Embryology

Normal Pharyngeal (Branchial) arches

· Branchial pouches

· Branchial clefts

· Floor of pharynx

· Respiratory system

Congenital malformations

· Branchial cysts

· Thyroglosal cyst

· Oesophagotracheal fistulae

· 1st arch syndrome

· Lung abnormalities

Development

· Begins in 4th week

· pouches (endodermal) and clefts (ectodermal) appear ® push mesenchyme into pharyngeal arches.

· Each arch (and \ associated pouch and cleft) have their own neurovascular supply

· Arch componenets

— Mesenchyme

— Ectoderm

— Endoderm

— Neural crest cells

— Nerve

— Artery

Arches

· C: cartilage, M: mesoderm, E: ecto / endoderm, N: nerve, A: artery

Arch I

N: Trigeminal (V)

A: Maxillary artery

C: Maxillary process, meckels cartilage (Mandible formed by membranous ossification around this), incus, malleus, sphenomandibular ligament

M: muscles of mastication (Temporal, masseter, pterygoid), mylohyoid, ant belly digastric, tensor tympani, tensor veli palatini

E: Glands of anterior 2/3 tongue

Arch II

N: Facial (VII)

A: Stapedial artery (ECA)

C: stapes, styloid process, stylohyoid ligament, lesser horn & upper body of hyoid

M: muscles of facial expression (Buccinator, auricularis, frontalis, platysma, orbicularis oris and oculi), stapedius, stylohyoid & post belly digastric

Arch III

N: Glossopharyngeal (IX)

A: Internal carotid

C: lower body and greater horn of hyoid

M: stylopharyngeus

E: glands post 1/3 tongue, mucous membrane of post 1/3 tongue and anterior surface of epiglottis

Arch IV

· The cartilaginous component of IV and VI fuse together

N: Vagus (X), Superior laryngeal

A: R subclavian, aortic arch

C: thyroid, cricoid, arytenoid, corniculate and cuneiform cartilages

M: cricothyroid, levator palatini, constricors of pharynx

Arch VI

N: Vagus (X), Recurrent laryngeal

A: R &L pulmonary, ligamentum areteriosum

C: thyroid, cricoid, arytenoid, corniculate and cuneiform cartilages

M: Intrinsic muscles of the larynx

Pouches

1. Tympanic cavity

Mastoid antrum

Tympanic membrane (where contacts 1st cleft)

Eustachian tube

2. Palatine tonsil (Pouch obliterated, epi buds into mesenchyme’ tonsil)

3. Inferior PT (Dorsal)

Thymus (Ventral)

4. Superior PT (Doral)

5. Ultimobranchial body (C cells from neural crest ® thyroid)

Clefts

1 External auditory meatus

2-4 Close over @ 6/52 Arch II grows over III and IV, incomplete closure results in Branchial cyst or sinus. Sinus invariably comes out in palatine tonsil and passes between internal and external carotids to the lateral aspect of the neck anterior to SCM. Cysts commonly at the angle of the jaw.

Floor

Tongue

· Appears 4/52 as swelling in floor

· 2 lateral lingual swellings, 1 median (tubercule impar) from arch I

· 1 posterior (copula) from arch II

Thyroid

· Appears 4/52

· epithelial proliferation in floor of mouth between tubercule impar and copula.

· Penetrates mesoderm forming the thyroid diverticulum (initially hollow, becomes solid),

· divides into 2 and descends anterior to pharynx in front of hyoid.

· Track of descent is the thyroglossal tract and site of origin marked by the foramen caecum @ juncn

of anterior 2/3 and posterior 1/3 of tongue.

· Reaches final position 7/52 and thyroglossal tract degenerates and dissapears.

· Thyroid begins to function @ 3/12.

· A pyramidal lobe is present in 50%, may be attached to the hyoid and occurs more comoonly to the

L of the isthmus.

· Parafollicular or C cells migrate from neural crest to 4th and 5th pouches and then to predominantly

the superior aspect of the thyroid

H&N 5

Developmental abnormalities

Preauricular cysts or sinus

· Probable 1st cleft abnormality

· Lined with squamous epithelium

· Can have close proximity to facial nerve

Collaural fistula

· Passes from external auditary meatus through parotid to neck

Surgery

· If symptomatic

· Incision anterior to pinna

· Extend into parotidectomy incision if required

· May need to mobilise parotid / do superficial parotidectomy to visulaise nerve

· Full excision of tract

Branchial cleft remnants

· All branchial cleft remnants are congenital abnormalities present at birth

· Branchial cleft sinuses present with cutaneous openings often noted in infancy marked by skin tags or subcutaneous cartilaginous remnants

· Branchial cysts present later in childhood when they accumulate secretions

· Peak incidence 2nd & 3rd decades

Defintions

· Branchial fistula: The fistula has both an internal and external opening

· Branchial sinus: The lower opening and main tract are present but the tract does not communicate with the pharynx internally

· Branchial cyst: The central portion only of the cleft remains patent with a spherical neck swelling

Aetiology

· Either formed during fusion of the 2nd and (6th) arch

— Failure of fusion of the 2nd - 5th clefts ® cervical sinus ® branchial cyst

· O r epithelial cell rests within cervical lymph nodes

— Become cystic in later life, ? stimulus

Clinical

First branchial cleft remnants

· Sinus opening near the angle of mandible in region of submandibular triangle

· Sinus tract typically runs superficial to mandible up to external auditory canal

· Tract associated with parotid gland and facial nerve

Second branchial cleft remnants

· External opening along the anterior border of SCM in its lower 1/3; 10% bilateral; six times more common than first arch remnants.

