The Correlation between Electroencephalography Amplitude and Interictal Abnormalities Audit study
Journal Title: Sultan Qaboos University Medical Journal - Year 2014, Vol 14, Issue 4
Abstract
Objectives: Te aim of this study was to establish the relationship between background amplitude and interictal abnormalities in routine electroencephalography (EEG). Methods: Tis 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 ≤20 μV; group two 21–35 μV; group three 36–50 μV, and group four >50 μV. Interictal abnormalities were defned as epileptiform discharges with or without associated slow waves. Abnormalities were identifed during periods of resting, hyperventilation and photic stimulation in each group. Results: Te 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 signifcant association (P <0.05). A total of 56 EEGs (3.3%) had amplitudes that were ≤20 μV and none of these showed interictal epileptiform abnormalities. Conclusion: EEG amplitude is an important factor in determining the presence of interictal epileptiform abnormalities in routine EEGs. Tis should be taken into account when investigating patients for epilepsy. A strong argument is made for considering long-term EEG monitoring in order to identify unexplained seizures which may be secondary to epilepsy. It is recommended that all tertiary institutions provide EEG telemetry services.
Authors and Affiliations
Sami F. Al-Rawas| Department of Clinical Physiology, Sultan Qaboos University Hospital, Rajesh P. Poothrikovil| Department of Clinical Physiology, Sultan Qaboos University Hospital, Khidir M. Abdelbasit| Department of Mathematics & Statistics, College of Science, Sultan Qaboos University, Muscat, Oman, Robert S. Delamont| Department of Neurology, Institute of Epileptology, King’s College Hospital, London, UK
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