Significance of Polyspikes on Electroencephalography in Children with Focal Epilepsy

Purpose: Epilepsy is one of the most common neurological disorders in both adults and children. After detailed history-taking, electroencephalography (EEG) is the most important investigation in the evaluation of epilepsy patients. Polyspikes, defined as a sequence of two or more spikes, are among the findings that can be seen on EEGs of epilepsy patients, but the literature on their significance in focal epilepsy patients is scarce. Therefore, in the current study, we investigated the significance of polyspikes on EEG in childhood focal epilepsy. Methods: A retrospective analysis was conducted of data from children who were diagnosed with focal epilepsy and received anti-seizure medications at Pusan National University Children’s Hospital. Results: Among the 1,125 children included in this study, 468 (41.6%) showed interictal polyspikes on their EEGs. In the multivariate analysis, only the presence of brain magnetic resonance imaging (MRI) abnormalities was significantly associated with the presence of interictal polyspikes on EEGs. Among patients with brain MRI abnormalities, localized polyspikes were significantly associated with focal cortical dysplasia, while multifocal polyspikes were significantly associated with perinatal insults (hypoxic-ischemic encephalopathy and destructive encephalomalacia). Conclusion: Focal epilepsy patients with interictal polyspikes were more likely to have a structural etiology. Furthermore, patients with localized polyspikes were more likely to have focal cortical dysplasia as the structural etiology, while patients with multifocal polyspikes were more likely to have perinatal insults as the structural etiology. This study demonstrates that focal polyspikes can be used as markers of the possible presence of a structural etiology in routine practice.