This issue will cover chiari malformation in both children and adult populations. In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that CM may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if at all. CMs occur more often in women than in men and Type II malformations are more prevalent in certain groups, including people of Celtic descent.