Anatomy
The thyroglossal duct arises embryologically between the first and second pharyngeal pouches. It runs as a hollow tube from the foramen caecum on the dorsal surface of the tongue, becoming a solid cord of cells migrating through the tongue and into the midline of the neck. The tract usually passes in front of the hyoid bone and then loops up behind it before descending in the midline of the neck where the cells divide to form the two lobes of the thyroid gland either side of the midline. The duct normally atrophies in the sixth week of
gestation.
gestation.
Clinical features
- Usually presents in children or young adults.
- 90% present as a painless midline cyst.
- 10% appear on one side of the midline, usually the left.
- 75% appear in front of the hyoid bone and the majority of the rest at the level of the thyroid or cricoid cartilage of the larynx.
- The cyst is mobile and moves up on swallowing.
- If large enough it will transilluminate.
- 5% become infected presenting as a painful, red neck swelling.
- 15% have a fistula to the skin (due to infection or incomplete excision).
- Papillary carcinoma of the thyroglossal ductal cells is rare. Treatment is by excision.
Diagnosis and investigations
- CT scan will often reveal a well circumscribed cyst related to the midline of the hyoid bone.
- Fine-needle aspiration may reveal a cloudy infected fluid or a straw-coloured fluid.
Treatment
Infected thyroglossal cyst
- Majority respond to antibiotics.
- Surgical drainage if abscess formed or failure to respond to antibiotics.
- Elective excision of the cyst once acute infection has resolved.
Surgery
- Excision is recommended for most cysts.
- Remove through a transverse midline incision in a skin crease.
- Divide the platysma muscle and dissect the cyst out bluntly.
- On the deep surface it will be found to be attached to the hyoid bone: excise approximately 1cm of the bone, removing any underlying thyroglossal duct epithelium.
- Close the wound in layers with a suction drain.
- If there is a fistula or sinus in the neck excise it through a transverse elliptical incision. Again use blunt dissection and remove the middle part of the hyoid bone (Sistruck procedure’).
Complications
These are usually very few. Remove the drain the next day and discharge the patient.
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| The anatomy of the region of the thyroid gland |
The important structures that must be considered when operating on the thyroid gland include:
- Recurrent laryngeal nerve
- Superior laryngeal nerve
- Parathyroid glands
- Trachea
- Common carotid artery
- Internal jugular vein (not depicted).
Branchial cyst, sinus, and fistula
Key facts
- Fluid-filled sac resulting from: the first, second, or third branchial cleft; or from epithelial inclusion in a lymph node; or proliferation of epithelium within a lymph node.
- 2nd cleft branchial cyst is the commonest cause of congenital neck lumps.
- Incidence < 1%. ‚: 1:1.
- 2nd cleft branchial fistula is a tract running from the neck skin through to the posterior pillar of the faucesthese are very rare.
- A branchial sinus occurs when the lower part of this tract remains open on to the neck skin surface.
- A branchial abscess is an infected branchial cyst.
Clinical features
- Presents as a neck lump, usually painless.
- Two-thirds occur in men and classically appear in the third decade, although there is a wide age range.
- 60-70% are anterior to the upper third of the sternomastoid muscle with the posterior border lying beneath the sternomastoid. Other sites include:
- parotid gland;
- anterior to the lower two-thirds of the sternomastoid;
- anterior to the pharynx;
- in the posterior triangle of the neck.
- Two-thirds occur on the left side; 2% are bilateral.
- May present with an acute branchial cyst abscess causing pain, increased swelling, and occasionally pressure symptoms (difficulty swallowing or breathing).
Diagnosis and investigation
For branchial cyst or abscess.
- MRI scan of the neckconfirms diagnosis, defines extent, indicates local relations.
- Fine-needle aspiration biopsy.
- Abscessespurulent fluid is obtained that may culture organisms.
- Cystsstraw-coloured fluid containing cholesterol crystals.
Treatment
Branchial abscess
- Drain via a transverse incision in the neck at the point of maximum convexity.
- Suture a Yeates drain into the incision line.
- Give antibiotics and make no attempt to remove the cyst until the infection has resolved completely.
Branchial cyst
- Most cysts are excised to achieve a diagnosis and prevent symptoms or complications.
- Place a transverse incision over the cyst, preferably in a transverse skin crease, long enough to match the size of the cyst.
- Divide the platysma and the deep fascia over the anterior border of the sternomastoid and retract the muscle posteriorly.
- Remove the cyst, usually by blunt dissection.
- Use suction drainage and close the wound in layers.
- If the cystic lesion is in the parotid gland and cannot be distinguished from any other parotid lesion, extend a preauricular incision into the neck as for a superficial parotidectomy.
Branchial fistula
- Excise a sinus of fistula through a horizontal elliptical incision around the neck opening.
- Bluntly dissect the sinus tract as far as possible.
- If the upper end of the tract cannot be reached, make a further transverse incision at a higher level (stepladder’ incisions).
- Sometimes the tract runs between the internal and external carotid arteries and sometimes up to the pharyngeal wall in the region of the middle constrictor.
- Close the wounds in layers with suction drainage.
Complications
A branchial cyst at any site often lies near to important nerves. Previous infections causing fibrosis will increase the risk of damaging them. The following nerves are at risk:
- hypoglossal nerve (tongue deviates to affected side on protrusion);
- mandibular branch of the facial nerve (movement of lower lip);
- great auricular nerve (numb ear);
- accessory nerve (paralysis of trapezius: weakness of arm abduction, asymmetry, and chronic pain).
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