Fontanel is convex/swollen outwards
Since a fontanel, in contrast to the skull plates, does not represent a bony structure, a statement about the pressure conditions inside the head can be made by its curvature or depression. A normal fontanel in an upright sitting infant should be either flat or slightly sunken. In a lying position, the fontanel of a healthy baby should be flat or slightly convex.
Furthermore, it should feel soft when gently stroked over. If the fontanel of a lying baby is slightly arched outwards, this is completely normal. If a fontanel is strongly bulging outwards in a lying position or when the baby is sitting upright, this may be an indication of increased intracranial pressure, for example due to a disturbance in the flow of cerebral fluid, or of an inflammation.
Bruising in the brain, for example after accidents, can also be the cause of an outwardly bulging fontanel. A fontanel that is very tense and does not yield to pressure can be a sign of inflammation. If such a bulging or tense fontanel is observed, a pediatrician should always be consulted to clarify what is involved. If a fontanel is clearly sunken in a lying infant, this can be a sign of a disturbed water balance, either due to severe fluid loss or lack.
