A clinical and genetic study of 33 new cases with early-onset absence epilepsy

PURPOSE: To investigate the electroclinical features and the outcome of patients with typical absences starting before the 3 years of life. METHODS: We reviewed the clinical data of patients with absences started before 3 years observed over a 15-year period. Mutation analysis of SLC2A1 (GLUT-1) gene was performed when possible. Their clinical features were compared with those of subjects with a diagnosis of childhood absence epilepsy (CAE). RESULTS: Among 33 children with absence epilepsy starting before 3 years of life, there were 20 boys and 13 girls. Mean seizure onset was at 28.0 ± 8.3 (range: 8-36) months of life. Two children displayed borderline intellectual functioning at long-term follow-up. Twenty-eight (85%) patients showed excellent response to therapy. Three subjects evolved into a different form of idiopathic generalized epilepsy (IGE). No SLC2A1 mutation was identified in 20 (60.6%) patients tested. The main clinical features of patients with early-onset absences did not differ from those of CAE except for increased prevalence of males (p=0.002) and longer treatment duration (p=0.001) in the former. CONCLUSIONS: Strong similarities in the electroclinical features and outcome between children with early-onset absences and those with CAE support the view that these conditions are part of the wide spectrum of IGE.