Vertebral artery hypoplasia--sex-specific frequencies in 36 parent-offspring pairs.

The major interest in vertebral artery (VA) hypoplasia comes from its possible connection to migraines with aura as well as from the fact that it is one of the risk factors for a stroke. Therefore, the aim of this preliminary study was to investigate the mode of inheritance of VA hypoplasia. Initially, color Doppler of VA was performed in 64 first- and second-degree relatives of 33 probands, and the presence of VA hypoplasia was confirmed according to the already established criteria. Since a higher prevalence of VA hypoplasia (15.6%) in probands'relatives in comparison with 2.34% in the general population of Croatia was indicative of a strong familial predisposition for this condition, an analysis of family data by means of Pearson's chi-square statistics has been performed. In this analysis, the observed sex-specific frequencies of 36 parent-offspring pairs composed only of affected parent and his/her (affected or non-affected) offspring are compared to the frequencies as expected under eight proposed models. For both--autosomal and X-linked monogenetic inheritance--four hypotheses have been chosen, assuming that the individuals having the affected allele (in combination with a healthy one) have 100%, 50%, 40% and 0% chances of developing VA hypoplasia. Out of eight tested models only two--completely dominant and completely recessive X-linked models--were rejected. But, from the six non-rejected models, goodness-of-fit statistics showed that the hypothesis of X-linked inheritance of VA hypoplasia with the "healthy" allele being stronger (60% effect on phenotype)--almost perfectly fit the data (chi2 = 2.0023; df = 7; p = 0.9597). Further research encompassing a more enlarged family sample is needed to confirm the present findings.