PREMATURE FUSION OF CRANIAL SUTURES

Cranial sutures represent structures where the bones of the skull join each other to form the cranial vault.

During the first year of life, the thrust of the rapidly growing brain exerts a separative force in a direction perpendicular to the intervening suture, resulting in normal growth of the skull.

When growth is complete, the sutures gradually become fused. Occasionally cranial sutures fuse prematurely. This pathological condition causes a variety of disturbances, ranging from a mild deformity of the shape of the head, to much more severe deformities and functional problems which are likely to affect the child’s health and development.

In synostosis of a single suture (although it is questionable that premature fusion of a single suture truly exists), growth is halted in the direction perpendicular to the suture involved. Because of this restriction, the continuing expansion of the brain pushes in a compensatory way other areas of the skull. A deformity develops which is specific of the obliteration of that particular suture.

Premature fusion of one side of the coronal suture results in a deformity called plagiocephaly. On the side of the fusion the forehead is flat or even concave, and the orbit (the bones of the facial skeleton containing the eye) is displaced upwards. On the opposite side the forehead bulges abnormally. If this condition is not corrected early in life, the jaws may also become asymmetrical making surgical correction a much more complex undertaking.

Plagiocephaly (Deformities yellow arrows - and compensatory deformations white arrows)

 If both sides of the coronal suture are fused prematurely, growth of the skull in a front to back direction becomes deficient, giving rise to a deformity called brachycephaly (short head).

In early fusion of the metopic suture (a vertical suture in the middle of the forehead) a triangular, keel shaped forehead develops. This condition is called trigonocephaly. 

Trigonocephaly (3D CT scan, pre and post surgery views)

Fusion of the sagittal suture (which runs from front to back along the top of the skull) produces an elongated head, a deformity characterized as scaphocephaly.

Scaphocephaly (top and profile views)

Finally early fusion of the lambdoid suture, located in the back of the head and shaped like an inverted V causes flattening of the occipital region (the back of the skull), for which the term occipital plagiocephaly has been used. This condition should however not be confused with a much more benign flattening of that region, called positional molding, a deformation caused by constant pressure application to the area when the infant is kept on its back for prolonged periods of time. This condition is treated by relieving the pressure from the flattened area with a custom made helmet.

It follows that a fusion of multiple sutures will result in a more complex (and serious) deformity.

In the past, treatment of suture fusion consisted in removing the involved suture, hoping that this would result in normalization of the shape of the skull. The outcome of such procedures was universally unsatisfactory.

It was not until surgeons realized that the attachments of the dura (the membrane covering the brain) should be widely detached from the involved regions of the skull, and a normal shape given to the deformed area at the time of the surgical operation, that satisfactory results were obtained.

Today, procedures specifically designed to remodel the deformed areas of the skull and facial skeleton are carried out in craniofacial centers by specialized teams of plastic surgeons and neurosurgeons.

Plagiocephaly (correction technique)

These procedures are carried out during the first months of life, in order to take the best possible advantage of the still growing brain, and of the ability of the infant’s tissues to form bone, which will fill the defects caused by surgery.