During the NINETEENTH century and early TWENTIETH century, the prevalence of the disease is estimated at 1:1000 (one in one thousand live births). However, the use of diagnostic imaging has shown that Chiari malformations are much more common.6 The diagnosis is even more difficult by the fact that the majority of infants born with this disease do not manifest symptoms until adolescence, adulthood or old age, if they ever show any.
The Chiari are more frequent in women than in men, and the type II is more prevalent in certain ethnic groups, such as afro-celtic.6