Screening for intracranial aneurysms

EDITOR,--Since migraine without aura aggregates in families of probands with migraine without aura, it is expected that migraine without aura is less common in families of probands who have never had migraine. We calculated the population relative risk, adjusting for sex and age, since migraine without aura depends on these factors. If the population relative risk significantly exceeds one an increased family aggregation is implied, whereas a result significantly below one implies a decreased family aggregation.

W E Waters states that the risk of migraine without aura among the first degree relatives …