First branchial cleft cyst

Branchial

cleft anomalies: a pictorial review of embryological development and spectrum of imaging findings. MR imaging from a child presenting with purulent ear discharge. Axial and coronal T1 post-contrast (left hand images) with axial and coronal STIR images (right hand images) demonstrating a thick-walled sinus tract (white arrows) that extended to the clinically apparent opening in the left external auditory canal. The tract was surgically excised and confirmed to represent a first branchial cleft anomaly

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Imaging of

parotid anomalies in infants and children. First branchial-cleft cyst and fistulas. Right isolated intraparotid cyst on axial T2-weighted image (a). Type II anomaly, with an intraparotid cyst and 2 fistulas, the upper fistula running from the cyst to the external auditory canal [white arrow] and the lower running from the cyst to the skin, in Pochet’s triangle [red arrow] (b, c and d). Isolated fistula running from the parotid area to the skin (e). Congenital defect of the floor of the left external auditory canal (tympanal bone) on frontal and axial CT images (f and g)

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Branchial

cleft anomalies: a pictorial review of embryological development and spectrum of imaging findings. Transverse ultrasound (US) image from the same child as in Fig. 5, confirming the presence of a thick-walled cystic structure that was part of the sinus tract that extended to the left external auditory canal (white arrow)

insightsimaging.springeropen.com • Open Access

Branchial

cleft anomalies: a pictorial review of embryological development and spectrum of imaging findings. A sinogram performed on a child prior to surgical excision for a presumed first branchial cleft fistula. The opening within the right external auditory canal was cannulated and water-soluble contrast media injected confirmed the presence of a fistulous tract. During the procedure, contrast media was noted to pass via the tract through an external cutaneous opening in the right submandibular region

insightsimaging.springeropen.com • Open Access

Preschooler

with right facial swelling. Axial CT with contrast of the face (above) shows a low density, poorly circumscribed lesion with faint rim enhancement expanding the right parotid gland. Inflammatory changes are noted in the adjacent subcutaneous tissues. Axial T2 MRI of the face from 7 months later (below left) shows areas of oval high signal intensity weaving in and out of the plane of the image representing a tract from the posterior aspect of the right parotid gland to the right external auditory canal which on axial DWI MRI (below right) also shows high signal intensity representing diffusion restriction in the tract.The diagnosis was a parotid abscess due to an infected first branchial cleft cyst.

pediatricimaging.org • CC-by-nc-sa 4.0

Radiopaedia • CC-by-nc-sa 3.0 • de

First branchial cleft cysts are a type of branchial cleft anomaly. They are uncommon and represent only ~7% of all branchial cleft cysts.

Epidemiology

They are usually diagnosed in middle-aged women .

Clinical presentation

Their presentation can in the form of :

asymptomatic, e.g. incidental finding on imaging
a palpable lump or inflammatory mass in the parotid region
spontaneous fluid draining from a pit-like depression on the skin, which may be mucus or pus depending on the presence of associated infection
facial nerve palsy

Pathology

First branchial cleft cysts develop as a result of the incomplete fusion of the cleft between the first and second branchial arches (see branchial apparatus). There may be a sinus with drainage to the external ear or skin. They typically occur within or close to the parotid gland or external auditory canal.

Subtypes

They can be divided into three types based on location:

type I: inferoposteromedial to the pinna
type II: between the angle of the mandible and the external auditory canal
type III: periparotid

They can also be classified based on histology:

type I
- purely ectodermal
- extremely rare
- appear histologically as cysts lined by squamous epithelium
- presents as a cystic mass or fistula posterior to the pinna
- usually located superior to the main trunk of the facial nerve and ends in a cul-de-sac on or near a bony plate at the level of the mesotympanum
type II
- contain ectodermal and mesodermal elements
- comparatively common
- represent a duplication of both membranous and cartilaginous portions of the external auditory canal
- contain skin as well as adnexal structures and cartilage
- may be associated with the parotid gland
- often associated with fistulae in the concha or external auditory canal +/- fistulous openings in the neck
- incorporates some portion of the first and second arch as well as the cleft

Radiographic features

They are typically well-defined cystic masses located superficial to, within, or deep to the parotid gland. If they form a sinus, the sinus tract can be identified draining into the external auditory canal or even extending to the hyoid bone.

Ultrasound

Sharply demarcated thin-walled cyst with variable echogenicity: anechoic (most common) do different degrees of heterogeneity depending on internal debris.

When infected, sonographic features of parotitis may be present.

CT

Sharply circumscribed, fluid density, and thin-walled mass. The wall thickness and enhancement are variable and tend to increase with recurrent infections .

MRI

T1: variable signal dependent on protein content
- high protein content: high signal
- low protein content: low signal
T2: high signal
T1 C+ (Gd): no enhancement in uncomplicated lesions