RESUMEN
The aim of this study was to establish the relationship between background amplitude and interictal abnormalities in routine electroencephalography [EEG]. This retrospective audit was conducted between July 2006 and December 2009 at the Department of Clinical Physiology at Sultan Qaboos University Hospital [SQUH] in Muscat, Oman. A total of 1,718 electroencephalograms [EEGs] were reviewed. All EEGs were from patients who had been referred due to epilepsy, syncope or headaches. EEGs were divided into four groups based on their amplitude: group one 50 microV. Interictal abnormalities were defined as epileptiform discharges with or without associated slow waves. Abnormalities were identified during periods of resting, hyper ventilation and photic stimulation in each group. The mean age +/- standard deviation of the patients was 27 +/- 12.5 years. Of the 1,718 EEGs, 542 [31.5%] were abnormal. Interictal abnormalities increased with amplitude in all four categories and demonstrated a significant association [P <0.05]. A total of 56 EEGs [3.3%] had amplitudes that were