Sensitivity of electroencephalogram after first onset seizures in patients presenting at Charlotte Maxeke Johannesburg Academic Hospital

Abstract

Introduction Routine electroencephalogram (rEEG) has a significant role in diagnosing and treating epilepsy. A common requirement for the diagnosis and categorisation of epilepsy is the presence of interictal epileptiform discharges (IEDs). rEEG recording has a low sensitivity of about 30-50%. Sleep-deprived EEG (SD-EEG) can increase the yield of IEDs by about 64%, while using 24-hour ambulatory EEG (24-hour AEEG) increases the yield of IEDs by about 84%. The study aimed to determine the sensitivity of rEEG compared with the SD-EEG and 24-hour AEEG on patients with first-onset seizures presenting at the CMJAH. Methods The research utilised a prospective cohort, quantitative, cross-sectional, descriptive design with n=50 patients aged ≥ 16 years with first onset seizures who underwent three EEG modalities (rEEG, SD-EEG and 24-hour AEEG), creating perfectly matched EEG samples. The three EEGs were compared (specificity, sensitivity, positive predictive value, negative predictive value and assessed for IEDs. Results Fifty patients participated in the study group. The participants sex distribution was (n=26) females, while (n=24) were males, presenting at the median age of 29 years. The evidence of IEDs on 24-hour AEEG was 70%, SD-EEG (40%) and rEEG (22%). Sensitivity was 57.1% on the 24-hour AEEG and 55%, on a SD-EEG detecting patients with epilepsy and the rate of false positives was 45% on SD-EEG and 42.9% on the 24-hour AEEG. Conclusions Our findings indicate that the 24-hour AEEG was a more sensitive diagnostic tool than the rEEG and SD-EEG for diagnosing and categorising epilepsy. An important risk factor for subsequent seizures is the presence of IEDs in the EEG following the first onset seizure. Using 24-hour AEEG can reduce the time needed to find the diagnosis.