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1. What does the first arch of the branchial system form?
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The lower face, its external cleft the external auditory meatus, and its internal cleft the Eustachian tube.
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2. What does the second arch of the branchial system form?
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This grows down over the third and fourth arches to form the skin of the neck. Normally there is no external cleft, while the internal cleft forms the tonsillar fossa.
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3. What will form if there is a persistence of the remnants of the second branchial arch?
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This may lead to formation of a branchial cyst, sinus or fistula.
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4. Where will a remnant of the external cleft of the second branchial arch open?
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This will open just anterior to the sternocleidomastoid, at the junction of the upper one-third and lower-two thirds. A sinus or fistula represents a patent second branchial arch sinus, which passes between the internal and external carotid artery to the tonsillar fossa.
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5. What is the underlying cause of a branchial cyst?
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That a branchial cyst is the remnant of the second branchial arch has been questioned recently, based on the observation that the cysts are lined with lymphatic tissue. This counter-theory suggests that the cyst arises from cystic degeneration of lymphoid tissue in the neck and is thus better termed a lateral cervical cyst.
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6. What is the alternative name for a branchial cyst? Why?
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A lateral cervical cyst. This is because it is thought that it may not be caused by a remnant of the second branchial arch and may be caused by involution of lymphoid tissue.
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7. What are the clinical features of a branchial cyst?
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A branchial cyst usually presents in early adult life and forms a soft swelling ‘like a half-filled hot water bottle’, which bulges forward from behind the anterior border of the sternocleidomastoid. It is lined by squamous epithelium and contains pus-like material, which is in fact cholesterol. It often presents following an upper respiratory tract infection. Clinical diagnosis can be achieved by aspirating a few drops of this fluid from the cyst and demonstrating cholesterol crystals under the microscope. Occasionally the cyst may become infected. Differential diagnosis is from a tuberculous gland of the neck or from an acute lymphadenitis.
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8. What type of epithelium lines a branchial cyst?
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Squamous epithelium.
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9. What can be aspirated from a branchial cyst? Why is this important?
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A pus-like material, which is in fact cholesterol may be diagnostic is aspirated and cholesterol crystals are seen under microscopy.
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10. What are the differential diagnoses of a branchial cyst?
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Differential diagnosis is from a tuberculous gland of the neck or from an acute lymphadenitis.
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11. At what age does a branchial cyst typically present?
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Early adult life.
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12. What are the clinical features of a first branchial arch cyst?
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This is rare. It may present just below the external auditory meatus at the angle of the jaw, with extension closely related to the VII nerve.
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13. What is the clinical presentation of a branchial sinus? In what age group does this usually present?
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Correct answer:
A branchial sinus presents as a small orifice, discharging mucus, which opens over the anterior border of the sternocleidomastoid in the lower part of the neck. The majority are present at birth but a secondary branchial sinus may form if an infected branchial cyst ruptures, or if part of the cyst is left behind at operation. The sinus extends upwards between the internal and external carotid arteries to the side wall of the pharynx. It may open into the tonsillar fossa (which represents the second internal cleft) to form a branchial fistula.
