DESCRIPTION

• Phylogenetically, the branchial apparatus represents the “gills” seen in fish and amphibians.
• The fetal branchial apparatus is a foregut derivative and develops in the 2nd fetal week.
• Five paired pharyngeal arches are separated by four endodermal pouches internally and four ectodermal clefts externally.
• Branchial cleft cysts are embryologic anomalies that are defined by the internal openings of the branchial sinuses arising from incomplete obliteration in embryogenesis.
• Overgrowth of the second through fourth cleft during weeks 4 and 5 creates the cervical sinus.
• Persistence of the cervical sinus produces a spectrum of cysts, sinus tracts, and fistulae.
• Classification
  • First branchial cleft anomalies
    • Site: anywhere from external auditory canal to angle of mandible, usually superior to or within parotid
    • Fistula tract: external auditory canal
    • Estimated to represent 5–25% of all branchial cleft anomalies
  • Second branchial cleft anomalies
    • Site: ventral to anterior border of sternocleidomastoid muscle, lateral to carotid sheath, and dorsal to submandibular gland
    • Fistula tract: palatine tonsil
    • Most common branchial cleft cysts, representing 40–95% of branchial anomalies
  • Third branchial cleft anomalies
    • Site: posterior triangle in middle to lower left side of the neck near level of upper thyroid lobe
    • Fistula: upper lateral piriform sinus wall to lower lateral neck posterior to sternocleidomastoid muscle
    • Estimated to represent 2–8% of all branchial cleft anomalies
  • Fourth branchial cleft anomalies
    • Site: close association to thyroid gland associated with clinical thyroiditis if cyst infected
    • Fistula: apex of piriform sinus to base of neck anterior to sternocleidomastoid muscle
    • Extremely rare, representing approximately 1% of all branchial cleft anomalies

EPIDEMIOLOGY

• There is no ethnic or gender predilection.
• Most branchial cleft anomalies are unilateral, only 10% estimated are bilateral.

ETIOLOGY

• Overwhelming majority of cysts in newborns and infants are developmental, whereas in children and adults, they are inflammatory or neoplastic.
• Branchial cleft cysts are the most common congenital neck lesion. Although congenital, they usually present in older children and adults.
• The majority of lesions present in childhood as a visible punctum on the skin, although they may present as bronchial fistula or sinuses. Cysts are more commonly seen in adults.
• Midline malformations are most often thyroglossal duct cysts or dermoids.
• Cysts occurring in the laterocervical region are usually branchial cleft malformations; the most common of these are derivatives of the second cleft, followed by those of the first cleft, of the fourth pouch and thymic cysts.
• Third and fourth branchial cleft anomalies are rare, with most presenting as sinus tracts rather than cysts.

RISK FACTORS

Familial history of branchial defects occasionally noted

COMMONLY ASSOCIATED CONDITIONS

• Branchio-oto-renal (BOR) syndrome is an association of branchial cleft malformations, auricular malformations, deafness, and hypoplastic renal anomalies. It is autosomal dominant and is found in approximately 2–3% of children with profound deafness (prevalence 1/40,000).
• Suspect congenital anomaly in the clinical setting of recurrent infection.