes. We remove as much glue as we can with a special liquid, and the residue can be washed out at home later, although it may take more than one hair wash. The EEG recording is analysed at a later date.
For children we use a similar procedure, except that the leads may be covered with a thin netting hat to discourage little fingers from investigating. The recorder is placed in a small rucksack worn on the child’s back, which is more comfortable than a belt round the waist. For babies and toddlers, the rucksack can be hung onto a buggy or, if the child is being carried, the strap can be worn slung over mum’s shoulder.