RESUMO
INTRODUCTION: In extended and multigenerational pedigrees, the idiopathic epilepsy phenotype shows an extreme variability. OBJECTIVE: The range of idiopathic epilepsy onset age in multigenerational pedigrees was studied in order to determine if genetic anticipation play a role in the heredity of Idiopathic Epilepsies. PATIENTS AND METHODS: We compare the seizures onset age among relative-pairs of (parents-children, grandfathers-grandsons and nephew uncles). The mean onset age was compared using the Wilcoxon sign-rank paired-sample non-parametrical test to determine whether or not significant differences over > 0 exist, which refutes the null hypothesis of not anticipation. 84 pairs of relatives were taken from 72 extended multigenerational pedigrees. RESULTS: The onset age of idiopathic epilepsy of the pairs showed a difference significantly > 0, which confirm the existence of intergenerational differences. This difference has a tendency to decrease in age which each successive generation. This difference occur in all relative pairs and therefore contradicts the ascertainment bias described by Penrose. CONCLUSIONS: The results outline the existence of unstable mutations (those produced by a nucleotidic variable number of tandem repeats) as a probable explanation of the susceptibility to develop some forms of idiopathic epilepsy.