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CRANIOSYNOSTOSIS

Craniosynostosis is a birth defect of the Skull (which may affect the Brain) that is characterized by the premature closure of one or more of the fibrous joints between the bones of the Skull (called the cranial sutures) before Brain growth is complete. While the premature fusion of the cranial sutures results in disproportionate growth of the cranial bones, it may also affect the growth of the facial bones. When a suture is fused there is no growth in a plain perpendicular to the line of the suture. The abnormally shaped Skull that results is due to the Brain not being able to grow in its natural shape because of the closure. Instead it compensates with growth in areas of the Skull where the cranial sutures have not yet closed.

The Skull has two different components, the first of which forms the "vault" of the Cranium and is called the "membranous" part. The other portion, the "chondrocranium" forms the Base of the Skull. After a certain age there is little likelihood of further growth in defects of the Skull vault whereas there may be subsequent growth of defects in the Skull Base (chondrocranium.)

Brain growth stimulates the progressive formation the bone of the Skull which normally occurs in a homogeneous and symmetrical manner. There is rapid Skull grows from birth to the 7th year with the greatest part of the increase of its cranial vault occurring in during the first year of life. This is due to the rapid growth of the Brain during this time period. The Brain is expected to reach its maximum growth at about the age of two years.

The Fontanelles are the "soft spots" in a baby's Skull. They are the locations where several of the various Skull bones have yet to grow together. There are six (6) Fontanelles at the edges of the Parietal bones (2 anterolateral and posterolateral as well as the Anterior and Posterior Fontanelle.) Due to the normally expected rapid bone growth, the Posterior and Anterolateral Fontanelles are usually closed within three months after birth. The Posterolateral Fontanelle is usually closed about the end of the first year of life and the Anterior Fontanelle about the middle of the second year.

The major Skull sutures are:

  1. The "Metopic" (or Frontal) suture separates the Frontal bone into two halves. Union starts in the first year and is completed by the 8th year.

  2. The "Sagittal" suture separates the two Parietal bones and extends from the Anterior Fontanelle to the Posterior Fontanelle.

  3. The "Coronal" suture separates the Frontal bones from the Parietal bones.

  4. The "Lambdoid" suture separates the posterior edge of the Parietal bone from the Occipital bone.

  5. The "Squamosal" suture is quite complex and is the superior border of the Squamous part of the Temporal bone while anteriorly it articulates with the Greater Wing of Sphenoid, superiorly it articulates with the Parietal bone and posteriorly and inferiorly it articulates with the Occipital bone.
Craniosynostosis can be gene-linked, or caused by metabolic diseases, such as rickets (Vitamin D deficiency) or an overactive thyroid. Some cases are associated with other disorders such as Microcephaly (abnormally small head) and Hydrocephalus (excessive accumulation of Cerebrospinal Fluid in the Brain).

TYPES OF CRANIOSYNOSTOSIS

Closure of a single suture is most common. Depending on the severity of the Craniosynostosis, the child may have some or all of these problems:
  • abnormal Skull shape
  • abnormal forehead
  • asymmetry of the eyes and/or ears
  • increases intracranial pressure which can possibly cause delays in development
The issue of a risk to permanent Brain damage if the Craniosynostosis is not corrected is controversial. In our opinion, there is no good scientific data to support this claim. However, in view of the fact that there is a risk to some "developmental delays", one should be aware of this potential.
  1. Scaphocephaly, the most common type of Craniosynostosis, is caused by the fusion of the Sagittal suture which runs from front to back down the middle of the top of the Skull. Characteristic appearance:

    • a long narrow shaped head from front to back
    • narrow from ear to ear
    • the head appears boat-shaped

  2. Trigonocephaly is the fusion of the Metopic suture, which runs from the top of the head, down the middle of the forehead, towards the nose. Characteristic appearance:

    • triangular shaped forehead
    • eyes are closer together than usual

  3. Plagiocephaly is the premature fusion of one of the Coronal sutures, which extend from ear to ear over the top of the head. Characteristic appearance:

    • fusion of either the right or left side
    • the forehead and brow look like they are pushed backwards
    • the eye on the affected side has a different shape than the one on the unaffected side

  4. Brachycephaly results from premature closure of both sides of the Coronal sutures. Characteristic appearance:

    • wide-shaped head, with short Skull
    • tall, flattened forehead (the entire forehead is prevented from growing in a forward direction)

DIAGNOSIS

The first sign of Craniosynostosis is an abnormally shaped Skull. Other features can include signs of increased intracranial pressure, developmental delays, or mental retardation, which are caused by constriction of the growing Brain. Seizures and blindness may also occur.

