Do pure absence seizures occur in myoclonic epilepsy of infancy? A case series

PURPOSE To assess if absence seizures (ASs) occur in patients with myoclonic epilepsy of infancy (MEI). METHODS A retrospective chart review was conducted in 37 patients with MEI followed at seven different paediatric epilepsy centres in Italy, between 2002 and 2014. To assess the possible occurrence of pure ASs or absences associated with myoclonias, ASs were defined according to the following criteria: (i) a sudden onset and interruption of ongoing activities; (ii) bilateral polyspikes or spike-and-wave (SW) complexes; spike SW complexes at 2-4Hz; (iii) duration of AS: 3-30seconds. RESULTS Thirty-seven MEI patients (25 boys and 12 girls) were identified. Nine patients (24.3%) had a history of simple FS during the first year of life. Ten patients (27%) had a family history of epilepsy, and six patients (16.2%) had a family history of FS. In 7/37 (18.9%) patients, during the occurrence of MSs, a total of nineteen brief ASs were captured by video-EEG recordings. ASs occurred both during a brief cluster of rhythmic MSs than after single myoclonic jerks. The ictal EEG abnormalities observed in patients with ASs were similar to the ictal EEG patterns associated with only myoclonias. No differences in relation to gender, family history, ictal EEG discharge were found between patients with myoclonic seizures with ASs and myoclonias without ASs. CONCLUSIONS Absence seizures can occur in approximately 20% of MEI patients and the occurrence of ASs, though not essential to formulate the diagnosis, do not automatically exclude the diagnosis of MEI.