Syndromes of the first and second branchial arches, part 1: embryology and characteristic defects

Abstract

A variety of congenital syndromes affecting the face occur due to defects involving the first and second BAs. Radiographic evaluation of craniofacial deformities is necessary to define aberrant anatomy, plan surgical procedures, and evaluate the effects of craniofacial growth and surgical reconstructions. High-resolution CT has proved vital in determining the nature and extent of these syndromes. The radiologic evaluation of syndromes of the first and second BAs should begin first by studying a series of isolated defects: CL with or without CP, micrognathia, and EAC atresia, which compose the major features of these syndromes and allow more specific diagnosis. After discussion of these defects and the associated embryology, we proceed to discuss the VCFS, PRS, ACS, TCS, Stickler syndrome, and HFM.

Fig 1.

Dorsal aspect of the germ disk from an approximately 15-day embryo.

Fig 2.

Frontal view of an approximately 30-day embryo showing the positions of the stomodeum relative to the medial and lateral nasal prominence and the maxillary and mandibular prominences.

Fig 3.

Ventral illustration of the palate, incisive foramen, gum, lip, and nose.

Fig 4.

A, A 44-year-old woman with CP. 3D bony reconstruction shows a bony cleft (arrow) extending from the left aspect of an asymmetrically enlarged pyriform aperture to the alveolar surface. B, Axial CT image shows a bony cleft (arrow) between the left central and lateral maxillary incisors. C, Coronal CT image shows the extension of the bony clefting (arrow) to involve the primary palate.

Fig 5.

Auricular atresia in various degrees of severity. A, Axial CT image in a 64-year-old woman with nonsyndromic EAC atresia shows marked narrowing of the bony EAC (arrow). B, Axial CT image in a 9-year-old girl shows severe atresia with a lateral bony plate (arrow). The middle ear cavity is small and dysplastic (arrowhead). There is also ipsilateral microtia. C, Axial CT image in a 3-year-old boy with Goldenhar syndrome shows complete bony atresia of the right EAC. D, Axial CT image in a 6-year-old boy with unilateral auricular atresia with associated ossicular chain fusion (arrow) and microtia (not shown).

Fig 6.

A 6-year-old boy with syndromic micrognathia. A−C, 3D bony reconstructions show mandibular hypoplasia and abnormal temporomandibular joints, condyles, and coronoid processes. D, Axial CT image shows severe micrognathia and malocclusion.