A Study of the Interparietal Bones.

Background: The squamous part of the occipital bone has an upper membranous part which is called as the interparietal part and a lower cartilage part which is called as the suboccipital part. There is a controversy regarding the ossification of these two parts. Aim: In this study, the incidence of the interparietal bone has been estimated and compared with the previous observations. Materials: A total of 150 adult dried skulls were examined to determine the incidence of the interparietal bone. Results: The skulls which were observed, displayed many variations in the occipital region. In 11 cases, single or multiple separated bones were observed. In 6 (4%) cases, the lower edge of these additional bones was situated slightly above the external occipital protuberance and such bones could be classified as interparietal bones. In 5 (3.3%) cases, the lower edge of these additional bones was much higher (higher than the midline, between the lambda region and the highest nuchal line). These bones were much smaller in size. The latter can be classified as either pre-interparietal or sutural bones or as non-fused parts of the interparietal bone. Further studies are required to clarify the origin of these bones. [ABSTRACT FROM AUTHOR]