Branchial cyst arises from the which branchial cleft: September 2009

Ans. B: Second Branchial cleft cysts are congenital cysts, that arise in the lateral aspect of the neck when the second branchial cleft fails to close during embryonic development. At about the fouh week of embryonic life, 4 branchial (or pharyngeal) clefts develop between 5 ridges known as the branchial (or pharyngeal) arches. These arches and clefts contribute to the formation of various structures of the head and neck. The second arch grows downwards and ultimately covers the third and fouh arches. The buried clefts normally disappear around the seventh week of development. If a poion of the cleft remains entrapped and fails to disappear, its remnants form a cyst. Branchial cleft cysts are the most common of congenital neck masses. They are bilateral in about 2-3% of the cases. Usually, they do not appear at bih, but become noticeable much later in life. They are usually lined by squamous epithelium, and contains thick, turbid fluid full of cholesterol crystals. They are usually located at the junction of the upper third and middle third of the sternomastoid muscle at its anterior border. It is a fluctuant swelling that may transilluminate. If they get infected, they may form a deep neck abscess or a draining fistula. USG and fine-needle aspiration both aids diagnosis. The treatment of branchial cleft cysts is surgical excision.