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 more information.
Types of Craniosynostosis
Sagittal Suture Synostosis
The sagittal suture is located on the midline, on top of the skull and extends from the soft spot towards the back of the head. Sagittal suture synostosis is the most common type of single suture synostosis and predominantly affects males. The suture is located at the midline, on top of the skull and extends from the soft spot towards the back of the head. Sagittal synostosis causes a shape that’s long and narrow, known as scaphocephaly. As the head grows in this long and narrow direction, the back of the head becomes prominent, pointed and the forehead protrudes. There is a low risk of abnormal brain growth and development. This form of synostosis is generally easy to diagnose.
Metopic Suture Synostosis
This midline suture is located in the middle of the forehead and extends from the soft spot to the root of the nose. Metopic Suture Synostosis affects the middle area of a baby’s forehead, and extends from the soft spot to the root of the nose. Both frontal lobes expand forward and sideways, and the eye socket will move to either side resulting in eyes lying closely together. When early closure occurs it can result in the baby developing an upwards bump, or midline ridge, and the forehead will slant backwards giving the forehead a triangular appearance when viewed from above. The back of the head will then protrude, due to the brain growing in that particular direction.
Coronal Suture Synostosis
The coronal suture is located on the side of the skull and extends from the soft spot to an area just in front of the ear. Coronal Suture Synostosis affects the side of the skull where the forehead and the frontal lobe grow and expand forward. When this suture closes too early, the condition is known as anterior plagiocephaly (a merge from either the right or left side of the coronal suture that runs from ear to ear). With this type of craniosynostosis, the forehead is recessed and flattened, and the eye socket is elevated and tilted. You will also notice your baby’s eyes protruding, while the nose deviates to the opposite side. Your baby may want to tilt their head to the side in order to prevent seeing double – this is a major indicator of this type of craniosynostosis and a result of Coronal Suture Synostosis being untreated.
Lambdoid Suture Synostosis
Premature closure of the lambdoid suture is the least common of all forms of Craniosynostosis and has been frequently confused with positional molding of the head. A premature closure in lambdoidal suture synostosis results in the flattening of the back of a baby’s skull on the affected side, protrusion of the bone behind the ear, the mastoid bone, and lowering of the affected ear. It may also cause the skull to tilt sideways.