The anesthetic propofol has a dose-depending effect on the EEG, which differs in comparison between scalp and intracerebral electrodes

The electrical activity of the brain (electroencephalogram EEG) is usually assessed from the surface of the head, which is approximately 1-2 cm above the cerebral cortex. Thus, the spatial resolution of the EEG is low, and the electrical activity recorded originates from a multitude of neurons.

Deep brain structures such as the hippocampus also generate electrical activity which cannot be assessed from the surface of the head. However, in some patients electrodes are implanted into the brain to look for the origin of epileptic seizures. Along the way, these intracerebral electrodes enable to record the EEG from intracerebral structures which are generated from few neurons only. Once the origin of epilepsy has been identified, the intracerebral electrodes are removed under general anesthesia.

Anesthetics such as propofol characteristically modify the EEG in a dose-dependant manner. More over, the propofol effect on the EEG recorded from the surface is likely to be different from the intracerebral EEG, however little is known so far. Therefore we aim to investigate the differential effect of propofol on the superficial versus intracerebral recorded EEG.

Inclusion Criteria:

• Patients with implanted intracerebral EEG electrodes

Exclusion Criteria:

• Pregnancy

Patients suffering from epilepsy