Congenital Anomalies of the First Branchial Apparatus

Epidemiology

First branchial anomalies (FBA) are an uncommon group of lesions that result from abnormal embryogenesis of the first branchial apparatus. FBA account for approximately 8% of all branchial complex anomalies. The spectrum of abnormal development includes cysts, sinuses, and fistulae, or various combinations of these entities. FBA are seen more in children than adults and usually present before 10 years of age. These lesions appear more often on the left than on the right. Females are involved twice as often as males. Associated abnormalities may involve any other structure that arises from the first branchial apparatus. These include congenital craniofacial malformations and syndromes [Crouzon’s disease (craniofacial dysostosis), Goldenhar’s syndrome (oculo-auricular-vertebral syndrome), Treacher Collins–Franceschetti syndrome (mandibulofacial dysostosis), Nager’s syndrome (preaxial acrofacial dysostosis), and Pierre Robin syndrome (Robin sequence)] and malformations of the external auditory canal, middle ear cavity, and ossicles.

Embryology

Due to the complex nature of these lesions, several classification systems have been developed to aid in the diagnosis and surgical management of these lesions.

Type I

Type I lesions are cysts or sinuses that are located in the parotid gland. These lesions are thought to represent either a duplication anomaly of the external auditory canal or buried cell rests of the first branchial cleft.

Type II

Type II defects are thought to arise from incomplete closure of the branchial cleft. They extend from the angle of the mandible to the vicinity of the membranous external auditory canal. These lesions typically communicate with the external auditory canal at the bony–cartilaginous junction.