They then grow together as part of normal growth. They stay connected throughout adulthood. The sutures and fontanelles are needed for the infant's brain growth and development. During childbirth, the flexibility of the sutures allows the bones to overlap so the baby's head can pass through the birth canal without pressing on and damaging their brain. During infancy and childhood, the sutures are flexible. This allows the brain to grow quickly and protects the brain from minor impacts to the head such as when the infant is learning to hold his head up, roll over, and sit up.
Without flexible sutures and fontanelles, the child's brain could not grow enough. The child would develop brain damage. Feeling the cranial sutures and fontanelles is one way that health care providers follow the child's growth and development.
Does it allow for a more intimate connection with our patient who cannot yet return a greeting? Does it reassure us to feel a subtle pulsation? Perhaps feeling its size helps convince us that the brain is growing well, or maybe we appreciate the fontanel because this unique window to the brain will not persist for long.
The information we gain from examining the fontanel is extensive. This article reviews the development of the fontanel, its clinical significance, the wide range of normal presentation, and discusses abnormalities of the fontanel and what this can teach us about our patients. The newborn calvaria is normally comprised of 7 bones: the paired frontal, temporal, and parietal bones, and the single occipital bone.
As these bones grow radially from membranous ossification centers, sutures form at the junctions of the calvaria and fontanels form at the intersection of sutures. The triangular posterior fontanel is found at the junction of the sagittal and lambdoid sutures, and normally closes by 8 weeks. The diamond-shaped anterior fontanel forms at the junction of the coronal, metopic, and sagittal sutures. In addition, the mastoid fontanel the asterion or star forms at the posterior end of the parietomastoid suture, at the junction of the squamosal suture, mendosal suture, and extraoccipital synchondroses.
The sphenoid fontanel pterion forms from the juncture of the sphenoparietal, sphenofrontal, and coronal sutures. Fontanel and suture widths are determined by a balance between the growth of the calvaria and brain Figure 2. The flexible sutures allow for molding during birth, as well as both prenatal and postnatal brain growth. Although the majority of calvarial sutures remain patent into the second decade, the metopic suture normally fuses during infancy, usually within the first 3 to 9 months of life.
Providers must recognize this condition during early infancy so that patients can be referred to a craniofacial center for timely management. Numerous investigators have measured fontanels of neonates to determine the normal range.
In the traditional measurement method, researchers averaged the length anterior-posterior dimension and width transverse dimension of the fontanel. In , Popich and Smith developed the first normal distribution of anterior fontanel sizes at birth and during the first year of life for Caucasian infants.
It is significant to note that even infants with measurements that were very small had no underlying problems. Another researcher has shown that African American infants had larger fontanels than Caucasians by measuring fontanels in African American and 73 Caucasian neonates.
Differences in fontanel size based on ethnicity have been confirmed by other groups, with larger mean measurements of fontanels reported for infants of Hispanic, Nigerian, and Chinese descent. Following this group of infants over 24 months, they concluded that prematurity does not contribute to differences in fontanel size at age 2 years. In conclusion, there is a range of normal size of anterior fontanels in newborns within and among infants of different ethnic backgrounds, but gestational age at birth and sex are not associated with significant differences in fontanel size.
Several studies have measured the size of the anterior fontanel at various times during the first 12 to 24 months of life. These consistently report that the size of the fontanel often increases during the first month of life before it begins to close. Various factors influence the size of the fontanel and its quality when palpated.
The Table summarizes disorders that affect fontanel size. These disorders are generally related to problems of skeletal morphogenesis, factors related to increased ICP, and associations with syndromes. The size of the anterior fontanel reflects the balance between growth of the brain and the calvaria Figure 2.
Anterior fontanel size may be smaller than expected when associated with primary microcephaly, an underlying brain malformation such as holoprosencephaly, hypoxic event secondary microcephaly , or other conditions associated with slow brain growth.
In addition anterior fontanel size reflects skeletal morphogenesis. Thyroid hormones are involved in the regulation of bone growth and resorption, and disruption of this balance affects the calvarial bones as well as other parts of the skeleton. Hyperthyroidism may accelerate skeletal development and cause a smaller anterior fontanel, and severe thyrotoxicosis has resulted in craniosynostosis.
Rather than the usual diamond shape of the fontanel that can be palpated when all sutures are patent, there is often blunting on the side of the suture that has fused. In cases of craniosynostosis, however, characteristic head shape differences allow for a clinical diagnosis. Many conditions are associated with large fontanels or delayed closure of the anterior fontanel.
Infants with hypothyroidism have been recognized for decades to have wider-than-expected fontanels because thyroid hormones are involved in bone growth. A number of other skeletal disorders are associated with a large fontanel and delayed closure of the fontanel, including hypophosphatasia, parietal foramina syndrome, osteogenesis imperfecta, and achondroplasia.
Skeletal surveys may prove diagnostic. Additionally assessment of thyroid hormone levels, calcium, phosphate, alkaline phosphatase, and vitamin D levels can serve as adjunct to history and exam. Trisomies 13, 18, and 21 have also been associated with enlarged fontanels and are often detected during the second trimester. Peroxisome biogenesis disorders, including Zellweger syndrome, should be suspected in a hypotonic infant who presents with large anterior fontanel and splayed sutures.
Congenital rubella and syphilis may also be associated with large fontanels as can prenatal exposures of various drugs, including angiotensin-converting enzyme inhibitors, methotrexate, fluconazole, hydantoin, and primidone. Colic is a pattern of unexplained, excessive crying in an otherwise healthy and well-fed baby and happens to 1 in 5 Australian babies.
Read more on myDr website. New parents often worry that they don't know what to do. However, there are practical ways to deal with the challenges so you can enjoy your baby more.
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Please enter your name Please enter your email Your email is invalid. This extends from the top of the head down the middle of the forehead, toward the nose. The 2 frontal bone plates meet at the metopic suture. Coronal suture. This extends from ear to ear. Each frontal bone plate meets with a parietal bone plate at the coronal suture.
Sagittal suture. This extends from the front of the head to the back, down the middle of the top of the head. The 2 parietal bone plates meet at the sagittal suture.
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