Craniosynostosis, Selected Craniofacial Syndromes, and Other Abnormalities of the Skull

Chapter 20

Craniosynostosis, Selected Craniofacial Syndromes, and Other Abnormalities of the Skull

The basic clinical and radiologic features of craniosynostosis result either from lack of sutural formation or from premature fusion of contiguous portions of calvarial bones across the membranous sutures between them. The prevalence of premature sutural closures is displayed in e-Table 20-1.1 Normal sutures permit growth of the skull in a direction perpendicular to their long axes. With normal endocranial stimulus to growth, cessation of growth in one suture is compensated by increased growth in others, with resulting craniofacial deformity (e-Table 20-2; Figs. 20-1 through 20-4).

The deformity of the shape of the head is present before the bony sutural changes are seen. Only a portion of the bony suture needs to be closed to have craniosynostosis (e-Fig. 20-5). The suture-associated dura mater is responsible for determining the development of the cranial suture. The dura supplies osteoinductive growth factors (e.g., transforming growth factor-β or fibroblast growth factor-2) and cellular elements. Abnormal head shape secondary to abnormal suture development can be diagnosed in utero at 13 weeks’ gestational age.2,3 Craniosynostosis is associated with genetic abnormalities (e-Box 20-1) and is a secondary finding in many systemic disorders (e-Box 20-2).4

Specific head shapes are associated with sutural synostoses (e-Fig. 20-6). The normal head has an egg shape, being widest in the parietal area posterior to the ears with a narrower, gently rounded forehead (Fig. 20-7).

Sagittal synosotosis is characterized by a long and narrow head (see Figs. 20-3 and 20-4). The back is usually narrower than the front, and anterior or posterior bossing may exist. Metopic synostosis (trigonocephaly) results in a triangular shape of the whole forehead (not just a rounded forehead with a ridge superimposed) (Fig. 20-8; see e-Fig. 20-6).

Unicoronal synostosis results in flattening of the ipsilateral forehead, flattening of the ipsilateral occipital area, the “harlequin eye” (the sphenoid is drawn up toward the closed suture and is thickened), ipsilateral temporal bulging and cheek protrusion, contralateral forehead bossing, and deviation of the nose away from the synostosed side (Fig. 20-9). Features that distinguish unicoronal synostosis from anterior deformational plagiocephaly are listed in e-Table 20-3.

Bicoronal synostosis causes a brachycephalic head (i.e., the head is wide and short). The supraorbital rims and forehead are recessed with bitemporal and upper forehead bulging (Fig. 20-10).

Lambdoid synostosis results in ipsilateral occipital flattening with compensatory bulging at the superior and inferior axes where the suture should have been (e-Fig. 20-11). The features differentiating unilateral lambdoid synostosis from posterior deformational plagiocephaly are listed in e-Table 20-4.

Synostosis of multiple sutures occurs in 14%, and the resultant head shape depends on which sutures are closed.1 The kleeblattschädel (“cloverleaf skull”) anomaly may result when all sutures except the squamosal are closed, resulting in severe temporal and vertex bulging with exophthalmos (Fig. 20-12). Unusual minor synostosis may exist, causing abnormal skull appearance.58

Microcrania, or a small neurocranium, may result when all sutures are closed. This usually occurs with failure of brain growth. Rarely, it may occur without failure of brain growth, and the child may develop increased intracranial pressure (Fig. 20-13).

Dec 20, 2015 | Posted by in PEDIATRIC IMAGING | Comments Off on Craniosynostosis, Selected Craniofacial Syndromes, and Other Abnormalities of the Skull
Premium Wordpress Themes by UFO Themes