palmar crease palmar crease a palmar crease is a type of crease on the palm. a single transverse palmar crease also called simian crease is sometimes associated with down syndrome. other types of creases include the sydney crease and the suwon, or double transverse palmar crease. a simian crease, one type of palmar crease. analysis of palmar creases is not very objective on the contrary to fingerprint analysis. palmar creases are sometimes used as a preoperative landmark for identification of deep anatomical structures. this method was shown to be unuseful.