Early-onset versus typical childhood absence epilepsy: Are they all the same thing?

Sir, We read with interest the article by Asadi-Pooya et al. who reported a cross-sectional retrospective study comparing the demographic and electroclinical data of 30 patients with newly diagnosed typical childhood absence epilepsy (CAE) and 16 with newly diagnosed early-onset CAE (i.e., absence seizures starting before 4 years of age). The differences between the two groups with regard to sex ratio, frequency of other seizure types (generalized tonic-clonic and myoclonic seizures), epilepsy risk factors (history of pregnancy complications or significant head trauma, history of febrile seizure, family history of epilepsy) and EEG findings were not statistically significant. Therefore, the authors concluded that clinical features of absence seizures do not show a syndrome-specific pattern, as also suggested by others. In two recent papers, we reviewed the electroclinical features and outcome of patients with typical absences starting before the 3 years of life. These patients were followed-up over a 15-year period and, when compared with patients with typical CAE, no significant difference was found with regard to family history of epilepsy, occurrence of generalized tonic-clonic seizures, intellectual function, and number of antiepileptic drugs (AEDs), except for an increased prevalence of males and longer treatment duration in patients with early-onset absences. These data are overall in agreement with those reported by Asadi-Pooya et al. However, the latter authors could not report the effect of AEDs in their patients, as they were newly diagnosed epileptic children. Notably, in our series, 82% of subjects became seizure-free with the first AED trial, usually with valproate. In the remaining 18% of individuals, add-on of another AED (mostly ethosuximide) was needed to obtain complete seizure control. During the follow-up period, up to 61% of patients were off medication. An additional issue not addressed by the study of Asadi-Pooya et al. was genetic analysis for SLC2A1, the gene encoding the glucose transporter type 1 (GLUT1), which have been found mutated in over 10% of subjects with early-onset absence epilepsy. In these patients, epilepsy outcome is quite variable, ranging from complete control at the first drug trial to severe refractoriness despite polytherapy. More importantly, some children show intellectual development of variable degree as well as disturbed behavior, movement abnormalities, and slowing of head growth. It would be of paramount importance to analyse