PURPOSE: To study modulation of epileptiform EEG discharges in patients with juvenile myoclonic epilepsy (JME).
METHOD: 50 subjects with JME underwent a sleep deprived EEG recording along with conventional provocative methods and testing with cognitive tasks (CTs). Both categories of tests were evaluated for their effect on occurrence of IEDs. Number of IEDs per unit time was calculated at baseline as well as with each task. Statistical and arbitrary methods were used to assess modulation. By arbitrary method if frequency of IEDs was more than twice that of baseline, it was considered as provocation and if less than half, it was considered as inhibition. To account for spontaneous fluctuation of IEDs, 95% CI was calculated for baseline IEDs in each patient and provocation/inhibition was considered if frequency of IEDs exceeded/remained below limits of CI respectively.
RESULTS: There was no significant difference in rates of provocation of IEDs by conventional or CTs. However there was exclusive provocation of IEDs by CTs in 4 patients, 3 of whom were already on AEDs. There was a significant inhibitory effect of CTs as mean baseline discharge frequency was 0.4?±?1.16 IEDS/min and during CTs was 0.1?±?0.38 IEDs/min. However when spontaneous fluctuation was accounted for, inhibition was seen in only 22.23% patients by statistical method as compared to 90.91% by arbitrary method.
CONCLUSIONS: Inclusion of cognitive tasks (CTs) may assist in provocation of interictal epileptiform discharges (IEDs), thereby increasing yield of routine EEG. Spontaneous fluctuation of IEDs accounts for much observed inhibition by CTs in juvenile myoclonic epilepsy patients.