The desmocranium and the skull of a newborn before ossification is soft during palpation and contains non- ossified spots of the connective tissue called cranial fontanels (fonticuli cranii). They are situated at the junctions of the skull’s sutures. The following fontanels are distinguished:
- Anterior fontanele (fonticulus anterior) exists in the midline between the coronal and the sagittal suture (anterior part) and between the frontal and parietal bone at the site of the bregma (bregma). It has a diamond shape. The intracranial pulsation is palpable and usually visible. It disappears before a child reaches two years of age. Anterior part of the fontanele is prolongated as the metopic suture. It is located in the median sagittal plane. It is easily visible in the newborn skull. It separates the two parts of the frontal bone.
- Posterior fontanele (fonticulus posterior) exists in the midline between the lambdoid and the sagittal suture (posterior part) at the place of the lambda. It has a triangular shape. It disappears in infants during the first year.
- Anterolateral or sphenoidal fontanele (fonticulus anterolateralis seu sphenoidalis) which is irregularly shaped. It forms paired areas at the anterior inferior angle of the skull where the frontal, parietal and temporal bones and the greater wing of the sphenoid bone meet together. It corresponds to the pterion when bones have ossified. It disappears by the third postnatal month.
- Posterolateral or mastoid fontanele (fonticulus posterolateralis seu mastoideus).
Anterior and posterior fontanels provide valuable landmarks information about the position of the fetal head during delivery.
A sunken fontanele can be a sign of serious dehydration in a child (vomiting, diarrhea). A bulging fontanele could be sign of intracranial hypertension (tumor, meningitis).