Neuroimaging usually includes CT Scanning including 3-D studies.


Figure 1A (Left): 3-D CT Scan of a child with Scaphocephaly (Sagittal Synostosis)

Figure 1B (Center): Pre-operative Photo of the same patient

Figure 1C (Right): Post-operative Photo after bicoronal approach ("zig-zag" incision indicated by the Arrows) for reconstruction by Craniofacial Plastic Surgeon, Dr. Jeffrey A. Fearon.


TREATMENT

Treatment for Craniosynostosis generally consists of surgery to relieve pressure on the Brain and the Cranial Nerves. For some children with less severe problems, cranial molds can reshape the Skull to accommodate Brain growth and improve the appearance of the head.

PROGNOSIS

The prognosis for Craniosynostosis varies depending on whether single or multiple cranial sutures are involved or other abnormalities are present. The prognosis is better for those with single suture involvement and no associated abnormalities.

CRANIOFACIAL SYNDROMES

"Craniofacial Syndrome" is a category comprising additional conditions involving the abnormal growth of the Skull and face. These syndromes are usually inherited and in many cases the abnormal genes have been identified. The most common of these syndromes include:
  1. Crouzon Syndrome

    Crouzon is the commonest among the Craniofacial Syndromes. While sporadic cases of this condition do occur, the majority are inherited as a "Mendelian dominant trait of high penetrance".

    The typical appearance of the child with this condition includes a brachycephalic Skull with a prominent nose, a protruding jaw with malocclusion, underdeveloped Maxilla and Exophthalmos (which is often severe and may constitute a serious risk to vision.)

    While the Skull deformities vary greatly from one patient to another, the Skull is distinctly brachycephalic in all. There is usually a diffuse premature fusion of other Skull sutures including the basal sutures.

    In this condition, the exophthalmos is due to small and shallow orbits which could result in corneal ulceration and conjunctival infection. In some cases the exophthalmos is so severe that the eyes are dislocated outside the orbit resulting in a high risk to loss of vision. Many of these patients experience compromise of the nasal airways and respiratory difficulties as a result of the maxillary hyperplasia. Raised intracranial pressure is frequently encountered in association with this syndrome. Hydrocephalus is also present in about 20% of cases.

    X-ray examinations often show a "copper beaten appearance" (an indicator of raised intracranial pressure) of the Skull in addition to the premature closure of the Skull sutures.

  2. Apert Syndrome

    Apert is the second most common syndrome after Crouzon and usually presents with a very high brachycephalic head and severe syndactyl (which involves bony fusion) affecting all limbs.

Additional Information

There exists considerable amount of information regarding these conditions. We invite your consideration to begin by visiting the nationally acclaimed websites involving one of our Craniofacial Plastic Surgeons, Dr. Jeffrey A. Fearon who is also a member of our Skull Base Tumor Team. They are accessible at:

The Craniofacial Center

Children's Craniofacial Association
P.O. Box 280297
Dallas, TX 75228
800-535-3643
Email: contactCCA@ccakids.com
Ask for the Guide to Understanding Craniosynostosis written by Dr. Fearon.

The reader may also wish to review the following websites:

http://www.ninds.nih.gov/disorders/craniosynostosis/craniosynostosis.htm

http://cumc.columbia.edu/dept/nsg/PNS/Craniofacial.html

http://www.health.adelaide.edu.au/paed-neuro/craniofacial.html

FACES: The National Craniofacial Association

AboutFace USA

CAPPS (Craniosynostosis and Positional Plagiocephaly Support, Inc.)

MUMS


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This page last edited on 2/22

All content ©2016 by Neurosurgical Consultants, P.A.
Author, Martin L. Lazar, MD, FACS
All Rights Reserved. See Usage Notices.