No single parameter or collective group of features present in the EEG can identify a tracing as normal. Because the routine interpretation of EEG as normal is most routinely a qualitative skill, the result is based upon one’s knowledge, training, and experience. The correct interpretation involves synthesizing complex waveforms from different bandwidths generated by a cerebral source to determine whether the combined result is normal. To be believable as a source of electrical activity that emanates from the brain, an appropriate polarity ( Table 5.1) and accompanying electrophysiological field must exist ( 3).

Scalp EEG is routinely used in the assessment of normal EEG, though three-dimensional source localization is possible ( 2). The origin of cerebral potentials is based upon the intrinsic electrophysiological properties of the nervous system ( 1). Most of the human cortex lies deep beneath the scalp surface where EEG has limited capabilities in assessing subcortical abnormalities. EEG represents a three-dimensional cerebral source graphically represented in a two-dimensional plane. To understand what constitutes an abnormal EEG, a solid foundation of what constitutes the normal boundaries is essential. The utility of EEG lies in its application to a number of neurological conditions associated with altered brain function. EEG has made a unique and valuable contribution to our understanding of the brain’s electrical function.

Normal eeg