Normative data for the unquantified EEG: examination of adequacy for neuropsychiatric research

Visual inspection of the unquantified electroencephalogram (EEG) remains the sole technique to confidently detect epileptiform discharges. Usefulness of this procedure in psychiatric research is hampered by reported prevalence of abnormalities in normal adults ranging from 4% to 57.5%. In this study, we examined the criteria used in available literature for selecting healthy individuals. Medline, PsychInfo, and textbook chapters were the primary sources for data. Analysis was restricted to studies examining the visual inspection of the EEG in humans. Thirty-eight articles met search criteria. Seven criteria for choosing healthy comparison subjects were used as the bases for this review. The majority of studies met no criteria, one criterion or two criteria. We conclude that the boundaries for normal unquantified EEG are poorly defined.