is the membrane that lies between the bones of the newborn and infant skull. All fontanels can be hollow or bulging depending on the tension inside the skull of the child, but the bregma, or anterior fontanel is the most commonly palpated because it closes last and is the widest. It can bulge as the result of an effort, cough, fever
, or crying. A bulging fontanel is always a cause of concern and may be a sign of increased intracranial pressure, often a side-effect
of an intracranial pathology
, which can sometimes lead to a brain scan or lumbar puncture
. In some cases of dehydration, fontanels may instead be hollow: this is called a sunken fontanel.