What is Craniosynostosis

To understand craniosynostosis, it’s important to first appreciate the changes happening inside a newborn’s brain. It is common for a newborn to have a misshapen head immediately after birth. This is often caused by the position of the baby in the womb or by the pressure of the birth canal during delivery. In such cases, the shape typically begins to resolve in the first couple of days of life.  However, a persistent misshapen head should be evaluated for craniosynostosis, a relatively common condition occurring in as many as 1 in 1,000 births.

Rapid Growth Phase: 9-36 Months 

Immediately following birth, the baby’s brain undergoes an extremely rapid phase of growth and development. It is calculated that a newborn’s brain will double in volume and size in 9 months and triple after 3 years. 

An infant's skull is made up of 6 cranial bones:

  • Frontal bone
  • Occipital bone
  • Two parietal bones
  • Two temporal bones

The bones listed above are held together by strong, fibrous, elastic tissues called sutures. Cranial bones remain separate for about 12-18 months, and as part of normal growth, grow together to stay connected throughout adulthood. 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 your baby is learning to hold his or her head up. Without the flexibility of these skull sutures, your baby’s brain could not grow properly. 

To accommodate such rapid brain growth, your baby’s skull cap must expand rapidly as well. Sutures respond to brain growth by “stretching” and producing new bone, thereby allowing the skull to grow along with the brain. 

How Craniosynostosis Comes into Play

Craniosynostosis is a birth defect in which one or more of the joints between the bones of an infant’s skull close too early. This defect happens before the infant's brain fully forms, and causes an abnormally shaped skull. With craniosynostosis, the brain is unable to grow in its natural shape, and in some cases, is associated with an underlying brain abnormality. The term cranial stenosis and simply synostosis are used to describe this condition. 

This condition occurs if any of your baby’s sutures close or fuse before or soon after birth, while the brain is growing at a rapid rate. The closed suture delays proper and parallel bone growth, which leads the brain to grow in the direction of least resistance, so that ultimately the shape of the brain, skull, and face become distorted. Each type of premature suture closure will lead to a specific abnormal head shape and unique set of complications.

If you are concerned about the shape of your baby’s head, we are happy to provide an initial opinion at no-cost through email with photographs. Please contact us for instructions.

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Department of Neurosurgery
UT Health San Antonio
4502 Medical Dr. 2nd Floor, Rio Tower
San Antonio, Texas 78229
Phone: 210-358-8555
Fax: 210-358-8576

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