Craniosynostosis is the premature closure of 1 or more cranial sutures during the embryonic period or early childhood. Cranial sutures are present throughout the skull, which is divided into 2 parts, the calvarium and the skull base, via an imaginary line drawn from the supraorbital rims to the base of the occiput (Fig 28-1).
Bony growth of the skull occurs in osteoblastic centers located at the suture sites. Bone is laid down parallel and perpendicular to the direction of the suture. Premature suture closure prevents perpendicular growth but allows parallel growth. This pattern is termed Virchow’s law and leads to clinically recognizable cranial bone deformations, all of which carry specific nomenclature (Fig 28-2). The following are important terms associated with craniosynostosis.
The term plagiocephaly literally means “oblique head.” Most often it is the consequence of a unilateral coronal suture synostosis. On the synostotic side, the forehead and supraorbital rim are retruded (depressed), the interpalpebral fissure is wider, and the orbit is often higher than on the nonsynostotic side. Because of brain growth and necessary cranial vault expansion, the nonsynostotic side will display protrusion or bulging of the forehead, lower supraorbital rim, narrower interpalpebral fissure, and often a lower orbital position (Fig 28-3).
Oxy-, turri-, acrocephaly
These terms all mean “tower head.” The condition occurs most often with multiple suture closures, such as both coronals, the sagittal, and possibly the lambdoidals.
“Short head”; specifically refers to growth in the anterior-posterior axis. Brachycephaly is often the result of bilateral closure of the coronal sutures. The forehead is most often wide and flat.
“Boat head.” Scaphocephaly usually results from premature closure of the sagittal suture; the skull is thus long in the anterior-posterior axis and narrow bitemporally.
“Long head”; the skull shape is much like that in scaphocephaly.
“Cloverleaf skull”; the skull shape is trilobar. Kleeblattschädel is typically the result of synostosis of the coronal, lambdoidal, and sagittal sutures.
Excessive distance between the medial orbital walls. This diagnosis is made not clinically but rather radiographically.
Excessive interpupillary distance when compared to standard nomograms; it implies orbital hypertelorism.
Increased distance between the medial canthi. This may be secondary to hypertelorism, but it can be a primary soft tissue abnormality.
Calvarial suture fusion affects cranial shape and orbital development. Skull base suture fusion affects facial and orbital development. In contrast to calvarial suture fusion, which causes different cranial deformations, skull base suture fusion causes just 1 constellation of abnormalities, midface hypoplasia (Fig 28-4), specifically consisting of the following:
shallow orbits with proptosis and lagophthalmos
high-arched palate with dental malocclusion
relative mandibular prognathism (prominent-appearing jaw is due to retruded maxilla)
Not all skull deformities are secondary to synostosis of a suture. Deformational plagiocephaly is a skull deformation secondary to intrauterine constraint (eg, oligohydramnios) and is characterized by ipsilateral occipital flattening with contralateral forehead flattening. The skull takes on a trapezoidal shape when viewed from above. The ear is displaced anteriorly on the side of the flattened occiput.