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

Radiographic Findings

Radiographic examination of the skull consists of anteroposterior or Caldwell, Towne, and both lateral views. The sagittal, coronal, and lambdoid sutures are all normally identified. The anterior fontanel is visible at least until 7 months of age. Although the metopic suture closes any time from before birth to after 3 months of age, as many as 10% remain open into adulthood. The same head deformity results from partial and total suture synostosis (see e-Fig. 20.5 ). The key findings to diagnosis craniosynostosis are (1) abnormal head shape and (2) suture obliteration.

Cranial restructuring techniques have focused on (1) release of sutural synostosis, (2) cranial remodeling, (3) reduction of abnormal skull expansion, and (4) expansion of abnormally narrow areas.

In most instances, three-dimensional (3D) computed tomography (CT) is required to plan for cranial restructuring. Radiation dose can be lowered to 65 mA and 80 kV at 0.5 second with a slice thickness of 1.25 mm and a CT dose index “dose” of approximately 2.37 mGy. Images are reconfigured to 0.625 mm for various reconstructions ( Figs. 20.22–20.24 and e-Fig. 20.25 ).

Magnetic resonance imaging (MRI) is not well suited for identifying cranial sutures. However, a recently reported gradient echo sequence has been used to minimize soft tissue contrast allowing the cranial sutures to be hyperintense against the signal void of the cranial bones. In syndromic children, brain MRI is performed for developmental anomalies.

While there are reports of successfully using ultrasound for diagnosing synostosis, this has not gained widespread acceptance and, if positive, requires further imaging to be performed.

Associated Abnormalities

Limb defects are the most common anomalies associated with craniosynostosis, occurring in up to 84%. Syndactyly and polysyndactyly constitute 30% of the limb defects, and deficiencies account for 22%.

Several types of acrocephalosyndactyly and acrocephalopolysyndactyly have been described. Some are clearly defined; others are less clear and may undergo reclassification as further information becomes available.

The best-known acrocephalosyndactyly is Apert syndrome (acrocephalosyndactyly type I), in which bicoronal synostosis is associated with symmetric syndactyly of the second, third, and fourth digits, resulting in the “mitten or paddle hand” ( e-Fig. 20.26 ). Developmental delay is variably present. Evaluation of craniofacial deformities may be assisted by CT ( e-Fig. 20.27 , Fig. 20.28 , and e-Fig. 20.29 ).

Acrocephalosyndactyly types II, III, and IV are known as Apert-Crouzon disease , Saethre-Chotzen syndrome , and Waardenburg syndrome , respectively; they involve varying degrees of facial abnormality and syndactylies in patterns particular for each type. Acrocephalosyndactyly type V, Pfeiffer syndrome , has only moderate soft tissue syndactyly, but the thumbs and great toes are deformed and broad ( Fig. 20.30 ).

Carpenter syndrome (acrocephalopolysyndactyly type II) is characterized by developmental delay and preaxial polydactyly of the feet. Types I and III are known as Noack syndrome and Sakati-Nyhan syndrome .

In Crouzon syndrome , the cardinal elements originally included (1) brachycephaly, (2) facial dysostosis with a hooked parrot nose and small maxilla, (3) bilateral exophthalmos, and (4) genetic transmission and familial incidence ( e-Fig. 20.31 and Fig. 20.32 ).

The complications of these syndromes include exophthalmos, loss of vision, increased intracranial pressure, and developmental delay. Maxillary hypoplasia may cause upper airway obstruction and sleep apnea. Surgical procedures are performed to improve the airway, dental occlusion, and deformities.

Kleeblattschädel (cloverleaf skull) results from closure of all sutures except the squamosal sutures, leading to severe temporal and vertex bulging with exophthalmos (see Fig. 20.16 and e-Fig. 20.17 ). Hydrocephalus develops in utero, deforming the skull into a superiorly elongated calvarium with dilated frontal and temporal regions. Most patients do not survive infancy (see Fig. 20.16 ). Kleeblattschädel may be found in thanatophoric dysplasia type II.