Craniosynostosis is a condition that affects an infant’s skull, and therefore growth of the infant’s head. In this article, learn exactly what this condition is, what causes it, and what the different types of craniosynostosis are.
Have you ever seen a newborn baby with a ‘cone head’? Or an older infant whose head appears flat on one side? There is a remarkable reason for that.When you see a skull on a TV crime show or at Halloween, it looks like one solid piece.
Actually, it’s several different bones joined together. But in babies, they’re not joined yet. Instead, they are connected by fibrous tissue called sutures.
These sutures allow the bones to move around some. That’s a good thing! For one, it allows the bones to overlap as the baby moves through the birth canal, which makes things much easier for Mom. More importantly, it allows space for the baby’s brain and head to grow.
As we age, these sutures close (some sutures don’t close until our mid-20s!)
Sometimes though, something goes a little wrong, and the baby is born with one or more of those sutures closed. This condition is called craniosynostosis (Cranio means related to the cranium, or skull; syn means with or together (think synergy, synonymous); osto means bone. Put those together and it means the bones of the cranium are together).
So, what exactly goes wrong?Often times we just don’t know. We call this nonsyndromic craniosynostosis.
Research suggests that it may be caused by the baby’s position in the uterus, medications taken during pregnancy, hormonal problems, or genes. The truth is, no one really knows for sure.Sometimes, though, the cause is a genetic condition that causes multiple birth defects. This is called syndromic craniosynostosis. Some examples of genetic conditions with craniosynostosis as a feature are Crouzan Syndrome, Pfeiffer Syndrome, and Apert Syndrome.
Syndromal and nonsyndromal is one way of classifying craniosynostosis (by cause). Craniosynostois can also be typed by how many and/or which sutures are closed.
(Hint: This section will make A LOT more sense if you refer to the diagram as you read it.)
When describing the type of craniosynostosis, first you pick the number of sutures involved (single, double, or complex multisuture), and then you pick the name of the suture involved (metopic, saggital, coronal, or lambdoidal). So, for example, one type could be a single suture saggital synostosis; another type could be a double suture coronal synostosis.
In a single suture synostosis, one suture is closed.In a double suture synostosis, two sutures are closed. The sutures that are involved usually run in the same direction; for example, the metopic and saggital sutures, or the left and right coronal sutures.In complex multisuture synostosis, two or more sutures are involved, and they don’t necessarily run in the same direction; for example, the metopic and coronal sutures.Metopic suture synostosis is also called trigonocephaly. The metopic suture joins the bones on the left and right side of the skull in between the bridge of the nose and the soft spot (technically called the anterior fontanelle).
Closure of this suture means the front of the skull can’t expand side to side, only from front to back. Babies with metopic suture synostosis will therefore have a ridge going down the middle of their forehead. The ridge can make the forehead look almost triangular. Remember high school trigonometry? Probably not. But it was about triangles, and that can help you remember what trigonocephaly looks like.Saggital suture synosotosis is also called scaphocephaly.
The saggital suture runs in the same direction, but between the two soft spots (the anterior and posterior fontanelles). Again, the bones can’t move apart side to side, so the only way the head can grow is from front to back. That means the middle to back portion of the baby’s head will be long and narrow.
If you’re into boating, this one is easy. Scapho refers to ‘boat’ and cephal refers to ‘head’; scaphocephaly means a boat-shaped head.Now let’s combine the two classification systems. In a double suture synostosis involving the saggital and metopic sutures, the entire head will be long from front to back and narrow from side to side.
Coronal suture synostosis is also called anterior plagiocephaly. The coronal sutures run in an ear-to-ear direction in the front part of the skull. (In medicine, coronal refers to something that separates the body into front and back. Plagio means flat.) There is a left and a right coronal suture. So, closure of one of these sutures means the forehead on that side can’t grow.
That side will appear flattened, and the other side will appear ‘pushed out’. In a double suture synostosis, where it involves both coronal sutures, the entire forehead would have a flattened appearance.Lambdoidal suture synostosis is also called posterior plagiocephaly. The lambdoidal sutures run in the same direction as the coronal sutures, but further back on the skull. The effect is exactly the same as for coronal suture synostosis, just in the back of the head instead of the front.
If the left lambdoidal suture is closed, the left side of the back of the baby’s skull will appear flat and the right side will appear pushed out. In double lambdoidal synostosis, the entire back of the baby’s skull would appear flat.So what happens in a double suture synostosis involving the lambdoidal and coronal sutures? The entire head would be short from front to back and wide from side to side.You may have noticed the word ‘plagiocephaly’ here. You have probably heard of another type of plagiocephaly, in which babies’ heads gets flat on one side because they lie on that side all the time. Don’t get confused; that is not the same as cranisynostosis. The cause of the plagiocephaly in that case is pressure on the bone, not a closure of the sutures.
Plagiocephaly caused by pressure is called positional plagiocephaly.Complex multisuture synostosis, as the name implies, is a little more complicated. Depending on the areas involved, the head can take on a triangular or cloverleaf appearance.
So you’ve read a lot of big medical words and complex descriptions.
What do you really need to know? Craniosynosotosis is a condition in which the sutures in a baby’s skull close early, limiting movement of the bones and interfering with normal skull growth. The cause is largely unknown unless it occurs as part of a genetic syndrome with craniosynostosis as one of many birth defects. The type of craniosynostosis is determined by the number of closed sutures and which sutures are closed. Each type results in a different pattern of abnormal skull growth that can be seen in the shape of the baby’s head.