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Craniosynostosis: Definition, Causes & Types

Instructor: Jennifer Brest

Jennifer has a Master's Degree in Nursing. Her specialty is pediatrics. She has worked in hospital care, primary care, home care, government, and teaching.

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.

Background

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!)

Definition

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).

Cause

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.

Types

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.)

Cranial sutures
Cranial Sutures

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.

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