What is a craniosynostosis?
Craniosynostosis is a condition affecting the skull. When babies are born, they have gaps called sutures between the plates of bone that make up the skull. These gaps allow the brain to grow. They close up gradually but sometimes one or more sutures closes before it is supposed to – before brain growth is complete, which is normally at 15 to 18 months.
The skull becomes deformed as the brain continues to grow, pushing into different directions.
If a baby has craniosynostosis it is usually present at birth, but it is not always noticeable straight away. One of the reasons for this is that it is common for skulls to be slightly misshapen by the passage down the birth canal, and they put themselves right after a few days or weeks. However, most craniosynostosis is picked up in the first few months of life.
There are several different types of craniosynostosis. Among the most common are:
- sagittal synostosis (or scaphocephaly) – affecting the suture at the top of the skull
- metopic synostosis (or trigonoscephaly) – affecting the suture down the middle of the forehead
- unilateral coronal synostosis – affecting the suture on one side of the skull
- bilateral coronal synostosis – affecting the sutures at both sides of the skull.
Craniosynostosis may also appear as part of a number of syndromes such as Apert’s syndrome.
The severity of craniosynostosis is determined by which sutures have fused, at what stage of development this occurred, and how the other parts of the skull have moved to compensate.
Symptoms of craniosynostosis
The most obvious symptom is generally the physical deformation of the child’s head. This may appear as a misshapen skull or one-sided deformation of the face, particularly around the eye sockets, causing a lop-sided expression.
A bony ridge may form over the fused suture and the ears may not be symmetrical (not at equal heights on each side).
Cases that are diagnosed when the child is slightly older (over 6 months) are less common, partly because the physical deformation tends to be mild in these cases and thus not so obvious.
Due to raised intercranial pressure (pressure building up inside the skull as the brain tries to expand, older children may experience severe headaches or vomiting, or become irritable.
Delays in the child’s mental development can be symptoms of craniosynostosis, and seizures or blindness might also occur in severe cases.
Children may also feel self-conscious about their appearance and lack confidence in social situations, if they have severe facial abnormalities.
The causes of craniosynostosis are not fully understood. It is sometimes occurs because of a genetic defect, but more often occurs spontaneously without any previous family history.
It might be caused by a condition affecting the metabolic system (the way your body processes energy), such as rickets (a type of bone disease) or an overactive thyroid (which can cause excessive bone production).
Craniosynostosis can also be part of a genetic syndrome that has wider effects. In Apert’s syndrome, for example, craniofacial anomalies (when the head appears short at the front and back and may be pointed) may accompany other symptoms such as webbed fingers and toes, widely spaced protruding eyes, and overcrowding of teeth.
In Crouzon’s syndrome the head appears short in the back and front and this is accompanied by a flat nose and flat cheekbones.
Certain brain disorders, where the brain does not grow properly to expand the skull, may also lead to craniosynostosis by causing the bones to fuse earlier than normal.
How to diagnose Craniosynostosis?
It is often possible to diagnose craniosynostosis simply through examination of the head by a doctor. Any severe distortions of the skull or face will be apparent on sight, and the existence of ridges over fused sutures, or misalignment of the ears, will also provide evidence.
For confirmation, an X-ray of the skull can be taken, but the best results are provided by a computerized tomography (CT) scan. These give a three-dimensional view, showing the sutures in detail, and can guide surgical correction.
Craniosynostosis should not be confused with positional plagiocephaly, in which the back or a side of the baby’s head becomes flattened. This is often due to the child being placed in the same position for much of the time (for example with the back of the head on the chair, bed or floor, for example).
It is quite common and normally corrects itself by the time the child has reached one year old.
Treatment of craniosynostosis
Surgery can be carried out to relieve the pressure inside the skull and to allow the brain to grow. It can also correct cosmetic defects, to make appearance look more conventional.
Procedures generally involve releasing the prematurely closed sutures. The scalp is opened and the edges of the parted bones are sealed, to delay their fusion until the brain has grown.
Depending on the type and severity of the condition, extensive remodelling of the skull bones may be carried out.
Mild positional plagiocephaly (flattened head) can be treated simply by re-positioning of the baby’s head for sleeping, and making sure it has time on its tummy to rest the back of the skull. Occasionally, in severe cases, a special helmet or headband may have to be worn to encourage the correct growth of the skull.