Excerpt from Generalized EEG Waveform Abnormalities
Synonyms, Key Words, and Related Terms: electroencephalography, EEG, EEG pattern, epileptiform pattern, alpha coma, diffuse slowing, intermittent delta, intermittent rhythmic delta activity, IRDA, Creutzfeldt-Jakob disease, mad-cow disease, mad cow disease, prion disease, electrocerebral inactivity, ECI, electrocerebral silence, ECS, seizures
Generalized EEG abnormalities typically signify dysfunction of the entire brain, although such dysfunction may not be symmetric in distribution. Generalized patterns thus may be described further as maximal in one region of the cerebrum (eg, frontal) or in one hemisphere compared to the other. Identification of an abnormality as generalized may require analysis of the EEG by several montages to determine lack of focal point. Careful elimination of external and bioelectric artifact is important to avoid misinterpretation of noncerebral activity (eg, ECG), which can contaminate multiple channels, appearing as generalized abnormalities.
This article discusses EEG patterns that usually are generalized and are not considered primarily ictal. Many of these patterns occur in encephalopathic states, which themselves can lower a patient's threshold for seizures. Some patterns can be considered "epileptiform" since they contain spikes, sharp transients, or rhythmic paroxysmal patterns. Remember that the term "epileptiform" is descriptive of an EEG's appearance only and does not necessarily imply that the pattern is "epileptogenic."
Patient education
For excellent patient education resources, visit eMedicine's Procedures Center. Also, see eMedicine's patient education article Electroencephalography (EEG).
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