History
Craniosynostosis may be evident at birth or in infancy from craniofacial abnormalities.
It may be noticed later when the child exhibits neurodevelopmental delays.
Physical
Typically, careful examination alone can make the diagnosis.
-
Microcephaly usually suggests a secondary craniosynostosis.
-
Scaphocephaly
Premature fusion of the sagittal suture is the most common craniosynostosis, constituting more than half of all cases. It occurs frequently in premature infants.
The head typically is elongated in the anterior-posterior diameter and shortened in the biparietal diameter. Ridging of the sagittal suture is palpable.
-
Anterior plagiocephaly - Premature fusion of 1 coronal suture.
-
Brachycephaly
Premature fusion of both coronal sutures results in increased biparietal diameter. This anomaly is often syndromic. The skull is shorter in the anterior-posterior diameter.
Because the coronal suture develops in conjunction with the sutures at the base of the skull, unilateral or bilateral mid and upper face hypoplasia may occur. Orbits may be elliptical (ie, Harlequin features), and the supraorbital ridge may not be formed well.
Consider these features when planning surgery for brachycephaly.
-
Posterior plagiocephaly
The 2 predominant causes of posterior plagiocephaly are craniosynostosis of the lambdoid suture (< 2%) or positional molding (vast majority).
Positional plagiocephaly. Note anterior position of the ear on the side with occipital flattening.
Since the American Academy of Pediatrics recommended that infants sleep on their backs to reduce sudden infant death syndrome (SIDS) incidence, positional molding has been seen with increased frequency. [6]
Torticollis is frequently associated with positional molding.
Viewed from above, the head shape in positional molding resembles a parallelogram, whereas that in lambdoid craniosynostosis is trapezoid shaped.
Positional molding. Note the anterior displacement of the right occiput and of the right frontal region on the same side, which differentiate positional molding from posterior plagiocephaly craniosynostosis.
Posterior view of 3-dimensional cranial CT demonstrating early fusion of the lambdoid suture.
In positional molding, ear position is more anterior on the side of flattening; in lambdoid synostosis, ear position is more posterior.
Frontal bossing is observed ipsilateral to the flattening in positional molding and contralateral in lambdoid synostosis.
Unilateral coronal deformity with retrusion of the orbit and harlequin eye deformity. Note the ipsilateral deviation of the nasal radix and the contralateral deviation of the nasal tip.
Fusion of coronal sutures bilaterally. Note the increase transverse dimension and retrusion of the orbital rim.
Intraoperative view of bilateral coronal synostosis. Note the decreased anterior-posterior dimension, increased transverse width and retruded orbital rim.
-
Trigonocephaly
Premature fusion of the metopic suture frequently results in pointed forehead (ie, triangular shaped head). The abnormality is usually mild and requires no surgical intervention. Surgery is performed if the abnormality is persistent and severe.
Pre- and postoperative photos of metopic synostosis. Note the prominent forehead keel corrected after surgical repair.
Oxycephaly (ie, turricephaly) is fusion of all skull sutures and the sutures at the base of the skull.
-
Craniosynostosis sometimes is associated with sporadic craniofacial syndromes such as Crouzon, Apert, Chotzen, Pfeiffer, or Carpenter syndromes. In this context, facial features, typically craniofacial abnormalities, suture ridging, and early closure of fontanelles, suggest the diagnosis.
-
Kleeblattschãdel (ie, cloverleaf skull) results from fusion of all sutures except the metopic and squamosal sutures, giving the head a cloverleaf appearance.
Infant with primary craniosynostosis. The specific deformity of the skull is Kleeblattschadel or cloverleaf skull.
-
Intracranial pressure may be elevated in primary multiple suture craniosynostosis, such as cloverleaf skull and the syndromic synostoses. Signs include sun-setting eyes, papilledema, vomiting, and lethargy.
Causes
Multiple theories have been proposed for the etiology of primary craniosynostosis, but the most widely accepted is a primary defect in the mesenchymal layer ossification in the cranial bones.
Secondary craniosynostosis typically results from systemic disorders such as the following:
-
Endocrine - Hyperthyroidism, hypophosphatemia, vitamin D deficiency, renal osteodystrophy, hypercalcemia, and rickets
-
Hematologic disorders that cause bone marrow hyperplasia (eg, sickle cell disease, thalassemia)
-
Inadequate brain growth, including microcephaly and its causes and shunted hydrocephalus
The syndromic causes appear to result from genetic mutations in the fibroblast growth factor pathway, particularly genes involving fibroblast growth factor receptors 2 and 3. A gene locus for single suture craniosynostosis has not been identified. [7]
Other important factors to consider include the following:
-
Differentiating plagiocephaly that results from positional molding (which does not require surgery and is seen frequently) from lambdoid suture fusion is extremely important.
-
The presence of multiple suture fusions strongly suggests a craniofacial syndrome, which frequently requires the diagnostic expertise of a pediatric geneticist.
Craniofacial morphogenesis is highly dependent on the patterning information of emigrant cranial neural crest (CNC) cells. CNC cells give rise to a wide variety of tissues and structures, including skull bones. During skull development, cranial sutures serve as growth centers for skeletogenesis that is mediated through intramembranous ossification. This process differs from endochondral ossification in the appendicular and axial skeletons, where prior formation of cartilage templates is required. Axin2 is highly expressed in CNC cells and developing sutures neural crest (nasal and frontal bones) but not mesoderm (parietal bones). Dependent osteogenesis is particularly sensitive to the loss of Axin2. [8]
-
Diagram of a neonate's skull demonstrating the location of the sutures.
-
Frontal view showing a fused and ridged metopic suture on 3-dimensional CT.
-
CT image demonstrating features of secondary craniosynostosis with cerebral atrophy. Cerebral atrophy is not present in primary craniosynostosis.
-
Positional molding. Note the anterior displacement of the right occiput and of the right frontal region on the same side, which differentiate positional molding from posterior plagiocephaly craniosynostosis.
-
Posterior view of 3-dimensional cranial CT demonstrating early fusion of the lambdoid suture.
-
Isolated fusion of the metopic suture. Note that the remaining sutures are open.
-
Trigonocephaly. Note the triangular shape of the head.
-
Infant with primary craniosynostosis. The specific deformity of the skull is Kleeblattschadel or cloverleaf skull.
-
Skull deformities associated with single suture synostosis.
-
Positional plagiocephaly. Note anterior position of the ear on the side with occipital flattening.
-
Sagittal synostosis and the associated scaphocephaly seen on skull radiograph and 3-dimensional craniofacial CT scan.
-
Sagittal synostosis before and after cranial vault surgery and the associate improvement of scaphocephaly.
-
Unilateral coronal deformity with retrusion of the orbit and harlequin eye deformity. Note the ipsilateral deviation of the nasal radix and the contralateral deviation of the nasal tip.
-
Fusion of coronal sutures bilaterally. Note the increase transverse dimension and retrusion of the orbital rim.
-
Intraoperative view of bilateral coronal synostosis. Note the decreased anterior-posterior dimension, increased transverse width and retruded orbital rim.
-
Pre- and postoperative photos of metopic synostosis. Note the prominent forehead keel corrected after surgical repair.
