Abstracts

Benign rolandic epilepsy (BRE) is considered a genetically determined idiopathic partial epilepsy, but family studies of BRE probands show few family members have BRE. Whilst monozygous (MZ) concordant pairs with BRE are reported, our preliminary data showed an absence of concordant pairs. Our aim is to elucidate the genetics of BRE by systematically studying twins in a multi-center international collaborative twin study. Large population-based twin databases in Melbourne (Australia), Odense, (Denmark), Oslo (Norway) and Richmond (USA) were reviewed for cases of BRE. Diagnosis of BRE was based on age of onset between 3-13 years, compatible clinical seizure pattern, absence of other neurological signs and centro-temporal spikes on EEG. All available information was reviewed to establish the diagnosis. Zygosity was determined clinically and confirmed where possible by polymorphic DNA markers. There were seventeen twin pairs (10 monozygous; 7 dizygous) with a definite diagnosis of BRE amongst a total sample of 1866 twin pairs. All pairs were discordant for BRE. The estimated MZ pairwise concordance of 0 (95 % CI, 0 - 0.3) for BRE was significantly different to the estimated MZ pairwise concordance of 0.7 (95 % CI, 0.5 - 0.9) for 26 IGE MZ pairs from our Australian cohort (p[lt]0.001). The absence of any concordant MZ pairs from our multi-center collaboration of twin pairs with BRE strongly suggests that conventional genetic influences in BRE are considerably less than for IGE, where MZ twin concordance is high. The often-quoted misconception of an autosomal dominant gene for classical BRE should be expunged. A full understanding of the cause of BRE must look beyond traditional genetics and consider mechanisms such as environmental factors, somatic mutations and epigenetic influences.