EEG in delirium.

Electroencephalography (EEG) is an inexpensive and noninvasive probe of functional brain activity that is one of the few clinically accessible measures capable of detecting changes in delirium. In EEG characteristics of delirium include slowing or dropout of the posterior dominant rhythm, generalized theta or delta slow-wave activity, poor organization of the background rhythm, and loss of reactivity of the EEG to eye opening and closing. These are paralleled by the quantitative EEG (QEEG) findings of increased absolute and relative slow-wave (theta and delta) power, reduced ratio of fast-to-slow band power, reduced mean frequency, and reduced occipital peak frequency. In alcohol and sedative withdrawal, EEG findings may include attenuation of voltage and prominence of beta activity. Specificity of EEG and QEEG findings in delirium has been questioned, particularly vis-'a-vis EEG changes in normal aging and in dementia. As noted in the text, however, specificity can be increased by the use of careful data acquisition and skillful interpretation. In the future, it is expected that QEEG methods will largely replace EEG in application to delirium.