Anatomic variations in the frontal and occipital bones: a comparative study of neurocranial morphology

Abstract

Developmental variations in the cranial vault arise during early ontogenesis due to premature or delayed suture closure, non-union between the normal ossification centers, and emergence of additional ossification centers. These variations cause abnormal calvarial partition and are often associated with modifications of the overall cranial configuration. This study aims to evaluate the impact of metopic suture persistence and the development of supernumerary bones in the occipital region on neurocranial morphology. A series of 245 crania of Bulgarian males was investigated. According to the presence or absence of developmental variations in the frontal and occipital bone they were divided into four series: control (n = 115); crania with a retained metopic suture (n = 32); crania with supernumerary bones in the occipital region (n = 67); and metopic crania with supernumerary bones in the occipital region (n = 31). Polygonal 3D models were generated, on which the 3D coordinates of 35 landmarks describing the neurocranium were collected. Geometric morphometric analyses were applied to compare the size and shape of the landmark configurations. Significant size differences were observed only in the frontal and occipital bone configurations between the metopic crania with occipital supernumerary bones and the non-metopic crania. Significant shape differences were found in all comparisons between the metopic and non-metopic groups for all configurations, except the occipital one. Metopism has a significant impact on overall neurocranial morphology, which is intensified by the presence of supernumerary bones in the occipital region.