Clinician

Electroencephalography (EEG)

Early studies in EEG

Electroencephalography (EEG) is a method used to record electrical activity of the brain. It is typically non-invasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used, as in electrocorticography.

History

The history of EEG dates back to the late 19th and early 20th centuries. The first recording of human EEG was made by Hans Berger, a German psychiatrist, in 1924. Berger's work laid the foundation for the development of EEG as a clinical tool.

Mechanism

EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain. The signals are captured by electrodes placed on the scalp and are amplified and recorded by a computer.

Clinical Applications

EEG is used in the diagnosis of several neurological disorders, including:

• Epilepsy: EEG is the most important diagnostic test for epilepsy. It helps in identifying abnormal electrical activity in the brain that is characteristic of epileptic seizures.
• Sleep disorders: EEG is used in sleep studies to diagnose conditions such as sleep apnea and narcolepsy.
• Brain death: EEG can be used to confirm brain death by showing a lack of electrical activity in the brain.

EEG Patterns

EEG patterns are classified into different frequency bands:

• Delta waves (0.5–4 Hz)
• Theta waves (4–8 Hz)
• Alpha waves (8–13 Hz)
• Beta waves (13–30 Hz)
• Gamma waves (30 Hz and above)

Each of these patterns is associated with different states of brain activity and consciousness.

Limitations

While EEG is a valuable tool, it has limitations. The spatial resolution is relatively low, meaning it is difficult to pinpoint the exact location of brain activity. Additionally, EEG is sensitive to artifacts from muscle activity, eye movements, and other sources.

Related pages

• Neuroimaging
• Functional magnetic resonance imaging
• Magnetoencephalography