Abstract
First branchial cleft anomalies (FBCA) such as duplication of the external auditory canal are due to failure to obliterate the ventral portion of the 1st cleft while external auditory canal stenosis and atresia are abnormalities of the dorsal portion.The annual incidence is 1:1000,000 and it’s been found to be commoner among females 69% than males 31% with the left ear most affected.FBCA can present as fistula, sinus or cysts located around/along the EAC, periauricular region and the neck above the hyoid bone. Keywords : Duplicate External auditory canal,First branchial anomaly,auditory canal stenosis DOI : 10.7176/JHMN/64-04 Publication date :July 31 st 2019
Highlights
1.Introduction External Auditory canal arises from of the first Branchial arch groove which deepens and meets the Tubotympanic recess of the Endoderm with the Mesoderm contributing from the sides
2.Embryology of external auditory canal In the 3rd week of embryonic life, the trilaminar flat embryo begin to fold on itself and by the 4th week, five(5) bilateral swellings are seen growing cranio-caudally separated by clefts externally & pouches internally
The dorsal portion form the external auditory canal and cavum concha while the ventral portion obliterates by the 7th week as the 1st and 2nd branchial arch fuse (Schoenwolf et al, 2009)
Summary
External Auditory canal arises from of the first Branchial arch groove which deepens and meets the Tubotympanic recess of the Endoderm with the Mesoderm contributing from the sides. The dorsal portion form the external auditory canal and cavum concha while the ventral portion obliterates by the 7th week as the 1st and 2nd branchial arch fuse (Schoenwolf et al, 2009). There is an unpredictable relationship between parotid gland, facial nerve and persistent ventral portion of the 1st branchial cleft.
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