First branchial cleft fistula

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First branchial cleft fistulae are rare congenital malformations arising from the branchial apparatus during embryogenesis . They are often in close relation to the parotid gland, facial nerve, external auditory canal and the anterior neck near the angle of the mandible . Diagnosis can be established clinically and confirmed using various imaging modalities, including fistulography, ultrasound, CT and MRI .

Epidemiology

Anomalies of the first branchial cleft make up less than 8% of all branchial cleft anomalies . The annual incidence has been estimated to be 1 per million live births . It occurs twice as frequently in females than in males . These patients typically present in the first two decades of life . 52% of first branchial cleft anomalies manifest as fistulae and they have been reported to occur more frequently on the left side (64%) .

Clinical presentation

Patients with first branchial cleft fistulae typically complain of a mass or recurrent mucopurulent discharge from a cutaneous pit . The cutaneous opening can usually be found anywhere on the lateral neck below the external auditory canal, above the hyoid bone, anterior to the sternocleidomastoid muscle and posterior to the submandibular angle .

Pathology

The embryology of the branchial apparatus is complex and associated with various malformations further described in branchial cleft anomalies.

Specifically, first branchial cleft fistulae arise from incomplete obliteration of clefts secondary to incomplete fusion of the ventral portion of the first and second branchial arches .

Classifications

Branchial cleft anomalies can be classified based on embryology and histology using Work’s classification :

  • type I
    • originates from the ectoderm
    • arises from the duplication of membranous external auditory canal
    • histologically cystic and consists of squamous epithelium
    • course lateral to facial nerve and parotid gland
  • type II
    • originates from the ectoderm and mesoderm
    • arises from the duplication of membranous and cartilaginous external auditory canal
    • histologically include squamous epithelium, cartilage and adnexal structures
    • course medial to facial nerve and often inferior to the angle of the mandible

Radiographic features

Fluoroscopy

Contrast injected into the cutaneous dimple allows for delineation of the course of the fistulous tract which provides great value in surgical planning . The tract is often smooth with a variable diameter, extending from the external cutaneous opening to its junction with the external auditory canal . The tract can pass superficially or deep to the facial nerve and parotid gland .

Ultrasound

The fistulous tract can be effectively demonstrated on ultrasound as an anechoic linear structure .

CT

CT, particularly used in conjunction with fistulography offers excellent anatomical visualization of the fistulous tract . Hence it is often used clinically to assist in surgical planning .

MRI

MRI provides a high degree of soft-tissue resolution and can be used to define lesions . However, Ultrasound and CT fistulography are more widely used.

Treatment and prognosis

Surgical excision of the entire fistulous tract is the only definitive treatment . Given the intimacy of the tract with the facial nerve, surgery can be complicated by temporary or permanent facial nerve palsy . Incision and drainage and antibiotics therapy can be considered, however, there is a high rate of recurrence associated .