Epileptiform discharges in the context of self-limited pediatric focal epilepsy (EDSelFEC) in pediatric hemispherotomy patients: Role of white matter abnormalities

Objective: To investigate the frequency of epileptiform discharges associated with self-limited focal epilepsy (EDSelFEC) in children who have undergone a hemispherotomy and to evaluate whether patients with coexistence of EDSelFEC and structural hemispheric epilepsies differ from patients without coexistence of EDSelFEC and whether there are differences between the two groups with regard to preoperative management and postoperative outcome.

Methods: Data on 131 children who underwent a hemispherotomy between January 1999 and January 2015 were retrieved from the Epilepsy center's epilepsy surgery database. Children with EDSelFEC were compared with children without EDSelFEC with respect to epileptogenic hemispheric pathology, family history, age at epilepsy onset, timing of surgery, lesion laterality, preoperative cognitive function, response to sodium channel blocker antiepileptic medication, and surgical outcome. Parental consent was obtained.

Results: EDSelFECs were present in the EEG in 27 (21%) of the 131 cases. None of the patients had seizures associated with EDSelFECs. The percentages of EDSelFECs varied between pathology groups: vascular lesions: 38%, focal cortical dysplasia: 16%, polymicrogyria: 5%, Rasmussen encephalitis: 10%, hemimegalencephaly: 8%, mild malformation of cortical development with oligodendroglial hyperplasia:20%, other pathologies: 22%. EDSelFEC in the vascular group were significantly correlated with MRI changes showing white matter damage in addition to cortical damage (p =.02). 82.1% of EDSelFEC were located multifocal versus 4.8% multifocality in EDs other than EDSelFEC. EDSelFEC were significantly more often exacerbated by sodium channel blockers than EDs caused by structural (cortical) lesions. No differences were found between EDSelFEC+ and EDSelFEC- patients with respect to other variables studied.

Significance: A significant number of children with hemispheric epileptogenic lesions, particularly children with pre-/perinatal vascular lesions, hemiplegia, and white matter lesions in addition to cortical lesions, presented with coexisting EDSelFEC.