Incaic or interparietal bone: Case report and literature review on an anatomical variant

Abstract

he sutural bones correspond to additional bony plates, produced by alterations in the fusion of the ossification centers of the flat bones of the cranial vault and are found in relation to the sutures. The Inca bone is an anatomical variant that comes from the non-fusion of these ossification centers at the level of the scale of the occipital bone. It is classified into two categories: first, according to the discontinuity it causes in the parieto-occipital suture, and second, in relation to the subdivisions it generates in the scale of the occipital bone. We analyzed a skull without mandible, anonymized, belonging to the skeletal collection of the Department of Morphology, Faculty of Medicine, Universidad Andrés Bello, with male features, in a regular state of preservation and in a total state of skeletonization, which presented division at the level of the occipital bone scale. A literature search was carried out in Google Scholar, PubMed, LILACS and SciELO, obtaining 57 scientific articles. By means of critical reading, only 11 articles and one book of forensic anthropology were selected. It was determined that the anatomical variation found corresponds to an interparietal or Inca bone, complete, tripartite or Type III. A craniometric analysis was performed characterizing the skull as Dolichocranium, Hypsicranium, Acrocranium, Eurimetopic, Cameconco, Mesorrino, with a death date of approximately 31.4 years and with male sexual characteristics. This study seeks to contribute through the analysis of adult skulls with the presence of the transverse suture and Inca bone formation, a feature documented in pre-Columbian populations, but rare in modern skulls. The research is relevant for the differential diagnosis in images of infant skulls from 2 to 5 years old, helping to distinguish between fractures and persistent sutures due to the mechanism of ossification of the occipital bone. It is suggested to extend the imaging analysis considering additional variables such as sex and skull morphology, since most of the current studies only link this characteristic with the geographic region of origin.