Neonatal skull, i.e. the skull of the new born, has many characteristic features that differentiate it from an adult skull. Some of the important ones are given below:
Size of cranium:
Neonatal skull has a disproportionately large cranium relative to the face, as compared to an adult skull. In childhood, the growth of the mandible, the maxillary sinuses and the alveolar processes of the maxillae result in a great increase in the length of the face.
Features of skull bones:
Neonatal skull bones are smooth and unilaminar (there is no diploe present). Most of the individual skull bones are ossified at birth but the overall process is incomplete and bones are mobile on each other. These mobile bones are connected to each other by fibrous tissue or cartilage.
In a neonatal skull, the bones of the vault are not closely knit at sutures, but are separated by unossified membranous intervals called fontanelles. The anterior and posterior fontanelles are important clinically.
- Anterior fontanelle: It is diamond shaped and lies between the two halves of the frontal bone in front and the two parietal bones behind. It is closed by about 18 months of age.
- Posterior fontanelle: It is triangular in shape and lies between the two parietal bones in front and occipital bone behind. It is usually closed by the end of the first year.
Tympanic part of temporal bone:
In a neonatal skull, the tympanic part of the temporal bone is merely a C-shaped ring, while in an adult skull it is a C-shaped curved plate. Thus, the external auditory meatus of the neonatal skull is almost entirely cartilaginous and the tympanic membrane is nearer the surface.
It is not present in the neonatal skull and develops later in response to the pull of the sternocleidomastoid muscle.
In the neonatal skull, the mandible has distinct right and left halves, united in the midline by fibrous tissue. The two halves fuse at symphysis menti by the end of first year.
In addition, the angle of mandible in neonatal skull is obtuse. It is only after the eruption of the eruption of the permanent teeth that the angle of the mandible assumes the adult shape.