Tests - EEG

The EEG is a special test that records the electrical activity from the brain. It is used particularly to look for clues about fits. Your child has wires stuck onto his/her head with special glue, which record electricity coming from the brain (it is simply recording the brain’s normal activity). During the recording, your child will be asked to open and shut his or her eyes, and at one point to breath deeply (or blow a windmill). He or she will also be asked to look at a flashing light. If possible the recording will include a period of sleep, which is particularly important to monitor with LKS. In some children these activities may increase or reveal abnormalities, which can then help to guide the medical treatment.

During the active phase of LKS, EEG recordings will usually show abnormal discharges on both sides of the brain over the centro-temporal regions, and these discharges often become continuous in sleep. Therefore a sleep record is usually required when assessing a child with LKS, and often this will be achieved by a period of video-telemetry (typically overnight).

Video-telemetry means using a closed circuit video camera, which is linked to an EEG machine. The camera records what is happening to the patient at the same time as the EEG records the brainwaves, and the screen displays the patient and the EEG trace simultaneously.

If surgery is being considered, the following specialised tests may be used:

Methohexital Suppression Test

In this test, your child is monitored using EEG. A light anaesthetic is given and a short-acting barbiturate drug (methohexitol) is given to put your child deeply asleep to the point where the EEG recording of brain activity becomes a flat line. The drug is then allowed to wear off, and the EEG begins to show electrical discharges again. The first place where this activity returns is thought to be related to the source of the seizures. This information is helpful in planning surgery.