Summary

The human cranium is a complex osseous structure whose development is subject to multiple variations, many of which have clinical, radiological, and surgical relevance. One such variation is the presence of the interparietal bone, a structure whose nomenclature and classification have long been the subject of controversy. The present study aims to review the relevant literature and to present the first reported cases of interparietal bones in a Uruguayan population. A literature search on the interparietal bone was conducted using Google Scholar, PubMed, and Scopus. Subsequently, two human crania presenting interparietal bones were analyzed and designated as cranium A and cranium B. Anthropometric measurements were obtained, and both specimens were classified according to the classifications proposed by Kandánov and by Hanihara and Ishida. Cranium A presented two interparietal bones, measuring 91 mm and 50 mm in maximum length, respectively, corresponding to type 3C according to the Kandánov and Hanihara and Ishida classification. In contrast, cranium B exhibited a single interparietal bone with a maximum length of 45 mm, corresponding to type 1B. The literature reveals significant discrepancies and inconsistencies regarding the terminology and classification of the interparietal bone. Based on the present analysis, the term “interparietal bone” is considered the most appropriate designation for this structure, and the use of the term “Incaic bone” should be avoided. Considering its developmental origin, the interparietal bone should be regarded as an intercalary bone rather than a Wormian bone. Finally, relevant clinical and demographic aspects of this anatomical variation are discussed.

Keywords

Interparietal bone, Incaic bone, Cranial variation, Skull development, Intercalary bones, Anatomical classification