Propagation of generalised discharges in idiopathic generalised epilepsy

• Main Author: Kibuuka, Moses
• Published: King's College London (University of London) 2012
• Subjects: 616.85
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.628132

Introduction: Patients with idiopathic generalised epilepsy (IGE) show generalised discharges, which are assumed to occur synchronously over the entire cortex. We hypothesis that (1) Generalised discharges are propagated and this can be shown by latency differences between EEG spikes recorded over homologous sites at discharge onset, and (2) Discharge synchronicity may predict treatment response. Methods: Eighty-five patients EEGs, containing generalised discharges were analysed to identify latency differences between spikes recorded at homologous regions between hemispheres at discharge onset. The discharges were either synchronous or non-synchronous generalised spike-and-waves (GSW), polyspike-and-waves (PSW) or GSW+PSW. Results: At onset, discharges were synchronous (with no latency differences between hemispheres) in 29 patients (34 %), were led by the left hemisphere in 17 patients (20%) and by the right hemisphere in 16 patients (19 %). In 23 patients (27%), discharges were a mixture of synchronous and non-synchronous discharges at onset. In non-synchronous discharges, the range of latency differences at discharge onset was 6-45 ms (mean latency 19.2ms). Interictal focal abnormalities were seen in 59 patients (69 %) in addition to the generalised discharges. There was an association between presence of synchronous discharges and one seizure type, and between presence of non-synchronous discharges and multiple seizure types (P =0.01). In addition, there was an association between presence of synchronous generalised discharges and good response to prescribed antiepileptic drugs (AED), and between non-synchronous discharges and poor response to AEDs (p=0.0001). The proportion of patients who responded favourably to medical treatment was significantly higher among those with synchronous discharges (>80 %) compared to those where one hemisphere led (<25 %). Conclusion: In IGE, generalised discharges are not always synchronous. EEG latency analysis could be used to identify non-synchronous discharges, which may be predictors for multiple seizure types and poor response to AEDs.