Introduction
Introduction[edit | edit source]
Electroencephalography (EEG) was first described by Hans Berger in 1929. He recorded brain waves from two electrodes placed at the back of the head and described the normal resting alpha rhythm. He also identified abnormal electrical patterns among brain injured subjects. Since then, EEG’s application in evaluating numerous clinical scenarios has been expanded and refined.
Though a relatively old technology, EEG remains the best available noninvasive method for evaluating brain function in real time. EEGs are often requested to assess paroxysmal neurologic events, define and characterize seizure disorders, and determine how overall brain function correlates with a variety of clinical states.
Identification of interictal epileptiform discharges may help confirm a diagnosis of epilepsy or clarify the diagnosis of specific epilepsy syndromes. Differentiating between a generalized epilepsy syndrome and a localization-related epilepsy syndrome can be crucial in prognosis and decision making for medical and/or surgical management. EEGs are also used to help establish diagnosis and prognosis in certain encephalopathic or coma states. Commonly the EEG will reveal slowing to some degree paralleling the clinical examination. If a particular coma pattern is seen on the EEG, the pattern and its evolution over time may provide prognostic information to assist in clinical decision making for further treatment. One condition where the information provided by EEG is indispensable is nonconvulsive status epilepticus. This condition is difficult to diagnose unless the index of suspicion is high at the onset because the clinical presentation can be subtle. The morbidity and mortality of status epilepticus can be high if proper diagnosis and treatment are delayed.