· Tract passes between the carotid bifurcation then behind the posterior belly of digastric and stylohyoid muscle and in front of the hypoglossal nerve to communicates with the pharynx at the tonsillar fossa

Third and forth cleft remnants

· Internal opening is typically located in the piriform sinus

· Often present as a firm mass in the subcutaneous tissue withoutwithout associated sinus or fistula.

· Third branchial cleft sinus presents as a mass lower in the neck than the second

·  3rd cleft, tract passes between common carotid and vagus

· 4th cleft, tract passes caudal to arch of aorta or R subclavian

· Often present as a left thyroid lobe abscess

Investigations

· Radiological Ix not usually required for first and second branchial abnormalities

· Barium studies or CT may be useful in piriform sinus fistula

· Contrast esophagogram may show the fistula between the piriform sinus and neck

Treatment

· Complete surgical excision

If an abscess is present, it is initially drained

If infection is present antibiotics are administered and formal excision is delayed as surgery in the presence of infection increases the risk of recurrence and injury to facial nerve (first cleft) or hypoglossal nerve (second cleft).

Excision is recommended at diagnosis for uninfected lesions

Surgery for infants is delayed until 3-6 mo of age

· Complications of surgery – see surgery

Branchial fistulae

· Less common than cysts

· Bilateral in 20%

· F>M

· Majority present in 1st decade

— Can present into adulthood

· Most likely arise from cervical sinus (branchial cyst)

External branchial fistula

· Communication with skin from cervical sinus

· Lined with squamous epithelium

· Most common 2nd cleft

— Lateral aspect of neck anterior to SCM

— Passes between ICA & ECA

· Fistulae involving 3rd and 4th clefts are rare

Internal branchial fistula

· Communication with pharynx from cervical sinus

· Can be lined with cilliated columnar epithelium

— Rare

— Generally opens in tonsillar region (2nd pouch)

— Less commonly opens in pyriform sinus (3rd pouch)

Complications

· Infection

— Can be recurrent

· SCC

— Very rare

Surgery

· Excise

· Need to include fistula opening

Discuss branchial cyst

• commonly presents in young adults (as epithelial debris accumulates and infection

may occur)

• lined by stratified squamous epithelium

• usually lie between carotid sheath and sternocleidomastoid, bulging into the

carotid triangle from behind the muscle

• yellow fluid, rich in cholesterol crystals on microscopy

Thyroglossal cyst

· Epithelial remnant of tract

— hypertrophies and secretes mucoid fluid

— Lining columnar or squamous ± thyroid tissue.

Clinical

· Occurs from foramen caecum to sternum.

— 75% @ or just below hyoid

— 15% @ level of thyroid cartilage

· Midline 90%

— L of midline 10%

· Usually presents in childhood

— Mean age 5yrs

· Symptoms

— Lump

— moves on swallowing and on tongue protrusion

— Transilluminates

· Complications

— Infection

— Rupture or trauma ’ sinus

— Cancer (tends to be papillary)

Investigations

— FNA

— USS to confirm presence of normal thyroid

Treatment

· 25% recurrence if cystectomy alone, 5% if hyoid also taken (Mastery p385)

Sistrunk operation

· Transverse incision over cyst through platysma

· Raise sub-platysmal flaps

· Dissect cyst free from below, leave attachment to hyoid

· Divide straps from mid hyoid

· pass right angle around hyoid, divide mylohyoid and geniohyoid from mid hyoid

· divide centre 1-1.5cm of hyoid

· follow duct remnant up (can assist by depressing base of tongue) suture ligate as high as possible.

Thyroglossal sinus

· persistence of tract or bursting of cyst

Discuss branchial fistulas

• most commonly of the second branchial cleft

• present in infancy

• second cleft

• arise tonsillar fossa

• Course between internal and external carotid arteries

• pass over hypoglossal nerve

• pass beneath glossopharyngeal nerve

• present anterior to sternocleidomastoid

• third cleft

• arise from piriform sinus

• pass posterior to carotid vessels

• pass over hypoglossal nerve

• present anterior to sternocleidomastoid

What is the incidence of thyroglossal duct cyst

• most common congenital cervical abnormalities (3x more common than branchial

cleft remnants)

• males=females

• most present in childhood

What are the clinical features of thyroglossal duct cyst

• anywhere from submental to suprasternal notch; usually located just below the hyoid

• midline

• rises with swallowing or protrusion of the tongue

• lined by pseudostratified ciliated columnar epithelium, squamous epithelium, or

both, ± thyroid remnants in wall

What is the management of a thyroglossal duct cyst

• USS to confirm normal thyroid (DDx ectopic thyroid)

• Sistrunk procedure

• transoral marsupialization or excision for a lingual TDC

What is the incidence of malignant change in thyroglossal duct

cysts

• 1%

• papillary ca most common

• also Hurtle cell, squamous and anaplastic ca

• requires total thyroidectomy (may be metastatic) and iodine ablation

Lingual thyroid

· Failure of decent F>M,

· can cause local symptoms eg stridor

· Can be (often?) only thyroid tissue present.

· Ca risk higher than normal

— But no MCT as no C-cells

· Rx: Decrease size with T4 . I131 ’ surgery

Thyroid hypoplasia/aplasia

· Rare

· ? 2° maternal antibodies

Thyroid dyshormonogenesis

Oesophagotracheal fistulae and Oesophageal atresia

· Oesophageal atresia prevents normal passage of amniotic fluid into GIT

— accumulation of XS fluid in amniotic sac and enlarged uterus

3 major forms

· Oesophageal atresia & oesophagotracheal fistula

— Most common

· Oesophageal atresia, fibrous oesophagotracheal connection

· Communication between proximal and distal oesphagus and trachea

— Rare

1st arch syndrome

· Dissapearance / abnormal development of various components of 1st arch

H&N 8