Cranial sutures
Fontanelles; Sutures - cranial
Cranial sutures are fibrous bands of tissue that connect the bones of the skull.
The sutures or anatomical lines where the bony plates of the skull join together can be easily felt in the newborn infant. The diamond shaped space on the top of the skull and the smaller space further to the back are often referred to as the soft spot in young infants.
Fontanelles are the soft spots on an infant's head where the bony plates that make up the skull have not yet come together. It is normal for infants to have these soft spots, which can be seen and felt on the top and back of the head. Fontanelles that are abnormally large may indicate a medical condition.
Information
An infant's skull is made up of 6 separate cranial (skull) bones:
- Frontal bone
- Occipital bone
- Two parietal bones
- Two temporal bones
These bones are held together by strong, fibrous, elastic tissues called sutures.
The spaces between the bones that remain open in babies and young children are called fontanelles. Sometimes, they are called soft spots. These spaces are a part of normal development. The cranial bones remain separate for about 12 to 18 months. They then grow together as part of normal growth. They stay connected throughout adulthood.
Two fontanelles usually are present on a newborn's skull:
- On the top of the middle head, just forward of center (anterior fontanelle)
- In the back of the middle of the head (posterior fontanelle)
The posterior fontanelle usually closes by age 1 to 2 months. It may already be closed at birth.
The anterior fontanelle usually closes sometime within 7 to 19 months.
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. They are able to assess the pressure inside the brain by feeling the tension of the fontanelles. The fontanelles should feel flat and firm. Bulging fontanelles may be a sign of increased pressure within the brain. In this case, providers may need to use imaging techniques to see the brain structure, such as CT scan or MRI scan. Surgery may be needed to relieve the increased pressure.
Sunken, depressed fontanelles are sometimes a sign of dehydration.
References
Goyal NK. The newborn infant. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 113.
Safier RA, Cleves-Bayon C, Gaesser J. Neurology. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 16.
Version Info
Last reviewed on: 1/24/2023
Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
