Interictal focal epileptic discharges in a pediatric patient with absence status epilepsy: a mimicker of focal epilepsy

Abstract

Absence status epilepsy (ASE) is a rare generalized epilepsy that usually manifests in adolescence or adulthood, although pediatric-onset cases have also been described. It is characterized by recurrent episodes of absence status epilepticus, presenting as prolonged confusion or unresponsiveness. Ictal electroencephalography (EEG) typically shows near-continuous generalized spike-and-wave (SW) or polyspike-and-wave (PSW) discharges. To date, interictal focal epileptic discharges have not been reported in ASE. A previously healthy 6-year-old girl presented with recurrent atypical absence seizures lasting several hours, during which she was confused, moved and spoke slowly, and made errors in daily activities. At age seven, ictal EEG revealed almost continuous, irregular generalized SW and PSW discharges with maximal amplitude over the frontal regions. Interictal EEG demonstrated occipital intermittent rhythmic delta activity, generalized SW and PSW, and focal epileptic discharges. Brain magnetic resonance imaging and laboratory tests were unremarkable. Despite initial treatment with levetiracetam and clobazam, absence status epilepticus recurred when continuous intravenous midazolam was discontinued. Introduction of valproic acid allowed successful withdrawal of midazolam, and the patient was discharged without seizure recurrence. This case illustrates that focal interictal epileptic discharges can occur in ASE. The interictal focal EEG abnormalities may lead to misdiagnosis of focal epilepsy, particularly when impairment of consciousness during absence seizures is mild. Diagnosing absence seizures in ASE is further complicated by their prolonged duration, which makes onset and termination difficult to document. Valproic acid was effective for long-term seizure control, whereas intravenous benzodiazepines achieved rapid seizure suppression.