Artifacts

The term “artifact” refers to any element of extra-cerebral origin which can be recorded in the EEG channels, disturbing the acquisition of the tracing. Artifacts may derive from many sources, internal or external to the patient, and have several characteristics that may suggest their origin. Both the technician and the physician should be able to recognize the artifacts, for the possibility of misinterpreting the examination. As a matter of fact, even though many artifacts are easily detectable, some may remind pathological graphoelements and, therefore, be the cause for incorrect EEG interpretation. However, some artifacts are not considered a disturbance in the EEG recording, and they are instead considered useful for its interpretation. For example, eye movement artifacts, due to their typical morphology and localization, provide immediate information on the correct position of the electrodes, amplification parameters, and the patient’s emotional state and alertness; they are also useful in identifying the sleep stages. Sometimes, the ECG artifact can reveal cardiac arrhythmias. In epileptic patients, the appearance of muscular, ocular, or movement artifacts may indicate the seizure onset. In this chapter, the most common artifacts will be described, to give physicians and technicians the tools to detect and - possibility - to avoid their recording.