Several major bones make up the skull of a newborn. The bones are connected together by fibrous material called sutures. The area of the skull where two bones unite with this fibrous connection is called fontanelle. A newborn has six fontanelles, but the most prominent is the anterior fontanelle, also called the “soft spot,” or the junction between the bones in the front and the bones in the back of the skull.
Brain volume in newborn infants doubles by the time he reaches six months old and triples by 2 and a half years old. Sutures and fontanelles allow the skull to meet the rapid growth demands of the brain. In a newborn, the normal fontanelle measures 2 centimeters (.8 inches), but it can range from 0.6 centimeters (.2 inches) to 3.6 centimeters (1.4 inches). The normal age of closure is 14 months, but can range from three to 24 months.
If your child experiences blunt trauma or minor bumps over the anterior fontanelle, treatment is the same as trauma to any other part of the head. Injuries that break the skin over the anterior fontanelle in infants and toddlers require urgent attention, but are very rare and usually associated with inflicted injury.
Your pediatrician should be able to recognize if your child’s fontanelle has closed early. Early closure can be normal, but the baby’s head circumference must be carefully monitored to ensure it’s growing at an appropriate rate. If your child’s head circumference begins to fall below expected values, for example, head circumference was in the 50th percentile at birth and later is at the 10th percentile, then further evaluation is required to rule out medical causes for early fontanelle closure.
A condition in which the sutures close too early, called craniosynostosis, has been associated with early fontanelle closure. Craniosynostosis results in an abnormal head shape and problems with normal brain and skull growth. Premature closure of the sutures may also cause the pressure inside of the head to increase. The condition can be diagnosed by physical exam, but often X-rays or a CT scan is required to confirm the diagnosis and rule out any other abnormalities.
Your pediatrician can make a referral to a pediatric plastic surgeon specializing in craniofacial surgery or a pediatric neurosurgeon at St. Louis Children’s Hospital for evaluation and treatment of abnormal head growth.