The word Craniosynostosis derives from “Kranion” (Skull) + “Syn” (Joined) + “Osteon” (Bone). It involves the premature fusion of one or more of the sutures (growth plates) of the skull.
The bones of your infant’s skull don’t normally begin to fuse until about 6 months of age, and fusion of all sutures is not complete until well into adulthood. This design allows the growing brain to dictate the shape of the head. Premature fusion of one or more sutures happens in-utero. While the fusion may not be apparent at the time of birth, it becomes more noticeable over time as the brain grows.
The majority of cases (about 90%) of these premature fusions involve a single suture and are not associated with any functional impairment. In rare cases, however, multiple sutures may be involved, and these have a higher probability of having functional problems, such as increased intracranial pressure (ICP), visual impairment, and developmental delay.
Epidemiology of Craniosynostosis
Craniosynostosis occurs in 1 in 2,000 to 1 in 2,500 live births. The most common sutures involved are the Sagittal (45-55%), Coronal (20-25%) and Metopic (5-15%). Males are slightly more commonly affected than females (3:2).
The type of craniosynostosis will dictate the way in which the skull shape forms as a result of the growing brain underneath. Normal brain growth occurs mostly during the first 2-3 years of life with approximately 85% of growth complete by age 3.
Cause of Craniosynostosis
It was noted in the 19th century that normal skull growth occurs in a direction perpendicular to the sutures and therefore premature fusion of a suture will cause a predictable abnormal head shape. Decades of research since then have shed much light on the mechanisms of craniosynostosis. It is reconginzed that gestations involving multiple babies, large birth weight, oligohydramnios (low amount of amniotic fluid) and advanced maternal age are at increased risk of developing craniosynostosis.
The basic underlying mechanism likely involves compression of the cranium while the fetus is in the uterus and this in turn stimulates the dura (lining of the brain) to produce bone prematurely at the suture. Genetics likely plays a role as well, as studies comparing identical (monozygotic) and fraternal (dizygotic) twins show an increased incidence in the identical twin group.
Types of Craniosynostosis
The human cranium consists of several bone plates that are connected by major and minor sutures:
This design allows flexibility of the skull, which facilitates passage through the birth canal, and allows unrestricted growth of the brain. Expansion and growth of the skull bones occurs in a direction perpendicular to each suture.
Sagittal Synostosis (Scaphocephaly)
Fusion of the sagittal suture is the most common form of single-suture synostosis. Males are affected 4 times as much as females. Growth is restricted in the transverse (width) dimension and patients typically have prominence of the forehead and occiput (back of head). (Fig.2) In many cases, a midline ridge over the fused suture can be felt (and sometimes seen).
Metopic Synostosis (Trigonocephaly)
Fusion of the metopic suture normally occurs by 8 months of age. Premature fusion restricts the transverse growth of the anterior portion of the skull, commonly referred to as the bitemporal distance. (Fig.3) Patients have a midline forehead ridge that may be felt and sometimes seen. In more severe cases, the eyes may be positioned close together and problems with vision can result.
Unicoronal or Lambdoid Synostosis (Plagiocephaly)
Plagiocephaly (“twisted head”) may result from either premature closure of one of the coronal or lambdoid sutures or from constant, prolonged pressure on one side of the head (deformational plagiocephaly). Clinical evaluation by your physician can delineate the cause in the majority of cases, but a low-dose CT scan is sometimes performed if there is any question. The affected side of the head is flattened and there may be compensatory prominence of the opposite side. (Fig.4) The eyebrow, orbit, nose, mouth, and chin may be affected as well. In the operating room, the difference between an open suture and fused suture is easily noticeable. (Fig.5)
Bicoronal Synostosis (Brachycephaly)
Brachycephaly, or “short head”, may result from either premature fusion of both coronal sutures or from prolonged pressure to the back of the head. In the latter senario, the back of the head is flat and the top may be taller than normal. Bicoronal synostosis causes a decrease in the anterior-posterior dimension and a compensatory increase in the transverse dimension as well as height.(Fig.6) The orbits may be shallow causing the globes to bulge (exorbitism).
New York Craniosynostosis Procedures
Treatment of cranial abnormalities, whether they be from premature fusion of one or more sutures or from deformation, begins with an evaluation by a multidisciplinary craniofacial team. An ophthalmologic and hearing evaluation is important and routinely part of the team work-up for our New York craniosynostosis patients. Some cases require imaging studies (CT, MRI, Ultrasound, X-ray) to evaluate the bones and brain.
Correction is aimed at treating the underlying cause. In cases of deformational plagiocephaly or brachycephaly, positional changes and “tummy-time” are a couple of common first-line therapies. Molding helmets are sometimes used as well. In more severe cases of deformation, surgery may be necessary to correct the head shape.
In cases of craniosynostosis, the prematurely fused suture can be treated in different ways. In very mild cases with no signs of growth constriction of the brain, surgery may not be necessary. In moderate to severe cases, the fused suture can be surgically removed and a molding helmet worn postoperatively (strip craniectomy), or a more traditional cranial vault remodeling (CVR) may be performed. The latter involves removing the fused suture and molding the skull bones to create a normal head shape. The determination of which surgery is most appropriate, as well as the specifics of the preoperative, operative, and postoperative course is a discussion that parents will have with their craniofacial surgeon and the rest of the team.
Let’s Get Started
Do you want to learn more about New York craniosynostosis treatment options? Contact one of our doctors online to meet with them at the New York Group for Plastic Surgery. You can also give us a call at 800-433-7410 to reach our New York City office or 914-366-6139 to reach our Tarrytown office. Call 845-294-2018 to reach our Goshen office in Orange County, New York.
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