electroencefalografie

Electroencefalografie (EEG) is a noninvasive method to record the brain's electrical activity using surface electrodes on the scalp. The recorded signals reflect the summed postsynaptic potentials of large populations of cortical neurons, primarily from the cerebral cortex.

The technique has a long history, beginning with Hans Berger's first EEG in 1929. Over the decades, standardized electrode layouts such as the 10-20 system were developed, and digital EEG recording along with long-term video- EEG monitoring expanded clinical use.

How it works: small electrical signals generated by cortical cells are picked up by electrodes, amplified, filtered, and digitized. Typical recordings use multiple electrodes arranged according to a standard montage; common sampling rates range from 256 to 1,000 samples per second, with bandwidth roughly 0.5–70 Hz. Recordings can be routine or extended, and may include sleep or video synchronization.

Clinical applications include diagnosis and characterization of epilepsy, evaluation of coma or encephalopathy, sleep disorders, and monitoring for neurosurgical planning or intensive care. Routine EEGs capture minutes of activity, while ambulatory or video- EEG provides longer data and state correlation.

Interpretation focuses on waveform patterns, frequency bands (delta, theta, alpha, beta, gamma), and events such as epileptiform discharges. EEG has limited spatial resolution and cannot reliably localize deep structures; results must be integrated with clinical data and imaging. Artifacts from eye movements, muscle activity, and electrical interference can obscure interpretation.

Safety is high; EEG is noninvasive and well tolerated, though skin irritation from electrodes or gel may occur. It remains a foundational tool in neurology and neuroscience research, with ongoing advances in quantitative analysis and neuronal source localization.