Craniostenosis: Understanding the suture classification and its implications
The skull is not made up of a single bone like a helmet, but of bony "plates" that are joined together by lines called sutures. The cranial sutures are there to help shape the head during childbirth and also to shape the growing head. They function as expansion areas that allow the brain to grow inside the skullcap. The sutures normally fuse after the skull has finished growing, however, in some cases they fuse before birth, causing changes to the shape of the head.
Craniostenosis or craniosynostosis is characterized by the premature fusion of one or more cranial sutures, resulting in deformation of the skull and can be responsible for a growth conflict between the skull and the brain, which sometimes results in chronic intracranial hypertension. This conflict can leave sequelae, notably visual and mental.
The main cranial sutures are: the sagittal suture, the coronal sutures, the metopic suture and the lambdoid sutures.
It is important to note that a simple change in the shape of the skull does not characterize craniostenosis. In reality, the main cause of skull deformation is related to external compression forces, often associated with a vicious position of the baby in bed. This alteration is known as positional plagiocephaly, discussed in another section, in which the skull is deformed but the cranial sutures are open.
It is important to note that a simple change in the shape of the skull does not characterize craniostenosis. In reality, the main cause of skull deformation is related to external compression forces, often associated with a vicious position of the baby in bed. This alteration is known as positional plagiocephaly, discussed in another section, in which the skull is deformed but the cranial sutures are open.
The diagnosis of craniostenosis, in the vast majority of cases, can be made on clinical examination of the baby, with simple observation of the craniofacial morphology. Generally, when a single suture closes, there is a reduction in growth in the area of the affected suture, with compensatory growth in the areas of the other sutures. This compensatory growth of the other sutures produces the characteristic skull shapes seen in patients with craniostenosis. Confirmation of the clinical suspicion can be made by requesting simple radiographs of the skull, which will show the area of the closed suture. Another imaging test that can be ordered is a CT scan of the skull. This is the best test to confirm whether a suture is open or closed. CT scans provide an excellent analysis of changes to the skull base and orbits, especially in those rare cases where the physical examination shows very subtle changes or when there is a suspicion that more than one suture has closed.
Some studies show a higher rate of developmental and behavioral changes in children with craniostenosis, due to an increase in intracranial pressure in a variable percentage of children with unoperated craniostenosis.
Intracranial hypertension is more frequent when more sutures are involved. In addition, its frequency increases with age: in most craniostenoses, intracranial hypertension is twice as frequent after one year of life.
Intracranial hypertension can lead to reduced visual acuity as a result of optic nerve damage. On the other hand, intracranial hypertension can affect the intellectual performance of children with craniostenosis. This impairment is often observed through slight developmental and learning delays, observed by the parents themselves, compared to children of the same age.
Brachycephaly corresponds to the closure of both coronal sutures, leading to a bilateral frontal retreat, predominantly in the supraorbital part. In general, the skull is retracted anteriorly and posteriorly, leading to a short forehead with a low nasal dorsum and flattened occipital region, and transversely widened. This transverse widening can lead to the orbits moving apart, called hyperteleorbitism. Its incidence is slightly higher in females (1.7:1). Bilateral involvement of the coronal suture is very common in cases of syndromic craniostenosis, or craniofacioestenosis, in which there is also involvement of the face with or without alteration of the extremities (hands and feet).
Scaphocephaly, also called dolichocephaly or clinocephaly, is a premature fusion of the sagittal suture. This suture crosses the skull anteroposteriorly, starting at the anterior fontanelle, or bregma. In some cases, the "mole" is closed when this suture is affected. It is the most common craniostenosis with an incidence of around 1 in every 2,000 live births and with a higher prevalence in males (in a ratio of approximately 3.5:1). The skull is exaggeratedly elongated in the anterior-posterior direction and the parietal region is transversely retracted. In profile, the back of the skull is lower than the front, unlike a normal child.
Plagiocephaly is craniostenosis that corresponds to early closure of the unilateral coronal suture. It is characterized by an asymmetry of the skull and face, presenting an ascension of the orbit on the affected side, with displacement of the nose and a frontal bulging contralateral to the compromised suture. Orbital asymmetry is the most striking clinical feature and the diagnosis can be made by looking at the child from above and observing the ascension of one orbit. On X-ray examination, this alteration is known as a "harlequin eye". Plagiocephaly has an approximate incidence of 1:3500 live births, and is more frequent in females, at a ratio of 2:1. Rarely, children with a fused coronal suture may have a gene mutation that could mean a condition called Muenke's Syndrome.
The main cause of altered skull shape in children is the skull deformity known as Positional Plagiocephaly or Deforming Plagiocephaly. It corresponds to a flattening of the posterior region of the skull, which is slightly more common on the right, but can occasionally affect both sides.
This flattening of the skull is the result of continuous pressure on the skull and has become more frequent since the American Association of Pediatrics advised in 1992 that babies should be placed on their stomachs at bedtime to prevent sudden infant death syndrome.
This is a relatively common deformity that can also be associated with prematurity and congenital torticollis, but is mainly related to a vicious position in the cradle, as mentioned above. It is a differential diagnosis with true posterior plagiocephaly, in which a lambdoid suture is fused.
Despite the altered shape, all the cranial sutures are open, allowing the brain to grow freely, which makes it unlikely that there will be any kind of cognitive impairment or mental development in the affected children. The head looks like a parallelogram, with flattening on the side with the longest bed contact, leading to frontal bulging on the same side. The ear is displaced anteriorly, unlike in true posterior plagiocephaly, where the ear is displaced posteriorly, pulled by the premature fusion of the lambdoid suture. Treatment is usually clinical, with postural changes in the crib at night and during the day and physiotherapy. In some cases of more severe cranial deformities or when there is no significant improvement with clinical treatment, the use of orthoses, commonly known as "helmets", can be used to help reshape the skull.
These are very rare craniostenoses, which occur due to the closure of the unilateral lambdoid suture. There is a flattening of the side of the affected suture, leading to the formation of a compensatory contralateral frontal boss. There is usually a posterior displacement of the ear on the affected side. Its incidence is unknown, but it is estimated to be less than 1:50,000 live births. It is therefore an extremely rare craniostenosis. Although it is infrequent, the importance of its diagnosis lies mainly in the fact that it makes a differential diagnosis with positional or deformational plagiocephaly, a very common cause of cranial deformity, usually associated with a vicious position of the baby in bed and which will be discussed in another topic.
© Dr. Clarice Abreu. All rights reserved. 2025
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