A diamond-shaped, membrane-covered ‘soft-spot’ situated at the front of the top of an infant’s head that corresponds to the junction of the frontal, saggital and coronal sutures. These fibrous sutures allow movements of the skull plates during delivery through the birth canal, and for brain growth during the first year. Typically, this fontanelle closes (or ossifies) some time between 7 and 19 months, usually in conjunction with the establishment of upright bipedal locomotion. With crying or vomiting, it bulges as it does in cases of increased intracranial pressure due, for example, to hydrocephalus or meningitis. If the infant is dehydrated, this open area shows a depression. The anterior fontanelle (or bregmatic fontanelle) is one of two ‘soft-spots’ on the human newborn’s skull, the other being the posterior fontanelle (see figure below) where the two parietal bones adjoin the occipital bone, and which closes some 2 to 3 months after birth.
