Electroencephalography (EEG)

During electroencephalography (the brain-wave trace), the electrical activity generated by the brain is recorded from the scalp. These currents arise from the constant activity and signalling of the nerve cells among one another. This activity depends on various factors — for example, it differs between sleep and wakefulness and is different in older age than in childhood.

To record the electrical brain activity, electrodes are placed on the patient's head under a cap. These electrodes transmit the brain's electrical activity to a computer, which displays the voltage changes as a series of lines.

The EEG is particularly important for diagnosing epilepsy and can help determine which type of seizures a patient experiences and whether there is an increased risk of further seizures. This guides the choice of medication and dose.

The EEG also often reveals signs of diffuse cerebral circulatory disturbances, especially in older patients. Patients with migraine or other headaches may show typical changes. Certain brain inflammations produce characteristic EEG changes, as do some metabolic disorders, intoxications, or psychotropic medications. The EEG is often altered after strokes or in brain tumours, which is why it is frequently used as a screening tool.