Diagnostic Tests

Blood Tests

These check the general health of the person and help to exclude the presence of abnormal amounts of various substances in the body as a cause for the seizures.

EEG - ElectroEncephalogram

This test measures the electrical activity of the surface of the brain. Electrodes are placed on the brain. Electrodes are placed on the scalp and the signals picked up are amplified and recorded onto paper. It is a painless procedure lasting about 30 minutes. It should be remembered that the EEG can only give information about the electrical activity of the brain during the period of the recording. Only if patterns characteristic of epilepsy are seen during the routine recording, is the EEG of value in the diagnosis. A normal EEG does not exclude the possibility of epilepsy.

Sometimes longer term EEG (ambulatory EEG) may be necessary. The person wears a small pack containing an audio cassette tape around their waist, with wires underneath their clothing, going up to their head. EEG monitoring can then take place over a number of days and the person can carry on with their normal activities.

Brain Scans

These help to exclude a structural cause for the seizures. CT or MRI scans of the brain may be requested. In many people, such tests will be normal.

  • CT Scan - a CT (computerised tomography) Scan uses x-rays to produce images of the brain, which are fed into a computer. The computer reconstructs these images into 'slices' - pictures of cross sections of the brain. A CT scan is an appropriate initial investigation to exclude the possibility of a brain tumour.
  • MRI Scan - instead of x-rays MRI uses magnetism (magnetic resonance imaging) the pictures of the brain are similar to those produced by CT scanning, but are more detailed and can detect very small brain lesions.
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