Describe the congenital swellings of the neck.

Congenital Neck Swellings

• Thyroglossal duct cyst is the commonest congenital neck swelling
• Its embryology explains everything about it: the thyroid descends from the foramen caecum at the tongue base, and its tract passes in intimate relation to, through, the developing hyoid bone
• Hence the cyst is midline (or just off it), at or below the level of the hyoid, and moves on swallowing and, characteristically, on protrusion of the tongue.
• It presents in childhood or young adult life, and may become infected or form a sinus, often after an upper respiratory infection
• The essential preoperative step is to confirm that normal thyroid tissue is present — by ultrasound — because in a small proportion the cyst contains the only functioning thyroid tissue (ectopic thyroid), and removing it renders the patient permanently hypothyroid
• Treatment is the sistrunk operation — excision of the cyst together with the central body of the hyoid bone and the tract up to the foramen caecum
• Removing the hyoid body is not optional: simple excision of the cyst alone has a recurrence rate of the order of 50%, because the tract through the hyoid is left behind — and this is the single most examinable point in the topic
• Branchial cyst arises from remnants of the second branchial cleft in the majority
• It presents in the late teens to thirties as a smooth, fluctuant, painless swelling at the anterior border of sternocleidomastoid at the junction of its upper and middle thirds, and frequently enlarges rapidly after an upper respiratory infection
• Aspiration yields turbid fluid containing cholesterol crystals
• A branchial fistula opens at the lower third of the anterior border of sternocleidomastoid, and its tract passes between the internal and external carotid arteries to the tonsillar fossa
• The critical clinical warning is that a cystic neck swelling in an adult over 40 may be a cystic metastasis — classically from an HPV-related tonsil or tongue base carcinoma, or from papillary thyroid carcinoma
• Therefore a "branchial cyst" presenting for the first time in an older adult must be investigated as a malignant node, with ultrasound, FNAC and full ENT examination including nasendoscopy, before it is simply excised