EEG bei Bewusstseinsstörungen, Koma und Intensivpatienten

Impairment of consciousness is usually associated with generalized EEG changes. EEG slowing may be indicative of a slight, medium-degree or severe encephalopathy, depending on its rate of occurrence and predominant frequencies. Triphasic waves have been described as a correlate of hepatic encephalopathy, but they are not specific. Coma is mostly accompanied by generalized delta slowing, but faster frequencies (theta or alpha) may predominate as well. However, this does not support a better prognosis. Burst suppression in intensive care EEGs is mostly due to anesthesia, but it may also be caused by hypoxia. Many sedative drugs cause increased diffuse beta. Periodic patterns may be lateralized (PLEDs), bilateral independent (BiPLEDs), or generalized. PLEDs are usually associated with an acute severe lesion. Most patients develop seizures in the course of disease; however, it is a matter of debate whether PLEDs represent status epilepticus pattern. BiPLEDs indicate severe lesions to both hemispheres and bad prognosis. Generalized periodic patterns are typical for Creutzfeldt-Jakob disease, but not specific. Electrocerebral inactivity is the hallmark of brain death, but it may also be due to hypoxia, hypothermia, or intoxication. There are specific technical requirements for EEGs used for suspected brain death. Intensive care EEGs are especially prone to artefacts. Knowledge about typical artefacts is essential for treating physicians.